Ochre star mortality during the 2014 wasting disease epizootic: role of population size structure and temperature

Abstract

Over 20 species of asteroids were devastated by a sea star wasting disease (SSWD) epizootic, linked to a densovirus, from Mexico to Alaska in 2013 and 2014. For Pisaster ochraceus from the San Juan Islands, South Puget Sound and Washington outer coast, time-series monitoring showed rapid disease spread, high mortality rates in 2014, and continuing levels of wasting in the survivors in 2015. Peak prevalence of disease at 16 sites ranged to 100%, with an overall mean of 61%. Analysis of longitudinal data showed disease risk was correlated with both size and temperature and resulted in shifts in population size structure; adult populations fell to one quarter of pre-outbreak abundances. In laboratory experiments, time between development of disease signs and death was influenced by temperature in adults but not juveniles and adult mortality was 18% higher in the 19°C treatment compared to the lower temperature treatments. While larger ochre stars developed disease signs sooner than juveniles, diseased juveniles died more quickly than diseased adults. Unusual 2–3°C warm temperature anomalies were coincident with the summer 2014 mortalities. We suggest these warm waters could have increased the disease progression and mortality rates of SSWD in Washington State.

Managing marine disease emergencies in an era of rapid change

“…Most recently, a wasting disease outbreak decimated populations of sea stars (Asteroidea) in intertidal and sub-tidal regions of eastern and western North America [4]. In addition to uncounted deaths in the east, millions of individuals died in California, Oregon and Washington in 2013 and 2014 and more are dying now in Alaska [5]. The high mortality rate, unprecedented geographical scope and multi-species scale of impacts caught the scientific and resource management community by surprise, emphasizing that we lack an effective framework for the detection and management of marine diseases.…”

Investigating the Complex Association Between Viral Ecology, Environment, and Northeast Pacific Sea Star Wasting

“…An apparent conundrum of SSWD is the presence (and in at least one asteroid species the active replication) of SSaDV in a large proportion of asymptomatic asteroids surveyed in 2013-2014, and detection of SSaDV in museum specimens since at least 1942, well before SSWD was first observed (Hewson et al, 2014). The rate of SSWD disease sign onset has been linked in experiments and some locations to elevated temperature (Bates et al, 2009;Eisenlord et al, 2016;Kohl et al, 2016), however elsewhere SSWD prevalence negatively correlated with water temperature (Hewson et al, 2014;Menge et al, 2016). SSWD is also associated with the frequency of heterozygous EF1α in P. ochraceus (Wares and Schiebelhut, 2016) and transcriptomic analyses of EF1α mutants suggest that these individuals have a greater cellular response to temperature stress (Chandler and Wares, 2017).…”

Marine disease impacts, diagnosis, forecasting, management and policy

“…Guo et al [10] review how marine diseases interact with the surprisingly sophisticated molluscan innate immune system, with an emphasis on how coevolved resistance degrades when animals (and their diseases) invade new regions. Eisenlord et al [11] investigate the role of temperature in the sea star wasting disease epizootic and the crash of sea stars following the outbreak. Groner et al [12] conclude this topic by synthesizing marine epizootic mathematical models, with a focus on sea louse-salmon interactions.…”