EFFECTS OF A SMALL-SCALE CLEARING ON HABITAT AND MACROINVERTEBRATES OF A COASTAL BOTTOMLAND STREAM IN LOUISIANA

Streams in the southeastern USA are commonly affected by streamside disturbance. We investigated the effects of a small-scale clearing (associated with a pipeline crossing) on a third-order stream in southwestern Louisiana by sampling habitat, water chemistry, stream microbes, and benthic and wood-dwelling macroinvertebrates in fall 2002 and spring 2003. We selected 3 locations for sampling, one in a forested section of stream 100 m upstream of a clearing, one within the clearing, and one in a forested section of stream 100 m downstream from the clearing. We detected significantly higher temperature and fecal coliform counts and significantly lower dissolved oxygen, specific conductance, pool-riffle ratio, coarse woody debris, fine organic detritus, and heterotrophic plate counts in the clearing location compared to the upstream and downstream locations. Depth and current velocity did not differ significantly among sampling locations. Despite differences in stream characteristics, we detected only a single statistical difference: Bezzia (Insecta: Diptera: Ceratopogonidae) was significantly lower in density in the clearing location. We conclude that the observed differences in stream characteristics were not biologically substantial enough to noticeably alter composition of the stream macroinvertebrate community. However, multiple small-scale disturbances that increase fragmentation in a watershed would be more likely have significant negative affects on macroinvertebrate community diversity.