Warm waters, disease responsible for predator sea star decline

Between 2013 and 2015, the sunflower starfish, a predator within the waters of the North Pacific, experienced a massive population drop. Citizen science diving surveys show that the sunflower starfish could not grapple with a serious disease that took hold of the North Pacific during these two years.

Now, the authors of a new study, put forth by the American Association for the Advancement of Science, have reported a link between the decline of sunflower star population within shallow waters and warmer sea surface temperatures.

The sea star wasting disease (SSWD) killed off a large amount of starfish along the west coast of North America, from Alaska to Mexico, between 2013 and 2015. The disease was carried by a sea star-associated densovirus and wreaked havoc in the intertidal zone. However, the effects of the North Pacific SSWD in the subtidal zone was unclear, except for the fact that scientists knew the sunflower starfish had dramatically declined in abundance.

Drew Harvell and his colleagues recruited divers between California and British Columbia to help report sunflower star population change. 10,956 diver surveys of shallow waters completed between 2006 and 2017 have shown a decrease in sunflower star abundance. Between 2006 and 2014, divers reported seeing an average of 100 sunflower stars during their dives. However, after 2014, 60-100% of diver surveys between California and Oregon reported zero to one sunflower star sightings per shallow water dive.

Authors further predict, based on 8,968 bottom trawls from California to Washington from 2004 to 2016, that the sunflower star’s biomass in deep offshore water has decreased 100% between 2013 and 2015 within this region. This decline matched up with the timeline of abnormally warm sea surface temperatures.

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By Olivia Harvey, Earth.com Staff Writer

Image Credit: Ed Gullekson