Coral reef encruster communities and carbonate production in cryptic and exposed coral reef habitats along a gradient of terrestrial disturbance |
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Authors: | J Mallela |
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Institution: | (1) Department of Environmental and Geographical Sciences, Manchester Metropolitan University, Manchester, M1 5GD, England;(2) Department of Life Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago |
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Abstract: | Encrusting calcareous organisms such as bryozoans, crustose coralline algae (CCA), foraminiferans, and serpulid worms are
integral components of tropical framework-building reefs. They can contribute calcium carbonate to the reef framework, stabilise
the substrate, and promote larval recruitment of other framework-building species (e.g. coral recruits). The percentage cover
of encrusting organisms and their rates of carbonate production (g m−2 year−1) were assessed at four sites within a coastal embayment, along a gradient of riverine influence (high-low). As the orientation
and type of substrate is thought to influence recruitment of encrusting organisms, organisms recruiting to both natural (the
underside of platy corals) and experimental substrates were assessed. The effect of substrate exposure under different levels
of riverine influence was assessed by orientating experimental substrates to mimic cryptic and exposed reef habitats (downwards-facing
vs upwards-facing tiles) at each site. Cryptic experimental tiles supported similar encruster assemblages to those recruiting
to the underneath (cryptic side) of platy corals, suggesting that tiles can be used as an experimental substrate to assess
encruster recruitment in reef systems. Encruster cover, in particular CCA, and carbonate production was significantly higher
at low-impact (clear water), high wave energy sites when compared to highly riverine impacted (turbid water), low wave energy
sites. Cryptically orientated substrates supported a greater diversity of encrusting organisms, in particular serpulid worms
and bryozoans. The inverse relationships observed between riverine inputs and encrusters (total encruster cover and carbonate
production) have implications for both the current and future rates and styles of reefal framework production. |
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Keywords: | Recruitment Coral reef framework Experimental tiles Sedimentation River runoff Encrusters |
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