Water-cover influences on diatom ingestion rates by meiobenthic copepods

Abstract

Laboratory experiments on meiobenthic copepods using 14C-diatoms were conducted to investigate whether: (1) feeding rates or (2) food sources (planktonically-suspended foods or benthic sebment-associated foods) vary in response to the presence or absence of water-cover (i.e. simulated High-water vs Low-water conditions). Three &atom-feeding harpacticoids were examined. Scottolana canadensis feeds at significantly higher rates (2 x) during figh-water (HW) conditions (P<0.001), at whlch time it consumes planktonic foods; during Low-water (LW), feeding is greatly reduced. These feeding patterns are related to its burrow-dwehng and to its subhdal habitat. Cletocarnptus dejtersi remains virtually unaffected by changes in ambient water-cover, feedlng at nearly equal rates during HW and LW conditions but always tending to consume more benthic diatoms. Microarthridion httorale consumes food at nearly equal rates during HW and LW conditions, but does so by shifting its feeding mode. Dunng HW-times it makes excursions into the water column, feeding on planktonically-suspended foods. During LW-times it feeds benthically, moving over the sediment surface. Such feeding differences must affect meso-scale distributions of meiobenthos in the field, total benthic consumpuon and energy-flow estimates over a tidal-cycle, and the coupling of benthic and pelagic systems.