Abstract

Since its first appearance off Miami in 2014 following the dredging of Government Cut. stony coral tissue loss disease (SCTLD) has spread rapidly throughout Florida’s coral reef tract & to numerous Caribbean territories. It has been shown through transmission experiments & hydrodynamic modeling that the disease is waterborne & highly infectious at both local & regional scales. We conducted a high-replication transmission experiment to determine whether reef sediments can also serve as an SCTLD reservoir. Coral fragments in independent 0.5 L vessels with flow-through seawater were exposed to disease-inoculated reef sediments using entire infected colonies (communal inoculation) or ~5 cm2 coral fragments (acute inoculation). We identified that reef sediments were able to transmit SCTLD to fragments of the species Orbicella faveolata & Montastraea cavernosa. albeit at lower rates as direct contact with diseased coral tissue. Transmission rates differed between species & treatments. with the initial onset of SCTLD lesions occurring at 10.3 ±2.8 & 12.2 ±1.9 d following exposure to communally-inoculated sediments. Exposure to acutely-inoculated sediments. however. resulted in disease transmission within 22 h for both species. suggesting temporal/spatial variation in distribution of SCTLD pathogens in sediments. Histological examination confirmed the presence of SCTLD across all disease treatments & microbial community profiling identified taxonomic differences among healthy & diseased sediments. This experiment determined that reef sediments can serve as an SCTLD reservoir. indicating a critical need to understand the roles of coastal development activities (e.g. port dredging & beach renourishment) on SCTLD transmission. as well as to evaluate management actions to mitigate further spread of SCTLD throughout Caribbean reefs.

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