Spatial variability in the diversity and structure of faunal assemblages associated with kelp holdfasts (Laminaria hyperborea) in the northeast Atlantic

Abstract

Kelp species are ecologically-important habitat-formers in coastal marine ecosystems, where they alter environmental conditions and promote local biodiversity by providing complex biogenic habitat for an array of associated organisms. While it is widely accepted that kelps harbour significant biodiversity, our current understanding of spatiotemporal variability in kelp-associated assemblages and the key environmental drivers of variability patterns remains limited. Here we examined the influence of ocean temperature and wave exposure on the structure of faunal assemblages associated with the holdfasts of Laminaria hyperborea, the dominant habitat-forming kelp in the northeast Atlantic. We sampled holdfasts from 12 kelp-dominated open-coast sites nested within four regions across the UK, spanning ~9° in latitude and ~2.7° C in mean sea surface temperature. Overall, holdfast assemblages were highly diverse, with 261 taxa representing 11 phyla recorded across the study. We examined patterns of spatial variability for sessile and mobile taxa separately, and documented high variability between regions, between sites within regions, and between replicate holdfasts for both assemblage types. Mobile assemblage structure was more strongly linked to temperature variability than sessile assemblage structure, which was principally structured by site-level variability in factors such as wave exposure. Patterns in the structure of both biogenic habitat and associated assemblages did not vary predictably along a latitudinal gradient in temperature, indicating that other processes acting across multiple spatial and temporal scales are important drivers of assemblage structure. Overall, kelp holdfasts in the UK supported high levels of diversity, that were similar to other kelp-dominated systems globally and comparable to those recorded for other vegetated marine habitats (i.e. seagrass beds), which are perhaps more widely recognised for their high biodiversity value.

Can ecosystem functioning be maintained despite climate‐driven shifts in species composition? Insights from novel marine forests

“…For instance, kelp forests dominated by the warm‐temperate species will still exhibit high rates of carbon capture, as plant primary production—and therefore carbon assimilation—was higher than that of the cool‐water kelp. Both species are also morphologically similar and form canopies of similar heights and plant densities (Smale et al., ; Supporting Information Table ) and, as such, kelp forests dominated by the range‐expanding species are likely to continue to provide habitat for fish, invertebrate, and algal species (O'Brien, Mello, Litterer, & Dijkstra, ; Teagle, Moore, Jenkins, & Smale, ). That said, recent work has shown that the epibiotic assemblages associated with kelp stipes, which are typically dominated by red seaweeds and sessile invertebrates, are less diverse in the warm‐temperate species (Teagle & Smale, ).…”

Environmental factors influencing primary productivity of the forest-forming kelp Laminaria hyperborea in the northeast Atlantic

“…The large kelp Laminaria hyperborea functions as the dominant foundation species along much of the wave-exposed rocky coastline of the northeast Atlantic 15 – 17 , where it forms extensive kelp forest habitat 18 , 19 , supports high levels of biodiversity 20 and stores and releases vast amounts of organic matter 21 , 22 . Despite the critical importance of L. hyperborea and the kelp forest habitats it creates in the northeast Atlantic, several important knowledge gaps pertaining to its biology and ecology still persist, including reliable estimates of NPP from multiple populations and across large spatial scales.…”

Multiple‐scale interactions structure macroinvertebrate assemblages associated with kelp understory algae

“…In the NE Atlantic, shallow subtidal reefs, fully or partially exposed to wave action, are dominated by the large stipitate kelp Laminaria hyperborea (Smale, Burrows, Moore, O'Connor, & Hawkins, 2013;Steneck et al, 2002;Teagle et al, 2017). Individual "plants" support diverse assemblages of epiphytic algae and associated invertebrates on their stipes, as well as rich invertebrate assemblages within their holdfasts (Christie et al, 2003;Moore, 1973;Teagle et al, 2017Teagle et al, , 2018. Beneath these, extensive kelp stands lie functionally diverse and structurally complex assemblages of understory algae, ranging from simple foliose species to more complex calcareous algae and corticated macrophytes (Leclerc et al, 2016;Maggs, 1986).…”