Water Quality Influences on Declining Coral Settlement from the Great Barrier Reef Region: Biofilms as Key Players
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2015-05
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[Honolulu] : [University of Hawaii at Manoa], [May 2015]
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Abstract
Biofilms (surface attached microbial communities in mucus) are common in coastal marine ecosystems but among the least studied. Their pivotal roles in the resilience of coral reefs stem from their interactions with coral larvae that must select permanent sites for attachment before metamorphosing into coral polyps, a process which can be disrupted by local watershed disturbances. In the laboratory, biofilm communities were exposed to moderately turbid water (50 mg/L sediment) and a doubling of particulate organic matter (POM). Acropora millepora and Pocillopora acuta coral larvae that were provided biofilms from each treatment settled less on those that had been exposed to sediments and organic matter. Pyrosequenced 16S and 18S rRNA gene fragments and scanning electron microscopy showed how community changes in the biofilms in each treatment related to settlement of both coral species’ larvae. We concluded that: 1) particulate carbon levels explained more variation in the community composition of biofilms and in coral settlement response than did turbidity changes; 2) community composition of the microbial eukaryote community shifts from diatom to fungal-dominated; 3) spatial distribution of settlement is driven more by negative cues from biofilms than it is by positive cues; 4) the complex, three dimensional structure of biofilm surfaces diminishes with increased POM and turbidity. Phaeobacter spp. affiliated sequences dominated biofilms before and after treatments. These and other Rhodobacteraceae affiliated sequences were positively associated with A. millepora settlement, but not with that of P. acuta. Phaeobacter spp. occur globally in biofilm communities, produce antibiotics, stimulate algal growth and then produce algaecides to digest algae as it ages, and decrease epibiont settlement on some algae. They may provide key functional roles in coral reef biofilms.
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Ph.D. University of Hawaii at Manoa 2015.
Includes bibliographical references.
Includes bibliographical references.
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Microbiology, biofilms, marine ecosystems, coral reefs
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Theses for the degree of Doctor of Philosophy (University of Hawaii at Manoa). Microbiology
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