Responses of tidal creek macrobenthic communities to the effects of watershed development
- Cite this article as:
- Lerberg, S.B., Holland, A.F. & Sanger, D.M. Estuaries (2000) 23: 838. doi:10.2307/1353001
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This study examined the effects of watershed development on macrobenthic communities in tidal creeks of Charleston Harbor, South Carolina, U.S. Two types of creeks were evaluated: upland creeks which drained watersheds consisting of at least 15% terrestrial land cover, and salt marsh creeks which drained no upland habitat (i.e., only intertidal habitat). Samples of macrobenthic organisms were taken along the longitudinal axis of twenty-three primary (first order) tidal creeks. Water and sediment quality data were also collected including measurements of dissolved oxygen, salinity, temperature, sediment characteristics, and toxic chemicals in the creek sediments. Hypoxic conditions occurred more than 15% of the time in both reference and developed creeks and were a natural attribute of these systems. The most severe and frequent hypoxia occurred in impacted salt marsh creeks. Salinity fluctuations were the greatest in developed upland creeks and salinity range was identified as a potentially reliable indicator of the degree to which watershed development has altered hydrodynamic processes. The creeks draining urban and industrial watersheds were degraded environments characterized by watersheds with high (>50%) levels of impervious surface, broad fluctuations in salinity, severe hypoxia, and potentially toxic levels of chemicals in the sediment. These creeks had low macrobenthic diversity and abundance and were numerically dominated by the oligochaeteMonopylephorus rubroniveus in mud sediments, and the polychaeteLaeoreis culveri in sand sediments. Suburban watersheds had 15–35% impervious surface and creeks draining them were exposed to frequent hypoxia and broad salinity fluctuations. The levels of chemical contaminants in sediments of suburban and impacted salt marsh creeks were generally not different from the levels in reference creeks. Macrobenthic diversity and abundance were higher for suburban and impacted salt marsh creeks than for urban and industrial creeks. However, suburban and salt marsh impacted creeks were numerically dominated by a few pollution indicative species including the oligochaetesM. rubroniveus andTubificoides brownae and the polychaeteL. culveri. These creeks appear to be exhibiting early signs of degradation (e.g., a simplified food web). Two promising community-level macrobenthic metrics for assessing environmental quality were identified: the proportional abundance of pollution indicative taxa, and the proportional abundance of pollution sensitive taxa. These indicators were significantly (p<0.05) correlated with the salinity range, the level of chemical contaminants in sediments, and amount of impervious surface in the watershed.