The ecological significance of large marine pelecypods in shallow-water benthic communities in British Columbia
Date
1974
Authors
Goddard, James Martin
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Abstract
Quantitative benthic sampling of the marine infauna at shallow water stations showed species associations dominated by small lamellibranchs. Two large lamellibranchs, Tresus capax and Modiolus rectus, occurred at the sampling sites but were not taken in grab samples. Census by divers showed the population densities of these animals to be 0.5 to 0.7 specimens/m² at the sampling sites. The contribution of T. capax and M. rectus to the total respiration rate of the infauna was determined by in situ measurements using a diver-operated bell jar technique. Tresus capax accounted for 17.2% of the macrofaunal respiration, whilst Modiolus rectus accounted for 26.9% and 61.8% at two sites. The respiration rates indicated that the large lamellibranchs rank high in importance amongst the macrofatmal species. A rank order of species by an index known to correlate with respiration rates placed T. capax and M. rectus much lower in importance in the consumption of energy available to the communities. Respiration rates of the sediments (excluding T. capax and M. rectus) were correlated with silt + clay content at the sample sites. The highest respiration rate occurred in a sediment type known to support high population levels of interstitial ciliates. It is suggested that the correlation between respiration rate and silt + clay content may be due in part to ciliate population levels.