Current Research
Nutrient Export from Rivers.
Humans can impact both the amount of nitrogen and phosphorus in aquatic systems and the stoichiometric ratios and biological availability of nutrients being exported. Nutrient changes can result in eutrophication problems, including toxic algal blooms, loss of habitat due to declines in aquatic plants and hypoxia. Some of this eutrophication can occur in the river itself, but it may be more pronounced in coastal waters receiving riverine inputs. Caraco is studying detailed nutrient dynamics and export from the Hudson River as well as variation in nutrient export among rivers with global distribution. This work has involved cross-system comparisons, modeling, long-term data sets and isotope studies. Representative publications related to topic.
Ecosystem Impacts of Introduced Species in the Hudson River.
Species introductions can change aquatic ecosystems in a number of important ways. In the Hudson River, species introductions have had dramatic impacts on the food web, biogeochemical processes and primary productivity at the ecosystem level. Zebra mussel invasion has increased light penetration and nutrient concentrations while decreasing phytoplankton biomass and oxygen concentrations. In some cases, zebra mussel impacts have been modified by the two aquatic plants that are dominant in the Hudson— native water celery (Vallisneria americana) and non-native water chestnut (Trapa natans). Read about it in a Coastlines article and in the IES Newsletter. Interestingly these two aquatic plants can have opposite impacts on the Hudson River Ecosystem and on the impacts of zebra mussel in this system. For example, while water-celery plays a role in oxygenating the Hudson River and has mediated oxygen declines caused by the zebra mussel, water chestnut decreases oxygen concentrations in the water column and could exacerbate the impacts of the zebra mussels. Representative publications related to topic.
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