Fluctuations in the level of dissolved oxygen (DO) are a major environmental stressor in the Chesapeake Bay and its tidal tributaries. Elevated nutrient levels have resulted in significant decreases in DO, leading to fish kills and other impacts on the ecosystem.
EPA partnered with the National Oceanic and Atmospheric Administration (NOAA) and the Maryland Department of Natural Resources to deploy, operate, and analyze the results of a vertical profiler, a monitoring technology that is able to measure DO, salinity, and temperature hourly at 1-meter intervals in a column of water. This technology has the potential to provide scientists and decision makers with information on the variability of DO that has not been available in the past.
Research results, combined with data from several similar concurrent projects, suggest the need to revisit the monitoring approaches now being used in the Chesapeake Watershed. The results have potential implications for the approach used by the Chesapeake Bay Program and the states for monitoring and assessing the instantaneous minimum criteria for their impaired waters listing assessments, and for implementation of Total Maximum Daily Loads of pollutants impacting DO levels. Results also point out the need for further development and validation of the technology available to monitor short term, deep water DO levels. Because of this research, researchers have made improvements to the vertical profiler and NOAA intends to continue deployment of this technology.