Sea Stars and Sea Star Wasting Disease

Introduction

Sea stars are one of the most abundant species to be seen along the coast of Vancouver Island, especially in the intertidal zone. Ochre stars (Pisaster ochraceus), bat stars (Asterina miniate), leather stars (Dermasterias imbricata), and spiny pink stars (Pisaster brevispinus) are currently the easiest to spot along rock formations, the sandy seafloor, and in tide pools. They brighten up the shores with pops of colour ranging from vibrant oranges, purples, blues, and reds.

For some quick scientific information, marine invertebrates are broken up into 8 different groups, or ‘phyla’ (phylum, sing.), based on specific characteristics. Sea stars belong to the phylum Echinodermata, which means ‘spiny skinned’, with one other major characteristic being they can all regenerate some part of their body! It is a well-known fact that sea stars can regenerate their limbs as long as part or all of the central disk is still attached – the central disk is what connects all limbs and surrounds the majority of the star’s organs. Regeneration is also enabled by each limb containing some vital organs. In fact, a severed limb with part of the central disk connected can regenerate into a whole new sea star.

Sea Star Wasting Disease

Sea Star Wasting Disease (SSWD) is “considered the largest epizootic outbreak of non-commercial marine life in history” by Tofino’s Strawberry Isle Marine Research Society. Around a decade ago, these sea stars were even more abundant alongside their larger cousins: sunflower stars (Pycnopodia helianthoides) and various sunstar species (Solaster sp.).Since 2013, the sea stars of the Pacific Northwest have been plagued by SSWD. This first wave of the disease caused drastic declines in abundance. This disease has affected populations of sunflower stars most severely, leaving sightings very rare, though no species was entirely unaffected. Every summer after 2013 showed outbreaks of SSWD, with 2018 being the next extreme year. Unfortunately, years of research and study still show no findings of an exact cause for this disease, though Sea Star Associated Densovirus is the proximate cause, as stated by the Oregon Department of Land Conservation and Development.

As well, the main epidemics of sea star wasting disease have appeared at the same time as the weather phenomenon known as ‘TheBlob’ and other heat waves occurred, leading many researchers to believe the resulting increase in water temperature is linked with SSWD. The diagram to the right indicates the 2015 temperature increases of up to 3oC just off the coast of British Columbia, Alaska, and Washington. Surprisingly, there was also an increase in infected stars during a cooler spell in Oregon.

This finding put a wrench in the theory claiming heat as SSWD’s trigger. In summer of 2021, there have been cases of a similar outbreak in California sea cucumbers (Apostichopus californicus) around Vancouver Island, though it is unknown currently if it is connected to SSWD and research is minimal at this time. SSWD causes sea stars to look like the name describes: like they are wasting away. Lesions will form on the arms and body first and then tissue will start to decay eventually causing limbs to fall off and, sadly, death. David Egan writes how some infected limbs that have severed will continue moving and will infect other stars it comes in contact with.

After the initial and subsequent outbreaks of SSWD since 2013, populations have not had a chance to sufficiently recover. Ochre stars and sunflower stars were hit the hardest; the Hakai Institute discovered populations in theSalish Sea had declined severely by 75% and 96% respectively by 2019.Both species are known as ‘keystone species’: a member of anecosystem whose existence is so crucial that elimination would causea massive shift and crash. With numbers of these important starsdropping each summer, the drastic changes to our local ecosystem willonly continue.

Sunflower Stars (Pycnopodia helianthoides)

Unfortunately, sunflower stars are essentially extinct from the majority of habitats they once thrived in. The large, multi-armed star could be easily spotted around piers and in the shallow waters of harbours and inlets across western coastlines. These stars are great predators despite their slow movements - they move 110m/360ft per hour, making them one of the fastest stars in the world! Sunflower stars prey on many marine invertebrates such as sea cucumbers, clams, scallops, and sea urchins. This loss of population created an explosion in the sea urchin population. This paired with the loss of the other major urchin predator, sea otters, has led to the loss of kelp forest habitats (but that is a blog post for another day).

