Disturbance ecology of the shallow Antarctic Benthos

Robinson, Ben J.O. ORCID: https://orcid.org/0000-0002-7450-686X. 2021 Disturbance ecology of the shallow Antarctic Benthos. University of Southampton, Faculty of Natural and Environmental Sciences, PhD Thesis, 283pp.

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Abstract/Summary

The shallow Antarctic benthos (10 -100 m depth) are predicted to undergo drastic changes, particularly with respect to the iceberg scour disturbance regimes. With this is in mind, the field of disturbance ecology provides a powerful lens through which to interpret the current and future changes within this environment. The top 100 m of the benthos within the Antarctic is largely characterised by a strong disturbance gradient, with infrequent scour occurring at depth and large swatches of the macro and megabenthos removed by scours in the shallows. Data were collected from photographs taken with a mini-ROV to measure the taxonomic, functional and structural changes within the macro and megabenthos across disturbance regimes and depths. Results showed the complex interplay between the disturbance, dispersal and diversity that can drive assemblage structure through migration and recruitment with no part of the benthos being truly independent of its neighbours. Across a wide-ranging disturbance gradient found across depth, peaks in biodiversity were detected at Intermediate disturbance levels and although strong evidence for the Intermediate-Disturbance Hypothesis (IDH) validity, this does call into question its relevance due to the breadth of disturbance required to detect it. This disturbance-diversity pattern was driven by selective (niche) mechanisms reducing diversity at the extremes of disturbance, resulting in a peak at intermediate levels, however models revealed this peak does not provide any additional redundancy and is in fact driven by non-selective (random) mechanisms. This would suggest that IDH is best considered as a resultant interaction between two selective forces cancelling each other out rather than disturbance causing the peak in biodiversity. The reduction of biodiversity at the extremes of disturbance gradients however does result in loss of functional redundancy and highlights a vulnerability of the assemblage to future environmental change, which mounting evidence suggests is within the near future for this environment. With the future of the shallow Antarctic benthos unclear, this thesis provides deeper insights into the interactions between disturbance and community structure, elucidating the key mechanisms underlying the patterns seen across the natural world. It also suggests several monitoring metrics and taxa (sentinel species), provides a base-line for a previously data-poor environment and discusses several hypothesised futures for the shallow Antarctic Benthos.