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MEPS 718:1-22 (2023)  -  DOI:

Macroalgal input into the coastal food web along a gradient of seasonal sea ice cover along the Western Antarctic Peninsula

Katrin Iken1,*, Charles D. Amsler2, Kristen B. Gorman1, Andrew G. Klein3, Aaron W. E. Galloway4, Margaret O. Amsler2, Sabrina Heiser2,6, Ross Whippo4, Alexander T. Lowe5, Julie B. Schram4,7, Zoe X. Schneider1, James B. McClintock2

1College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA
2Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama 35233, USA
3Department of Geography, Texas A&M University, College Station, Texas 77843, USA
4Department of Biology, University of Oregon, Charleston, Oregon 97420, USA
5Tennenbaum Marine Observatories Network, Smithsonian Institution, Edgewater, Maryland 21037, USA
6Present address: Marine Science Institute, University of Texas at Austin, Port Aransas, Texas 78373, USA
7Present address: Department of Natural Science, University of Alaska Southeast, Juneau, Alaska 99801, USA
*Corresponding author:

ABSTRACT: Coastal food webs that are supported by multiple primary producer sources are considered to be more stable against perturbations. Here, we investigated how declining macroalgal abundance and diversity might influence coastal food web structure along an annual sea ice cover gradient along the Western Antarctic Peninsula (WAP). The most common benthic invertebrate consumers, macroalgae, and surface particulate organic matter were collected at 15 stations along the WAP. Stable carbon and nitrogen isotope values of primary producers changed negligibly in relation to the sea ice cover gradient, while isotope values of most invertebrate feeding groups increased with higher sea ice cover, although at low explanatory power. Food web length became shorter and consumer trophic niche width smaller in regions with higher sea ice cover. Changes in food web structure were mostly associated with shifts in trophic position of lower trophic levels. Food web structure in higher ice-covered regions resembled that of more generalist feeders with a loss of specialist species, concurrent with an increased reliance on a more reworked detrital food source. These results suggest that a number of benthic invertebrates are able to adjust to differences in basal energy sources. Conversely, these food webs dominated by generalist feeders are likely less efficient in energy transfer, which can create less-stable systems with lower adaptive capacity to disturbance. The predicted sea ice loss along the WAP may ultimately lead to a longer food web with higher macroalgal abundance, more specialist species, and wider consumer trophic niches in the currently more ice-covered regions.

KEY WORDS: Invertebrates · Stable isotope · Trophic structure

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Cite this article as: Iken K, Amsler CD, Gorman KB, Klein AG and others (2023) Macroalgal input into the coastal food web along a gradient of seasonal sea ice cover along the Western Antarctic Peninsula. Mar Ecol Prog Ser 718:1-22.

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