Abstract
Understanding the variation of biodiversity along environmental gradients and multiple spatial scales is relevant for theoretical and management purposes. Hereby, we analysed the spatial variability in diversity and structure of intertidal and subtidal macrobenthic Antarctic communities along vertical environmental stress gradients and across multiple horizontal spatial scales. Since biotic interactions and local topographic features are likely major factors for coastal assemblages, we tested the hypothesis that fine-scale processes influence the effects of the vertical environmental stress gradients on the macrobenthic diversity and structure. We used nested sampling designs in the intertidal and subtidal habitats, including horizontal spatial scales ranging from few centimetres to 1000s of metres along the rocky shore of Fildes Peninsula, King George Island. In both intertidal and subtidal habitats, univariate and multivariate analyses showed a marked vertical zonation in taxon richness and community structure. These patterns depended on the horizontal spatial scale of observation, as all analyses showed a significant interaction between height (or depth) and the finer spatial scale analysed. Variance and pseudo-variance components supported our prediction for taxon richness, community structure, and the abundance of dominant species such as the filamentous green alga Urospora penicilliformis (intertidal), the herbivore Nacella concinna (intertidal), the large kelp-like Himantothallus grandifolius (subtidal), and the red crustose red alga Lithothamnion spp. (subtidal). We suggest that in coastal ecosystems strongly governed by physical factors, fine-scale processes (e.g. biotic interactions and refugia availability) are still relevant for the structuring and maintenance of the local communities. The spatial patterns found in this study serve as a necessary benchmark to understand the dynamics and adaptation of natural assemblages in response to observed and predicted environmental changes in Antarctica.
Highlights
Processes that operate at different spatial scales influence the occurrence and abundance of natural species [1,2]
These patterns in community structure and diversity can vary across horizontal scales of observation, which can confound our conclusions about biological patterns along the most obvious environmental gradients [9,10]
Fourteen macroalgal taxa were found in the intertidal and 25 in the subtidal habitat
Summary
Processes that operate at different spatial scales influence the occurrence and abundance of natural species [1,2]. Attenuation of solar radiation and water movement stimulate the formation of vertical patterns in subtidal communities [8]. These patterns in community structure and diversity can vary across horizontal scales of observation, which can confound our conclusions about biological patterns along the most obvious environmental gradients [9,10]. Several studies focused on intertidal and subtidal communities suggest that local processes, including physical disturbance [11], competition [12,13], availability of refugia [14], and consumption [15,16] generate a high amount of horizontal biological variability at fine scales of observation (i.e. cm to few metres between sampling units [14,17,18,19])
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