Evaluating coral ecosystem health in Aruba – the development and future of Aruba’s coral reefs

Abstract

Hard coral cover throughout the Caribbean has been in decline for at least fifty years due to large-scale disturbances such as White-Band-Disease, die-off of sea urchin populations, and coral bleaching. Local stressors, like coastal water pollution and eutrophication, have amplified this decline. The ecosystem services of coral reefs offer opportunities for tourism, recreation, employment and biodiversity. In Aruba, coral cover is naturally low due to a high abundance of sand, leaving less benthic area available for coral growth. The outbreak of stony coral tissue loss disease in Aruba in December 2022 presented a new threat for local coral reef communities. Assessment of coral cover is necessary to devise methods to mitigate the stressors that corals in Aruba face. In this study, 12 sites were identified that reflect the heterogeneous status of Aruba’s coral reefs for investigation to examine coral health and the development of the ecosystem since 2019. While on average, coral cover remained constant, almost half of the surveyed sites showed an increase in (macro)algae cover coupled with a decrease in coral cover, indicating stress on coral reefs. Five out of 12 sites showed a degrading ecosystem trend within the last four years. By assessing the spread of stony coral tissue loss from the surveyed data, a metric for the development of Aruba’s coral reefs was determined. We found that nine coral species, including important reef-building coral species such as Montastraea cavernosa, Orbicella annularis and Orbicella faveolata have been infected by the disease. About six months after the outbreak of the disease,  13 % of all coral showed signs of the disease. This number is expected to increase, indicating strong changes for Aruba’s coral reefs in the near future.