Morphological characterization of growth anomalies on coral genera Acropora and Pachyseris

Outbreaks of coral diseases have recently emerged as a significant threat for the fitness and survival of corals, exacerbated by climate change effects. Factors like ocean warming and acidification are identified as significant environmental stressors that may heighten the susceptibility of corals to diseases. In recent times, attention is rising towards a particular type of coral lesion, growth anomalies (GAs) or skeletal tissue anomalies. The etiology of such lesions is still under investigation and poorly known, with potential links to anthropogenic stressors and extreme temperature conditions. GAs are recognized as true tumors that not only impact the morphology of the polyps but also disrupt biological functioning, compromising the reproductive capabilities, feeding abilities and the capacity of defending against external agents. Although they are becoming more common and are observed worldwide, there is still a lack of comprehensive understanding regarding their presence in the Maldivian area. Here, we present the first evidence of four distinct GAs across three coral species, Acropora sp., Montipora sp., and Pachyseris speciosa, observed across multiple locations within the Maldivian Archipelago. Moreover, we analyzed samples of tumoral and healthy skeleton samples of two genera, Acropora and Pachyseris, throughout Scanning Electron Microscope (SEM) imagery. We investigated morphometrical parameters such as corallite dimensions and general structure, such as presence of columella and septa apperance. Although the results must be implemented by additional analysis, the outcomes of our study gave a first insight on differences in the morphology of growth anomalies and possible implications on coral survival.