Ochre Sea Stars (Pisaster Ochraceus)

Ochre stars are still one of the most common stars in the areas we paddle, yet the outbreak in 2021 dramatically decreased the numbers to be seen in the Ucluelet Harbour. Temperatures in Ucluelet spiked to the high 30s (Celsius), an unprecedented high for our small coastal town alongside the massive outbreak. Prior to this, paddlers on our Ucluelet Harbour Tour could easily see many brightly coloured ochre stars against the rocks, but now guides and guests alike must look closely to spot them. Losing ochre sea stars has allowed the mussels in which they prey upon to increase as well, thus reducing the abundance of alga species and other marine invertebrates.

Author’s Observations

When I started at Majestic in 2019, Ucluelet Harbour was filled with ochre stars and leather stars. Most rocks were almost completely covered by these creatures then; even at high tide the brilliant oranges and purples could be seen in great numbers below the water. Guests and guides alike were always thrilled to see the abundance of these creatures and could easily get close to see the detailed characteristics of these stars. During my time working with Majestic Ocean Kayaking as a guide, I cannot say I have seen a sunflower star. I remember seeing them frequently as a kid in the bay close to my home in Victoria, but I have not seen any there either in the past decade. As of May 2022, I have seen very few ochre stars in the Ucluelet Harbour in comparison to the vast number of stars seen in the past few years. I have also not noticed signs of SSWD in any stars. It saddens me to see such an incredible and important part of our ecosystem being decimated and I worry about what future summers have in store for sunflower and ochre stars.

Lasting Effects

The stunning biodiversity of the West Coast is severely threatened by SSWD. The domino effect of outbreaks to the destruction of kelp forests has very serious outcomes for not only that specific marine ecosystem, but also other nearby ecosystems and for humans as well. The kelp forests that grow in coastal areas from Alaska, through British Columbia, past California, and into Mexico are home to an immense variety of marine invertebrates, fish, and marine mammals. Sea otters (Enhydra lutris) use kelp to stay together while they rest and to swaddle their pups while the parent looks for food. Northern kelp crabs (Pugettia producta) climb giant kelp from depths of 175ft/53m to the surface snacking as they climb. Harbour seals (Phoca vitulina), California sea lions (Zalophus californianus), and Stellar sea lions (Eumetopias jubatus) hunt for their next meal in kelp forests. At least 150 species of marine invertebrates and fish call British Columbia’s kelp forests home. The recovery of sea stars is vital to the health of all the amazing creatures we share our homes with.

The important species of kelp such as giant kelp (Macrocystis pyrifera) and bull kelp (Nereocystis leutkeana) we are losing aid immensely in carbon sequestration. It is estimated that these larger species of kelp sequesters about 20 million tons of carbon each year, making up a significant part of the global total 19 gigatons.

Sea Star Wasting Disease has proven itself to be a tough opponent. Researchers throughout British Columbia, Alaska, and coastal United States have been looking into SSWD since 2013 with unfortunately little to show for their efforts. This elusive epidemic seems to only get worse as the years go on and there seems to be little to no solution. Without correction soon, sunflower stars coming closer and closer to functional extinction in our local waters with ochre stars heading for the same fate.

What Can We Do?

In order to help solve SSWD, we have to remain hopeful in finding a solution. For our readers who would like to assist more in Alaska, British Columbia, Washington, Oregon,or California, consider contacting a localresearch program to volunteer or donate. For those who spend time in these coastal pacific towns, it is worth keeping an eye on your local sea star species – ochre stars, especially – to check for signs of sea star wasting disease throughout the summer. For Port Alberni, Ucluelet, and Tofino locals, the Strawberry Isle Marine Research Society (SIMRS) has hosted an incredible volunteer program over the past few years aiming to cover more ground in the surveying of sea stars. They also have an online system in place to report sightings of sunflower stars including specific locations and details on their health.