US EPA

2995537 

Journal Article 

Effects of oyster reefs on water quality in a tidal creek estuary 

Cressman, KA; Posey, MH; Mallin, MA; Leonard, LA; Alphin, TD 

2003 

1 

Journal of Shellfish Research
ISSN: 0730-8000
EISSN: 1943-6319 

22 

3 

753-762 

WOS:000188365100023 

The importance of oyster filtering in moderating aspects of water quality has received increased attention over the past several years. This study examined the influence of intertidal oyster reefs on chlorophyll a, fecal coliform bacteria, and total suspended solid concentrations under field conditions in a tidal creek estuary. Oyster reefs of varying live oyster density were sampled during summer 2002, winter 2003, and spring 2003. Water samples were taken upstream and downstream of each reef as well as over a mud flat control area on an ebb tide and analyzed for concentrations of these water column constituents. Summer data showed consistent, significant decreases in chlorophyll a concentrations as water moved over the reefs, usually by 10-25%. Fecal coliform counts were frequently lower downstream, by up to 45%, but were much more variable and not statistically different in most cases. Data taken in winter, when temperatures and oyster feeding rates were lower, showed less consistency in upstream versus downstream patterns. In spring, chlorophyll a decreases were less frequent than in summer, but significant fecal coliform decreases were more frequent. Total suspended solid concentrations were not changed by the presence of oyster reefs during any season. Data from this study indicate that feeding by oysters and changes in water flow caused by the presence of reefs, may both play a role in reducing chlorophyll a and bacterial concentrations in the water column. 

Crassostrea virginica; fecal coliform bacteria; chlorophyll a; tidal creek