Oceanic Pandemics from Foundation to Keystone Species

While an epidemic as wide-ranging and destructive as COVID-19 is new to human society, large-scale, destructive disease outbreaks are an age-old process in our oceans. These outbreaks are rapidly accelerating with climate change. Infectious disease pandemics of the last 50 years have reshaped coral reefs, seagrass beds, our Pacific shorelines and aquaculture practices on salmon and shrimp farms. Disease outbreaks are transformative when they attack foundation species like seagrasses or keystone predators like seastars.

The ongoing seastar wasting disease outbreak, first observed in 2013 and fueled by the heat wave of 2015, has driven a pivotal predator to near extinction along much of the west coast. The extirpation of this keystone, triggered a trophic cascade that has transformed kelp-bed ecosystems and their dependent fisheries in California.

An ongoing eelgrass disease outbreak, driven in part by an oceanic heatwaves in 2015 and 2016 in the pacific northwest, is affecting critical eelgrass habitat from San Diego to Alaska. Using a surveillance toolbox that includes aerial drones, artificial intelligence, remote sensing and molecular diagnostics, we monitor this eelgrass disease outbreak on a latitudinal scale. Time series data from wild eelgrass meadows show that the disease outbreak expands in response to marine heatwaves. Sentinel plant experiments reveal that the disease spreads through rapid waterborne transmission in the wild, with new infections accumulating over several weeks during summer.

Against this backdrop of increasing disease outbreaks in the ocean, our improving knowledge of the interactions between host species and their infectious micro-organisms is laying the foundation for improved management, taking advantage of nature's capacity for fighting off pathogens. New research showing tropical and temperate seagrasses can significantly reduce bacterial pathogen load in today's oceans reveals the way forward to discover more of nature's superpowers for stewardship of marine microbes and pathogen reduction.