Temporal and Spatial Dynamics of Meiofauna within the Hyporheic Zone of Goose Creek, Virginia

Abstract

Despite the vast number of ecological studies on marine meiofauna, little is known about freshwater meiofauna. As part of a larger project on the active and passive movement patterns of stream meiofauna, I report here on an intensive sampling effort undertaken to gather temporal and spatial information on the composition and abundance of meiofauna in a fourth-order stream (Goose Creek) in northern Virginia, Meiofaunal abundance and vertical distribution in the hyporheic zone (0 to 50 cm) were measured from Jan 1988 -Jan 1989. Median grain size at the stie was 1000 .mu.m and discharge varied significantly with highest flows in April and May following heavy spring rains. Total meiofaunal abundance in the streambed averaged > 2000/10 cm2 over the year but reached nearly 6000/10 cm2 during late June, primarily due to rotifers. Five taxa constituted 85-99% of the community: rotifers, oligochaetes, early instar chironomids, nematodies and copepods. Pronounced seasonal variation occurred for each group. Rotifer, oligochaete, and copepod abundances were significantly related to discharge with abundances declining in surface layers after major floods. Meiofauna were distributed through all depths in the hyporheic zone for most of the year but abundances were more shallow in July and August when water flow and oxygen penetration decreased.