St. Eustatius GCRMN Caribbean Final Report 2018

Twenty-two sites across four monitoring zones of St. Eustatius’s marine ecosystem were assessed using the Global Coral Reef Monitoring Network Caribbean Initiative (GCRMN-Caribbean) guidelines between June and August 2018. The protocol extracted data that indicated the biomass of key fish species and overall reef health including but not limited to relative abundance of macroalgae and hard coral, coral disease prevalence, coral recruit density and rugosity to name a few. Using the Reef Health Index (McField and Kramer 2007), St. Eustatius’ coral reef ecosystem is in “fair” condition (RHI Score = 3.25). Coral cover continues to decline slowly from previous estimates (2015 = 5.19%, 2016 = 4.99%, 2017 = 4.73% and 2018 = 4.21%) with macroalgae continuing to dominate with an insignificant decrease since 2017 (2015 = 27.93%, 2016 = 27.92%, 2017 = 25.33% and 2018 = 23.89%). This decrease has been replaced by an increase in turf algae and cyanobacteria. Overall increase in fish biomass and density hints at the success of the marine reserves and the spillover effect. Herbivorous fish (Parrotfish/surgeonfish) biomass. Populations of these key species are relatively the same when compared to other Eastern Caribbean territories. Biomass of groupers and snappers have increased drastically compared to 2017 but these findings are statistically insignificant, possibly due to sampling error. Due to an increased sampling effort, two additional survey sites, benthic cover for reef building corals increased but coral cover was not affected. Porites astreoides, remains the dominant species on Statia’s reefs due to its successful reproductive strategy as a hermaphroditic brooder with it accounting for 20% of the species composition of observed recruits. Key reef building genera such as Orbicella spp, Montastrea and Pseudodiploria spp which have a benthic cover range between 0.86 – 15.31% only accounted for 0-1 % per species of recruits observed. This implies that the future of corals on Statia’s reefs is gravely uncertain as the abundance of new reef building recruits are too low. Mitigative and restorative measures are desperately needed. Focus should be placed on diversifying coral restoration techniques that target reef building genera such as Orbicella and Psuedodiploria along with the repopulation of Diadema antillarum. Diadema densities recorded during this survey effort where < 1 individual/m.

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