Coral predation versus herbivory
Started on February 10, 2017
Start: June, 2016
Coral reef restoration is an active act of conservation that requires a substantial investment of resources such as time and manpower. REEFolution is continuously looking for ways to improve coral growth and survival to make their restoration activities more cost-efficient. At numerous coral reef restoration initiatives around the world the current paradigm is to place coral nurseries on isolated locations far from natural reefs. Ewout Knoester, student at Wageningen University (MSc aquaculture and marine resource management), is looking at the effects of positioning the nursery structures near natural reef patches.
Positioning of coral nurseries near natural reefs places the cultured coral within reach of a diverse set of marine organisms, most notably reef fish. The expected impact of this is twofold: (1) herbivorous fish can help to keep the nursery structures clean by consuming unwanted fouling organisms (e.g. algae). The removal of these competitors is likely to enhance growing conditions for the corals. In contrast, (2) corallivorous (coral consuming) fish can impede growth and survival of corals through predation and the transmission of diseases. At pristine reefs, coral colonies thrive in the presence of an abundant fish community, including both herbivorous and corallivorous fish. Therefore, nurseries near natural reefs might experience better coral growth compared to isolated nurseries. The positive impact of herbivorous fish might outweigh the negative effects of corallivorous fish.
To test this, three structures (replicated 15-fold) were placed in the Wasini Channel: (1) an uncaged coral nursery structure that experiences both herbivory and corallivory, (2) a caged nursery structure that excludes fish and thus experiences neither herbivory nor corallivory and (3) an open cage structure (experiencing herbivory and corallyvory) to test for cage artefacts. It is expected that coral growth and survival will be higher in the uncaged and open-caged structure compared to the caged structure. If nurtured coral is indeed performing better near natural reef patches with their associated fish community, this information can be used to optimize coral nurseries while simultaneously reducing diver-mediated cleaning time and expenses.
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