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Water quality of Lower Deer Creek, Harford County, MD, home of the federally endangered Maryland darter

The Maryland darter (Etheostoma sellare) is one of the rarest fish in the world, existing in one riffle of Deer Creek, Harford County. There have been several speculations on why the Maryland darter has declined, including loss of habitat from historic submergence of coastal areas or from recent damming, siltation, or overcollection.

Regardless of the cause of decline, the Maryland darter population, existing in a single location, is in a precarious situation. This study was a first step in identifying whether contaminants may be threatening the Maryland darter by focusing on one group of contaminants, the organochlorines. The following samples were collected near the darter riffle and at two sites upstream: sediment, common shiners (Notropis cornutus), Asian clams (Corbicula fluminea) and a variety of benthic invertebrates. To assess water quality, three bioassay organisms were exposed to ambient water: fathead minnow, Ceriodaphnia, and bacteria from the Microtox assay. Organochlorines were not detected in samples with one exception. Common shiners at the most upstream site contained polychlorinated biphenyls at levels which may be of concern, and contained DDE at levels which are probably not of concern. In general, organochlorine contamination is not a problem in the lower reaches of Deer Creek. Ambient water collected in May 1989, did not cause significant toxicity to bioassay organisms. However, observations during the summer of 1990 suggested that fish populations may have significantly declined in lower Deer Creek. Deer Creek is designated by the State of Maryland as a scenic river and was believed to have relatively high water quality. If impacts are caused by contaminants, they are likely to be related to pesticide runoff from the primarily agricultural watershed. Water quality-based impacts related to increased sedimentation are also a possibility. Additional studies are currently in progress which will further define the degree and nature of impacts.

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États-Unis d'Amérique
agINFRA The RING is part of the agINFRA project EC 7th framework program INFRA-2011-1.2.2 - Grant agr. no: 283770