Epifauna of the Patuxent River Estuary, Maryland, for 1963 and 1964

Abstract

Methods of collection and analysis of epifaunal communities from six stations in the Patuxent estuary are described. The stations were distributed from Solomons near the mouth of the estuary , upstream to Lower Marlboro, near the limit of salt water intrusion. Species composition and abundance, seasons of attachment, and production of the epifaunal community were determined on material collected from panels submerged for 1, 3, and 12 month periods covering the years 1963 and 1964 . Salinity was highest downstream, as was the number of species. Salinity decreased rapidly between the Patuxent River Bridge station and Lower Marlboro, where the number of species was reduced to half. Seasons of attachment corresponded with seasonal temperature changes, with the greatest attachment taking place during the summer months. Over 40 species were identified with 7 of them comprising the bulk of the biomass produced. For the 7 most productive species, seasons of attachment and total numbers collected from areas of one square decimeter from monthly and quarterly panels from each station are shown. The seven species were the barnacle Balanus improvisus; the tunicate, Molgula manhattensis; the hydroids, Cordylophora lacustris and Bimeria franciscana; the amphipod, Corophium lacustre; the anemone Sagartia leucolena; the tubeworm, Polydora ligni. Their respective importance varied with seasons of attachment and location. Comments on the distribution and abundance of the less significant forms are included. Dry and ash-free dry weight (organic carbon) production of the epifaunal community varied from month to month depending on the seasons of attachment of the various species. The highest production for a single month was observed at the upriver station, Lower Marlboro, where barnacles and amphipods produced 2,754 g/m 2 /30 days dry weight and 351 g c /m 2 /30 days organic weight during August 1963 . At the same station, barnacles, amphipods, and hydroids produced, on quarterly panels, the highest yearly average weight of about 1150 g c /m 2 /yr organic carbon and on monthly panels, about 6,500 g/m 2 /yr dry weight or about 3.5 times the least organic weight and 8 times the least dry weight produced at the downriver Station, Queentree Landing.