Community structure and demographic drivers of partial mortality in corals throughout the Papahānaumokuākea Marine National Monument.

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2019-05
Authors
Pascoe, Kailey Hoohokuokalani
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Burns, John H.
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Tropical Conservation Biology & Environmental Science
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Understanding the association between coral community demographics and coral health is critical in the face of increasing environmental stressors driven by an ever-expanding human population. Within the last several decades, reefs around the globe have experienced substantial increases in levels of coral disease as well as large-scale outbreaks and mortality. Corals can experience partial mortality lesions because they are colonial organisms. A coral colony is constantly experiencing partial mortality lesion, fission and fusion. Corals exhibit highly variable levels of partial mortality, which is a useful indicator of overall coral health, thus it is important to identify drivers of this condition. This study examines monitoring data on coral health and disease from surveys (n= 4449) conducted throughout the Papahānaumokuākea Marine National Monument for the Reef Assessment and Monitoring Program (RAMP). Linear mixed-effects models were used to identify coral community demographic parameters that were associated with coral partial mortality. Significant variability in mean coral colony size, density, diversity, morphology, and partial mortality of corals was found among the sites in the NWHI. Mean coral size, density, and diversity decreased with increasing latitude. Mean coral partial mortality were also found to be statistically greater at sites in the high latitude atolls. Twelve morphologies in this study also exhibited differences in mean values of partial mortality. The results from the linear mixed-effects models showed coral partial mortality is predicted by the size of individual colonies (0.02±0.26(S.D.)), density (-0.33±0.07(S.D.)), species diversity (-0.03±0.01(S.D.)), and colony morphology. Colony size was positively correlated with partial mortality, whereas density and diversity showed slightly negative relationships with partial mortality. Columnar and mounding lobate morphologies exhibited the strongest effects with partial mortality. Understanding the relationship between coral community demographics and coral health can provide useful insight into how various coral populations may respond to increased levels of stress and disturbance. This research provides an example of how long-term monitoring data and hierarchical statistical modeling can provide information to help managers better understand coral health.
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Ecology, Colony Size, Coral Ecology, Mixed Effect Modeling, Monitoring Data, Partial Mortality
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61 pages
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