RELATIONSHIPS BETWEEN LAND COVER, BASIN MORPHOMETRY, FISH COMMUNITIES, AND WATER CHEMISTRY IN RURAL WATERSHEDS IN NORTHWESTERN SOUTH CAROLINA

In some regions, pasture land cover has been associated with high rates of stream sedimentation, which can degrade the habitat quality of fishes and other aquatic organisms. Our study investigated the effects of contemporary land cover and basin morphometry on the physical, chemical, and biotic characteristics of streams in the South Carolina Piedmont. We collected water, sediment, and fish samples under baseflow conditions from sixteen 2^nd- to 4^th-order streams in drainage basins ranging from 3 to 33 km². Land cover in these basins was predominantly (≥ 50%) forest or pasture. We analyzed water samples for turbidity, major ions, dissolved organic carbon, and total dissolved nitrogen. Simpson’s Diversity and species richness were calculated from fish samples. Grain size analyses were conducted on sediment samples. A number of basin morphometrics, including total relief and slope index were determined for each basin.

Contrary to expectations, fish diversity, richness, and total abundance did not correlate significantly with turbidity or with percent pasture, nor did turbidity correlate with percent pasture. However, Simpson’s diversity correlated negatively with percent developed land, and species richness correlated positively with sampling point elevation. Cyprinids accounted for the majority of fishes collected (median 87% of fish per sample). Percent of fish abundance accounted for by cyprinids (percent cyprinids) correlated positively with percent developed land. Percent cyprinids also correlated negatively with basin area, length, and relief. Stream nitrate, chloride, and base cation concentrations correlated negatively with percent forest and positively with percent pasture. However, concentrations of those ions did not correlate significantly with either non-pasture grass cover or with percent developed land. Relationships between current pasture and ion concentrations may result from fertilization of pasture to increase grass production, although the proportion of actively-grazed pasture land in the study area was not determined. Low species richness at all sites (maximum richness of 11 species) suggests a lasting negative influence of antecedent land use (especially intensive cotton cultivation).