This note is motivated by the classical Vollenweider eutrophication models which were instrumental in the phosphorus abatement provisions of the Great Lakes Water Quality Agreement. The models were revisited as a tool for assessing the ecosystem health of Areas of Concern in terms of Beneficial Use Impairments and potential recovery. The models indicated that Hamilton Harbour is a hyper-eutrophic environment in spite of continued phosphorus abatement management efforts. The utility and potential of these models have been demonstrated and recommended for application not only in Areas of Concern, but also other stressed environments.

Introduction

Much has already been written about Richard Vollenweider's contributions to our collective understanding of eutrophication in lakes, particularly following the publication of his seminal report for the Organization for Economic Co-operation and Development in 1968 (reprinted as OECD, 1971). In a similar vein, Dr. Vollenweider's arrival in Canada to address issues of eutrophication in the North American Great Lakes is also well documented. One particular aspect of his work that we would like to revisit is the trophic classification of the lakes based on the relationship between phosphorus loadings and annual primary production, and the relationship between algal standing crop (chlorophyll a) and annual primary production (Vollenweider et al., 1974). Together these two models, hereinafter referred to as Vollenweider's eutrophication models, predict that eutrophic conditions (high standing crop and high primary production) can be alleviated via reductions in phosphorous loadings. The paper that spawned these models has been highly cited according to Web of Science (www.thomsonreuters.com).

The role of Vollenweider's models as an ecosystem management tool in the Great Lakes was formally recognized with the signing of the Great Lakes Water Quality Agreement (GLWQA) between Canada and the United States in 1972 and the adoption of phosphorus load reduction targets beginning in 1978 (International Joint Commission, 1988). Despite the importance of these models to management objectives in the Great Lakes with respect to alleviating eutrophication and the overall influence of the work within the broader scientific canon, the Vollenweider model has been under utilized and ignored in the Great Lakes. For example, only two recent studies have applied these models in the Great Lakes basin (Fitzpatrick et al., 2007; Munawar et al., 2011): in western Lake Erie and in the Bay of Quinte, Lake Ontario, respectively.

The scope of the Great Lakes Water Quality Agreement was later expanded to include the impacts of other pollutants and 43 highly degraded Areas of Concern (AoCs) were identified as focal points for remediation efforts (IJC, 1989). These AoCs were designated on the basis of having at least 1 of 14 possible Beneficial Use Impairments or BUIs (Hartig and Zarull, 1992), although multiple impairments are the norm. Of these BUIs, two are directly relevant to eutrophication: Eutrophication or undesirable algae and Degradation of phytoplankton and zooplankton communities (ibid). Vollenweider's eutrophication models, however, have not been utilized in the remediation and management efforts at the various Areas of Concern in the United States and Canada. Part of the reason for this is because objective criteria for defining Beneficial Use Impairments and assessing recovery were never firmly established (Krantzberg, 2004; George and Boyd, 2007); hence scientifically defensible indicators of ecosystem health are needed.

Fisheries and Oceans Canada, as part of its commitment to remediation efforts in Areas of Concern, is currently developing a suite of ecological indicators with a body of evidence approach for assessing Beneficial Use Impairments with a focus on Bay of Quinte and Hamilton Harbour (both of which are eutrophic AoCs in Lake Ontario). We propose that Vollenweider's eutrophication models will be highly useful as one of such tools for assessing possible impairments and recovery. Other tools would include phytoplankton species composition, the Phytoplankton biomass trophic ladder (Munawar and Munawar, 1982), the Planktonic Index of Biotic Integrity (Kane et al., 2009) and the food web dynamics and linkages model which is currently under development (Munawar et al., 2010, 2011).

The eutrophication models of Vollenweider et al. (1974) were developed and applied mainly to open and pelagic ecosystems and proved well suited to the phosphorus management objectives of the original Great Lakes Water Quality Agreement. Currently, the GLWQA is being renegotiated by the Governments of Canada and the United States with an increasing emphasis on nutrient management issues at the land – water interface as well as on nearshore – offshore interactions. The remediation efforts carried out in some AoCs provides an ideal case study for testing the models in enclosed nearshore environments subject to terrestrial and anthropogenic pressures such as Hamilton Harbour.

The current study demonstrates the application Vollenweider's eutrophication models to Hamilton Harbour, a shallow embayment located on the western end of Lake Ontario, which has a long history of eutrophication (Harris et al., 1980; Charlton and Le Sage, 1996). Our previous work shows mean chlorophyll a in the harbour was: 15.7 μg l−1

(Burley, 2007), total phosphorous was 30.8 μg l−1 (ibid) and phytoplankton biomass was 2.0 g m−3

(Munawar and Fitzpatrick, 2007). This short note will demonstrate the utility of these models to assess Beneficial Use Impairments and provide guidance for remediation and management efforts at other nearshore zones that experience beneficial use impairments related to eutrophication.

