Raw Data and Parametric tests.

Caribbean reefs have experienced significant declines in live coral cover due to extreme events such as bleaching and disease outbreaks. However, the effects of chronic disturbances, such as long-term pollution, are less frequently assessed.This study examines the Barú reef in the Colombian Caribbean, which has maintained relatively good live coral cover despite being exposed to the chronic influence of the Magdalena River for approximately 70 years. Through the Dique Channel, this river reduces water quality by introducing high temperatures, low salinity, high sediment loads, reduced light penetration, excess nutrients, pathogens, and heavy metals. This makes the site ideal for evaluating multiple causes of coral mortality, assessing overall reef health, and identifying species that are either tolerant or vulnerable to chronic stressors.In 2014, researchers surveyed 2,339 coral colonies to determine the prevalence and severity of 13 signs of coral deterioration, categorized into: (1a) transmissible infectious diseases (WPD, WBD, WPX, BBD), (1b) non-transmissible, non-infectious diseases (DSD, YBD, tumors), (2) bleaching, (3) biotic interactions (overgrowth, macro-bioerosion, predation), and (4) physical damage (fragmentation and overturning). Out of the 35 scleractinian coral species recorded in the area, 31 were affected. The study found that 40% of colonies showed signs of deterioration, with a severity of 7% coral tissue loss, particularly in shallow (0–8m) and deep zones (15.1–30m).The primary cause of coral mortality was biotic interactions, particularly bioerosion, followed by overgrowth and predation. To a lesser extent, diseases (fungal infections, DSD, WBD, WPD, WPX, YBD, BBD), bleaching, and physical damage also contributed to coral decline. Species with the highest prevalence and severity of deterioration included <i>Orbicella faveolata, O. annularis, Agaricia tenuifolia, A. agaricites, A. lamarcki, Porites astreoides, Montastraea cavernosa, Pseudodiploria strigosa, O. franksi, Siderastrea siderea,</i> and <i>P. porites</i>. In contrast, more resistant species included <i>Favia fragum, Eusmilia fastigiata, Dichocoenia stokesi, Agaricia undata, Meandrina danaana, Stephanocoenia intersepta, Scolymia spp., Isophyllia spp., Madracis spp.,</i> and the zoantharian <i>Palythoa sp.</i>The findings suggest that chronic stressors, particularly freshwater discharge, are disrupting biotic interactions, leading to significant coral tissue loss and driving the ecosystem toward a phase shift, threatening reef-building species. This study highlights the importance of simultaneously monitoring multiple causes of coral mortality over different time scales, rather than focusing solely on extreme events like ENSO, bleaching, or disease outbreaks.