SEDIMENT MICROTOPOGRAPHY AND THE SMALL-SCALE SPATIAL-DISTRIBUTION OF MEIOFAUNA

Direct comparisons between sediment microtopography and the distribution of chlorophyll-a (Chl-a) and meiofauna were examined by contiguous coring (with a 10 by 10 array of small cores, 6.3 mm i.d.) and image analysis of photographs taken on a intertidal saltmarsh mudflat. We discovered a statistically significant correlation between microtopographic features (depressions that range from 0.5 to few cm in diameter) and the abundance of harpacticoid copepods. Harpacticoids were about twice as abundant inside depressions relative to non-depressions. No relationship was found for nematodes, nor were Chl-a and harpacticoids associated. Autocorrelation analysis further indicated that large and deep depressions also housed larger aggregations of the harpacticoid Scottolana canadensis (Willey). Photographs between consecutive low tides demonstrated that microtopography was dynamic. Most features disappeared within one tidal cycle (24 h), implying that aggregations of meiofauna were of a similar longevity. Thus, physical conditions associated with sediment microtopography appear to greatly influence the distribution of harpacticoids at our study site.