Abstract

Outbreaks of stony coral tissue loss disease (SCTLD) have occurred sporadically in the Caribbean. The spatial distributions of these outbreaks are inconsistent with natural transport processes and often occurred near ports. suggesting the potential for ship-mediated transport of the disease. Waterborne transmission of SCTLD has been demonstrated. indicating infected corals shed the unknown causative agent into the environment. Assuming this agent is microbial. its ability to form biofilms on and within ships (e.g.. ballast water tanks) could represent a potential transport mechanism for the disease. Here we investigated whether coral-shed microbes are capable of biofilm formation and whether source coral differences (e.g. health status) are discernible in these biofilm microbial communities. Stainless steel plates (~7.50 cm x 5.75 cm) were cleaned. autoclaved. and added to mesocosms (n = 15) containing ~18L of UV-treated. 0.2 um-filtered seawater and either: SCTLDinfected corals (n = 10). healthy corals (n = 4). or no corals (n = 1). Plates were exposed to mesocosm water for three days. then preserved in RNAlater. Adhered biofilms were removed with sterile razor blades and a sterile buffer rinse. DNA was extracted and sequenced using bacterial / archaeal primers. and resulting sequences were analyzed with QIIME2. We determined that coral-shed microbes formed biofilms consisting of highly diverse microbial communities. and these communities reflect differences between source mesocosms. While it is currently unknown if the SCTLD pathogen is a member of these biofilm communities. this work suggests biofilms warrant additional investigation as a contributing factor in the spread of SCTLD.

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