Environmental status of Yemen's Gulf of Aden coast determined from rapid field assessment and satellite imagery

Ninety-one sites covering 1400 km of the Gulf of Aden coast of Yemen were examined by rapid field assessment, yielding ordinal data on the extent of habitats, abundance of species groups and magnitude of human uses/environmental impacts. Satellite imagery was used to determine sea surface chlorophyll concentrations. Mangroves and seagrasses were largely absent, due to the high-energy conditions and unstable substrata. Coral development was also limited, principally because of cold upwelling sea temperatures. Macroalgal prevalence and abundance were greater on account of high nutrient levels. Nesting sites of three turtle species (Green, Hawksbill, and Loggerhead) were all impacted at low levels. Coastal construction was small-scale and located near larger towns (Al Mukalla, Foua and Shehir), while water- and land-based pollution and fishing were widespread but minimal. Fish abundance showed significant positive correlation with chlorophyll concentration. These and other associations observed probably involve causal links, although habitat effects and other factors may also be important. Classification of sites by cluster analysis using biological data and use/impact data separately revealed considerable environmental heterogeneity. The lack of clear geographical patterns contrasts with results from the Red Sea, where latitudinal related groupings using comparable biological data are evident.