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Linking nitrogen in estuarine producers to land‐derived sources
Author(s) -
McClelland James W.,
Valiela Ivan
Publication year - 1998
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1998.43.4.0577
Subject(s) - estuary , bay , eutrophication , environmental science , nitrate , groundwater , watershed , wastewater , primary producers , wetland , hydrology (agriculture) , oceanography , ecology , environmental engineering , nutrient , phytoplankton , biology , geology , geotechnical engineering , machine learning , computer science
It is clear that anthropogenic nitrogen inputs from watersheds to estuaries stimulate eutrophication. It has been difficult, however, to explicitly link anthropogenic N entering estuaries to N found in estuarine producers. To explore this link, we compared stable isotope ratios of N in groundwater and producers from the Waquoit Bay watershedestuary system, Cape Cod, Massachusetts. The δ 15 N values of groundwater nitrate within the Waquoit Bay watershed increase from −0.9‰ to + 14.9‰ as wastewater contributions increase from 4 to 86% of the total N pool. As a result, the average δ 15 N of dissolved inorganic nitrogen (DIN, nitrate + ammonium) received by different estuaries around Waquoit Bay increases from +0.5‰ to +9.5‰. This increase is strongly correlated to increases in δ 15 N of eelgrass, macroalgae, cordgrass, and suspended particulate organic matter. The increase of all producers examined in Waquoit Bay with increasing δ 15 N of DIN in groundwater demonstrates a tight coupling between N contributed to coastal watersheds and N used by primary producers in estuaries. The ability to identify effects of increasing wastewater N loads on δ 15 N of estuarine producers may provide a means to reliably identify incipient eutrophication in coastal waters.