Food web structure of a coastal Arctic marine ecosystem and implications for stability

Document Type

Article

Publication Date

5-22-2013

Publication Title

Marine Ecology Progress Series

Volume

482

First Page

17

Keywords

Arctic marine ecology, Climate warming, Ecological patterns, Fatty acids, Food web, Macroalgae, Resource coupling, Stable isotopes

Last Page

28

Abstract

There is little doubt that Arctic ecosystems will continue to face unprecedented change in the coming decades. The identification of food web structures that confer stability to these systems is, therefore, a priority. Here, we use stable isotopes and fatty acids to resolve the food web structure of a seasonally ice-covered fjord (Cumberland Sound, Baffin Island, Canada) sampled in late summer. We show that the food web is structured such that upper trophic levels couple separate energy channels (based on phytoplankton or macroalgae), a previously documented food web structure that has been linked with stability in temperate ecosystems, but never established in a seasonally dynamic, ice-covered ecosystem. Herbivorous zooplankton (e.g. Calanus hyperboreus) relied exclusively on phytoplankton, whereas herbivorous benthos used either phytodetritus (e.g. Hiatella arctica) or macroalgae (e.g. Tectura testudinalis), supporting the existence of separate energy channels. Upper trophic level fishes and marine mammals relied more heavily on phytoplankton- than macroalgal-derived carbon (58 to 100% reliance on phytoplankton), but 6 out of 8 species sampled derived energy from both carbon sources. Since benthic invertebrate predators used both phytodetrital- and macrolgal-based resources, the coupling of separate energy channels was also iterated within the benthos. The temporally pulsed nature of phytoplankton production, characteristic of Arctic seas, indicates that Arctic consumers also act as couplers of resources in time because phytoplankton- and detrital-based carbon would likely reach upper trophic levels earlier and later in the season, respectively. Potential changes in the relative production of macroalgae and phytoplankton under climate change scenarios could impact the stability-promoting food web structure reported here. © Inter-Research 2013.

DOI

10.3354/meps10278

ISSN

01718630

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