Coral reefs are brimming with biological diversity, but most are threatened by multiple stressors - climate change, pollution, invasions. Sponges on reefs are the most primitive animal but they may still educate us on fundamental biological concepts, such as the role of microbial symbioses (foreign cells that living with larger organisms but causing no harm). A marine epidemic called "sponge orange band" (SOB) disease of the common iconic "barrel" sponge, Xestospongia muta, re-emerged in South Florida in April 2012. Gross SOB symptoms appeared as bleaching, and crumbling of the affected sponge tissues, followed by rapid death of the whole sponge individual. During this outbreak, anecdotal reports and video surveys carried out by REEF-RESCUE.org found that 10-20% of local large barrel sponges died or were adversely affected. The SOB condition has been previously witnessed periodically, and has been histologically described in scientific studies. However, the question remains "What is the cause of this blight and destruction?" TO DATE, NO CLEAR CAUSE OR PATHOGEN HAS BEEN IDENTIFIED. Our laboratory made sample collections of diseased tissue during this outbreak, but until adequate funds are obtained, the Xestospongia muta samples will remain mostly frozen archived and unanalyzed. Recent studies and breakthroughs in DNA and RNA sequencing technologies are revealing the inner mechanisms of how our cells and bodies work. Therefore, the overall goals of this project are to identify and characterize the SOB marine epizootic and apply molecular tools to help predict and prevent future SOB outbreaks. Using a multi-disciplinary approach of 16Samplicon library sequencing, bacterial metagenomics and genomics, Illumina RNAseq, microscopy, and FISH, we aim to definitively determine what pathogen(s) and/or environmental factors are responsible for this disease and how it affects host physiology. We also will develop new diagnostic tools to identify and quantify the causal factor(s).