| dc.description.abstract |
Nutrient pollution from human activities leads to coastal eutrophication and degradation of critical habitat for threatened species, including the Florida manatees (<italic>Trichechus manatus latirostris</italic>). Recovery of these damaged habitats relies on water quality assessments over a long period of time. With the absence of long-term diet and water quality data, manatee bones will serve as proxies for environmental reconstruction. Isotopic composition of skeletal nitrogen (N) reflects plants that manatees consume and the predominant N source driving primary productivity within the ecosystem. Sewage, as a consequence of rapid coastal development, is isotopically distinct from natural sources of N. Thus, δ15N values are predicted to increase over time and would be highest in densely-populated areas. Collagen in manatee bones were analyzed from 173 necropsied individuals since 1975. Mean δ15N values have decreased from 8.8 / in the 1970s to 6.3 / in 2010 mainly because fertilizer is the source of depleted N. Coastal and regional mean δ15N values were very high, suggesting a mixing of enriched N sources that include sewage and atmospheric deposition. |
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