The Great Lakes basins were carved from ancient river valleys by continental ice sheets that receded from the region less than 10,000 years ago. Not only did the glaciers create the basins now holding the lakes, but they are responsible for many of the shallow depressions in the coastal margin that have since developed as coastal wetlands of various types. For the past four thousand years, coastal processes in the lakes have further modified the shore topography to form embayments, coastal lagoons, estuaries, deltas, and solution basins where thousands of hectares of wetlands have become established. This paper will explore the origin of the various morphometric forms which these wetlands have taken and their characteristic hydrologic processes.

Physiography of the Great Lakes

The five adjoining Laurentian Great Lakes—Superior, Michigan, Huron, Erie, and Ontario—extend 1,370 km from westernmost point to easternmost point and 1,130 km from north to south (Figure 1). With a total surface area of 244,160 km2, this is the largest freshwater system on earth. The total shoreline of these lakes measures 17,017 km and is nearly equally divided between Canada and the United States, although Lake Michigan is totally within the United States and Lake Huron's Georgian Bay lies completely in Canada. The lakes in this immense system contain about 22,700 km3 of water or nearly one-fifth of the all the freshwater on the planet. Lake Superior contains 53% of that water; Lake Michigan, 22%; Lake Huron, 16%; Lake Erie, 2%; and Lake Ontario, 7%.

Figure 1.

St. Lawrence Great Lakes and drainage basin (NOAA, Great Lakes Environmental Research Laboratory).

Figure 1.

St. Lawrence Great Lakes and drainage basin (NOAA, Great Lakes Environmental Research Laboratory).

The Great Lakes are located in zones of weaker sedimentary rocks that were excavated for many millennia by steam erosion. Major valleys were deepened and reshaped by glacial ice during the Pleistocene Epoch. The lakes originated late in this epoch when the margin of the waning ice sheet retreated northward into the newly carved lake basins, some of which were dammed by glacial end moraines. The early ice-margin lakes expanded as the glacial ice masses shrank. However, as new and lower outlets were uncovered to the north, the lakes drained to ever lowering levels except during periods of minor readvances of the ice front (Hough, 1962). Following deglaciation, the Earth's crust rebounded from the hundreds of meters of depression experienced under the weight of the ice masses, causing old outlets to be closed and the levels of the lakes to again rise, but not as high as their initial levels. Continued uplift of the land to the north and erosion of the shores and outlet channels have continued to cause slow changes to the configuration of the lakes.

The watershed of the Great Lakes is about 764,000 km2 and extends over parts of three different physiographic (landform) provinces—Canadian Shield, Central Lowlands, and St. Lawrence Lowlands. The streams that flow into the lakes reflect the character and variations of these regions. The rivers that enter Lake Superior and the northern parts of Lakes Michigan and Huron change elevation rapidly as they descend from the rocky cliffs of the Canadian Shield to the lakes in many falls and rapids. Rivers flowing into the southern Lakes—Michigan, Erie, and Ontario—originate in the Central Lowlands and are more likely to flow gently through well-defined channels and to have broad floodplains. The St. Lawrence Lowlands is restricted to the wide, flat valley of the river for which it is named.

Lake Superior

With a volume of 12,230 km3 and a surface area of 82,100 km2, Lake Superior is the largest of the Great Lakes. The lake bottom is divided into two basins; the Keweenaw Peninsula and a prominent north-south submerged ridge at depths of 150 to 180 m separate the eastern and western basins. The western basin is characterized by a comparatively smooth bottom consisting of thick lake sediments and glacial deposits, while the eastern basin is more rugged with numerous north-south ridges of bedrock flanked by sediment-filled valleys, thought to be the remnants of a preglacial drainage system. The Keweenaw Peninsula, Apostle Islands, Isle Royale, and connecting submarine ridges are outcrops of ancient Precambrian volcanic and sedimentary rocks which are more resistant to erosion. The southern border of the eastern basin consists of Paleozoic strata, most noteworthy being the colorful sandstone cliffs of Pictured Rocks National Lakeshore. Lake Superior lies almost wholly within the Precambrian Canadian Shield, the Paleozoic Central Lowlands rocks of the southeastern shore being the only exception.

An escarpment borders the shore of Lake Superior which rises 120 to 240 m above the surface of the lake on all sides. Interspersed along this precipitous coast of spectacular cliffs are small, rocky, pocket beaches. Offshore the lake bottom rapidly drops to depths greater than 60 m. In the vicinity of Whitefish Point the bottom slope is more gentle and the shore is characterized by shallow reaches composed of sand, derived from nearby glacial deposits, that have been transported into the area by alongshore currents (Upchurch, 1976). The maximum depth of the lake, 406 m, is located east of Keweenaw Peninsula.

Lake Superior owes its origin to a combination of events. First being the formation of a midcontinent rift and associated igneous activity in the Precambrian Era. This rift was later filled with soft sedimentary rocks which eventually became eroded into a ridge and valley system. The older, harder rocks around the edges of the Superior basin (lava flows, gabbros, and granites) form parts of the bordering escarpment and Keweenaw Peninsula. Faulting may have also weakened the bedrock and formed graben-type fault-block depressions. Lastly, as continental glaciers swept across Canada and into the Superior basin, they were guided by the valleys. The immediate cause of the present submarine topography was deepening by successive lobes of glacial ice that occupied the bottom of the rift zone, thus eroding the softer sediments but modifying only to a moderate degree the resistant Precambrian rocks of the sides.

As they retreated, the glaciers and glacial lakes covered the bottom surface with a thin layer of drift and sediment. Irregularities and deep canyons in the western part of the lake basin were filled with sediment, yielding a smooth bottom, whereas, depressions in the eastern part of the lake were not filled, leaving the many irregular north-south submarine canyons and ridges. While the glacial lakes were receding and establishing a series of temporary levels, waves carved ancient lake terraces into the shoreline resembling gigantic stair steps. Several channels have drained Lake Superior at different times. Outcrops of sandstone in the St. Marys River, the present outlet, form a natural weir that restricts the discharge of the lake. The water level in Lake Superior, at an average elevation of 183 m above sea level, is now controlled by engineering works constructed across the rapids at Sault Ste. Marie.

Lake Michigan

The third largest in area and second in volume of the Great Lakes, Lake Michigan has a surface area of 57,750 km2 and a volume of 4,920 km3. The bottom of the lake is characterized by three basins. The southern basin is separated by a limestone sill extending from Sheboygan, WI to Ludington, MI that is covered by a veneer of glacial morainic material. The southern basin has a relatively smooth bottom, over 500 feet deep, that consists of silt and clay lake sediments over Devonian-Mississippian shales. North of the sill, which rises to a depth of 60–90 m at mid lake, a deep north central basin drops to the lake's maximum depth of 281 m. The bottom of this basin has an irregular floor caused by outcrops of resistant Devonian limestones separated by Devonian declivities (Upchurch, 1976). A northeastern basin consists of numerous north-south trending valleys and ridges similar to those of eastern Lake Superior. This basin contains a number of islands and its bottom is characterized by a number of deep troughs, 75 to 150 m deep, separated by ridges with only 8 to 15 m of water over them (Hough, 1958). Green Bay, with a surface area of 4,100 km2, constitutes a fourth physiographic element of Lake Michigan. Green Bay is a relatively shallow embayment, mostly less than 30 m deep, that is separated from the main lake by the Door Peninsula (a western extension of the crescent-shaped cuesta known as the Niagara Escarpment that also separates Georgian Bay from Lake Huron and Lake Erie from Lake Ontario).

Lake Michigan lies wholly within the Paleozoic bedrock province. Rock exposures are not common around the lake because glacial deposits mantle the bedrock almost everywhere. However, exposures are sufficient to show that Paleozoic rock formations control the major topographic feature of the lake basin. Silurian-aged Niagaran Dolomite forms the cuesta that bounds the lake on the west and north and dips under the lake toward the center of the Michigan structural basin centered under the Lower Peninsula of Michigan. Middle Devonian-aged Traverse Group limestones form the shore from the Straits of Mackinac to the headlands of Grand Traverse Bay. The shoreline of Lake Michigan ranges from Paleozoic bedrock that forms precipitous cliffs and glacial debris along the northern and western shores, to expansive sandy beaches with enormous dune ridges on portions of the eastern and southern shores. Offshore slopes are gentle in most areas.

Lake Michigan was formed during the Pleistocene ice age when continental glaciers gouged out the lowlands between present-day Michigan and Wisconsin, and removed the overburden and softer rock formations, leaving ridges of harder, more resistant rocks. As the glaciers retreated, morainic drift buried the rock outcrops and filled many of the preglacial valleys and ice scoured troughs with glacial till, outwash deposits, and glacial lake sediments. A major outlet for ancient glacial lakes in the basin was near Chicago which drained to the Gulf of Mexico. As lower post-glacial levels were established in Lake Michigan, this outlet was abandoned as flow to the north through the Straits of Mackinac dominated. Because Lakes Michigan and Huron have tihis relatively deep connection, they are hydrologically the same lake, with the same average surface elevation, 176.5 m above sea level.

Lake Huron

This lake has the second largest surface area, 59,500 km2, and the third largest volume, 3,537 km3 of the Great Lakes. The lake bottom is composed of three basins. The eastern basin (Georgian Bay), is separated from the main lake by the Niagara Escarpment, which forms the Bruce Peninsula, Manitoulin Island (world's largest freshwater island), Cockburn Island, and Drummond Island. Georgian Bay, at 16,300 km2, is underlain by shales that are less resistant to erosion than the limestones and dolomites that form the escarpment. Lake Huron proper is nearly equally divided into two basins by a ridge that extends southeast from Alpena, MI to Kincardine, ON. This ridge is a cuesta of Devonian limestone with the basins on each side underlain by softer shales and sandstones (Upchurch, 1976). The deepest point in Lake Huron, 229 m, occurs north of the ridge in the northern or main basin about 37 km southwest of the northern tip of Bruce Peninsula. The irregular bathymetry of the northern basin is attributed to the presence of Silurian reefs and the possible collapse of strata resulting from solutioning of Silurian salt beds (Lewis and Herdendorf, 1976). Saginaw Bay, a 3,400 km2 shallow extension of the southern basin, formed in less resistant Mississippian and early Pennsylvanian rocks to the northwest of Michigan's ‘thumb’ area.

The periphery of Lake Huron, from the shoreline out to about 20 km, generally consists of a sand and gravel bottom. The presence of some coarse gravel and boulders of igneous, metamorphic, and sedimentary rocks represents lag deposits from glacial till (Lewis and Herdendorf, 1976). Dark gray to brown silty clay occupies the deeper parts of the basin. Saginaw Bay's bottom is predominately composed of silty clay, but fine-grained sand is also found throughout the bay. In Georgian Bay, bedrock outcrops and boulder debris are common around the ‘flower pot’ islands and submerged reefs from depths of 5 to 30 m; mud covers the deeper bottoms. The Lake Huron shoreline is diverse. Sandy beaches with dune ridges occur where morainal or glacial lake deposits serve as sediment sources. Consequently, the shore of the southern basin and southwestern shore of the northern basin are low and have well-developed beaches. Areas bordered by erosion-resistant rock, such as the Paleozoic limestones and dolomites of the Bruce Peninsula and Manitoulin Island, ON, and Presque Isle, MI, and by the Precambrian crystalline rocks of the North Channel shores, have sheer cliffs and small, rocky, pocket beaches.

