Variation in measures of immunocompetence of sea fan coral, <Emphasis Type="Italic">Gorgonia ventalina</Emphasis>, in the Florida Keys |
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Authors: | C S Couch L D Mydlarz C D Harvell N L Douglas |
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Institution: | (1) Department of Ecology and Evolutionary Biology, Corson Hall, Cornell University, Ithaca, NY 14853, USA;(2) Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA |
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Abstract: | Aspergillosis is a widespread disease that has impacted the demography of the Caribbean sea fan coral, Gorgonia ventalina. The innate coral immune defenses can be measured as constitutive levels of immune proteins (peroxidase POX], prophenoloxidase
PPO], lysozyme-like activity LYS], exochitinase EXOC]), antioxidant (superoxide dismutase SOD]), and antimicrobial (antibacterial
AB] and antifungal AF]) activity. Therefore, variations in these parameters across a geographic region could provide clues
to the role of environment in disease. This study examined healthy sea fans collected in July 2005 from six offshore sites
in the Florida Keys lying between 24.569°N and 25.220°N, a distance of ~145 km. Contrary to expectations, small (<15 cm) colonies
did not differ significantly from large colonies (>15 cm) in the protein-based levels of activity in any of the measured parameters.
However, there were significant differences in many of the parameters among sites, and Molasses Reef and Looe Key Reef were
the most different in POX, PPO, SOD, and AF activity. This suggests that there are potential site-specific environmental factors
that shape the immune physiology of colonies. Several proxies of environmental stress were also regressed against levels of
the immune parameters. The proxies included 10 year averages of benthic community composition, 5 year averages of water quality,
and historic aspergillosis disease prevalence and severity. Generality about environmental drivers was limited by assaying
only six sites, but several patterns did emerge. SOD, EXOC, and AF activity were all correlated with percent bare substrate
cover, suggesting that certain immune components may be activated in low coral environments. LYS and EXOC activity were positively
correlated with dissolved inorganic nitrogen (DIN), one proxy of water quality. There were no relationships between any of
the measured immune parameters and previous disease prevalence and severity. This study is a first step in evaluating levels
of within- and between-site variation in coral immunity and investigating possible environmental drivers. |
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