Abstract
Climate warming influences structure and function of Arctic benthic ecosystems. Assessing the response of these systems to perturbations requires long-term studies addressing key ecological processes related to recolonization and succession of species. Based on unique time-series (1980–2017), this study addresses successional patterns of hard-bottom benthos in two fjords in NW Svalbard after a pulse perturbation in 1980 and during a period of rapid climate warming. Analysis of seafloor photographs revealed different return rates of taxa, and variability in species densities, through time. It took 13 and 24 years for the community compositions of cleared and control transects to converge in the two fjords. Nearly two decades after the study initiation, an increase in filamentous and foliose macroalgae was observed with a subsequent reorganization in the invertebrate community. Trait analyses showed a decrease in body size and longevity of taxa in response to the pulse perturbation and a shift towards small/medium size and intermediate longevity following the macroalgae takeover. The observed slow recovery rates and abrupt shifts in community structure document the vulnerability of Arctic coastal ecosystems to perturbations and continued effects of climate warming.This article is part of the theme issue ‘The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning’.
Highlights
Arctic marine ecosystems are experiencing unprecedented environmental change due to climate warming and expanding human activities [1,2]
The impact of climate warming can be severe in coastal waters, where the above pressures are compounded by increased freshwater discharge and associated runoff from rivers and thawing glaciers [2,7,8]
The pairwise comparisons were performed on data for all taxa, and for a selection of taxa excluding rare, large, motile ones, which might affect dissimilarity between transects in ways that are unrelated to the process of community recovery after clearance, as well as the small bristle worm, Spirorbis spirorbis, highly abundant in later years
Summary
Arctic marine ecosystems are experiencing unprecedented environmental change due to climate warming and expanding human activities [1,2]. In coastal hard-bottom habitats, such reorganization of benthic communities has been characterized by a sudden increase in foliose macroalgae, linked to altered light regimes due to sea ice loss, followed by structural changes in macrozoobenthos [7]. Other Arctic coastal studies find an increase in kelp biomass and a shift in the vertical distribution of kelp to shallower depths, resulting from reduced disturbance from ice-scouring, an extended ice-free period and increased turbidity [11,12]. Earlier polar studies document slow recovery rates after disturbance in coastal areas and abrupt community shifts related to climate warming, implying that benthos are vulnerable to environmental change and perturbations. We expect a marked structural change related to climate warming, due to the changing habitat characteristics and macroalgae takeover favouring different functional groups
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