Patch sizes and spatial patterns of meiobenthic copepods and benthic microalgae in sandy sediments: a microscale approach

Meiobenthic copepods and benthic microalgae exhibit patchiness at centimetre scales. Recent studies have related the distribution of meiobenthic copepods to a primary food resource, benthic microalgae, using spatial auto-correlation procedures. However, these studies have only examined the copepod–microalgae spatial relationships in soft and relatively silty sediments. The purpose of this study was to determine the microscale distribution and patch sizes of copepods and microalgae in the relatively sandy (median grain size 2.90φ; 7.6% silt and clay), intertidal sediments of Barnstable Harbor, Massachusetts, USA. Samples were collected at three sites using an array of 96 cores covering a 180.5 cm2 area. Non-parametric statistical analyses proved to be inapplicable in this kind of study since they revealed no significant correlations between microalgal biomass and copepod abundances. However, microalgae and most copepods (Microarthridion littorale, Nannopus palustris, and Coullana canadensis) were spatially auto-correlated and exhibited patchy distributions. Patch sizes for copepods ranged from 7 to 121 cm2 while microalgal patches ranged from 30 to 191 cm2. Patch sizes measured in this study are larger than previously reported for meiobenthic copepods and microalgae, suggesting that fine-sand habitats may promote larger patches than silty, muddy sediments.