How do harpacticoid grazing rates differ over a tidal cycle? Field verification using chlorophyll-pigment analyses

Abstract

Four specles of meiobenthic copepods were examined for dlatom feeding Microscopic analysis of gut-pellet contents from field-collected in&viduals ~n&cated frequent Ingestion of diatoms by 3 harpacticoids (Scottolana canadensis, Microarthndon Ottorale Cletocamptus deitersi) whlle occasional &atom ingestion occurred m Paronychocamptus huntsmani Frustules were usually empty and broken indicahng that contents were d~gested Laboratory expenments using 14C-labehng showed assimilation of diatoms by the 3 species examined Fleld grazing rate s t u b e s were conducted over different portions of a hdal cycle using fluorescent chlorophyll-plgment analysls of gut-contents H ~ g h e s t dlatom consumphon (p < 0 05) occurred just after the mudflat became exposed (i e Early Low Water level, ELW) for S canadensis, while consumptlon at Late Low Water (LLW i e after mudflat is exposed for several hours) was reduced M llttorale showed a somewhat similar pattern in that highest consumptlon rates (p < 0 05) also occurred dunng ELW However, during High Water (HW) and LLW a similar (but reduced) feeding rate was measured P huntsmani appeared to only ingest &atoms (1 e chl-pigments) dunng HW Relationships of feeding processes over a tidal cycle are discussed with regard to distributional patterns in intertidal and subtidal habitats