Depth alone is an inappropriate proxy for physiological change in the mesophotic coral Agaricia lamarcki

Laverick, J. H., Green, T. K., Burdett, H. L., Newton, J. and Rogers, A. D. (2019) Depth alone is an inappropriate proxy for physiological change in the mesophotic coral Agaricia lamarcki. Journal of the Marine Biological Association of the United Kingdom, 99(7), pp. 1535-1546. (doi: 10.1017/S0025315419000547)

Abstract

The physiology of mesophotic Scleractinia varies with depth in response to environmental change. Previous research has documented trends in heterotrophy and photosynthesis with depth, but has not addressed between-site variation for a single species. Environmental differences between sites at a local scale and heterogeneous microhabitats, because of irradiance and food availability, are likely important factors when explaining the occurrence and physiology of Scleractinia. Here, 108 colonies of Agaricia lamarcki were sampled from two locations off the coast of Utila, Honduras, distributed evenly down the observed 50 m depth range of the species. We found that depth alone was not sufficient to fully explain physiological variation. Pulse Amplitude-Modulation fluorometry and stable isotope analyses revealed that trends in photochemical and heterotrophic activity with depth varied markedly between sites. Our isotope analyses do not support an obligate link between photosynthetic activity and heterotrophic subsidy with increasing depth. We found that A. lamarcki colonies at the bottom of the species depth range can be physiologically similar to those nearer the surface. As a potential explanation, we hypothesize sites with high topographical complexity, and therefore varied microhabitats, may provide more physiological niches distributed across a larger depth range. Varied microhabitats with depth may reduce the dominance of depth as a physiological determinant. Thus, A. lamarcki may ‘avoid’ changes in environment with depth, by instead existing in a subset of favourable niches. Our observations correlate with site-specific depth ranges, advocating for linking physiology and abiotic profiles when defining the distribution of mesophotic taxa.

• Item Type: Articles
• Additional Information: The authors would like to thank the Royal Geographical Society (Ralph-Brown Award), the Zoological Society of London (EDB Expeditions fund), the Oxford University Expeditions Council, Oxford University Press (John-Fell fund), the Natural Environment ResearchCouncil (NE/L002612/1; EK258‐13/15), Merton College Oxford and Operation Wallacea for funding. TG is supported by a 7th Century University scholarship. Fieldwork was completed when HB was in receipt of a Marine Alliance for Science and Technology for Scotland (MASTS) Research Fellowship. DMSO analyses were supported by a MASTS Small Grant awarded to TG. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. We thank the Natural Environment Research Council (NERC) Field Spectroscopy Facility for loan of the Diving-PAM instrument.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Newton, Dr Jason
• Authors: Laverick, J. H., Green, T. K., Burdett, H. L., Newton, J., and Rogers, A. D.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Journal of the Marine Biological Association of the United Kingdom
• Publisher: Cambridge University Press
• ISSN: 0025-3154
• ISSN (Online): 1469-7769
• Published Online: 24 June 2019
• Copyright Holders: Copyright © Marine Biological Association of the United Kingdom 2019
• First Published: First published in Journal of the Marine Biological Association of the United Kingdom 99(7):1535-1546
• Publisher Policy: Reproduced in accordance with the publisher copyright policy