Survival and physiological responses of corals exposed to elevated turbidity in the Varadero reef, Colombian Caribbean

The degradation of water optical properties, or increased turbidity, due to anthropogenic disturbances is a common phenomenon in coastal waters. The effects on the underwater light climate and the physiology of symbiotic corals, who largely depend on light to survive and maintain high calcification, have been relatively unexplored. This research describes the effects of the turbid plume of water from the Canal del Dique on the light climate, coral physiology and survival in Varadero reef. A reciprocal transplant experiment was conducted with fragments of Orbicella faveolata between a shallow area in Varadero (3.5 m) and a deeper reef area (12 m) with clear-water conditions, where total light exposure was comparable. The water column was strongly stratified in Varadero, which favors the isolation of the reef from the influence of the plume. Corals transplanted to Varadero had higher survivorship, potentially as a result of reduced light stress and increased heterotrophic nutrition. Their physiological traits suggest acclimation to low-light and limited autotrophic potential, which represents a risk for coral survival at greater depths. The results indicate that a further degradation of the water optical properties of the Cartagena Bay due to human disturbances in the Magdalena River basin and the coastal zone represents a threat to Varadero reef maintenance.