Estimation of Phosphorus Bioavailability in the Water Column of the Bronx River, New York

Phosphorus (P) is a primary limiting nutrient in rivers and streams, and excessive P results in eutrophication of freshwater systems, in turn, excessive algal growth/toxic algal blooms, oxygen depletion, and water quality degradation. This study analyzed P pool, and hydrolysis of organic P (OP) by native phosphatases (NPase) in the water samples collected in the Bronx River. The soluble reactive P (SRP) of most of the sites’ water collected in 2006 and 2007 were higher (average 67 μg·L and 68 μg·L, respectively) than the US Environmental Protection Agency’s (EPA) standard of 15 μg·L. The SRP% (SRP/TP%) average was 27% in 2006, much lower than in 2007 of SRP% average 83%. The OP% (OP/TP%) average was 73% in 2006, which was much higher than the OP% in 2007 (which was only 17%). The SRP concentrations and distributions (%), and the total P (TP) concentrations were in substantial amounts compared with other rivers. The NPase hydrolyzed OP% was up to 100% in 2006 and 2007 water samples. The average of NPase% was 59% in 2006 and 73% in 2007. The NPase average concentrations were 348 μg·L in 2006, and 175 μg·L in 2007. The NPase hydrolyzed up to 100% of OP% in the Bronx River water samples at 37 ̊C, indicating a potential threat of eutrophication of freshwater systems as the global rise in temperature may continue to occur.