There are sentimental as well as scientific reasons for choosing Hamilton Harbour as the study area for this paper. Dr. Vollenweider made his home in Canada in the Aldershot neighbourhood of Burlington, ON, which is located on the shores of the harbour, he worked out of the Canada Centre for Inland Waters, also located on the harbour and he commenced his Great Lakes research journey from Hamilton Harbour.

Methods

Hamilton Harbour (21 km2) is located on the western end of Lake Ontario with a maximum depth of 24 m. One station (Stn 258–24 m) was sampled bi-weekly from May 1st to October 31st in each of the years 2002, 2004, 2006 and 2007 (Figure 1). Integrated epilimnetic water samples were collected on each date and subsamples were drawn for primary production and chlorophyll a estimates.

Figure 1.

Map of the Hamilton Harbour Area of Concern including sampling location.

Figure 1.

Map of the Hamilton Harbour Area of Concern including sampling location.

Point and non-point source phosphorous loadings for Hamilton Harbour were compiled by K. O’Connor, Environment Canada, Burlington, Ontario (pers. com.).

Chlorophyll a concentrations were determined by filtering up to 1 L of water through Whatman GF/C filters followed by cold acetone pigment extraction and spectrophotometric analysis (Strickland and Parsons, 1968).

Annual primary production was estimated by 14Carbon uptake. Samples from each cruise were spiked with Na14CO3 and incubated for 2–4 hours at irradiance levels ranging from 10–120 μE s−1 m−2. Following incubation, acidification and bubbling was used to remove excess 14C and radioactivity was determined by liquid scintillation counting (Millard et al., 1999). Seasonal areal primary production was then estimated according to the model of Fee (1990). These estimates were increased by 10% in order to account for winter primary production (Fitzpatrick et al., 2007; Vollenweider et al., 1974).

Estimates of annual phosphorus loadings (point and non-point), annual primary production and annual mean chlorophyll a were then compared against the two models of Vollenweider et al. (1974).

1. The relationship between annual phosphorus loadings and annual primary production:

A= 420 [10 P0.6 (9 + 10P0.6)−1], where

A= Annual Primary Production (g C m−2 y−1)

P= Annual Phosphorus Loadings (g m−2 y−1)

2. The relationship between mean chlorophyll a and annual primary production:

A= 420 [1.15C1.33 (9 + 1.15C1.33)−1], where

A= Annual Primary Production (g C m−2 y−1)

C= Annual Mean Chlorophyll a (μg l−1)

Results and Discussion

Eutrophication remains a major stressor affecting the North American Great Lakes, particularly in the nearshore areas (Higgins et al., 2008; Munawar and Munawar, 2001) which comprise most of the Areas of Concern. In fact, eight of the Canadian Areas of Concern designated under the GLWQA had “eutrophication or undesirable algae” listed as one of the impairments (Environment Canada, 2003) with Hamilton Harbour being among them. Major efforts have been made to reduce phosphorous loadings through improvements in sewage treatment (Charlton and Le Sage, 1996).

The results of Vollenweider's eutrophication models applied to Hamilton Harbour are shown in Figures 2 a and b for 2002, 2004, 2006 and 2007 and summarized in Table 1. Phosphorous loadings ranged from 4.8–6.2 g m−2 y−1, average chlorophyll a ranged from 11.4–15.7 μg l−1 and primary production ranged from 314.6–437.8 g C m−2 y−1.

Figure 2.

Vollenweider's Eutrophication Models (after Vollenweider et al. 1974) applied to the Hamilton Harbour Area of Concern.

Figure 2.

Vollenweider's Eutrophication Models (after Vollenweider et al. 1974) applied to the Hamilton Harbour Area of Concern.

Table 1.

Annual estimates of phosphorus loadings (g m−2) including point and non-point sources, primary production (g C m−2) and mean chlorophyll a (μg l−1) for 2002, 2004, 2006 and 2007 in Hamilton Harbour.

Phosphorus Loadings (g m−2)
μg l−1g C m−2
PointNon-PointTotalChlorophyll aPrimary Production
2002 4.4 0.8 5.1 15.7 437.8 
2004 5.2 1.0 6.2 11.4 319.0 
2006 4.4 1.5 5.9 14.6 314.6 
2007 3.7 1.1 4.8 12.7 356.4 
Phosphorus Loadings (g m−2)
μg l−1g C m−2
PointNon-PointTotalChlorophyll aPrimary Production
2002 4.4 0.8 5.1 15.7 437.8 
2004 5.2 1.0 6.2 11.4 319.0 
2006 4.4 1.5 5.9 14.6 314.6 
2007 3.7 1.1 4.8 12.7 356.4 

Vollenweider's model defines eutrophic conditions as those where:

Annual Phosphorous Loadings >3.5 g m−2 y−1

Annual Mean Chlorophyll a> 9.0 μg l−1

Annual Primary Production >295.5 g C m−2 y−1

The threshold for eutrophication was exceeded in all observations.

