Researchers Investigate Declines of Abalone, Sea stars, and Bull Kelp Beds

ODFW staff conducting snorkel surveys at Nellies Cove to document unusually high densities of purple sea urchins in shallow water rocky reef sites

ODFW’s Marine Resources Program received a federal grant to investigate recent disruption of ecological communities in rocky reef habitats along the southern Oregon coast.

The U.S. Fish and Wildlife Service provided $250,000 to support work by ODFW marine researchers to fill critical data gaps in population declines of abalone and sunflower sea stars and disruption of their primary habitat in kelp beds. This grant also provides needed equipment to measure changes in ocean temperature and oxygen levels.

Like other regions of the West Coast, Oregon observed a record-breaking marine heatwave beginning in 2013-2015. Coupled with unprecedented hypoxia (low ocean oxygen conditions) in 2019-2021, Oregon’s nearshore waters have experienced important ecosystem changes.

“The shift in nearshore ocean conditions coincided with mass mortality of sunflower sea stars,” said Steve Rumrill, ODFW Shellfish Program Leader. “We think that loss of these large and hungry multi-armed predators may be a contributing factor in the dramatic increase in numbers of purple sea urchins at many sites along the southern Oregon coast. Seaweed and kelp are the primary food sources for the urchins.”

Populations of red abalone have recently declined along the Oregon coast, in part due to loss of seaweeds and kelp as a source of food. -ODFW photos-

Marine scientists also observed reductions in the extent of bull kelp beds and declines in populations of abalone. Bull kelp beds are recognized as a high priority habitat essential to survival of sea stars, sea urchins, abalone, and numerous species of fishes.

“The magnitude of ecological changes to kelp bed habitat and their associated communities down along the south coast are unprecedented in recorded history” said Rumrill.

The new grant funds will support four integrated components of the research:

• Scientists will measure ocean oxygen and temperature conditions over the next two-years.

• SCUBA divers will conduct underwater surveys in shallow rocky areas to document populations of purple sea urchins, sea stars, abalone, resident fishes, seaweeds, and kelp.

• Local charter vessels will be used to conduct surveys with a remotely operated vehicle (ROV) in deep rocky reef sites.

• Aerial surveys and work from small boats will help document the location, spatial cover, and biomass of kelp.

Information generated by this research will help ODFW update the Oregon Nearshore Conservation Strategy and help identify an effective plan to address emerging concerns for the marine species, priority marine habitats, and impacts from climate change.