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Marine Ecology Progress Series

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MEPS 316:17-22 (2006)  -  doi:10.3354/meps316017

Trophic importance of kelp-derived suspended particulate matter in a through-flow sub-Antarctic system

S. Kaehler1,*, E. A. Pakhomov2,3, R. M. Kalin4, S. Davis4

1Southern Ocean Group, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
2Department of Earth and Ocean Sciences, 6339 Stores Road, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
3Department of Zoology, Faculty of Science and Technology, University of Fort Hare, Private Bag X1314, Alice 5700, South Africa
4Environmental Engineering Research Centre, David Keir Building, Stranmillis Road, Queens University, Belfast BT9 5AG, UK

ABSTRACT: Spatial dynamics of surface chlorophyll concentrations, diatom abundance and carbon and nitrogen stable isotope signatures of surface suspended particulate matter (SPM) were investigated during a bloom event observed in March 2003 in the vicinity of the sub-Antarctic Prince Edward Islands. The surface water composition was studied to estimate the overall importance and spatial extent of kelp derived SPM in the water column of the islands. It was observed that high chlorophyll concentrations (up to 2 mg m–3) between and downstream of the islands could not be explained by the development of the diatom bloom. Instead, microscopic and stable isotope analyses suggested that the chlorophyll signal was largely derived from the residual chlorophyll in fresh and decaying particles of small fragments of the kelp Macrocystis laevis, an endemic kelp species abundant along the shoreline of the islands. The findings of this study suggest that the dietary subsidy of kelp-derived carbon and nitrogen to benthic communities and possibly the plankton is not limited to the vicinity of kelp beds, but rather is a widespread phenomenon between the islands. Due to the dominating unidirectional Antarctic Circumpolar Current, large quantities of kelp-derived SPM may be transported and utilised tens of kilometres downstream of the islands.

KEY WORDS: Kelp · Suspended particulate matter · SPM · Tropic subsidy · Sub-Antarctic ·Stable isotopes

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