Our estimated values of primary production based on 14C uptake were generally in agreement with the predicted values from Vollenweider's models at given levels of phosphorous loads and chlorophyll a respectively. However, annual primary production estimated for 2002 (437. 8 g C m−2 y−1) was much greater than the other years and greater than the value predicted by the models (≈314–345

g C m−2 y−1). This elevated level of primary production was likely the consequence of the warmer surface temperatures and shallower epilimnion observed during the summer of 2002 (Burley, 2007) creating optimum photosynthetic conditions.

The results confirm the hyper-eutrophic state of Hamilton Harbour. Other measures of trophic state carried out simultaneously also confirm this. For example, the harbour phytoplankton was mainly composed of Chlorophyta, Cyanophyta and Diatomeae containing several species which are commonly found in eutrophic environments (Munawar and Fitzpatrick, 2007). From the model, one can predict the magnitude of phosphorous abatement needed to change the harbour's trophic status as required (mesotrophy or oligotrophy). From current estimates of 5–6 g m−2 y−1, phosphorus loads need to be reduced by a further 2–3 g m−2 y−1 to achieve mesotrophy. This is not to diminish the successful accomplishments to date. Phosphorous loadings have declined significantly from over 27 g m−2 y−1 in 1974 as a direct result of improvements in wastewater treatment which came on stream in the early 1980s (Charlton and Le Sage, 1996; Hiriart-Baer et al., 2009). Vollenweider's models do not explicitly distinguish between point and non point source phosphorous loadings. However, point source loads are 75–85% of the total loads going into Hamilton Harbour (Table 1) so future improvement are most likely to be realized via reductions in point source loads.

Conclusions

The above data demonstrate that the Vollenweider eutrophication models should be applied in the management of eutrophic environments and embayments. The obvious extension and application of this approach will be in assessing the ecosystem health of other Areas of Concern so that scientifically sound delisting criteria can be developed. Work is progressing in our laboratory to collect similar data and apply Vollenweider's models in conjunction with a suite of ecological indicators.

Acknowledgements

This paper is dedicated to the memory of Dr. R. V. Vollenweider for his global contributions to aquatic science. We would like to thank our field crew (A. Bedford, R. Bonnell, M. Burley, J. Gerlofsma and H. Niblock) who braved the harbour and its everchanging conditions on a regular basis. We are grateful to Dr. Abdel El-Shaarawi (Environment Canada), Dr. Joseph Leach (Ontario Ministry of Natural Resources) and Dr. Marten Koops (Fisheries and Oceans Canada) for their advice and suggestions.

