April 7, 2021

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Written by Madison Churchill; photos by Hannah Gabrielson


Donned in thick neoprene and extra-long fins, we dive below the surface. One breath at a time takes us deeper into an underwater world, bringing everything into focus with each descent. We are freediving at Lime Kiln State Park on San Juan Island, a historically thriving kelp forest that’s now under threat. What we see now is alarming. One dip beneath the surface reveals a barren of sea urchins as far as the eye can see. These spiny invertebrates serve their function in small numbers, but when left unchecked, can devour kelp like no other. Some stalks of kelp have been spared and continue to grow, but there’s been a clear shift. Something is out of balance.

We are freedivers from PNW Protectors, an organization dedicated to conserving Salish Sea marine life. Over the past few years, we have been returning to the same dive sites to document the changes in the kelp forest. While there is still ample biodiversity to be seen here, it’s apparent that something in the environment is changing rapidly. We have now begun to look to their natural predators, or lack thereof, as a possible clue as to why the urchins are becoming so invasive.

 

PNW Protectors co-founder Snow, observing a purple sea star while freediving off San Juan Island (c) Hannah Gabrielson

 

The Salish Sea hosts an incredible number of species interactions. Everything here is connected, from the tiniest nudibranch to the great orcas who patrol our coasts. In an ecosystem that has self-regulated for millennia, there’s cause for concern when one species begins to dominate. Marine mammals like otters who traditionally eat urchins are becoming more of a rarity in these waters, but they aren’t the only absent species. One slow but effective predator that’s undergone a massive population hit, is the sea star.

 

Sea stars can often be found hunting urchins (c) Hannah Gabrielson

 

Throughout the past decade, sea stars around the world have been dying off in exponential numbers. Sea Star Wasting disease is a condition that is still largely misunderstood and kills sea stars at an accelerated rate. While there are a few working theories, scientists don’t definitively know what causes this condition, which results in an oozing gelatinous effect on the star’s body, causing their limbs to appear to melt. Sea stars, especially large ones like sunflower stars, normally predate on urchins. Historically, this has helped keep the population in check, but their recent absence has coincided with a spike in urchin numbers. 

 

Sea urchins pose threat to kelp forests in great numbers (c) Hannah Gabrielson

 

This ecological shift is more serious than just a spiny seabed. These urchins have a voracious appetite for kelp, and can quickly decimate an entire kelp forest. In turn, this impacts all of the other species that reside in these forests. The deep interconnectedness of this habitat means it is largely self-regulating, but this can create massive repercussions when one species is removed. 

 

Purple sea star at high tide (c) Hannah Gabrielson

 

These kelp forests hold immense biodiversity and create ocean communities that are so full of life. Everywhere you look underwater, you see unique species of fish, invertebrates, and mammals who’ve made their home in the kelp. Even the kelp itself has the ability to produce oxygen and sequester massive amounts of carbon, making it an important tool in the fight against climate change.

 

Bull kelp forest off San Juan Island (c) Hannah Gabrielson

 

Mission Blue’s recent designation of the Salish Sea as a Hope Spot is a leap in the right direction. If we can show the world how truly dynamic and productive this ecosystem is, we still stand a chance at repairing the damage and loss of biodiversity that we are seeing. We will continue documenting this habitat and advocating for more stringent regulation and protection. Our hope at PNW Protectors is to continue documenting this ecosystem and work with local scientists and lawmakers to help manage and protect this critical habitat. With this new Hope Spot designation, we can begin working towards revitalizing this truly sacred ecosystem. 

Madison Churchill, editor for The Marine Diaries, research diver for PNW Protectors.

Hannah Gabrielson, photographer and research diver for PNW Protectors.

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