Relative Abundance Of Dominant Taxa Research Articles

A study of the effects of shrimp trawling on benthic communities in two South Carolina sounds

Two estuarine sounds in South Carolina were studied to evaluate the effects of commercial shrimp trawling on the abundance, diversity and species composition of benthic infaunal assemblages. In each sound, two areas were sampled just prior to the opening of the shrimp trawling season and then again after 5 months of trawling activities. One area was located in a portion of the sound which was actively trawled and the other area was located in a nearby portion of the sound closed to trawling. Significant differences were observed between sampling periods in both sounds with respect to total faunal abundance, the relative abundance of dominant taxa, and the total number of species. Changes in species composition were also noted between sampling dates. Indices of species diversity and the relative proportion of species representing major taxonomic groups in each area were generally similar over time. The reduction in faunal abundance and number of species observed in all four areas during the second sampling period was more likely due to natural seasonal variability rather than trawling effects since there were no significant differences between trawled and non-trawled sites with respect to these parameters. There were also no obvious differences in species composition among the trawled vs. non-trawled areas based on cluster analysis. Although this study was not designed to address all of the potential impacts of trawling activities on benthic organisms, lack of any consistent differences among sites with respect to the community parameters assessed suggests that 5 months of trawling in the areas studied did not have a pronounced effect on the abundance, diversity or composition of the soft-bottom communities sampled.

Characterization of Stream Benthic Communities Using Substrate-Filled Trays: Colonization, Variability, and Sampling Selectivity

ABSTRACT This research examined colonization rate, variability and sampling selectivity of substrate-filled trays collected from six streams (second-sixth order) in Virginia and West Virginia. The length of time required to obtain equilibrium communities in trays varied among streams. Community composition in a second order stream was highly variable among days. In contrast, benthic communities collected from fourth and sixth order streams after 18–20 d colonization were similar to those collected on day 30. These results suggest that longer colonization periods may be necessary to characterize the benthic communities of small streams. Sampling selectivity of substrate-filled trays was examined by comparing relative abundance of dominant taxa in trays and in a natural substrate sampler (0.1 m2 Hess sampler). Trays were selective for collector-filterers, which comprised 19–73% of total individuals; however, most dominant taxa present in the natural substrate were also present in trays. Sampling variability...