References

Burley, M.
2007
. “
Water quality and phytoplankton photosynthesis
”. In
Assessment of lower food web in Hamilton Harbour, Lake Ontario, 2002–2004. Can. Tech. Rep. Fish. Aquat. Sci.
Edited by: Dermott, R., Johannsson, O., Munawar, M., Bonnell, R., Bowen, K., Burley, M., Fitzpatrick, M., Gerlofsma, J. and Niblock, H. Vol.
2729
,
Charlton, M. N. and Le Sage, R.
1996
.
Water quality trends in Hamilton Harbour: 1987 to 1995
.
Water Qual. Res. J. Canada
,
31
(
3
):
473
484
.
Environment Canada
.
2003
.
Canada's RAP progress report 2003
,
Ottawa
:
Government of Canada
.
Fee, E. J.
1990
.
Computer programs for calculating in situ phytoplankton photosynthesis
.
Can. Tech. Rep. Fish. Aquat. Sci. No.
, :
1740
Fitzpatrick, M. A. J., Munawar, M., Leach, J. H. and Haffner, G. D.
2007
.
Factors regulating primary production and phytoplankton dynamics in western Lake Erie
.
Fundam. Appl. Limnol. (Archiv. Hydrobiol.)
,
169
:
137
152
.
George, T. K. and Boyd, D.
2007
.
Limitations on the development of quantitative monitoring plans to track progress of Beneficial Use Impairment restoration at Great Lakes Areas of Concern
.
J. Great Lakes Res.
,
33
:
686
692
.
Harris, G. P., Piccinin, B. P., Haffner, G. D., Snodgrass, W. and Polak, J.
1980
.
Physical variability and phytoplankton communities: I
.
The descriptive limnology of Hamilton Harbour. Arch. Hydrobiol.
,
88
(
3
):
303
327
.
Hartig, J. H. and Zarull, M. A.
1992
.
Towards defining aquatic ecosystem health for the Great Lakes
.
J. Aquat. Ecosyst. Health
,
1
:
97
107
.
Higgins, S. N., Malkin, S. Y., Howell, E. T., Guildford, S. J., Campbell, L., Hiriart-Baer, V. and Hecky, R. E.
2008
.
An ecological review of Cladophora glomerata (chlorophyta) in the Laurentian Great Lakes
.
J. Phycol.
,
44
(
4
):
839
854
.
Hiriart-Baer, V. P., Milne, J. and Charlton, M. N.
2009
.
Water quality trends in Hamilton Harbour: two decades of change in nutrients and chlorophyll a
.
J. Great Lakes Res.
,
35
(
2
):
293
301
.
International Joint Commission (IJC)
.
1988
.
Revised Great Lakes Water Quality Agreement of 1978
.
Agreement, with Annexes and Terms of Reference, between the United States and Canada signed at Ottawa, November 22, 1978 and Phosphorus Load Reduction Supplement signed October 7, 1983 as amended by protocol signed October 7, 1983, as amended by protocol signed November 18, 1987
International Joint Commission
.
1989
.
Revised Great Lakes Water Quality Agreement of 1978 between the United States and Canada, as amended by protocol
.
signed November 18, 1987
Kane, D. D., Gordon, S. I., Munawar, M., Charlton, M. N. and Culver, D. A.
2009
.
The Planktonic Index of Biotic Integrity (P IBI): an approach for assessing lake ecosystem health
.
Ecol. Ind.
,
9
:
1234
1247
.
Krantzberg, G.
2004
.
Science must inform Great Lakes policy
.
J. Great Lakes. Res.
,
30
:
573
574
.
Millard, E. S., Fee, E. J., Myles, D. D. and Dahl, J. A.
1999
. “
Comparison of phytoplankton photosynthesis methodology in Lakes Erie, Ontario, the Bay of Quinte and the Northwest Ontario Lake Size Series
”. In
State of Lake Erie (SOLE) – Past, Present and Future
, Edited by: Munawar, M., Edsall, T. and Munawar, I. F.
441
468
.
the Netherlands
:
Backhuys Publishing
.
Munawar, M. and Munawar, I. F.
1982
.
Phycological studies in Lakes Ontario, Erie, Huron and Superior
.
Can. J. Bot.
,
60
:
1837
1858
.
Munawar, M. and Munawar, I. F.
2001
. “
An overview of the changing flora and fauna of the North American Great Lakes. Part I. Phytoplankton and microbial food web
”. In
The Great Lakes of the World (GLOW): Food-web, health and integrity
, Edited by: Munawar, M. and Hecky, R. E.
219
275
.
the Netherlands
:
Backhuys Publishing
.
Munawar, M. and Fitzpatrick, M.
2007
. “
An integrated assessment of microbial and planktonic communities of Hamilton Harbour
”. In
Assessment of lower food web in Hamilton Harbour, Lake Ontario, 2002–2004. Can. Tech. Rep. Fish. Aquat. Sci.
Edited by: Dermott, R., Johannsson, O., Munawar, M., Bonnell, R., Bowen, K., Burley, M., Fitzpatrick, M., Gerlofsma, J. and Niblock, H.
2729
Munawar, M., Fitzpatrick, M., Munawar, I. F. and Niblock, H.
2010
.
Checking the pulse of Lake Ontario's microbial-planktonic communities: a trophic transfer hypothesis
.
Aquat. Ecosyst. Health Mgmt.
,
13
(
4
):
395
412
.
Munawar, M., Fitzpatrick, M., Niblock, H. and Lorimer, J.
2011
.
The relative importance of autotrophic and heterotrophic microbial communities in the planktonic food web of the Bay of Quinte, Lake Ontario 2000–2007
.
Aquat. Ecosyst. Health Mgmt.
,
14
(
1
):
21
32
.
Organization for Economic Cooperation and Development (OECD)
.
1971
.
Scientific fundamentals of the eutrophication of lakes and flowing waters, with particular reference to nitrogen and phosphorus as factors in eutrophication
,
Paris, France
:
Organization for Economic Co-operation and Development
.
Strickland, J. D. H. and Parsons, T. R.
1968
.
A practical handbook of seawater analysis
.
Bull. Fish. Res. Board Can.
,
Ottawa, ON, Canada
Vollenweider, R. A., Munawar, M. and Stadelmann, P.
1974
.
A comparative review of phytoplankton and primary production in the Laurentian Great Lakes
.
J. Fish. Res. Board Can.
,
31
:
739
762
.