Changes in octocoral communities and benthic cover along a water quality gradient in the reefs of Hong Kong

Australian Institute of Marine Science, CRC Reef Research, P.M.B. 3, Townsville, Qld 4810, Australia.
Marine Pollution Bulletin (Impact Factor: 2.99). 02/2006; 52(1):22-33. DOI: 10.1016/j.marpolbul.2005.08.004
Source: PubMed


Cover of the main reef benthic groups, and abundances and taxonomic richness of octocorals were surveyed in the reefs of Hong Kong, and related to spatial and water quality gradients. Nutrient and particle concentrations are high throughout the area, with concentrations declining from the south towards the north-eastern region. Regression tree analyses showed that hard coral cover was most strongly related to water clarity, that macroalgal cover was highest in areas with high wave action and high water clarity, and that crustose coralline algae were negatively related to sedimentation. Octocoral communities (42 species in 23 genera) were dominated by zooxanthellae-free taxa; those few species with zooxanthellae were restricted to reefs with low wave action and high water clarity in the north-eastern region. The water quality gradient spans from conditions that are marginal for zooxanthellate octocorals while still supporting diverse scleractinian communities, towards an estuarine endpoint where zooxanthellate octocorals cease to exist and hard coral communities are reduced to a few resilient colonies. The data suggest that the types, abundances and richness of zooxanthellate octocorals, and the shift from zooxanthellate to azooxanthellate octocoral communities, may act as useful indicators of water clarity in regions where long-term water quality data are unavailable.

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    • "Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License 2014; McClanahan et al., 2012; Palumbi et al., 2014) and anthropogenic disturbances, especially increases in human activities and associated development (West and Woesik, 2001; Wolanski et al., 2009; Hughes et al., 2010). In many cases, these declines have been linked to human induced perturbations that influence gradients of water quality and levels of exploitation that lead to increased sea surface temperature (SST) and atmospheric CO 2 (Fabricius, 2005; Pandolfi et al., 2005; Fabricius and McCorry, 2006; Richmond et al., 2007; Doropoulos et al., 2012; Logan et al., 2014). Recently, local and regional risk assessments have ranked the degree of vulnerability of reefs to anthropogenic stressors based primarily on potential landbased sources of disturbances (Burke and Maidens, 2004; Nyström et al., 2000; Wolanski et al., 2009). "
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    • "g . Hong Kong ; Fabricius and McCorry , 2006 ) and in Australia ( e . g . "
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