During the Pleistocene ice age, continental glaciers deepened pre-glacial lowlands and gouged out softer rock formations on the north and east sides of the Michigan highlands to form Lake Huron. The transgressing glacier stripped soils from the rock surface and exposed the Niagara Escarpment. Retreating glaciers filled depressions with drift and glacial lake deposits. These ancient lakes are evidenced by abandoned beach ridges and terraces carved into the shoreline. The outflow from Lake Huron passes through an outlet channel composed of the St. Clair River, Lake St. Clair, and Detroit River. There are no artificial controls in the channels between Lake Huron and Lake Erie, but dredging operations in these waterways over the years have deepened the natural channels resulting in a substantial lower of the levels of Lakes Huron and Michigan.

Lake Erie

Relatively narrow and shallow Lake Erie is the fourth largest of the Great Lakes by surface area at 25,657 km2 and smallest by volume at 483 km3. The lake is oriented with its long axis in a east-northeast direction and is naturally divided into three basins: western, central, and eastern. The western basin, lying west of a line from the tip of Point Pelee, ON, to Cedar Point, OH, is the smallest and shallowest basin with most of the bottom depths between 8 and 11 m. In contrast with the other basins, a number of bedrock islands and shoals are situated in the western basin and form a partial divide between it and the central basin. The bottom is flat except for the steep-sided islands and shoals in the eastern part. The deepest soundings are 19 m in a small depression north of Starve Island Reef and 16 m in another depression south of Gull Island Shoal (Lewis and Herdendorf, 1976). The central basin is separated from the eastern basin by a relatively shallow sand and gravel bar between Erie, PA and the base of Long Point, ON. The central basin has an average depth of 19 m and a maximum depth of 26 m. Except for the rising slopes of a low morainal bar extending south-southeast from Point Pelee, ON, the bottom of the central basin is extremely flat. The eastern basin is relatively deep and bowl-shaped. A considerable area lies below 37 m, and the deepest sounding of 64 m is about 13 km east-southeast of Long Point, ON.

The varying depths of the Lake Erie basins are attributed to differential erosion by preglacial streams, glaciers, and postglacial lacustrine processes. The strata of the central and eastern basins of Lake Erie dip slightly to the southeast and have a general east-west strike direction roughly paralleling the lake. Lake Ontario is separated from Lake Erie by the resistant Silurian limestones and dolomites of the Niagara Escarpment. The central and eastern basins of Lake Erie are underlain by nonresistant shale, shaly limestone, and shaly sandstone of Upper Devonian age. The southward advance of Pleistocene glacial ice was obstructed by the Mississippian Escarpment and the ice was directed westward along the outcrop of the softer Upper Devonian shales. These shales were deeply eroded to form the narrow eastern basin. Farther west, where the dip of the beds is less and the width of the soft shale belt is greater, glacial erosion resulted in the broader, but shallower central basin.

The Devonian shales trend inland between Cleveland and Sandusky and the shallow western basin is underlain by Silurian and Devonian limestone and dolomite on the northward plunging end of the Findlay Arch. Glacial erosion had relatively slight effects on these resistant rocks. The islands in western Lake Erie are arranged in two north-south belts that correspond with the outcrop patterns of the two most resistant rock formations. The Kelleys Island-Pelee Island belt is underlain by Columbus Limestone and the Bass Islands are underlain by Put-in-Bay Dolomite.

The bottom sediments of Lake Erie consist of silt and clay muds, sand and gravel, peat, compact glacio-lacustrine clays, glacial till, shoals of limestone and dolomite bedrock and rubble, shale bedrock shelves, and erratic cobbles and boulders composed chiefly of igneous and metamorphic rocks. The distribution of bottom sediments is related to the bottom topography. The broad, flat areas of the western and central basin, and the deep areas of the eastern basin have mud bottoms. Midlake bars and nearshore slopes are comprised of mostly sand and gravel or glacial till. Rock is exposed in the shoals of western Lake Erie and along the south shore of the eastern basin.

Most of the shoreline of Lake Erie consists of low marshy coasts or high bluffs of clay-rich glacial till or shale. Along the wetlands the shores are commonly protected by barrier beaches or dikes, whereas the bluffs are commonly fronted by narrow cobble and shingle beaches. The western Lake Erie Islands and peninsulas, and the eastern basin's northeast shore are bound by Silurian-Devonian limestone and dolomite cliffs and rocky shelving bottoms. In general, sand is limited along the shoreline, but extensive dune and beach deposits are found at several places. Notable dunes have been formed at the base and southwest side of Long Point, Point Abino, and Sturgeon Point, all in eastern Lake Erie. These dunes are formed presumably under the influence of the prevailing southwest winds. Littoral currents have concentrated sand in spits and baymouth bars at such places as Point Pelee, Point Aux Pins, and Long Point, ON; North Cape, MI; East Harbor and Cedar Point, OH; and Presque Isle, PA. The natural outlet for Lake Erie is the Niagara River which has a length of 60 km and a total drop of 99 m to Lake Ontario. Navigation to the east of Lake Erie is via the Welland Canal and New York State Barge Canal.

Lake Ontario

This lake is the smallest of the Great Lakes with a surface area of 19,000 km2 and fourth largest by volume at 1,637 km3. Lake Ontario is elongated approximately east-west and has a surface elevation 75 m above sea level. The lake is 245 m deep at its deepest location, where the bottom is 170 m below sea level (a feature known as a cryptodepression), lower than the bottom of any of the other Great Lakes except Lake Superior at 223 m below sea level. Lake Erie is the only one of the Great Lakes that does not possess such a feature. Four depositional basins have been identified in Lake Ontario, three of which are separated by glacial moraines (west to east, Niagara basin, Mississauga basin, and Rochester basin) and a fourth which is isolated by a bedrock sill (Kingston basin). Bottom gradients along the south shore are quite variable, ranging from 1.9 m km- 1 near the Niagara River mouth to 11.7 m km- 1 near Rochester (Lewis and Herdendorf, 1976).

The Lake Ontario basin is a lowland bordered on the north by an escarpment of the Canadian Shield, on the east by the Adirondack Mountains, on the south by the Appalachian Plateau, and on the west by the Niagara Escarpment. The Niagara Escarpment is 60 m high at Niagara Falls, but decreases in height along the south shore of Lake Ontario. Near Oswego, NY, glacially deposited ridges, known as drumlins, form dramatic cliffs that are separated by lush wetland lagoons. On the north shore, east of Toronto, ON, the high bluffs of gray glacial till at Scarborough are eroding at an rapid rate.

As continental glaciers of the Pleistocene ice age crossed the basin, they gouged out the soft red shales of the Queenstone Formation to form the lake depression. The depth of scour and shape of the depression were influenced by hard limestone formations along the north shore of the lake. The retreating glaciers deposited sediment (till) in the lake creating the morainal ridges separating the depositional basins and along the shore forming the drumlins and high bluffs.

The St. Lawrence River is the natural outlet for the Great Lakes, flowing about 1,300 km from Lake Ontario across the St. Lawrence Plain into the Atlantic Ocean at the Gulf of St. Lawrence. This plain is a lowland between the Adirondack Mountains of New York and the Canadian Shield. The broad, multiple-channel river head is broken into by numerous islands (Thousand Islands region). Downstream the channel narrows abruptly where the river flows over hard, resistant Precambrian rocks protruding south from the Canadian Shield. The lower course of the river is a long, horn-shaped, tidal estuary which opens into the Gulf of St. Lawrence. Outflow of Lake Ontario typically ranges from 4,250 to 8,500 m3 s-1.

Morphometric types of Great Lakes coastal wetlands

The Great Lakes are noted for their severe westerly and northeasterly storms and the resultant wave attack and dramatic fluctuations of water levels at their shorelines, as much as 2 m within a few hours. In most reaches of the Great Lakes, the high energy produced at the shore by these storms precludes the development of fringing coastal wetlands. Only where some natural or artificial protection is available against the harsh coastal process of wave attack, erosion, ice scour, and rapid transportation or deposition of sediments can coastal wetlands become established and continue to thrive. Certainly coastal wetlands can survive water level fluctuations, and are often rejuvenated by them, but generally quiescent conditions and the absence of marked turdidity favor their formation. Fortunately a number of morphometric situations occur along the shorelines of the Great Lakes which have created these favorable conditions and tend to foster wetland development. The following categories of coastal wetlands are based on the type of morphometric feature which has created the necessary protection for the establishment of wetland vegetation.

For the purpose of this paper, coastal wetlands are considered as those situated within at least 300 m of the high water mark of one of the Great Lakes or their connecting waterway, including the St. Lawrence River within the boundaries of New York and Ontario. For a wetland that occurs within this coastal margin but extends inland beyond the 300-m limit, the entire contiguous wetland is here considered to be a coastal wetland. Thus, wetlands located wholly or partly within 300 m of a coastal body of water, such as a bay, lagoon, estuary, harbor, or small lake with a direct connection to a Great Lake, are here included.

Great Lakes coastal wetlands can be classified into at least seven morphometric groups: (1) coastal lagoon wetlands, (2) estuarine wetlands, (3) delta wetlands, (4) kettle lake wetlands, (5) solution basin (karst) wetlands, (6) riverine wetlands, and (7) diked wetlands (Figure 2). This classification scheme cuts across several of the functional or ecological systems (lacustrine, palustrine, and riverine wetlands) proposed by the U.S. Fish and Wildlife Service (Cowardin et al., 1979) for the Great Lakes. For example, portions of coastal lagoons, freshwater estuaries, and deltas may be within the lacustrine system, while more elevated portions of the same morphometric wetland might be classified within the palustrine or riverine systems. The relationships of these two classification schemes are further discussed at the end of this section.

Figure 2.

Morphometric classification of Great Lakes coastal wetlands.

Figure 2.

Morphometric classification of Great Lakes coastal wetlands.

Table 1 presents a listing, by lake, of 309 significant coastal wetlands or wetland complexes of the Great Lakes. The table contains an estimate of the surface area of each wetland or wetland complex, as well as an attempt to place each in a morphometric category. ‘Significant’ is here defined as wetlands over 40 ha (100 acres) in size or, if smaller, a particularly good example of a morphometric type.

Significant wetlands of the Great Lakes. Data sources: Ball et al. (2003), Duffy et al. (1987), Geis and Kee (1977), Glooschenko et al. (1987), Herdendorf et al. (1981a,b,c,d,e,f), and Herdendorf et al. (1986).

