Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health

Increasingly frequent large-scale pelagic Sargassum algae blooms in the Atlantic have become a problem for coastal ecosystems. The mass decay of these blooms reduces water quality for coastal flora and fauna. However, the effects of living Sargassum blooms on seawater quality and consequently coral...

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Main Authors: Johann D. Lankes, Heather N. Page, Amanda Quasunella, Jaclyn F. Torkelson, Clöe Lemaire, Robert J. Nowicki, Lillia Blasius, Emily R. Hall
Format: Article
Language:English
Published: Frontiers Media S.A. 2025-02-01
Series:Frontiers in Marine Science
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Online Access:https://www.frontiersin.org/articles/10.3389/fmars.2025.1487102/full
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author Johann D. Lankes
Johann D. Lankes
Heather N. Page
Amanda Quasunella
Jaclyn F. Torkelson
Clöe Lemaire
Robert J. Nowicki
Lillia Blasius
Emily R. Hall
Emily R. Hall
author_facet Johann D. Lankes
Johann D. Lankes
Heather N. Page
Amanda Quasunella
Jaclyn F. Torkelson
Clöe Lemaire
Robert J. Nowicki
Lillia Blasius
Emily R. Hall
Emily R. Hall
author_sort Johann D. Lankes
collection DOAJ
description Increasingly frequent large-scale pelagic Sargassum algae blooms in the Atlantic have become a problem for coastal ecosystems. The mass decay of these blooms reduces water quality for coastal flora and fauna. However, the effects of living Sargassum blooms on seawater quality and consequently coral reef ecosystems that rely on delicately balanced carbonate chemistry are more ambiguous. Future oceans are predicted to be more acidic as additional anthropogenic CO2 emissions are absorbed, potentially tipping the balance in favor of algal blooms at the cost of coral survival. This study aimed to simulate the indirect interaction between pelagic Sargassum spp. and Acropora cervicornis coral fragments from the Florida Reef in current-day and future ocean pH conditions over the course of 70 days in a mesocosm experimental system. Measurements of coral growth and health via buoyant weight and Pulse Amplitude Modulated (PAM) fluorescence measurements reveal an unexpected coral-algal interaction. After 1 month, coral growth was significantly reduced under ocean acidification conditions and exposure to Sargassum; at the same time quantum yield and maximum electron transport rate of photosynthesis were increased relative to control counterparts in ambient and future pH scenarios by up to 14% and 18% respectively. These improvements in photosynthetic efficiency did not translate to significant differences in growth by the final measurement time point. In addition, the presence of Sargassum spp. did not raise seawater pH in the system, raising questions about how it benefited photosynthetic efficiency in exposed corals. Heterotrophy of detrital algal matter is suspected to compensate for impaired photosynthesis of pH stressed corals. Therefore, despite their current negative reputation, Sargassum blooms could provide short term localized benefits to corals in present and future ocean conditions.
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spelling doaj-art-cd43bfb4db0b440b9a6fdd34d17ba2902025-08-20T02:11:13ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452025-02-011210.3389/fmars.2025.14871021487102Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis healthJohann D. Lankes0Johann D. Lankes1Heather N. Page2Amanda Quasunella3Jaclyn F. Torkelson4Clöe Lemaire5Robert J. Nowicki6Lillia Blasius7Emily R. Hall8Emily R. Hall9Elizabeth Moore International Center for Coral Reef Research and Restoration, Mote Marine Laboratory, Summerland Key, FL, United StatesIsometric, London, United KingdomSea Education Association, Woods Hole, MA, United StatesSouthern Cross University, Lismore, NSW, AustraliaDepartment of Chemistry and Biochemistry, Northern Arizona University, Flagstaff, AZ, United StatesDepartment of Marine and Environmental Science, Savannah State University, Savannah, GA, United StatesStorm Anchor Insights, Key West, FL, United StatesDepartment of Biological Science, Purdue University, West Lafayette, IN, United StatesElizabeth Moore International Center for Coral Reef Research and Restoration, Mote Marine Laboratory, Summerland Key, FL, United StatesOcean Acidification Research Program, Mote Marine Laboratory, Sarasota, FL, United StatesIncreasingly frequent large-scale pelagic Sargassum algae blooms in the Atlantic have become a problem for coastal ecosystems. The mass decay of these blooms reduces water quality for coastal flora and fauna. However, the effects of living Sargassum blooms on seawater quality and consequently coral reef ecosystems that rely on delicately balanced carbonate chemistry are more ambiguous. Future oceans are predicted to be more acidic as additional anthropogenic CO2 emissions are absorbed, potentially tipping the balance in favor of algal blooms at the cost of coral survival. This study aimed to simulate the indirect interaction between pelagic Sargassum spp. and Acropora cervicornis coral fragments from the Florida Reef in current-day and future ocean pH conditions over the course of 70 days in a mesocosm experimental system. Measurements of coral growth and health via buoyant weight and Pulse Amplitude Modulated (PAM) fluorescence measurements reveal an unexpected coral-algal interaction. After 1 month, coral growth was significantly reduced under ocean acidification conditions and exposure to Sargassum; at the same time quantum yield and maximum electron transport rate of photosynthesis were increased relative to control counterparts in ambient and future pH scenarios by up to 14% and 18% respectively. These improvements in photosynthetic efficiency did not translate to significant differences in growth by the final measurement time point. In addition, the presence of Sargassum spp. did not raise seawater pH in the system, raising questions about how it benefited photosynthetic efficiency in exposed corals. Heterotrophy of detrital algal matter is suspected to compensate for impaired photosynthesis of pH stressed corals. Therefore, despite their current negative reputation, Sargassum blooms could provide short term localized benefits to corals in present and future ocean conditions.https://www.frontiersin.org/articles/10.3389/fmars.2025.1487102/fullSargassumAcropora cervicornisocean acidificationalgal bloomfuture oceans
spellingShingle Johann D. Lankes
Johann D. Lankes
Heather N. Page
Amanda Quasunella
Jaclyn F. Torkelson
Clöe Lemaire
Robert J. Nowicki
Lillia Blasius
Emily R. Hall
Emily R. Hall
Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health
Frontiers in Marine Science
Sargassum
Acropora cervicornis
ocean acidification
algal bloom
future oceans
title Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health
title_full Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health
title_fullStr Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health
title_full_unstemmed Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health
title_short Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health
title_sort quantifying coral algal interactions in an acidified ocean sargassum spp exposure mitigates low ph effects on acropora cervicornis health
topic Sargassum
Acropora cervicornis
ocean acidification
algal bloom
future oceans
url https://www.frontiersin.org/articles/10.3389/fmars.2025.1487102/full
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