Climate change alters the structure of arctic marine food webs due to poleward shifts of boreal generalists.

Michaela Aschan,Susanne Kortsch,Raul Primicerio,Andrey V Dolgov,Maria Fossheim

doi:10.1098/rspb.2015.1546

Abstract

Climate-driven poleward shifts, leading to changes in species composition and relative abundances, have been recently documented in the Arctic. Among the fastest moving species are boreal generalist fish which are expected to affect arctic marine food web structure and ecosystem functioning substantially. Here, we address structural changes at the food web level induced by poleward shifts via topological network analysis of highly resolved boreal and arctic food webs of the Barents Sea. We detected considerable differences in structural properties and link configuration between the boreal and the arctic food webs, the latter being more modular and less connected. We found that a main characteristic of the boreal fish moving poleward into the arctic region of the Barents Sea is high generalism, a property that increases connectance and reduces modularity in the arctic marine food web. Our results reveal that habitats form natural boundaries for food web modules, and that generalists play an important functional role in coupling pelagic and benthic modules. We posit that these habitat couplers have the potential to promote the transfer of energy and matter between habitats, but also the spread of pertubations, thereby changing arctic marine food web structure considerably with implications for ecosystem dynamics and functioning.

Highlights

Arctic marine ecosystems are exposed to rapid environmental change driven by accelerated warming [1,2]
Food webs with greater modularity should be more persistent, as any pertubation effects may be retained within the modules, delaying or stopping their propagation to other modules [10,11]
On the food web level, we focus on structural properties with particular importance for food web dynamics such as the degree of modularity

Summary

Introduction

Arctic marine ecosystems are exposed to rapid environmental change driven by accelerated warming [1,2]. The sub-webs specific for the boreal and the arctic regions were constructed by choosing subsets of taxa according to their occurrence (presence/absence) in the respective regions based on the Barents Sea Ecosystem Survey data (see further details in the electronic supplementary material, figure S2). To evaluate the effect of the poleward movements of boreal fish on food web structure in the Arctic, we updated the arctic food web (hereafter referred to as arctic II) by including four fish species: atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), golden redfish (Sebastes norvegicus) and beaked redfish (Sebastes mentella) These fish were chosen because they have boreal affinities and display substantial responses to climate warming in terms of poleward shifts and biomass increases in the arctic region of the Barents Sea [5,23]. Number of links from species i to species in other modules, normalized by the degree (ki) of species i: PC 1⁄4

NM kit

Results

Concluding remarks

Findings

Poloczanska ES et al 2013 Global imprint of climate