Abstract
Climate change has ecosystem‐wide cascading effects. Little is known, however, about the resilience of Arctic marine ecosystems to environmental change. Here we quantify and compare large‐scale patterns in rocky intertidal biomass, coverage and zonation in six regions along a north‐south gradient of temperature and ice conditions in West Greenland (60–72°N). We related the level and variation in assemblage composition, biomass and coverage to latitudinal‐scale environmental drivers. Across all latitudes, the intertidal assemblage was dominated by a core of stress‐tolerant foundation species that constituted > 95% of the biomass. Hence, canopy‐forming macroalgae, represented byFucus distichussubsp.evanescensandF. vesiculosusand, up to 69°N, alsoAscophyllum nodosum, together withSemibalanus balanoides, occupied > 70% of the vertical tidal range in all regions. Thus, a similar functional assemblage composition occurred across regions, and no latitudinal depression was observed. The most conspicuous difference in species composition from south to north was that three common species (the macroalgaeAscophyllum nodosum, the amphipodGammarus setosusand the gastropodLittorina obtusata) disappeared from the mid‐intertidal, although at different latitudes. There were no significant relationships between assemblage metrics and air temperature or sea ice coverage as obtained from weather stations and satellites, respectively. Although the mean biomass decreased > 50% from south to north, local biomass in excess of 10 000 g ww m−2was found even at the northernmost site, demonstrating the patchiness of this habitat and the effect of small‐scale variation in environmental characteristics. Hence, using the latitudinal gradient in a space‐for‐time substitution, our results suggest that while climate modification may lead to an overall increase in the intertidal biomass in north Greenland, it is unlikely to drive dramatic functional changes in ecosystem structure in the near future. Our dataset provides an important baseline for future studies to verify these predictions for Greenland's intertidal zone.
Highlights
The rocky intertidal zone is one of the most studied marine habitats, and has provided a wealth of information about the ecological processes that shape assemblage structure and dynamics
The most conspicuous difference in species composition from south to north, was that three common species disappeared completely from the mid-intertidal zone along the latitude gradient: The amphipod Gammarus setosus was only found in Cape Farewell (60°N), while G. oceanicus was found in all regions
Besides the absence of the foundation species Ascophyllum nodosum in north Greenland, the mid-intertidal assemblage dominance was maintained by a few habitat forming species (i.e. Fucus vesiculosus, F. distichus subsp. evanescens and Semibalanus balanoides) across all latitudes
Summary
The rocky intertidal zone is one of the most studied marine habitats, and has provided a wealth of information about the ecological processes that shape assemblage structure and dynamics. The Arctic accounts for more than 30% of the world’s coastline (Lantuit et al 2012), but Arctic intertidal habitats have received little attention, and rocky Arctic shores were until recently thought to be sparsely colonized (Ellis 1955, Węsławski et al 1993). Scattered studies from different sub-Arctic and Arctic rocky shores on Svalbard (Kuklinski and Barnes 2008, Węsławski et al 2010, 2018), Iceland (Ingolfsson 1992, Ingólfsson 1996) and southern Greenland (Blicher et al 2013, Høgslund et al 2014, Sejr et al 2021) have documented species diversity, and revealed high biomasses locally, but most of the Arctic intertidal zone remains unexplored. The physical parameters driving regional differences, and the rates of change in key ecosystem metrics, such as biomass and coverage, remain poorly understood, hindering assessments of climate change effects on the ecosystem. The Arctic is warming at rates 2- to 3-fold greater than the global average (AMAP 2017), the scarcity of Arctic baseline and time-series data prevent quantifications of how this rapid warming affects intertidal organisms and ecosystem functioning
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