Benthic communities and their drivers: A spatial analysis off the Antarctic Peninsula

Julian Gutt,Boris Dorschel,Michael Schröder,Janina Arndt,Astrid Bracher,Dieter Piepenburg,Casper Kraan

doi:10.1002/lno.11187

Abstract

AbstractMultiple environmental factors control benthic community patterns, and their relative importance varies with spatial scale. Since this variation is difficult to evaluate quantitatively, extensive sampling across a broad range of spatial scales is required. Here, we present a first case study on Southern Ocean shelf benthos, in which mega‐epibenthic communities and biota‐environment relationships have been explored at multiple spatial scales. The analyses encompassed 20 seafloor, water‐column, and sea‐ice parameters, as well as abundances of 18 mega‐epibenthic taxa in a total of 2799 high‐resolution seabed images taken at 28 stations at 32–786 m depth off the northern Antarctic Peninsula. Based on a priori nesting of sampling stations into ecoregions, subregions, and habitats, analyses indicated most pronounced patchiness levels at finest (within transects among adjacent seabed photos) and largest (among ecoregions) spatial scale considered. Using an alternative approach, explicitly involving the spatial distances between the geo‐referenced data, Moran's Eigenvector mapping (MEM) classified the continuum of spatial scales into four categories: broad (> 60 km), meso (10–60 km), small (2–10 km), and fine (< 2 km). MEM analyses generally indicated an increase in mega‐epibenthic community complexity with increasing spatial scale. Moreover, strong relationships between biota and environmental drivers were found at scales of > 2 km. In contrast, few environmental variables contributed to explaining biotic structures at finer scales. These are likely rather determined by nonmeasured environmental variables, as well as biological traits and interactions that are assumed to be most effective at small spatial scales.

Highlights

The waters of the Bransfield Strait are generally characterized by a broad temperature range, in the southern part by low temperatures, due to the influence of the glaciers of the Antarctic Peninsula, and in the north by even lower temperature, due to the inflow of water from the Weddell Sea surrounding the tip of the Peninsula
Data collection Our study was based on a photographic seabed survey that was conducted during expedition ANT-XXIX/3 (PS81) of R/V Polarstern to the waters off the northern Antarctic Peninsula in January–March 2013 (Fig. 1; for a cruise report, see Gutt 2013)
At the coarser spatial scale, i.e., among stations (= photo transects), similarities in faunistic composition were generally low, even between adjacent transects (Fig. 3). This pattern was especially evident for dominant animal groups, with some exceptions, e.g., in the Drake Passage

Summary

Introduction

One reason for the high diversity may be that species occurring in this region are adapted to high-latitude conditions, in terms of hydrography and ice cover, and to a less polar environment, where the southern boundary of the Antarctic Circumpolar Current hits the Peninsula (Orsi et al 1995; Sokolov and Rintoul 2009). These conditions cause complex oceanographic patterns (Huneke et al 2016) and seasonally pulsed primary production (Thomalla et al 2011; for details, see Supporting Information Table S1). In the Weddell Sea, banks with slopes, of which one was classified as a shoal (Dorschel et al 2014), and inner-shelf depressions characterize the bottom topography

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Discussion

Conclusion