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Curr Biol. 2018 Nov 5;28(21):3355-3363.e4. doi: 10.1016/j.cub.2018.08.057. Epub 2018 Oct 18.

Gradients in Primary Production Predict Trophic Strategies of Mixotrophic Corals across Spatial Scales.

Author information

1
Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92037, USA. Electronic address: mfox@whoi.edu.
2
School of Ocean Sciences, Bangor University, Anglesey LL59 5AB, UK.
3
Smithsonian Marine Station, Fort Pierce, FL 34949, USA.
4
Global Change Institute, Australian Research Council Centre of Excellence for Coral Reef Studies, University of Queensland, St. Lucia, QLD 4072, Australia.
5
Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92037, USA.
6
Department of Biology, San Diego State University, San Diego, CA 92182, USA.

Abstract

Mixotrophy is among the most successful nutritional strategies in terrestrial and marine ecosystems. The ability of organisms to supplement primary nutritional modes along continua of autotrophy and heterotrophy fosters trophic flexibility that can sustain metabolic demands under variable or stressful conditions. Symbiotic, reef-building corals are among the most broadly distributed and ecologically important mixotrophs, yet we lack a basic understanding of how they modify their use of autotrophy and heterotrophy across gradients of food availability. Here, we evaluate how one coral species, Pocillopora meandrina, supplements autotrophic nutrition through heterotrophy within an archipelago and test whether this pattern holds across species globally. Using stable isotope analysis (δ13C) and satellite-derived estimates of nearshore primary production (chlorophyll-a, as a proxy for food availability), we show that P. meandrina incorporates a greater proportion of carbon via heterotrophy when more food is available across five central Pacific islands. We then show that this pattern is consistent globally using data from 15 coral species across 16 locations spanning the Caribbean Sea and the Indian and Pacific Oceans. Globally, surface chlorophyll-a explains 77% of the variation in coral heterotrophic nutrition, 86% for one genus across 10 islands, and 94% when controlling for coral taxonomy within archipelagos. These results demonstrate, for the first time, that satellite-derived estimates of nearshore primary production provide a globally relevant proxy for resource availability that can explain variation in coral trophic ecology. Thus, our model provides a pivotal step toward resolving the biophysical couplings between mixotrophic organisms and spatial patterns of resource availability in the coastal oceans.

KEYWORDS:

chlorophyll-a; coral reef; heterotrophy; nutrients; oceanography; phytoplankton; remote sensing; stable isotopes

PMID:
30344114
DOI:
10.1016/j.cub.2018.08.057

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