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Marine Ecology Progress Series

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MEPS 119:77-86 (1995)  -  doi:10.3354/meps119077

Winter population structure and feeding of the chaetognath Eukrohnia hamata and the copepod Euchaeta antarctica in Gerlache Strait, Antarctic Peninsula

Øresland, V.

Eukrohnia hamata and Euchaeta antarctica are 2 dominant macrozooplankton predators in the Southern Ocean. Zooplankton samples were taken at 3 stations during July and August 1992, in waters west of the Antarctic Peninsula. E. hamata constituted up to 97% of all chaetognaths by number and up to 20% of net zooplankton by wet weight. E. hamata breeds at a low intensity and E. antarctica breeds at a high intensity during midwinter. Gut content analyses showed that Metridia gerlachei and the small copepods Oncaea spp. and Microcalanus pygmaeus were the main prey in both species. Estimated feeding rates between 0.3 and 0.5 copepods d-1 in E. hamata and the number of prey items found in the stomach of E. antarctica (Stages CV and CVI) indicated a feeding intensity during winter that was no less than earlier summer estimates. Rough estimates of daily predation impact showed that E. hamata could eat up to 0.2% of prey standing stock by number. It is suggested that the accumulative predation impact during winter by E. hamata and other carnivorous zooplankton may be large, especially since there was little evidence of prey reproduction that could counteract such a predation impact. About 1% of the E. hamata population was parasitized or decapitated by a small ectoparasitic polychaete. At 2 stations, 8 and 16% of all E. hamata were infected by a cercoid cestode larvae of the order Pseudophyllidea. E. hamata may therefore be an important transport host for cestodes that infect Antarctic vertebrates.

Zooplankton . Chaetognatha . Copepods . Euchaetidae . Predation . Feeding . Parasites . Cestodes . Reproduction . Southern Ocean

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