Adaptation of estuarine ecosystems to the biodegradation of nitrilotriacetic acid: Effects of preexposure

The biodegradation of nitrilotriacetic acid (NTA) was examined in three estuarine ecosystems, one of which had been exposed previously to the chemical. Biodegradation was measured as the conversion of radiolabeled NTA to 14CO2, 14C-labeled cells and the amount of label remaining in solution. The relatively unpolluted Newport River estuary system in North Carolina metabolized NTA slowly, with no apparent increase in rate over time. Jamaica Bay in New York showed an adaptation response, with approximately 50 d required for the onset of relatively rapid rates of biodegradation. The Fraser River estuary in Canada, exposed to NTA for more than 10 years, showed rapid degradation with no lag period at a concentration of 10 μg/L. At 100 and 2,000 μg/L, short lag periods (2 to 4 d) were observed before rapid degradation rates were achieved. Measurements of NTA-degraders indicated that the Fraser River estuary contained 650/ml versus fewer than 10 in the Newport River and Jamaica Bay communities. The results demonstrate that NTA can be degraded by estuarine microorganisms. Estuarine bacteria will adapt to the presence of NTA in the environment and, after adaptation, can respond to increased levels of the compound after relatively short lag periods.