Table 1.
Significant wetlands of the Great Lakes. Data sources: Ball et al. (2003), Duffy et al. (1987), Geis and Kee (1977), Glooschenko et al. (1987), Herdendorf et al. (1981a,b,c,d,e,f), and Herdendorf et al. (1986).
Wetland Name Location Morphometric Type Area (ha) 
Lake Superior & St. Marys River 
  Agate Harbor Wetlands Keweenaw County, MI Coastal lagoon 82 
  Agawa Bay Algoma County, ON Coastal lagoon 300 
  Allouez Bay/Nemadji River Douglas County, WI Coastal lagoon/estuarine 187 
  Apostle Islands Wetlands Ashland & Bayfield Coastal lagoon 705 
 Counties, WI   
  Au Train Bay & Point Alger County, MI Coastal lagoon/riverine 255 
  Bark Bay Wetlands Bayfield County, WI Coastal lagoon/estuarine 275 
  Batchawana Bay Algoma County, ON Coastal lagoon 500 
  Bear Lake Wetland Houghton County, MI Coastal lagoon 123 
  Bibon Lake/Flag River Bayfield County, WI Coastal lagoon/riverine 376 
  Big Bay Wetland Keweenaw County, MI Coastal lagoon 132 
  Big Bay Wetlands Marquette County, MI Coastal lagoon 164 
  Big Garlic River Wetland Marquette County, MI Coastal lagoon/estuarine 182 
  Black Bay Thunder Bay County, ON Coastal lagoon 900 
  Blind Sucker River Luce County, MI Coastal lagoon 108 
  Brewery Creek Keweenaw County, MI Coastal lagoon/riverine 81 
  Cedar Swamp Keweenaw County, MI Coastal lagoon 212 
  Chequamegon Wetland Ashland County, WI Coastal lagoon/estuarine 3,850 
  Dollar Bay Wetland Houghton County, MI Coastal lagoon 82 
  Fish Creek Wetland Ashland & Bayfield Coastal lagoon/estuarine 316 
 Counties, WI   
  Flintsteel River Wetlands Ontonagon County, MI Coastal lagoon/riverine 196 
  Gogomain River Wetland Chippewa County, MI Coastal lagoon/estuarine 397 
  Goulais Bay Algoma County, ON Coastal lagoon 500 
  Grand Island Wetlands Alger County, MI Coastal lagoon 285 
  Grand Traverse Bay Keweenaw County, MI Coastal lagoon 277 
  Gratiot River Wetland Keweenaw County, MI Coastal lagoon/riverine 42 
  Graveyard Creek Wetland Iron County, WI Coastal lagoon/riverine 51 
  Huron Mountains Wetlands Marquette County, MI Coastal lagoon 75 
  Isle Royale Wetlands Keweenaw County, MI Coastal lagoon 1,037 
  Izaak Walton Bay Wetlands Chippewa County, MI Coastal lagoon/riverine 211 
  Keweenaw Bay Wetlands Baraga County, MI Coastal lagoon 482 
  Lac LaBelle Wetlands Keweenaw County, MI Coastal lagoon 854 
  Lake George Algoma County, ON Coastal lagoon/riverine 927 
  Lake Lily Wetland Keweenaw County, MI Coastal lagoon 59 
  Lake Nicolet Wetland Chippewa County, MI Riverine 102 
  Laughing Whitefish Point Alger County, MI Coastal lagoon 68 
  LeChance Creek Wetland Houghton County, MI Coastal lagoon 192 
  Lightfoot Bay Wetland Baraga County, MI Coastal lagoon 175 
  Michipicoten Bay Algoma County, ON Coastal lagoon 400 
  Middle Bay Wetland Marquette County, MI Coastal lagoon/estuarine 103 
  Mud Lake Wetland Keweenaw County, MI Coastal lagoon 142 
  Munuscong Lake Wetlands Chippewa County, MI Coastal lagoon/riverine 1,170 
  Neebish Bay Wetlands Chippewa County, MI Coastal lagoon/riverine 800 
  Nipigon Bay Thunder Bay County, ON Coastal lagoon 900 
  Oliver Bay Wetlands Keweenaw County, MI Coastal lagoon 192 
  Oskar Wetland Houghton County, MI Coastal lagoon 109 
  Pendills Bay Wetlands Chippewa County, MI Coastal lagoon 136 
  Pictured Rocks Wetlands Alger County, MI Coastal lagoon 359 
  Powell Point Wetlands Alger County, MI Coastal lagoon 217 
  Raber Bay Wetland Chippewa County, MI Coastal lagoon/riverine 645 
  Raspberry Bay Wetland Bayfield County, WI Coastal lagoon/estuarine 57 
  Salmon Trout River Marquette County, MI Coastal lagoon/riverine 599 
  Sand River Wetland Bayfield County, WI Coastal lagoon/estuarine 95 
  Shot Point Wetland Marquette County, MI Coastal lagoon 146 
  Sioux River Wetland Bayfield County, WI Coastal lagoon 82 
  Siskiwit Bay Wetlands Bayfield County, WI Coastal lagoon/estuarine 101 
  St. Joseph Island Algoma County, ON Coastal lagoon/riverine 2,257 
  St. Louis River Wetlands St. Louis County, MN Estuarine 443 
  Sturgeon & Snake Rivers Baraga & Houghton Delta/riverine 3,300 
 Counties, MI   
  Sugar Island Wetlands Chippewa County, MI Coastal lagoon/riverine 1,318 
  Tahquamenon Bay Chippewa County, MI Coastal lagoon 2,400 
  The Marshes Keweenaw County, MI Coastal lagoon 267 
  Thunder Bay Thunder Bay County, ON Coastal lagoon 1,500 
  Torch Bay & Lake Houghton County, MI Coastal lagoon 486 
  Whitefish Bay & Point Chippewa County, MI Coastal lagoon 700 
  Yellow Dog Point Wetlands Marquette County, MI Coastal lagoon 101 
Lake Huron, Georgian Bay & North Channel 
  Albert Sleeper Wetland Huron County, MI Coastal lagoon 700 
  Au Sable Point Wetland Iosco County, MI Coastal lagoon 53 
  Bell River Wetland Presque Isle County, MI Coastal lagoon/estuarine 136 
  Black Lake Wetland Presque Isle County, MI Coastal lagoon 211 
  Bois Blanc Island Wetlands Mackinac County, MI Coastal lagoon 860 
  Cheboygan Wetlands Cheboygan County, MI Coastal lagoon 98 
  Daie du Dore Wetland Bruce County, ON Coastal lagoon 95 
  Drummond Island Wetlands Chippewa County, MI Coastal lagoon 747 
  East Saginaw Bay Wetland Huron & Tuscola Coastal lagoon 6,770 
 Counties, MI   
  Edgewater Wetlands Cheboygan County, MI Coastal lagoon 46 
  Gore Wetlands Huron County, MI Coastal lagoon 179 
  Greenbourgh Harbour Bruce County, ON Coastal lagoon 27 
  Hardwood Point Wetland Huron County, MI Coastal lagoon 79 
  Hill & LaSalle Islands Mackinac County, MI Coastal lagoon 41 
  Hog's Bay Marsh Simco County, ON Coastal lagoon 32 
  Howdenvale Bay Fen Bruce County, ON Kettle 37 
  Long Lake Creek Wetland Alpena County, MI Coastal lagoon 45 
  Marquette Island Wetlands Mackinac County, MI Coastal lagoon 99 
  Matchedash Bay Marsh Simco County, ON Coastal lagoon 807 
  McLeod Bay Wetland Cheboygan County, MI Coastal lagoon/estuarine 336 
  Misery Bay Wetlands Alpena County, MI Coastal lagoon 763 
  Mismer-Hessel Bay Mackinac County, MI Coastal lagoon 186 
  Mulligan Creek Wetland Presque Isle County, MI Coastal lagoon 146 
  North Thunder Bay Alpena County, MI Coastal lagoon 260 
  Old Shore Wetland Huron County, MI Coastal lagoon 42 
  Oliphant Wetland Bruce County, ON Coastal lagoon 173 
  Pointe Aux Barques Huron County, MI Coastal lagoon 776 
  Port Franks Wetland Lambton County, ON Estuarine 123 
  Prentiss Bay Wetland Mackinac County, MI Coastal lagoon 57 
  Sandy Point Wetlands Huron County, MI Coastal lagoon 675 
  Schnitzelbank Creek Arenac County, OH Coastal lagoon 1,068 
  Skipness Wetland Bruce County, ON Riverine 83 
  South Thunder Bay Alcona & Alpena Counties, MI Coastal lagoon 2,930 
  Squaw Bay Wetland Alpena County, MI Coastal lagoon 314 
  St. Martin Bay & Point Mackinac County, MI Coastal lagoon 1,760 
  St. Martin Island Wetland Mackinac County, MI Coastal lagoon 40 
  Stokes Bay/Gauley Bay Bruce County, ON Coastal lagoon 237 
  Sturgeon Bay Wetland Simco County, ON Coastal lagoon 192 
  Sucker Creek Wetland Bruce County, ON Estuarine 146 
  Swan Lake Wetland Presque Isle County, MI Coastal lagoon/estuarine 312 
  Tawas Point Wetland Iosco County, MI Coastal lagoon 332 
  Thompsons Harbor Presque Isle County, MI Coastal lagoon 130 
  Tobico Marsh Bay County, MI Coastal lagoon 229 
  Waterfowl Bay Wetland Huron County, MI Coastal lagoon 128 
  West Saginaw Bay Wetland Arenac & Bay Counties, MI Coastal lagoon 3,790 
  Whitestone Point Wetland Arenac County, MI Coastal lagoon 217 
  Wreck Point Wetland Presque Isle County, MI Coastal lagoon 81 
Lake Michigan & Green Bay 
  Arcadia Lake Wetland Manistee County, MI Estuarine 146 
  Atkinson Marsh Brown County, WI Coastal lagoon/estuarine 206 
  Baileys Harbor Swamp Door County, WI Coastal lagoon/estuarine 2,044 
  Bar Lake Wetlands Manistee County, MI Coastal lagoon 480 
  Bass Lake Wetlands Mason & Oceana Counties, MI Coastal lagoon 67 
  Beaver Island Wetlands Charlevoix County, MI Coastal lagoon 1,526 
  Betsie River Wetland Benzie County, MI Estuarine 154 
  Big Stone Pond Emmet County, MI Coastal lagoon/riverine 75 
  Border Wetland Delta County, MI Coastal lagoon 43 
  Cedar River Wetlands Menominee County, MI Coastal lagoon/riverine 630 
  Charles Pond Oconto County, WI Coastal lagoon 69 
  County Line Swamp Manistee/Mason Counties, MI Coastal lagoon 59 
  Dead Horse Bay Brown County, WI Coastal lagoon 134 
  Deepwater Point Wetlands Delta County, MI Coastal lagoon 111 
  Egg Harbor Wetland Door County, WI Coastal lagoon 53 
  Ford River Wetlands Delta County, MI Coastal lagoon/delta 157 
  Gallien River Wetland Berrien County, MI Coastal lagoon/estuarine 178 
  Garfield Wetlands Mackinac County, MI Coastal lagoon 81 
  Good Harbor Bay Leelanau County, MI Coastal lagoon 118 
  Grand Mere Lakes Berrien County, MI Coastal lagoon 103 
  Grand Traverse Bay Grand Traverse County, MI Coastal lagoon 74 
  Granskog Creek Wetlands Delta County, MI Coastal lagoon 295 
  Hamlin Lake Wetlands Mason County, MI Estuarine/riverine 326 
  Henderson Lake Wetland Delta County, MI Coastal lagoon 102 
  High/Hog/Garden Islands Charlevoix County, MI Coastal lagoon 193 
  Horseshoe Point Wetlands Door County, WI Coastal lagoon 110 
  Illinois Beach Wetlands Lake Co., IL & Kenosha Co., WI Coastal lagoon 1,176 
  Indiana Dunes Wetland Porter County, IN Coastal lagoon 163 
  Kangaroo Lake Wetlands Door County, WI Coastal lagoon 65 
  Kewaunee River Wetlands Kewaunee County, WI Estuarine 146 
  Lake Calumet Wetlands Lake Co., IN & Cook Co., IL Estuarine 428 
  Lilly Bay Wetland Door County, WI Coastal lagoon/riverine 170 
  Little Harbor Wetlands Schoolcraft County, MI Coastal lagoon 56 
  Little Sturgeon Bay Door County, WI Coastal lagoon/diked 127 
  Little Sucker Creek Wetland Emmet County, MI Coastal lagoon/estuarine 76 
  Little Tail Point Wetland Brown County, WI Coastal lagoon 85 
  Long Tail Point Wetland Brown County, WI Coastal lagoon 66 
  Lower Millecoquins River Mackinac County, MI Coastal lagoon 42 
  Mackinaw Wetland Emmet County, MI Coastal lagoon 76 
  Manistee Lake & River Manistee County, MI Estuarine/riverine 3,800 
  Martin Bay Wetlands Delta County, MI Coastal lagoon 208 
  Mattix Creek Wetland Mackinac County, MI Coastal lagoon/riverine 594 
