Benthic algal community dynamics on Palmyra Atoll throughout a decade with two thermal anomalies

Coral reef algae serve many important ecological functions, from primary production to nutrient uptake and reef stabilization, but our knowledge of longer-term effects of thermal stress on algae in situ is limited. While ocean warming can facilitate proliferation of algae and potential phase shifts...

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Main Authors: Adi Khen, Maggie D. Johnson, Michael D. Fox, Jennifer E. Smith
Format: Article
Language:English
Published: Frontiers Media S.A. 2025-01-01
Series:Frontiers in Marine Science
Subjects:
Online Access:https://www.frontiersin.org/articles/10.3389/fmars.2025.1539865/full
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author Adi Khen
Maggie D. Johnson
Michael D. Fox
Jennifer E. Smith
author_facet Adi Khen
Maggie D. Johnson
Michael D. Fox
Jennifer E. Smith
author_sort Adi Khen
collection DOAJ
description Coral reef algae serve many important ecological functions, from primary production to nutrient uptake and reef stabilization, but our knowledge of longer-term effects of thermal stress on algae in situ is limited. While ocean warming can facilitate proliferation of algae and potential phase shifts from coral to macroalgal-dominated states, algal responses may vary by species, genus, functional group, or type (e.g., calcareous vs. fleshy). We used 11 years of annual monitoring data (2009-2019) that spans two El Niño-associated heatwaves to examine benthic algal community dynamics on Palmyra Atoll in the central Pacific Ocean. We quantified the percent cover of algal taxa via image analysis of permanent benthic photoquadrats from two habitats on Palmyra: the deeper, wave-exposed fore reef (10 m depth) and the shallower, wave-sheltered reef terrace (5 m depth). Each habitat was characterized by distinct algal communities: predominantly calcareous taxa on the fore reef and predominantly fleshy taxa on the reef terrace. Patterns in abundance fluctuated over time and/or in response to thermal anomalies in 2009 and 2015. Fleshy algae generally increased in cover post-warming, which coincided with large declines of the calcified macroalgae, Halimeda spp. Long-term monitoring of coral reef algal communities is critical for understanding their differential responses to thermal stress and can improve projections of ecosystem functioning in the context of global change.
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spelling doaj-art-a92baeca1b194dbeb46e7799a0ad56ec2025-01-28T05:10:56ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452025-01-011210.3389/fmars.2025.15398651539865Benthic algal community dynamics on Palmyra Atoll throughout a decade with two thermal anomaliesAdi Khen0Maggie D. Johnson1Michael D. Fox2Jennifer E. Smith3Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, United StatesBiological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi ArabiaBiological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi ArabiaCenter for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, United StatesCoral reef algae serve many important ecological functions, from primary production to nutrient uptake and reef stabilization, but our knowledge of longer-term effects of thermal stress on algae in situ is limited. While ocean warming can facilitate proliferation of algae and potential phase shifts from coral to macroalgal-dominated states, algal responses may vary by species, genus, functional group, or type (e.g., calcareous vs. fleshy). We used 11 years of annual monitoring data (2009-2019) that spans two El Niño-associated heatwaves to examine benthic algal community dynamics on Palmyra Atoll in the central Pacific Ocean. We quantified the percent cover of algal taxa via image analysis of permanent benthic photoquadrats from two habitats on Palmyra: the deeper, wave-exposed fore reef (10 m depth) and the shallower, wave-sheltered reef terrace (5 m depth). Each habitat was characterized by distinct algal communities: predominantly calcareous taxa on the fore reef and predominantly fleshy taxa on the reef terrace. Patterns in abundance fluctuated over time and/or in response to thermal anomalies in 2009 and 2015. Fleshy algae generally increased in cover post-warming, which coincided with large declines of the calcified macroalgae, Halimeda spp. Long-term monitoring of coral reef algal communities is critical for understanding their differential responses to thermal stress and can improve projections of ecosystem functioning in the context of global change.https://www.frontiersin.org/articles/10.3389/fmars.2025.1539865/fulllong-term monitoringseaweedmacroalgaeHalimedacommunity compositionthermal stress
spellingShingle Adi Khen
Maggie D. Johnson
Michael D. Fox
Jennifer E. Smith
Benthic algal community dynamics on Palmyra Atoll throughout a decade with two thermal anomalies
Frontiers in Marine Science
long-term monitoring
seaweed
macroalgae
Halimeda
community composition
thermal stress
title Benthic algal community dynamics on Palmyra Atoll throughout a decade with two thermal anomalies
title_full Benthic algal community dynamics on Palmyra Atoll throughout a decade with two thermal anomalies
title_fullStr Benthic algal community dynamics on Palmyra Atoll throughout a decade with two thermal anomalies
title_full_unstemmed Benthic algal community dynamics on Palmyra Atoll throughout a decade with two thermal anomalies
title_short Benthic algal community dynamics on Palmyra Atoll throughout a decade with two thermal anomalies
title_sort benthic algal community dynamics on palmyra atoll throughout a decade with two thermal anomalies
topic long-term monitoring
seaweed
macroalgae
Halimeda
community composition
thermal stress
url https://www.frontiersin.org/articles/10.3389/fmars.2025.1539865/full
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AT maggiedjohnson benthicalgalcommunitydynamicsonpalmyraatollthroughoutadecadewithtwothermalanomalies
AT michaeldfox benthicalgalcommunitydynamicsonpalmyraatollthroughoutadecadewithtwothermalanomalies
AT jenniferesmith benthicalgalcommunitydynamicsonpalmyraatollthroughoutadecadewithtwothermalanomalies