Signs of Disease Versus Mechanical Damage in the Acropora palmata Reef Formation, Isla Aguja—Colombian Caribbean

Abstract

Coral diseases have contributed to the decline of coral populations in the Colombian Caribbean. One of the main causes is the infection of pathogenic bacteria, which are transported through marine currents and deposited in the sediment, making it a potential vector and reservoir. In the Torín sector of Isla Aguja, there is an important reef formation of Acropora palmata influenced by river discharges with possible impacts on their condition. To evaluate whether signs of the disease were reducing the population, in 2019, the formation was delimited, and monthly surveys were performed in 65 tagged colonies to calculate the incidence and prevalence of white pox in the population. Samples of water, sediment, healthy mucus and disease mucus were collected to isolate bacterial members and characterize them through amplifications of the V1–V3 hypervariable region of the 16S gene. Because of pandemic restrictions, monitoring was restarted in September 2020 and ended in December 2021, recording only the appearance of signs of disease. Nineteen bacterial strains were isolated. Enterobacter cloacae was found in water and disease mucus, Klebsiella variicola was found in healthy mucus and disease mucus, Klebsiella pneumoniae was found in water and healthy mucus, and Staphylococcus aureus was common in sediment and healthy mucus. Escherichia coli was found only in water. Signs of disease were frequent, with low prevalence but a rapid and evident natural recovery of the colonies, thus not constituting, yet, a threat to the reef formation of A. palmata. In contrast, the gillnets registered on four occasions between 2019 and 2021 caused the breakage of large colonies that impacted the population. It is urgent to establish management strategies for this local formation or strengthen surveillance activities that ensure good fishing practices to protect and prevent impacts on these species.