  McGeach Creek Wetland Charlevoix County, MI Coastal lagoon/riverine 216 
  McNeil Creek Wetland Mackinac County, MI Coastal lagoon/riverine 149 
  Muskegon Lake & River Muskegon County, MI Estuarine/riverine 2,450 
  North Bay Wetland Door County, WI Coastal lagoon 870 
  Oconto Marsh Oconto County, WI Estuarine/riverine 3,792 
  Ogontz Bay Wetlands Delta County, MI Coastal lagoon/estuarine 712 
  Paquin Creek Wetland Mackinac County, MI Estuarine/coastal lagoon 168 
  Pensaukee River Wetlands Oconto County, WI Estuarine 198 
  Pentwater Lake & River Oceana County, MI Estuarine/riverine 122 
  Pere Marquette River Mason County, MI Estuarine/riverine 2,500 
  Peshtigo River Wetland Marinette County, WI Delta 2,040 
  Pigeon River/Sloan Pond Ottawa County, MI Coastal lagoon/riverine 63 
  Point au Sable Wetlands Brown County, WI Coastal lagoon 45 
  Point Aux Chenes Wetlands Mackinac County, MI Estuarine/coastal lagoon 1,229 
  Point Beach Wetland Manitowoc County, WI Coastal lagoon/estuarine 603 
  Point O'Keefe Wetlands Schoolcraft County, MI Coastal lagoon 43 
  Point Patterson Wetlands Mackinac County, MI Estuarine/coastal lagoon 599 
  Port Oneida Wetland Leelanau County, MI Kettle 110 
  Portage Bay Wetlands Delta County, MI Coastal lagoon/estuarine 432 
  Portage Marsh Delta County, MI Coastal lagoon/estuarine 527 
  Rocky Point Wetlands Door County, WI Coastal lagoon 563 
  Rowleys Bay Wetlands Door County, WI Coastal lagoon 219 
  Rupert Bayou Mason County, MI Coastal lagoon/estuarine 110 
  Sand Bay Wetland Door County, WI Coastal lagoon 49 
  Sand Bay Wetlands Delta County, MI Coastal lagoon 73 
  Seul Choix Point Wetlands Schoolcraft County, MI Coastal lagoon 2,361 
  South River Bay Wetland Delta County, MI Coastal lagoon 45 
  Squaw Point Wetland Delta County, MI Coastal lagoon 295 
  Stony Lake & Creek Oceana County, MI Estuarine/riverine 157 
  Stony Point Wetland Schoolcraft County, MI Coastal lagoon 1,762 
  Sturgeon River Wetland Delta County, MI Coastal lagoon/estuarine 2,710 
  Sucker Lake Wetland Delta County, MI Coastal lagoon 118 
  Sutton Bay Wetland Leelanau County, MI Coastal lagoon 42 
  Threemile Creek Wetland Kewaunee County, WI Coastal lagoon/riverine 65 
  Toft Point Wetland Door County, WI Coastal lagoon 40 
  Torch Lake Wetlands Antrim County, MI Coastal lagoon/riverine 416 
  Trails End Wetland Emmet County, MI Coastal lagoon 149 
  Upper Big Bay de Noc Delta County, MI Coastal lagoon/riverine 3,687 
  Washington Island Wetland Door County, WI Coastal lagoon 109 
  West Moran Bay Wetland Mackinac County, MI Coastal lagoon 522 
  Whiskey Creek Wetland Charlevoix County, MI Coastal lagoon/riverine 232 
  White Lake & River Oceana/Muskegon Counties, MI Estuarine/riverine 1579 
  Whitefish Bay Wetlands Door County, WI Coastal lagoon/estuarine 61 
  Whitefish River Wetlands Delta County, MI Coastal lagoon 259 
  Whitney Slough Brown County, WI Coastal lagoon/diked 185 
Lake St. Clair, St. Clair River & Detroit River 
  Algonac Wetland St. Clair County, MI Riverine 140 
  Canard River Marshes Essex County, ON Estuarine/diked 416 
  Clinton River Wetland Macomb County, MI Coastal lagoon/estuarine 237 
  Detroit River Islands Wayne County, MI Riverine/coastal lagoon 239 
  Mitchell Bay/Thames River Kent County, ON Coastal lagoon/estuarine 6,280 
  Rockwood Wetland Wayne County, MI Coastal lagoon/diked 73 
  St. Clair Flats St. Clair County, MI Delta 14,000 
  Walpole Island Wetland Lambton County, ON Delta 16,000 
Lake Erie & Niagara River 
  Bay View Wetland Erie County, OH Coastal lagoon/diked 259 
  Big Creek Marsh Essex County, ON Estuarine 1,000 
  Big Creek Wetland Haldimand-Norfolk, ON Estuarine 770 
  Catawba Island & Harbors Ottawa County, OH Coastal lagoon/solution 850 
  Cedar Creek Essex County, ON Estuarine 250 
  Cedar Point Wetland Lucas County, OH Coastal lagoon/diked 644 
  East Sandusky Bay Erie County, OH Coastal lagoon 800 
  Fish Point, Pelee Island Essex County, ON Coastal lagoon 45 
  Grand Island Wetlands Erie County, NY Riverine 144 
  Grand River Marshes Dunnville/Port Maitland, ON Estuarine/riverine 1,076 
  Hillman Marsh Essex County, ON Estuarine 362 
  Huron River Wetland Erie County, OH Estuarine 280 
  Lighthouse Point Essex County, ON Coastal lagoon/diked 85 
  Long Point Sandspit Haldimand-Norfolk, ON Coastal lagoon 6,230 
  Maumee River & Bay Lucas & Monroe Counties, OH/MI Coastal lagoon/estuarine 680 
  Mentor Marsh Lake County, OH Coastal lagoon 294 
  Mouillee Marsh Monroe & Wayne Counties, MI Coastal lagoon/estuarine 553 
  Muddy Creek Bay Sandusky/ & Ottawa Counties, OH Coastal lagoon/diked 1,328 
  Nanticoke Creek Haldimand-Norfolk, ON Riverine/estuarine 311 
  Old Woman Creek Erie County, OH Estuarine 63 
  Ottawa Wetlands Ottawa County, OH Coastal lagoon/diked 1,788 
  Otter Creek Wetland Monroe County, MI Estuarine 67 
  Peripheral Marsh Haldimand-Norfolk, ON Coastal lagoon 1,385 
  Point Pelee Sandspit Essex County, ON Coastal lagoon 1,012 
  Presque Isle Wetlands Erie County, PA Coastal lagoon 166 
  River Raisin Wetland Monroe County, MI Estuarine 52 
  Rondeau Bay & Sandspit Kent County, ON Coastal lagoon 1,201 
  Swan Creek Wetland Monroe County, MI Estuarine/coastal lagoon 150 
  Toledo Beach Wetland Monroe County, MI Coastal lagoon 125 
  Toussaint River Wetlands Ottawa County, OH Estuarine/coastal lagoon 1,076 
  Turkey Point Marsh Haldimand-Norfolk, ON Coastal lagoon 3,088 
  Wainfleet Bog Niagara Regional Muni., ON Kettle 1,006 
  Willow Point Wetland Erie & Sandusky Counties, OH Diked/solution 91 
Lake Ontario & St. Lawrence River 
  Albury Swamp Prince Edward County, ON Coastal lagoon 435 
  Bainsfield Bay Marsh Glengarry County, ON Riverine 472 
  Barnett Marsh Jefferson County, NY Coastal lagoon 71 
  Beaver Creek Wetland Wayne County, NY Coastal lagoon/estuarine 164 
  Big Island Marsh Prince Edward County, ON Coastal lagoon 772 
  Big Sand Bay Prince Edward County, ON Coastal lagoon 195 
  Black Creek Wetland Cayuga County, NY Coastal lagoon/estuarine 206 
  Black Pond Wetland Jefferson County, NY Coastal lagoon 178 
  Black River Bay Jefferson County, NY Coastal lagoon 315 
  Blind Bay Jefferson County, NY Coastal lagoon 38 
  Blind Bay St. Lawrence County, NY Coastal lagoon 34 
  Braddock Bay Wetland Monroe County, NY Coastal lagoon/estuarine 240 
  Buck Pond Wetland Monroe County, NY Diked 144 
  Butterfly Swamp Oswego County, NY Estuarine/coastal lagoon 164 
  Chalk Lake & Lynde Creek Durham Regional Muni., ON Kettle/estuarine 110 
  Charlottenburgh Marsh Glengarry County, ON Riverine 851 
  Chaumont Bay Wetland Jefferson County, NY Coastal lagoon 78 
  Chippewa Creek Marsh St. Lawrence County, NY Estuarine 275 
  Cobourg Marsh Northumberland County, ON Coastal lagoon 78 
  Cootes Paradise Hamilton Regional Muni., ON Coastal lagoon 122 
  Cranberry Marsh Durham Regional Muni., ON Delta 33 
  Cressy Swamp Prince Edward County, ON Coastal lagoon 104 
  Crooked Creek Wetland St. Lawrence County, NY Estuarine 344 
  Deer Creek Wetland Oswego County, NY Estuarine/coastal lagoon 546 
  Delaney Bay Jefferson County, NY Coastal lagoon 85 
  Densmore Wetland Jefferson County, NY Coastal lagoon 40 
  Doran Creek Marsh Dundas County, ON Riverine 42 
  East Bay Wetland Wayne County, NY Coastal lagoon/estuarine 507 
  Eel Bay Marsh Jefferson County, NY Coastal lagoon 69 
  Fifteen Mile Creek Niagara Regional Muni., ON Estuarine 23 
  Flynn Bay Marsh Jefferson County, NY Coastal lagoon 96 
  Fox Island Wetland Jefferson County, NY Coastal lagoon 69 
  French Creek Marsh Jefferson County, NY Coastal lagoon 261 
  Frenchman's Bay Durham Regional Muni., ON Coastal lagoon 45 
  Galloo Island Wetland Jefferson County, NY Coastal lagoon 83 
  Goose Bay Marsh Jefferson County, NY Coastal lagoon 208 
  Grenadier Island Wetland Leeds County, ON Riverine 868 
  Hoople Creek Wetland Stormont County, ON Riverine 169 
  Huyck's Bay Prince Edward County, ON Estuarine 245 
  Irondequoit Bay Wetland Monroe County, NY Coastal lagoon/estuarine 67 
  Jacques Cartier Wetland St. Lawrence County, NY Riverine 59 
  Jones Creek Marsh Leeds County, ON Riverine 140 
  Little Sucker Brook St. Lawrence County, NY Estuarine 57 
  McCrae Marsh Jefferson County, NY Coastal lagoon 71 
  Moon Beach Wetland Cayuga County, NY Coastal lagoon 56 
  Mud Creek & Bay Jefferson County, NY Estuarine 127 
  Mullet Creek Wetland Jefferson County, NY Coastal lagoon 208 
  North Walcott Wetland Wayne County, NY Coastal lagoon 94 
  Oak Island Wetland St. Lawrence County, NY Riverine 57 
  Oshawa Marsh Durham Regional Muni., ON Coastal lagoon 105 
  Payne Beach Wetland Monroe County, NY Coastal lagoon 51 
  Point Peninsula Marsh Jefferson County, NY Coastal lagoon 134 
  Port Bay Wetland Wayne County, NY Coastal lagoon/estuarine 168 
  Presqúile Bay Marsh Northumberland County, ON Coastal lagoon 970 
  Ray Bay Wetland Jefferson County, NY Coastal lagoon 96 
  Red Creek Wetland Cayuga County, NY Coastal lagoon/estuarine 139 
  Rift Marsh Jefferson County, NY Coastal lagoon 49 
  Riverside Marsh Dundas County, ON Riverine 134 
  Root Swamp Wayne County, NY Coastal lagoon 73 
  Rouge River Wetland Durham Regional Muni., ON Estuarine 56 
  Round Pond Wetland Monroe County, NY Coastal lagoon 91 
  Sage Creek Wetland Oswego County, NY Estuarine/coastal lagoon 39 
  Sandy Creek/Colwell Pond Jefferson County, NY Coastal lagoon 911 
  Sawguin Creek Marsh Prince Edward County, ON Riverine 1,956 
  Snake Creek Wetland Oswego County, NY Estuarine/coastal lagoon 55 
  Sodus Bay Wetland Wayne County, NY Coastal lagoon/estuarine 299 
  Southwick Beach Marsh Jefferson County, NY Coastal lagoon 97 
  Sparrowhawk Point St. Lawrence County, NY Riverine 62 
  St. Lawrence State Park St. Lawrence County, NY Coastal lagoon 111 
  Sterling Creek Wetland Cayuga County, NY Coastal lagoon/estuarine 369 
  Stoney Creek Marsh Jefferson County, NY Estuarine 42 
  Twenty Mile Creek Niagara Regional Muni., ON Estuarine 136 
  Upper Canada Wetland Dundas County, ON Diked 321 
  Weller's Bay Wetland Prince Edward County, ON Estuarine 125 
  West Lake Prince Edward County, ON Coastal lagoon 706 
