The Coastal Bays of Maryland and Virginia are a network of multiple bays that include the Assawoman, Isle of Wight, Newport, Sinepuxent, and Chincoteague bays located behind Assateague Island. The bays connect to the Atlantic Ocean via inlets located at the northern Maryland end and southern Virginia end of Assateague Island. Functioning as shallow lagoons, they flush only about 7 percent of their volume per day and do not stratify. Since the bays are poorly flushed, they tend to retain nutrients, suspended solids, and other inputs. The contributing watershed is mostly agricultural and forest lands, but the demand for residential property is growing rapidly.
Several assessment endpoints were reviewed in EPA’s case study of the Coastal Bays presented in the Agency’s Nutrients in Estuaries report. The authors discussed spatial and temporal conditions and trends for the endpoints: DO; turbidity and light; chlorophyll, primary production, algal blooms, and species composition; and benthic primary producers such as seagrass. All the assessment endpoints are affected either directly or indirectly by nitrogen and phosphorus loading and ambient nutrient concentrations in the bays.
Compared to many eutrophic estuaries, the Coastal Bays have chlorophyll a concentrations in the water column that are fairly low, even during times of maximum summer biomass. Although there are no significant algal blooms, even in the spring, a significant fraction of algal biomass can be composed of harmful algal bloom species, notably brown tide, which blooms annually with increasing intensity. Hypoxia occurs in many locations during the summer months and water clarity is fairly good but tends to worsen in response to wind and storms. Submerged aquatic vegetation is estimated to occupy about 67 percent of the potential habitat in the Maryland portion of the bays. Macroalgae are abundant, well-distributed, and increasing in some areas.
Water quality stations established by various research groups are located throughout the Coastal Bays and used to collect nutrient, Secchi disk, temperature, DO, and other data. The data are used to examine spatial and temporal trends and relationships between parameters. In general, the data indicate poor or degraded water quality in or close to tributaries and good-to-excellent water in the open bay regions (National Estuarine Experts Workgroup 2010).
Reference:
National Estuarine Experts Workgroup. 2010. Nutrients in Estuaries: A Summary Report of the National Estuarine Experts Workgroup 2005–2007. U.S. Environmental Protection Agency. Accessed October 2016. https://www.epa.gov/sites/production/files/documents/nutrients-in-estuaries-november-2010.pdf.