Turning up the Heat on Sea Star Wasting DIsease

A sea star wasting disease (SSWD) epizootic linked to a densovirus devastated populations of Asteroidea over thousands of miles of the North American Pacific Coast in 2013, 2014 and 2015. Time series monitoring of the keystone intertidal species Pisaster ochraceus from the San Juan Islands, South Puget Sound, and Washington outer coast, showed rapid progression of the outbreak, extremely high mortality rates in 2014, and continuing levels of wasting in the survivors in 2015. Peak prevalence of disease and mortality at 16 sites ranged to 100%, with a mean of 61%. Analysis of field surveys showed strong size-specific and temperature-dependent disease risk. In laboratory experiments increased temperature accelerated disease progression and differentially affected adult and juvenile ochre stars. Warm temperature anomalies recorded in the summer of 2014 may have contributed to the rate and extent of SSWD impacts in the San Juan Islands. A subtidal species, Pycnopodia helianthoides, is more severely affected and currently undetected in our San Juan Island surveys and many diver reports from California to SE Alaska. This raises the question of what the longer term biodiversity impacts will be from this epizootic