  Westminster Marsh Jefferson County, NY Coastal lagoon 61 
  Wilson Bay Marsh Jefferson County, NY Coastal lagoon 85 
Wetland Name Location Morphometric Type Area (ha) 
Lake Superior & St. Marys River 
  Agate Harbor Wetlands Keweenaw County, MI Coastal lagoon 82 
  Agawa Bay Algoma County, ON Coastal lagoon 300 
  Allouez Bay/Nemadji River Douglas County, WI Coastal lagoon/estuarine 187 
  Apostle Islands Wetlands Ashland & Bayfield Coastal lagoon 705 
 Counties, WI   
  Au Train Bay & Point Alger County, MI Coastal lagoon/riverine 255 
  Bark Bay Wetlands Bayfield County, WI Coastal lagoon/estuarine 275 
  Batchawana Bay Algoma County, ON Coastal lagoon 500 
  Bear Lake Wetland Houghton County, MI Coastal lagoon 123 
  Bibon Lake/Flag River Bayfield County, WI Coastal lagoon/riverine 376 
  Big Bay Wetland Keweenaw County, MI Coastal lagoon 132 
  Big Bay Wetlands Marquette County, MI Coastal lagoon 164 
  Big Garlic River Wetland Marquette County, MI Coastal lagoon/estuarine 182 
  Black Bay Thunder Bay County, ON Coastal lagoon 900 
  Blind Sucker River Luce County, MI Coastal lagoon 108 
  Brewery Creek Keweenaw County, MI Coastal lagoon/riverine 81 
  Cedar Swamp Keweenaw County, MI Coastal lagoon 212 
  Chequamegon Wetland Ashland County, WI Coastal lagoon/estuarine 3,850 
  Dollar Bay Wetland Houghton County, MI Coastal lagoon 82 
  Fish Creek Wetland Ashland & Bayfield Coastal lagoon/estuarine 316 
 Counties, WI   
  Flintsteel River Wetlands Ontonagon County, MI Coastal lagoon/riverine 196 
  Gogomain River Wetland Chippewa County, MI Coastal lagoon/estuarine 397 
  Goulais Bay Algoma County, ON Coastal lagoon 500 
  Grand Island Wetlands Alger County, MI Coastal lagoon 285 
  Grand Traverse Bay Keweenaw County, MI Coastal lagoon 277 
  Gratiot River Wetland Keweenaw County, MI Coastal lagoon/riverine 42 
  Graveyard Creek Wetland Iron County, WI Coastal lagoon/riverine 51 
  Huron Mountains Wetlands Marquette County, MI Coastal lagoon 75 
  Isle Royale Wetlands Keweenaw County, MI Coastal lagoon 1,037 
  Izaak Walton Bay Wetlands Chippewa County, MI Coastal lagoon/riverine 211 
  Keweenaw Bay Wetlands Baraga County, MI Coastal lagoon 482 
  Lac LaBelle Wetlands Keweenaw County, MI Coastal lagoon 854 
  Lake George Algoma County, ON Coastal lagoon/riverine 927 
  Lake Lily Wetland Keweenaw County, MI Coastal lagoon 59 
  Lake Nicolet Wetland Chippewa County, MI Riverine 102 
  Laughing Whitefish Point Alger County, MI Coastal lagoon 68 
  LeChance Creek Wetland Houghton County, MI Coastal lagoon 192 
  Lightfoot Bay Wetland Baraga County, MI Coastal lagoon 175 
  Michipicoten Bay Algoma County, ON Coastal lagoon 400 
  Middle Bay Wetland Marquette County, MI Coastal lagoon/estuarine 103 
  Mud Lake Wetland Keweenaw County, MI Coastal lagoon 142 
  Munuscong Lake Wetlands Chippewa County, MI Coastal lagoon/riverine 1,170 
  Neebish Bay Wetlands Chippewa County, MI Coastal lagoon/riverine 800 
  Nipigon Bay Thunder Bay County, ON Coastal lagoon 900 
  Oliver Bay Wetlands Keweenaw County, MI Coastal lagoon 192 
  Oskar Wetland Houghton County, MI Coastal lagoon 109 
  Pendills Bay Wetlands Chippewa County, MI Coastal lagoon 136 
  Pictured Rocks Wetlands Alger County, MI Coastal lagoon 359 
  Powell Point Wetlands Alger County, MI Coastal lagoon 217 
  Raber Bay Wetland Chippewa County, MI Coastal lagoon/riverine 645 
  Raspberry Bay Wetland Bayfield County, WI Coastal lagoon/estuarine 57 
  Salmon Trout River Marquette County, MI Coastal lagoon/riverine 599 
  Sand River Wetland Bayfield County, WI Coastal lagoon/estuarine 95 
  Shot Point Wetland Marquette County, MI Coastal lagoon 146 
  Sioux River Wetland Bayfield County, WI Coastal lagoon 82 
  Siskiwit Bay Wetlands Bayfield County, WI Coastal lagoon/estuarine 101 
  St. Joseph Island Algoma County, ON Coastal lagoon/riverine 2,257 
  St. Louis River Wetlands St. Louis County, MN Estuarine 443 
  Sturgeon & Snake Rivers Baraga & Houghton Delta/riverine 3,300 
 Counties, MI   
  Sugar Island Wetlands Chippewa County, MI Coastal lagoon/riverine 1,318 
  Tahquamenon Bay Chippewa County, MI Coastal lagoon 2,400 
  The Marshes Keweenaw County, MI Coastal lagoon 267 
  Thunder Bay Thunder Bay County, ON Coastal lagoon 1,500 
  Torch Bay & Lake Houghton County, MI Coastal lagoon 486 
  Whitefish Bay & Point Chippewa County, MI Coastal lagoon 700 
  Yellow Dog Point Wetlands Marquette County, MI Coastal lagoon 101 
Lake Huron, Georgian Bay & North Channel 
  Albert Sleeper Wetland Huron County, MI Coastal lagoon 700 
  Au Sable Point Wetland Iosco County, MI Coastal lagoon 53 
  Bell River Wetland Presque Isle County, MI Coastal lagoon/estuarine 136 
  Black Lake Wetland Presque Isle County, MI Coastal lagoon 211 
  Bois Blanc Island Wetlands Mackinac County, MI Coastal lagoon 860 
  Cheboygan Wetlands Cheboygan County, MI Coastal lagoon 98 
  Daie du Dore Wetland Bruce County, ON Coastal lagoon 95 
  Drummond Island Wetlands Chippewa County, MI Coastal lagoon 747 
  East Saginaw Bay Wetland Huron & Tuscola Coastal lagoon 6,770 
 Counties, MI   
  Edgewater Wetlands Cheboygan County, MI Coastal lagoon 46 
  Gore Wetlands Huron County, MI Coastal lagoon 179 
  Greenbourgh Harbour Bruce County, ON Coastal lagoon 27 
  Hardwood Point Wetland Huron County, MI Coastal lagoon 79 
  Hill & LaSalle Islands Mackinac County, MI Coastal lagoon 41 
  Hog's Bay Marsh Simco County, ON Coastal lagoon 32 
  Howdenvale Bay Fen Bruce County, ON Kettle 37 
  Long Lake Creek Wetland Alpena County, MI Coastal lagoon 45 
  Marquette Island Wetlands Mackinac County, MI Coastal lagoon 99 
  Matchedash Bay Marsh Simco County, ON Coastal lagoon 807 
  McLeod Bay Wetland Cheboygan County, MI Coastal lagoon/estuarine 336 
  Misery Bay Wetlands Alpena County, MI Coastal lagoon 763 
  Mismer-Hessel Bay Mackinac County, MI Coastal lagoon 186 
  Mulligan Creek Wetland Presque Isle County, MI Coastal lagoon 146 
  North Thunder Bay Alpena County, MI Coastal lagoon 260 
  Old Shore Wetland Huron County, MI Coastal lagoon 42 
  Oliphant Wetland Bruce County, ON Coastal lagoon 173 
  Pointe Aux Barques Huron County, MI Coastal lagoon 776 
  Port Franks Wetland Lambton County, ON Estuarine 123 
  Prentiss Bay Wetland Mackinac County, MI Coastal lagoon 57 
  Sandy Point Wetlands Huron County, MI Coastal lagoon 675 
  Schnitzelbank Creek Arenac County, OH Coastal lagoon 1,068 
  Skipness Wetland Bruce County, ON Riverine 83 
  South Thunder Bay Alcona & Alpena Counties, MI Coastal lagoon 2,930 
  Squaw Bay Wetland Alpena County, MI Coastal lagoon 314 
  St. Martin Bay & Point Mackinac County, MI Coastal lagoon 1,760 
  St. Martin Island Wetland Mackinac County, MI Coastal lagoon 40 
  Stokes Bay/Gauley Bay Bruce County, ON Coastal lagoon 237 
  Sturgeon Bay Wetland Simco County, ON Coastal lagoon 192 
  Sucker Creek Wetland Bruce County, ON Estuarine 146 
  Swan Lake Wetland Presque Isle County, MI Coastal lagoon/estuarine 312 
  Tawas Point Wetland Iosco County, MI Coastal lagoon 332 
  Thompsons Harbor Presque Isle County, MI Coastal lagoon 130 
  Tobico Marsh Bay County, MI Coastal lagoon 229 
  Waterfowl Bay Wetland Huron County, MI Coastal lagoon 128 
  West Saginaw Bay Wetland Arenac & Bay Counties, MI Coastal lagoon 3,790 
  Whitestone Point Wetland Arenac County, MI Coastal lagoon 217 
  Wreck Point Wetland Presque Isle County, MI Coastal lagoon 81 
Lake Michigan & Green Bay 
  Arcadia Lake Wetland Manistee County, MI Estuarine 146 
  Atkinson Marsh Brown County, WI Coastal lagoon/estuarine 206 
  Baileys Harbor Swamp Door County, WI Coastal lagoon/estuarine 2,044 
  Bar Lake Wetlands Manistee County, MI Coastal lagoon 480 
  Bass Lake Wetlands Mason & Oceana Counties, MI Coastal lagoon 67 
  Beaver Island Wetlands Charlevoix County, MI Coastal lagoon 1,526 
  Betsie River Wetland Benzie County, MI Estuarine 154 
  Big Stone Pond Emmet County, MI Coastal lagoon/riverine 75 
  Border Wetland Delta County, MI Coastal lagoon 43 
  Cedar River Wetlands Menominee County, MI Coastal lagoon/riverine 630 
  Charles Pond Oconto County, WI Coastal lagoon 69 
  County Line Swamp Manistee/Mason Counties, MI Coastal lagoon 59 
  Dead Horse Bay Brown County, WI Coastal lagoon 134 
  Deepwater Point Wetlands Delta County, MI Coastal lagoon 111 
  Egg Harbor Wetland Door County, WI Coastal lagoon 53 
  Ford River Wetlands Delta County, MI Coastal lagoon/delta 157 
  Gallien River Wetland Berrien County, MI Coastal lagoon/estuarine 178 
  Garfield Wetlands Mackinac County, MI Coastal lagoon 81 
  Good Harbor Bay Leelanau County, MI Coastal lagoon 118 
  Grand Mere Lakes Berrien County, MI Coastal lagoon 103 
  Grand Traverse Bay Grand Traverse County, MI Coastal lagoon 74 
  Granskog Creek Wetlands Delta County, MI Coastal lagoon 295 
  Hamlin Lake Wetlands Mason County, MI Estuarine/riverine 326 
  Henderson Lake Wetland Delta County, MI Coastal lagoon 102 
  High/Hog/Garden Islands Charlevoix County, MI Coastal lagoon 193 
  Horseshoe Point Wetlands Door County, WI Coastal lagoon 110 
  Illinois Beach Wetlands Lake Co., IL & Kenosha Co., WI Coastal lagoon 1,176 
  Indiana Dunes Wetland Porter County, IN Coastal lagoon 163 
  Kangaroo Lake Wetlands Door County, WI Coastal lagoon 65 
  Kewaunee River Wetlands Kewaunee County, WI Estuarine 146 
  Lake Calumet Wetlands Lake Co., IN & Cook Co., IL Estuarine 428 
  Lilly Bay Wetland Door County, WI Coastal lagoon/riverine 170 
  Little Harbor Wetlands Schoolcraft County, MI Coastal lagoon 56 
  Little Sturgeon Bay Door County, WI Coastal lagoon/diked 127 
  Little Sucker Creek Wetland Emmet County, MI Coastal lagoon/estuarine 76 
  Little Tail Point Wetland Brown County, WI Coastal lagoon 85 
  Long Tail Point Wetland Brown County, WI Coastal lagoon 66 
  Lower Millecoquins River Mackinac County, MI Coastal lagoon 42 
  Mackinaw Wetland Emmet County, MI Coastal lagoon 76 
  Manistee Lake & River Manistee County, MI Estuarine/riverine 3,800 
  Martin Bay Wetlands Delta County, MI Coastal lagoon 208 
  Mattix Creek Wetland Mackinac County, MI Coastal lagoon/riverine 594 
  McGeach Creek Wetland Charlevoix County, MI Coastal lagoon/riverine 216 
