MEPS 310:1-14 (2006)  -  doi:10.3354/meps310001

Benthic community response to ice algae and phytoplankton in Ny Ålesund, Svalbard

Kelton W. McMahon1,7,*, William G. Ambrose Jr.1,6, Beverly J. Johnson2, Ming-Yi Sun3, Glenn R. Lopez4, Lisa M. Clough5, Michael L. Carroll6

1Department of Biology, and 2Department of Geology, Bates College, Lewiston, Maine 04240, USA
3Department of Marine Sciences, University of Georgia, Athens, Georgia 30605, USA
4Marine Sciences Research Center, Stony Brook University, Stony Brook, New York 11794, USA
5Department of Biology, East Carolina University, Greenville, North Carolina 27858, USA
6Akvaplan-niva, Polar Environmental Centre, 9296 Tromsø, Norway
7Present address: Woods Hole Oceanographic Institution, MS 50, Woods Hole, Massachusetts 02543, USA

ABSTRACT: We assessed the digestibility and utilization of ice algae and phytoplankton by the shallow, subtidal benthos in Ny Ålesund (Kongsfjord) on Svalbard (79°N, 12°E) using chlorophyll a (chl a), essential fatty acids (EFAs) and stable isotopes as tracers of food consumption and assimilation. Intact benthic communities in sediment cores and individuals of dominant benthic taxa were given ice algae, phytoplankton, 13C-enriched ice algae or a no food addition control for 19 to 32 d. Ice algae and phytoplankton had significantly different isotopic signatures and relative concentrations of fatty acids. In the food addition cores, sediment concentrations of chl a and the EFA C20:5(n-3) were elevated by 80 and 93%, respectively, compared to the control after 12 h, but decreased to background levels by 19 d, suggesting that both ice algae and phytoplankton were rapidly consumed. Whole core respiration rates in the ice algae treatments were 1.4 times greater than in the other treatments within 12 h of food addition. In the ice algae treatment, both suspension and deposit feeding taxa from 3 different phyla (Mollusca, Annelida and Sipuncula) exhibited significant enrichment in δ13C values compared to the control. Deposit feeders (15% uptake), however, exhibited significantly greater uptake of the 13C-enriched ice algae tracer than suspension feeders (3% uptake). Our study demonstrates that ice algae are readily consumed and assimilated by the Arctic benthos, and may be preferentially selected by some benthic species (i.e. deposit feeders) due to their elevated EFA content, thus serving as an important component of the Arctic benthic food web.

KEY WORDS: Ice algae · Phytoplankton · Food quality · Arctic benthos · Climate change · Stable isotopes · Essential fatty acids · Svalbard

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