Spatial and temporal dynamics of a subtidal estuarine gastrotrich assemblage

The community and population ecology of the gastrotrich fauna from a single subtidal sand flat in North Inlet, South Carolina, USA, was studied over a 15 month period. An analysis of the temporal and small-scale spatial (horizontal and vertical) distribution of the total assemblage and its component species was used to gain insight into the types of processes (biological and physical) which serve to organize the structure of this meiobenthic taxocene. Samples, consisting of replicate cores which were spaced at 4 horizontal scales (1 m, 25 cm, 10 cm, and 4 cm) and vertically partitioned, were collected at least once each month between February 1976 and April 1977. The assemblage was characterized by both high monthly densities (x) and species richness (38 species identified). The 8 dominant species, 5 of which are in the family Thaumastodermatidae, numerically comprise 89% of the total gastrotrich population. Horizontally, individuals are only slightly to moderately aggregated, forming clumps on the order of 4 to 10 cm in size. The patches of the dominant species tend to coincide. The vertical distribution of the fauna in the sediment is restricted to the top 10 cm, with species being segregated with respect to each other in this dimension. Temporal density fluctuations of all species tend to parallel changes in water temperature. Indirect evidence suggests that interspecific competition is the single most important process structuring this gastrotrich assemblage.Contribution No. 213 from the Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina. Based on a thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, University of South Carolina, 1977. This research was supported in part by the Oceanography Section, National Science Foundation, NSF Grant OCE 72-01573 A02.