Date of Award

1987

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Feeding processes and their relationship to microspatial patterns were examined for several harpacticoid species. Field evidences and laboratory radiolabel experiments suggest that diatoms comprise a major portion of the food resources ingested by harpacticoids. Bacteria and mucus-exopolymer secretions (associated with the bacteria and diatoms) are also ingested, coincidently while ingesting diatoms. Also, significant ontogenetic shifts in food resource utilization occur from naupliar to adult stages. Field grazing rate studies were conducted on an intertidal mudflat over different portions of a tidal cycle using several harpacticoid species (Scottolana canadensis, Microarthridion littorale, Paronychocamptus huntsmani). Highest grazing rates for S. canadensis occurred just after the mudflat becomes exposed (i.e. early low-water ELW) with very low grazing rates during late low-water (i.e. after mudflat is exposed for several hours LLW). M. littorale also showed highest grazing rates during ELW. Similar grazing rates occurred during high-water (HW) and LLW. Laboratory experiments indicated that M. littorale maintained similar grazing rates at HW and LLW by changing its food resource utilization. During HW, M. littorale feeds planktonically while swimming in the water column. During LLW it feeds benthically while actively crawling over the sediment surface. S. canadensis feeds during HW by drawing suspended plankton into its burrow. During LLW feeding is greatly reduced by the absence of water cover. Microspatial (mm) patterns of harpacticoids in the field as determined by spatial autocorrelation indicate that at low-water high density patches of the harpacticoid M. littorale were positively correlated with microbial food resource patchiness (as measured by chlorophyll-a concentrations). Laboratory experiments show that this harpacticoid actively seeks out sediment patches containing high concentrations of diatom food resources and their exudates. Microspatial patchiness of M. littorale may be regulated by patchiness of its microbial food resources. During HW patchiness patterns disappear as individuals leave the sediment to feed in the water column. The patchiness of S. canadensis is not correlated with benthic food abundances and this harpacticoid does not actively migrate to food patches in the laboratory. Its microspatial patchiness is probably regulated by other factors. Mechanisms of microspatial patchiness for intertidal mudflat harpacticoids vary depending on the species and portion of the tidal cycle examined.

Pages

141

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