Nutrient Concentrations and Loads and Escherichia coli Densities in Tributaries of the Niantic River Estuary, Southeastern Connecticut

Nutrient concentrations and loads and Escherichia
coli(E. coli) densities were studied in 2005 and from 2008
through 2011 in water-quality samples from tributaries of the
Niantic River Estuary in southeastern Connecticut. Data from
a water-quality survey of the base flow of subbasins in the
watershed in June 2005 were used to determine the range of
total nitrogen concentrations (0.09 to 2.4 milligrams per liter),
instantaneous loads (less than 1 to 62 pounds per day) and
the yields of total nitrogen ranging from 0.02 to 11.2 pounds
per square mile per day (less than 1 to 7.2 kilograms per
hectare per year) from basin segments. Nitrogen yields were
positively correlated with the amount of developed land in
each subbasin. Stable isotope measurements of nitrate (δ
15 N) and oxygen (δ18 O) ranged from 3.9 to 9.4 per mil and 0.7
to 4.1 per mil, respectively, indicating that likely sources of
nitrate in base flow are soil nitrate and ammonium fertilizers,
sewage or animal waste, or a mixture of these sources.