The Coastal Bays of Maryland and Virginia contain large, healthy beds of submerged aquatic vegetation (SAV), of which 90 percent occur within the Assateague Island National Seashore. The National Park Service (NPS) recognizes that SAV beds in the Coastal Bays are a significant natural resource crucial to the maintenance of regional biological diversity and ecosystem health. SAV is a well-known indicator of water quality and plays an important role as a food source and nursery for a variety of organisms. Accordingly, NPS has been conducting a long-term monitoring program since 1987 of parameters pertinent to the maintenance of estuarine water quality in the bays. Results showed an increase in coverage of the SAV beds between 1986 and 1997. One of the objectives of monitoring is to determine if water quality is high enough to support SAV (Zostera marina L.) habitat.
NPS compared 7 nonvegetated bottom monitoring sites and 9 vegetated bottom monitoring sites to (1) determine how much habitat parameters—chlorophyll a, total suspended solids (TSS), light attenuation, dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphorus (DIP)—varied from similar stations in other areas of the Coastal Bays; and (2) estimate the values of the parameters within SAV beds as empirical evidence of minimum possible values for threshold levels.
Results showed that median values for light attenuation and DIP in nonvegetated monitoring stations did not differ significantly from those SAV stations. Median values for DIN and for chlorophyll a were found to be slightly higher at nonvegetated stations, but the differences were relatively minor and NPS concluded that the parameters represented similar conditions in SAV beds. Median values for TSS were significantly greater in nonvegetated stations, suggesting that NPS’s water quality monitoring program might be overestimating TSS levels in vegetated areas, relative to what is actually experienced by SAV in the Coastal Bays (Lea et al. 2003).
Reference:
Lea, C., R.L. Pratt, T.E. Wagner, E.W. Hawkes, and A.E. Almario. 2003. Use of Submerged Aquatic Vegetation Habitat Requirements as Targets for Water Quality in Maryland and Virginia Coastal Bays – Assateague Island National Seashore, Maryland and Virginia. Technical Report NPS/NRWRD/NRTR-2003/316. National Park Service. Accessed October 2016. https://www.nature.nps.gov/water/technicalreports/National_Capital/ASIS_2003.pdf EXIT.