Sea star wasting disease demography and etiology in the brooding sea star Leptasterias spp.

Noah Jaffe,Renate Eberl,C Sarah Cohen,Jamie Bucholz,Heather M Patterson

doi:10.1371/journal.pone.0225248

Noah Jaffe, Renate Eberl + Show 3 more

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https://doi.org/10.1371/journal.pone.0225248

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Abstract

Sea star wasting disease (SSWD) describes a suite of disease signs believed to have led to catastrophic die-offs in many asteroid species, beginning in 2013. While most studies have focused on large, easily visible sea stars with widely-dispersing larvae, less information is available on the effect of this disease outbreak on smaller sea star species, such as the six-armed sea star Leptasterias spp. Unlike many larger sea stars, Leptasterias brood non-feeding young instead of broadcast-spawning planktonic larvae. Limited dispersal and thus limited gene flow may make these sea stars more vulnerable to local selective pressures, such as disease outbreaks. Here, we examined Leptasterias populations at sites along the California coast and documented abundance changes coincident with recent Pacific coast SSWD in 2014. Detection of Leptasterias in central California declined, and Leptasterias were not detected at multiple sites clustered around the San Francisco Bay outflow in the most recent surveys. Additionally, we categorized disease signs in Leptasterias in the field and laboratory, which mirrored those seen in larger sea stars in both settings. Finally, we found that magnesium chloride (MgCl2) slowed the progression of physical deterioration related to SSWD when applied to sea stars in the laboratory, suggesting that MgCl2 may prolong the survival of diseased individuals.

Highlights

Since 2013, sea star wasting disease (SSWD) has affected over 20 different species of sea stars on both the east [1] and west coasts of North America [2,3,4,5,6,7], and has caused the largest epizootic of marine invertebrate wildlife currently known [6]
We used four different data sources available for sites in California: 1) timed counts (S1 Table “Cohen TC”), 2) Leptasterias-specific data from other projects that did not assess abundance via timed counts (S1 Table “Cohen other”), 3) published Leptasterias abundance data [32] (S1 Table “Jurgens et al.”) and 4) data from ongoing long-term rocky intertidal monitoring focused mainly on P. ochraceus [35] (S1 Table “Multi-Agency Rocky Intertidal Network (MARINe)”). 1) and 2) were long-term surveys focused on central California sites near San Francisco Bay, sites largely excluded by 3) and 4)
We report regional differences in detection in 2015–2016, with a notable absence of Leptasterias observations in at least five sites in a region associated with the San Francisco Bay outflow, spanning approximately 35 km of outer coastline extending both north and south of the Golden Gate Bridge (Fig 1 orange points; Fig 2; source data, as in Sup file: Cohen TC, Cohen other, MARINe)

Summary

Introduction

Since 2013, sea star wasting disease (SSWD) has affected over 20 different species of sea stars on both the east [1] and west coasts of North America [2,3,4,5,6,7], and has caused the largest epizootic of marine invertebrate wildlife currently known [6]. The scale and severity of impact on multiple ecologically important species of asteroids has caused great concern about ecosystemwide effects, leading researchers and managers to call for emergency measures to track disease effects and develop models to predict future disease outbreaks [8, 9]. Reports of SSWD pathology describe a range of gross morphological signs, including necrotic lesions, twisting rays, change in turgor, “melting” appearance, ray loss and eventual.

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