  McNeil Creek Wetland Mackinac County, MI Coastal lagoon/riverine 149 
  Muskegon Lake & River Muskegon County, MI Estuarine/riverine 2,450 
  North Bay Wetland Door County, WI Coastal lagoon 870 
  Oconto Marsh Oconto County, WI Estuarine/riverine 3,792 
  Ogontz Bay Wetlands Delta County, MI Coastal lagoon/estuarine 712 
  Paquin Creek Wetland Mackinac County, MI Estuarine/coastal lagoon 168 
  Pensaukee River Wetlands Oconto County, WI Estuarine 198 
  Pentwater Lake & River Oceana County, MI Estuarine/riverine 122 
  Pere Marquette River Mason County, MI Estuarine/riverine 2,500 
  Peshtigo River Wetland Marinette County, WI Delta 2,040 
  Pigeon River/Sloan Pond Ottawa County, MI Coastal lagoon/riverine 63 
  Point au Sable Wetlands Brown County, WI Coastal lagoon 45 
  Point Aux Chenes Wetlands Mackinac County, MI Estuarine/coastal lagoon 1,229 
  Point Beach Wetland Manitowoc County, WI Coastal lagoon/estuarine 603 
  Point O'Keefe Wetlands Schoolcraft County, MI Coastal lagoon 43 
  Point Patterson Wetlands Mackinac County, MI Estuarine/coastal lagoon 599 
  Port Oneida Wetland Leelanau County, MI Kettle 110 
  Portage Bay Wetlands Delta County, MI Coastal lagoon/estuarine 432 
  Portage Marsh Delta County, MI Coastal lagoon/estuarine 527 
  Rocky Point Wetlands Door County, WI Coastal lagoon 563 
  Rowleys Bay Wetlands Door County, WI Coastal lagoon 219 
  Rupert Bayou Mason County, MI Coastal lagoon/estuarine 110 
  Sand Bay Wetland Door County, WI Coastal lagoon 49 
  Sand Bay Wetlands Delta County, MI Coastal lagoon 73 
  Seul Choix Point Wetlands Schoolcraft County, MI Coastal lagoon 2,361 
  South River Bay Wetland Delta County, MI Coastal lagoon 45 
  Squaw Point Wetland Delta County, MI Coastal lagoon 295 
  Stony Lake & Creek Oceana County, MI Estuarine/riverine 157 
  Stony Point Wetland Schoolcraft County, MI Coastal lagoon 1,762 
  Sturgeon River Wetland Delta County, MI Coastal lagoon/estuarine 2,710 
  Sucker Lake Wetland Delta County, MI Coastal lagoon 118 
  Sutton Bay Wetland Leelanau County, MI Coastal lagoon 42 
  Threemile Creek Wetland Kewaunee County, WI Coastal lagoon/riverine 65 
  Toft Point Wetland Door County, WI Coastal lagoon 40 
  Torch Lake Wetlands Antrim County, MI Coastal lagoon/riverine 416 
  Trails End Wetland Emmet County, MI Coastal lagoon 149 
  Upper Big Bay de Noc Delta County, MI Coastal lagoon/riverine 3,687 
  Washington Island Wetland Door County, WI Coastal lagoon 109 
  West Moran Bay Wetland Mackinac County, MI Coastal lagoon 522 
  Whiskey Creek Wetland Charlevoix County, MI Coastal lagoon/riverine 232 
  White Lake & River Oceana/Muskegon Counties, MI Estuarine/riverine 1579 
  Whitefish Bay Wetlands Door County, WI Coastal lagoon/estuarine 61 
  Whitefish River Wetlands Delta County, MI Coastal lagoon 259 
  Whitney Slough Brown County, WI Coastal lagoon/diked 185 
Lake St. Clair, St. Clair River & Detroit River 
  Algonac Wetland St. Clair County, MI Riverine 140 
  Canard River Marshes Essex County, ON Estuarine/diked 416 
  Clinton River Wetland Macomb County, MI Coastal lagoon/estuarine 237 
  Detroit River Islands Wayne County, MI Riverine/coastal lagoon 239 
  Mitchell Bay/Thames River Kent County, ON Coastal lagoon/estuarine 6,280 
  Rockwood Wetland Wayne County, MI Coastal lagoon/diked 73 
  St. Clair Flats St. Clair County, MI Delta 14,000 
  Walpole Island Wetland Lambton County, ON Delta 16,000 
Lake Erie & Niagara River 
  Bay View Wetland Erie County, OH Coastal lagoon/diked 259 
  Big Creek Marsh Essex County, ON Estuarine 1,000 
  Big Creek Wetland Haldimand-Norfolk, ON Estuarine 770 
  Catawba Island & Harbors Ottawa County, OH Coastal lagoon/solution 850 
  Cedar Creek Essex County, ON Estuarine 250 
  Cedar Point Wetland Lucas County, OH Coastal lagoon/diked 644 
  East Sandusky Bay Erie County, OH Coastal lagoon 800 
  Fish Point, Pelee Island Essex County, ON Coastal lagoon 45 
  Grand Island Wetlands Erie County, NY Riverine 144 
  Grand River Marshes Dunnville/Port Maitland, ON Estuarine/riverine 1,076 
  Hillman Marsh Essex County, ON Estuarine 362 
  Huron River Wetland Erie County, OH Estuarine 280 
  Lighthouse Point Essex County, ON Coastal lagoon/diked 85 
  Long Point Sandspit Haldimand-Norfolk, ON Coastal lagoon 6,230 
  Maumee River & Bay Lucas & Monroe Counties, OH/MI Coastal lagoon/estuarine 680 
  Mentor Marsh Lake County, OH Coastal lagoon 294 
  Mouillee Marsh Monroe & Wayne Counties, MI Coastal lagoon/estuarine 553 
  Muddy Creek Bay Sandusky/ & Ottawa Counties, OH Coastal lagoon/diked 1,328 
  Nanticoke Creek Haldimand-Norfolk, ON Riverine/estuarine 311 
  Old Woman Creek Erie County, OH Estuarine 63 
  Ottawa Wetlands Ottawa County, OH Coastal lagoon/diked 1,788 
  Otter Creek Wetland Monroe County, MI Estuarine 67 
  Peripheral Marsh Haldimand-Norfolk, ON Coastal lagoon 1,385 
  Point Pelee Sandspit Essex County, ON Coastal lagoon 1,012 
  Presque Isle Wetlands Erie County, PA Coastal lagoon 166 
  River Raisin Wetland Monroe County, MI Estuarine 52 
  Rondeau Bay & Sandspit Kent County, ON Coastal lagoon 1,201 
  Swan Creek Wetland Monroe County, MI Estuarine/coastal lagoon 150 
  Toledo Beach Wetland Monroe County, MI Coastal lagoon 125 
  Toussaint River Wetlands Ottawa County, OH Estuarine/coastal lagoon 1,076 
  Turkey Point Marsh Haldimand-Norfolk, ON Coastal lagoon 3,088 
  Wainfleet Bog Niagara Regional Muni., ON Kettle 1,006 
  Willow Point Wetland Erie & Sandusky Counties, OH Diked/solution 91 
Lake Ontario & St. Lawrence River 
  Albury Swamp Prince Edward County, ON Coastal lagoon 435 
  Bainsfield Bay Marsh Glengarry County, ON Riverine 472 
  Barnett Marsh Jefferson County, NY Coastal lagoon 71 
  Beaver Creek Wetland Wayne County, NY Coastal lagoon/estuarine 164 
  Big Island Marsh Prince Edward County, ON Coastal lagoon 772 
  Big Sand Bay Prince Edward County, ON Coastal lagoon 195 
  Black Creek Wetland Cayuga County, NY Coastal lagoon/estuarine 206 
  Black Pond Wetland Jefferson County, NY Coastal lagoon 178 
  Black River Bay Jefferson County, NY Coastal lagoon 315 
  Blind Bay Jefferson County, NY Coastal lagoon 38 
  Blind Bay St. Lawrence County, NY Coastal lagoon 34 
  Braddock Bay Wetland Monroe County, NY Coastal lagoon/estuarine 240 
  Buck Pond Wetland Monroe County, NY Diked 144 
  Butterfly Swamp Oswego County, NY Estuarine/coastal lagoon 164 
  Chalk Lake & Lynde Creek Durham Regional Muni., ON Kettle/estuarine 110 
  Charlottenburgh Marsh Glengarry County, ON Riverine 851 
  Chaumont Bay Wetland Jefferson County, NY Coastal lagoon 78 
  Chippewa Creek Marsh St. Lawrence County, NY Estuarine 275 
  Cobourg Marsh Northumberland County, ON Coastal lagoon 78 
  Cootes Paradise Hamilton Regional Muni., ON Coastal lagoon 122 
  Cranberry Marsh Durham Regional Muni., ON Delta 33 
  Cressy Swamp Prince Edward County, ON Coastal lagoon 104 
  Crooked Creek Wetland St. Lawrence County, NY Estuarine 344 
  Deer Creek Wetland Oswego County, NY Estuarine/coastal lagoon 546 
  Delaney Bay Jefferson County, NY Coastal lagoon 85 
  Densmore Wetland Jefferson County, NY Coastal lagoon 40 
  Doran Creek Marsh Dundas County, ON Riverine 42 
  East Bay Wetland Wayne County, NY Coastal lagoon/estuarine 507 
  Eel Bay Marsh Jefferson County, NY Coastal lagoon 69 
  Fifteen Mile Creek Niagara Regional Muni., ON Estuarine 23 
  Flynn Bay Marsh Jefferson County, NY Coastal lagoon 96 
  Fox Island Wetland Jefferson County, NY Coastal lagoon 69 
  French Creek Marsh Jefferson County, NY Coastal lagoon 261 
  Frenchman's Bay Durham Regional Muni., ON Coastal lagoon 45 
  Galloo Island Wetland Jefferson County, NY Coastal lagoon 83 
  Goose Bay Marsh Jefferson County, NY Coastal lagoon 208 
  Grenadier Island Wetland Leeds County, ON Riverine 868 
  Hoople Creek Wetland Stormont County, ON Riverine 169 
  Huyck's Bay Prince Edward County, ON Estuarine 245 
  Irondequoit Bay Wetland Monroe County, NY Coastal lagoon/estuarine 67 
  Jacques Cartier Wetland St. Lawrence County, NY Riverine 59 
  Jones Creek Marsh Leeds County, ON Riverine 140 
  Little Sucker Brook St. Lawrence County, NY Estuarine 57 
  McCrae Marsh Jefferson County, NY Coastal lagoon 71 
  Moon Beach Wetland Cayuga County, NY Coastal lagoon 56 
  Mud Creek & Bay Jefferson County, NY Estuarine 127 
  Mullet Creek Wetland Jefferson County, NY Coastal lagoon 208 
  North Walcott Wetland Wayne County, NY Coastal lagoon 94 
  Oak Island Wetland St. Lawrence County, NY Riverine 57 
  Oshawa Marsh Durham Regional Muni., ON Coastal lagoon 105 
  Payne Beach Wetland Monroe County, NY Coastal lagoon 51 
  Point Peninsula Marsh Jefferson County, NY Coastal lagoon 134 
  Port Bay Wetland Wayne County, NY Coastal lagoon/estuarine 168 
  Presqúile Bay Marsh Northumberland County, ON Coastal lagoon 970 
  Ray Bay Wetland Jefferson County, NY Coastal lagoon 96 
  Red Creek Wetland Cayuga County, NY Coastal lagoon/estuarine 139 
  Rift Marsh Jefferson County, NY Coastal lagoon 49 
  Riverside Marsh Dundas County, ON Riverine 134 
  Root Swamp Wayne County, NY Coastal lagoon 73 
  Rouge River Wetland Durham Regional Muni., ON Estuarine 56 
  Round Pond Wetland Monroe County, NY Coastal lagoon 91 
  Sage Creek Wetland Oswego County, NY Estuarine/coastal lagoon 39 
  Sandy Creek/Colwell Pond Jefferson County, NY Coastal lagoon 911 
  Sawguin Creek Marsh Prince Edward County, ON Riverine 1,956 
  Snake Creek Wetland Oswego County, NY Estuarine/coastal lagoon 55 
  Sodus Bay Wetland Wayne County, NY Coastal lagoon/estuarine 299 
  Southwick Beach Marsh Jefferson County, NY Coastal lagoon 97 
  Sparrowhawk Point St. Lawrence County, NY Riverine 62 
  St. Lawrence State Park St. Lawrence County, NY Coastal lagoon 111 
  Sterling Creek Wetland Cayuga County, NY Coastal lagoon/estuarine 369 
  Stoney Creek Marsh Jefferson County, NY Estuarine 42 
  Twenty Mile Creek Niagara Regional Muni., ON Estuarine 136 
  Upper Canada Wetland Dundas County, ON Diked 321 
  Weller's Bay Wetland Prince Edward County, ON Estuarine 125 
  West Lake Prince Edward County, ON Coastal lagoon 706 
  Westminster Marsh Jefferson County, NY Coastal lagoon 61 
  Wilson Bay Marsh Jefferson County, NY Coastal lagoon 85 

