Exaiptasia longitudinal microbiomes across temperatures

Under global warming scenarios, the deterioration of host and microbiome health will likely co-occur across our coastal oceans, posing a significant threat to complex symbioses. Photosymbiotic invertebrates, such as corals, must manage a complex set of microbial partners, a challenge that becomes substantially more difficult under rising ocean temperatures. Despite the centrality of these organisms to reef ecosystems, the changes in microbiome under long-term decline and temperature stress remain poorly understood. To track the shift in microbiome communities over time under heat scenarios, we undertook a tiered experiment in which multiple populations of the cnidarian model Exaiptasia diaphana were monitored for host physiological stress. Examining a range, from current temperatures to future warming scenarios, across six months. Under these conditions, we find microbial networks that become increasingly well-connected at higher temperatures, and a small suite of potential indicator taxa that signal a host under heat stress well before population- level declines. Overall, we describe a highly dynamic microbiome with fewer than 1% of ASVs reliably linked to heat stress.