Effects of variability in daily light integrals on the photophysiology of the corals Pachyseris speciosa and Acropora millepora

DiPerna, Stephanie, Hoogenboom, Mia, Noonan, Sam, and Fabricius, Katharina (2018) Effects of variability in daily light integrals on the photophysiology of the corals Pachyseris speciosa and Acropora millepora. PLoS ONE, 13 (9). e0203882.

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Abstract

Phototrophic sessile organisms, such as reef corals, adjust their photosynthetic apparatus to optimize the balance of light capture versus protection in response to variable light availability (photoacclimation). In shallow marine environments, daily light integrals (DLI) can vary severalfold in response to water clarity and clouds. This laboratory study investigated the responses of two coral species to fluctuations in DLI. Corals were exposed to four contrasting DLI treatments: 'highlight' (potentially photoinhibiting conditions, 32 mol photons m(-2) d(-1)), 'lowlight' (potentially lightlimiting conditions, 6 mol photons m(-2) d(-1)), and two ` variable light' treatments that alternated between high and low conditions every 5 days. In the variable treatments, the shadetolerant coral Pachyseris speciosa displayed cycles of rapid declines in maximum quantum yield during highlight and subsequent recoveries during lowlight, showing photoacclimation at a time scale of 3 +/- 5 days. In contrast, the shallowwater coral Acropora millepora showed slow (> 20 days) photoacclimation, and minimal changes in photosynthetic yields despite contrasting light exposure. However, growth (change in buoyant weight) in A. millepora was significantly slower under variable light, and even more so under lowlight conditions, compared with highlight conditions. The responses of yields in P. speciosa match their preference for lowlight environments, but suggest a vulnerability to even short periods of highlight exposure. In contrast, A. millepora had better tolerance of highlight conditions, however its slow photoacclimatory responses limit its growth under low and variable conditions. The study shows contrasting photoacclimatory responses in variable light environments, which is important to identify and understand as many coastal and midshelf reefs are becoming increasingly more turbid, and may experience higher variability in light availability.

Item ID: 55823
Item Type: Article (Research - C1)
ISSN: 1932-6203
Copyright Information: © 2018 DiPerna et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funders: National Environmental Science Program (NESP) Tropical Water Quality (TWQ) Hub, Australian Institute of Marine Science (AIMS)
Projects and Grants: NESP TWQ project 2.3.1
Date Deposited: 10 Oct 2018 07:55
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 50%
06 BIOLOGICAL SCIENCES > 0605 Microbiology > 060504 Microbial Ecology @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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