Coastal lagoon wetlands

This category includes the protection afforded to wetland development by a variety of embayments and isolated raised depressions within the shorelands of the Great Lakes that were primarily created or modified by coastal processes during the present or predecessor lake stages. These processes include wave attack and erosion, sediment transport and deposition by alongshore currents, ice shove, dune-forming wind, and mass wasting of bluffs. Offshore bars, barrier beaches, and sand spits are also created by these agents that result in quiescent regions where aquatic macrophytes can flourish.

In large bodies of water such as the Great Lakes, the shifting of sediments by nearshore currents can form basins where wetlands eventually develop. If sediments are deposited across the mouth of an embayment, a tributary outlet or a freshwater estuary, the blockage may result in the formation of a new pond or lagoon. Wave activity, too, has formed bars of sand and gravel, which likewise have closed off the mouths of embayments. The usual way in which a lagoon capable of supporting a wetland is formed is by accretion of a bar across some irregularity or indentation of the coastline. The term ‘bar’ is used here in a generic sense to include the various types of submerged or emergent embankments of sand and gravel built on the lake bottom by waves and currents. One of the most common types of bars associated with wetlands in the Great Lakes is a spit. This feature is a sand ridge attached to the mainland at one end and terminating in open water at the distal end. Spits that have extended themselves across or partially across embayments are termed baymouth or barrier bars. Commonly the axis of a spit will extend in a straight line parallel to the coast, but where currents are deflected landward a recurved spit or hook can result. Several stages of hook development may produce a compound recurved spit with a series of ponds separated by beach ridges. Such ponds have provided excellent sites for wetland development along the Great Lakes.

Kormondy (1969, 1984) described wetland succession in beach ponds on a 6.4 km-long spit in Lake Erie known as Presque Isle near Erie, PA. Owing to a combination of its sandy shore and exposure to violent lake storms, this spit developed as a series of hooks with the establishment of numerous, fingerlike beach ponds over the past several thousand years. The ponds were created when an elevated bar of sand developed, thereby isolating a small portion of the lake; the ponds were seldom more than 100 to 200 m long, 10 to 20 m wide, and 1 m deep. Some of the ponds were destroyed in a few days, months, or years by subsequent storms which either breached the sand bar or blew enough sand to fill in the depression. The better protected ponds survived these geological processes only to be subjected to a biological fate, wetland succession. A four-year-old pond is characterized by sparse pioneer vegetation, such as stonewort, algae, bulrushes, cattail, and cottonwood seedlings. At 50 years, filling has occurred in the basin and encroaching vegetation has reduced the open water portion to about half of its former area. The major vegetation consists of water milfoil, cattail, bulrushes, bluejoint, willow, bayberry, and cottonwood. After 100 years the open water portion is almost obliterated and the vegetation has increased in complexity and the dominant forms include water milfoil, pondweed, yellow water lily, bulrushes, bluejoint, spikerush, bayberry, and cottonwood. Sparseness of distribution and limitation of plant species mark the early ponds; increased density and heterogeneity characterize the older ponds, and the contrast is striking. From this analysis of succession, Kormondy concluded that the ponds or lagoons at the northeast end of Presque Isle were the youngest and that the spit had grown from the southwest because the ponds were increasingly older in that direction.

Coastal lagoon wetlands, in their various morphological forms, are the most common types of Great Lakes coastal wetlands. Some of the most noteworthy examples of these wetlands are found in the large bays:

 Wetland Area (ha) 
Lake Superior  
  Keweenaw 4,200 
  Thunder Bay 1,500 
  Whitefish Bay 2,700 
Lake Huron  
  Saginaw Bay 12,800 
Lake Michigan  
  Green Bay 8,700 
Lake Erie  
  Long Point Bay 11,400 
  Maumee Bay 1,300 
  Pigeon Bay 2,300 
  Rondeau Bay 1,200 
  Sandusky Bay 2,500 
Lake Ontario  
  Bay of Quinte 4,000 
 Wetland Area (ha) 
Lake Superior  
  Keweenaw 4,200 
  Thunder Bay 1,500 
  Whitefish Bay 2,700 
Lake Huron  
  Saginaw Bay 12,800 
Lake Michigan  
  Green Bay 8,700 
Lake Erie  
  Long Point Bay 11,400 
  Maumee Bay 1,300 
  Pigeon Bay 2,300 
  Rondeau Bay 1,200 
  Sandusky Bay 2,500 
Lake Ontario  
  Bay of Quinte 4,000 

Estuarine wetlands

The lower courses of several tributaries to the Great Lakes, particularly the more southerly lakes, are characterized by estuarine-type or drowned stream mouths (Brant and Herdendorf, 1972, Herdendorf, 1990). The flooded flat areas adjacent to these estuaries afford ideal sites for wetland development. The lower 24 km of the Maumee River, which flows into Lake Erie at Toledo, OH and possesses the largest drainage of any Great Lakes tributary, is an excellent example of a freshwater estuary. The formation of this estuary on Lake Erie is the result of a series of geologic events related to Pleistocene glaciation. The flow of the Maumee River was reversed from its southwestern direction when the glacial lakes drained from the Erie Basin as the ice sheet melted, exposing a lower Niagara River outlet. At that time, river velocities were accelerated by the base-level lowering, and the Maumee Valley was cut deeply into lacustrine deposits, glacial tills, and bedrock. With the weight of the ice removed, the outlet eventually rebounded and produced a rise in lake level. The lake encroached up the valley and formed the present drowned stream mouth which is analogous in many ways to a marine estuary. The Maumee River estuary begins near Perrysburg, OH, at the most downstream bedrock riffle. As the water enters the estuary from the river, its velocity abruptly diminishes except during major runoff events, causing sedimentation of suspended particles. The deposits have formed a series of elliptical islands which foster wetland formation. Similar deposits are found in the Sandusky River estuary and in the tributaries along the east shore of Lake Michigan. Virtually all of the tributaries entering Lake Erie on the Ohio shore have estuarine-type lower reaches and attendant wetlands, where lake water masses affect water level and quality for several kilometers upstream from traditional mouths (Herdendorf, 1992).

