Sea stars keep kelp forests alive

This December 2017 video says about itself:

Sunflower Seastar: Terrifying Predator? | National Geographic

This animal is more than three feet wide and one of the fastest animals in its biome! It’s also a very efficient scavenger.

From Simon Fraser University in Canada:

Sea stars critical to kelp forest resilience

August 13, 2018

A study by Simon Fraser University resource and environmental management researcher Jenn Burt reveals that sunflower sea stars play a critical role in the resilience of B.C. [British Columbia] ‘s kelp forests, which are among the most productive ecosystems on Earth. Similar to land-based forests, kelp forests provide essential habitat for species and also help remove CO2 from the atmosphere.

Burt and her team discovered sea otters and sunflower stars are complementary predators of sea urchins, which inhabit rocky reefs and voraciously eat kelp. Without natural predators, sea urchins quickly devour entire kelp forests.

“We showed that sea otters feed on large sea urchins, whereas the sunflower sea stars eat the small and medium-sized urchins that otters ignore”, says Burt. “We observed kelp density was highest at reefs with both sea otters and sunflower stars.”

The researchers made this discovery after Sea Star Wasting Disease killed 96 per cent of the sunflower star biomass on the Central coast in 2015 and 2016. During this period there was a 311 per cent increase in small and medium-sized sea urchins, which corresponded to a 30 per cent decrease in kelp density.

Burt says ecological surprises such as mass mortality events can reveal new insights into species interactions and ecosystem dynamics. She says these will become more important to learn from as climate change and other stressors make our future ocean ecosystems more unpredictable.

The combination of ocean warming and an infectious wasting disease has devastated populations of large sunflower sea stars once abundant along the West Coast of North America in just a few years, according to research co-led by the University of California, Davis, and Cornell University published Jan. 30 in the journal Science Advances: here.

California sheephead and spiny lobsters may be helping control sea urchin populations in Southern California kelp forests, where sea otters — a top urchin predator — have long been missing, according to a new study. The research provides new insight into the complex predator-prey relationships in kelp forests that can be seen in the absence of sea otters: here.

Sea urchins have gotten a bad rap on the Pacific coast. The spiky sea creatures can mow down entire swaths of kelp forest, leaving behind rocky urchin barrens. An article in the New York Times went so far as to call them “cockroaches of the ocean.” But new research suggests that urchins play a more complex role in their ecosystems than previously believed: here.