Climate warming heats up the web of biological interactions and accelerates community change from the base and top of oceanic food chains. Warming oceans have fueled the decade long epidemic of sea star wasting disease, causing a top-down trophic cascade and massive changes to near-shore kelps from California to British Columbia. Our recent work unveils Vibrio pectenicida as a causative agent of sea star wasting disease and the decline of the sunflower star to endangerment. Knowledge of the causative microbe activates conservation breeding strategies and recovery actions for this species.  Our 12 year study of eelgrass-protist dynamics,  also shows a role for warming events in large decline of seagrasses.  Continental scale surveys reveal that the protist L. zosterae is a damaging pathogen, characterized by diverse strains varying in virulence and likely temperature sensitivity, from San Diego to Alaska. The host-pathogen interaction is embedded in wider community interactions, from facilitation by herbivores to a changing plant microbiome. A suite of models focuses on the interacting factors driving outcomes from the daily spatial scales of how infection begins at a single site to the continental, decadal scale in a changing climate. The future of this essential foundation species will depend on developing strategies for climate resilience through understanding the full scenario of biotic and abiotic influences.