Several investigations have demonstrated the encroachment of lake water into the estuaries and the subsequent mixing of lake and river water. Measurements of water quality and currents (Schroeder and Collier, 1966; Brant and Herdendorf, 1972) at Lake Erie tributary mouths along the Ohio shore provided the first substantial information regarding the occurrence of this phenomenon. For example, within the estuary of the Cuyahoga River, a nearly fourfold decrease in river mineralization was observed as it mixed with and was diluted by Lake Erie water. Klarer and Millie (1989) studied the role of Old Woman Creek estuary in ameliorating the quality of storm water flow as it passed through this freshwater estuary en route to Lake Erie. Outflow/inflow ratios of chemical concentrations, used as estimates of the estuary's relative effectiveness to modify waters passing through it, indicated that 12 to 60% of the metals and 35 to 80% of the biologically-important nutrients were retained within the estuary. Amelioration of storm-water quality was attributed to sedimentation, biological uptake, and geochemical processes. They concluded that Old Woman Creek estuary acted as a chemical processor and filter of storm-water flow and, therefore, demonstrates functional similarity to brackish-water estuaries. They also found that the dominant circulation in the estuary was storm-driven. Studying the same estuary, Reeder and Mitsch (1989) found that conductivity, turbidity, and total suspended solids generally had highest concentrations at the inflow, then decreased up to sevenfold as the water flowed through the estuary. Bedford (1989) contrasted transport mechanisms in Lake Erie tributaries with those in marine estuaries and concluded that although there is no propagation of solar/lunar driven tide waves, there are estuary transport analogies within Lake Erie tributaries.

Delta wetlands

A stream reaching a body of standing water, such as the St. Clair River flowing into Lake St. Clair, at times builds a massive deposit or delta, composed of the stream's sediment load. These deposits are commonly the site of extensive wetland development. Not all rivers build deltas; deltas may be lacking at the mouths of streams which enter the Great Lakes because their mouths are so exposed to wave and current action that sediments are removed as rapidly as they are deposited. Some streams also lack deltas because they carry so little load. Although each delta has its own individual form, Strahler (1971) has recognized four basic outlines for deltas: (1) arcuate, triangular outline, (2) digitate, bird-foot type, (3) cuspate, tooth-shaped form and, (4) estuarine, drowned valley.

The typical arcuate delta originates at an upstream apex and radiates lakeward by means of branched distributary channels to form a triangular shape. Sediments reaching the lakes from the distributary mouths are swept along the coast by wave-induced currents to form curved bars enclosing shallow wetland lagoons; the delta shoreline is thus arcuate in plan, bowed convexly outward. The digitate, or bird-foot delta, contains long extensions of its branching distributaries into open water. This type of delta requires a gently sloping lake bottom in front of the river mouth, such as Lake St. Clair, on which natural levees can be built up quickly. The cuspate or tooth-shaped delta is normally formed when the stream has a single dominant mouth. Sediment from this mouth builds the delta forward into deeper water while wave action sweeps the sediment away from the discharge to form a curving beach on both sides of the mouth, concave toward the lake. An estuarine delta commonly fills a long narrow estuary that resulted from drowning of the lower part of the river valley because of a rise in lake level. Estuarine deltas are characterized by depositional islands containing wetlands such as Ewing Island in the Maumee River near Rossford, Ohio and in the Toussaint River near Oak Harbor, Ohio.

Delta growth occurs when a stream enters a standing body of water as a jet or plume. The jet velocity is rapidly checked and sediment is deposited in lateral embankments (natural levees) in zones of less turbulence on either side of the jet, thus extending the stream channel into the lake. The stream repeatedly breaks through the embankments to occupy different radii (distributary channels) and in time produces a deposit in semi-circular form, closely analogous to the alluvial fans found at the base of mountain ranges. The natural levees serve to isolate shallow interdistributary ponds and marshes containing fine muds and organic detritus or peat (Stanley and Swift, 1976). An excellent example of a delta wetland can be seen at the base of the Keweenaw Peninsula, Michigan, where the Surgeon and Snake Rivers flows into Portage Lake.

The sediment structure of most deltas on the Great Lakes is produced by three sets of beds: (1) bottomset, (2) foreset, and (3) topset. Bottomset beds consist of fine-grained materials (silt and clay) carried farthest offshore and laid down on the bottom of the lake embayment into which the delta is being built. Foreset beds are somewhat coarser (fine sand) and they represent the advancing front of the delta and the greater part of its bulk; they usually have a distinctly steeper slope (dip) than the bottomset beds over which they are slowly advancing. Topset beds lie above the foreset beds and are in reality a continuation of the alluvial plain of which the delta is the terminal portion. It is on the foreset beds that delta wetlands normally develop. Unlike deltas formed along the ocean, freshwater deltas do not contain aggregates of fine particles induced by electrolyte flocculation (due to the dissolved salts in the sea). Therefore, fine particles are carried offshore in lakes and are not incorporated into the delta sediments.

Although few in number, delta wetlands form a significant portion of the coastal wetlands in the Great Lakes region. Delta wetlands are gradational to embayment, estuarine, riverine, and floodplain wetlands.

Kettle lake wetlands

Bogs are the typical types of wetlands that develop in kettle lakes, however when kettles lie near the coast and communicate with the lake they can take on characteristics more associated with coastal lagoon marshes. The numerous kettle lakes that occur in the glaciated upland areas adjacent to the Great Lakes were formed by the incorporation of ice blocks in the drift material washed out from a melting ice front. As the mass of ice melted, a basin was left in the drift, and if the basin penetrated below the water table, a body of water or kettle lake came to occupy the site of the original ice block. Kettles are extremely variable in shape and size; some are less than 30 m across, such as Fern Lake in Geauga County, OH, while others, such as Trout Lake, Wisconsin, have a diameter of nearly 5 km (Hutchinson, 1957). In general, kettle lakes depths do not exceed 50 m (Flint, 1971).

Kettle lakes and other northern basins, which are protected from wind and poorly drained, often become bog lakes. They first become fringed by floating mats of sedge vegetation growing inward to encroach upon the open water; this change is accompanied by a drop in pH as the waters become more acid. The succession then continues as the mat covers the lake surface and sphagnum moss (Sphagnum spp.) and ericaceous shrubs, such as leatherleaf (Chamedaphnecalyculata) and Labrador tea (Ledumgroenlandicum), become established. When growth exceeds decomposition, the lake basin begins to fill and peat deposits are formed. Ultimately a sequence of tree species, commonly tamarack (Larixlaricina) followed by black spruce (Piceamarinana), leads to a climax forest association.

Solution basin (Karst) wetlands

The Lake Erie shoreline of Catawba and the Bass Islands, OH contains many indentations and headlands which owe their origin to solution processes in the carbonate rock. Roughly circular lagoons in the bedrock are particularly common along the west shore of Catawba as evidenced by springs issuing from their bottoms. Formerly lagoons such as these provided excellent protection for coastal wetlands, but in recent years most of them have been developed as small boat harbors. A few natural lagoons still exist along the rocky shores (i.e., Terwilliger's Pond on South Bass Island, OH), but even these are threatened by the rapid increase in recreational use of the region.

The south shore of Sandusky Bay, OH also contains a number of related solution features known as ‘blue holes’. These relatively small lakes are fed by groundwater under artesian conditions. Wetlands commonly develop at the periphery of these lakes and along their discharge streams. Elsewhere in the Great Lakes region where similar carbonate rocks occur, particularly in association with the Niagara Escarpment, solution lagoons may be present but are masked by larger wetlands in which they are inclusions.

Riverine wetlands

This type of wetland is typified by flowing water as coincides for the most part with the Riverine system of Cowardin et al. (1979). For the Great Lakes, riverine wetlands generally occur in the connecting waterways such as the St. Marys River, St. Clair River, Detroit River, and St. Lawrence River, as well as in the lower reaches of some of the major tributaries to the lakes. Such wetlands are restricted to the stream's channel, but terminate where estuarine conditions exist, such as where the water level is controlled by the level of a Great Lake. For the purposes of this paper, riverine wetlands that are not contiguous with wetlands in the coastal margin (330 m) have been excluded.

Riverine coastal marshes are particularly prevalent along the Michigan and Wisconsin shores of Lake Michigan. Here, marshes are usually separated from the lake by dunes or barrier beaches with only a narrow connecting channel to a small inland lake. Marshes often form where rivers join the small lake. This type of riverine coastal marsh is illustrated by Pentwater Marsh. This marsh is influenced by seiche activity with periodic water level and flow direction fluctuations of 30 minutes to two hours (Burton, 1985).

Diked wetlands

Large diked marshes are common along the Ohio shoreline of western Lake Erie. Primarily owned by state/federal agencies and private shooting clubs, most are managed for waterfowl habitat. A few, lake-diked areas used for disposal harbor dredgings, support wetland vegetation as a secondary benefit. Earthen dikes were used extensively a century ago, but most have been replaced by stone rip-rap, particularly were the dike is exposed to direct wave attack. Recently, openings have been installed in some of the dikes to permit spawning fish access to formerly closed wetlands.

Relationship to US Fish and Wildlife Service Classification

Lacustrine wetlands

Cowardin et al. (1979) defined these wetlands as permanently flooded lakes where wind is the dominant force generating circulation pattern and there is considerable wave action. For the purpose of this paper, wetlands in embayments, coastal lagoons, and other protected situations, but with direct lake-level connection with a Great Lake are considered within the lacustrine system of Cowardin et al. (1979). In many cases, particularly for coastal lagoons, a gradation exists between lake-level wetlands and those occur at higher elevation. These elevated wetlands could be considered as palustrine, as could be contiguous upland wetlands in estuarine (drown stream mouths) and riverine situations, but for simplicity in the absence of detailed field data a single designation has been used here.

Palustrine wetlands

The word palustrine (or paludal) has traditionally been used to refer to marshes and to material growing or deposited in a marsh or marsh-like environment (Bates and Jackson, 1980). Cowardin et al. (1979) has restricted this term to include upland vegetated wetlands traditionally called by such names as marsh, swamp, bog, fen, wet prairie, and pond that are to some degree isolated from other types such as riverine, estuarine, and lacustrine wetlands. Within the coastal margin of the Great Lakes (300 m) a number of more or less isolated wetlands occur at elevations well above the high water mark. Some of these wetlands are gradational from lacustrine types such as coastal lagoons and estuarine wetlands while others are situated in closed depressions. From inspection of topographic maps, and even cursory field investigation, it is not always possible to determine the degree of connectivity these wetlands have with the Great Lakes. Thus for the purpose of this paper, palustrine refers to wetland basins whose origins are not associated with coastal processes, but could include glacially created basins such as those which hold a kettle lake.

Summary

Approximately 1,500 coastal wetlands fringe the Great Lakes and their connecting waterways, for a combined wetland area of 1,730 km2. The greatest number and area of coastal wetlands ring Lake Michigan, the only Great Lake entirely within the United States. Lake Superior has the second highest number of wetlands, but they are relatively small in size. On the average, the largest wetlands are found along Lake Huron and its discharge channel to the south, particularly the delta wetland of the St. Clair River which covers 35 km2. The highly industrialized Lake Erie shore has the smallest number and area of wetlands while Lake Ontario has the smallest average size of wetlands, largely due to isolated marshes in the Thousand Islands area of the St. Lawrence River.

By area and number, coastal lagoons are by far the most common morphometric type, representing about 53% of the total coastal wetland area in the Great Lakes. Next, the few massive deltas comprise 18% of the coastal wetlands. The estuarine wetlands, typical of the drowned river mouths of the southern portions of the Great Lakes, account for 15% while the more riverine wetlands of the northern portions and the connecting waterway add another 12%. Diked wetlands amount to a little over 1%, while kettle lake and solution basin wetlands are each less than 1% of the total.

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