The importance of sea stars 

Sea stars play a crucial role in ecosystems, with their work often going unnoticed. Although they may not produce food or pharmaceuticals, they are key players in coastal waters. Sea stars (notably sunflower stars and northern sun stars, which have taken a hard hit from SSWD) maintain healthy kelp forests and rocky intertidal zones by keeping urchins, mussels, and barnacles in check. Kelp forests and intertidal zones are habitats for commercially important fish species and shelter coastlines from wave action while increasing ocean productivity. Well-loved species like otters also make their homes in kelp forests and surrounding rocky ecosystems, while orcas use the areas to hunt. As keepers of the kelp, sea stars have been dubbed a “keystone species,” meaning they disproportionately impact the ecosystem around them relative to their population size. Sea stars are such a prominent source of biological control that the keystone species concept was modelled after the dynamics of ochre stars (Pisaster ochraceus) in the rocky intertidal zone.

Despite their importance in maintaining marine ecosystems (even with our updated theories), we have a long way to go before we can identify any verifiable cause of SSWD. Some researchers have undertaken the vital role of finding a cause, but only a select few. Because sea stars are not “commercially viable” organisms, providing little direct economic value, funding for researching their conservation is limited.

Looking forward, a collaboration between Canadian and US research groups facilitated through The Nature Conservancy has led to promising advances in the field, and Gehmen is hopeful that her team will have an answer for a causative agent in the near future. While the Hakai Institute continues to focus on the “how” of SSWD,  Bates predicts that with “shifts in disease, pests may be one of the biggest impacts of changing climate,” with a focus on the involvement of pests and parasites as well as the wider repercussions of disease impacting such an important species.  

In the US, the Multi-Agency Rocky Intertidal Network (MARINe) is also tackling the challenge of pinning down the cause of SSWD. The team is taking a broader approach, studying the impact of sea star mortality events on surrounding communities and developing citizen science programs for monitoring local populations. Carrie Melissa Miner, an Academic Specialist with UC Santa Cruz and researcher at MARINe, says that instances of SSWD are difficult to study due to the limited stress responses that sea stars exhibit. “When sea stars are observed with lesions or tissue necrosis, particularly when there are just a handful of individuals, we cannot be sure whether symptoms are a result of disease or from another cause such as injury incurred from a predation attempt that exposed tissue to bacteria/infection,” she says. So, whether sea stars are experiencing low salinities, high temperatures, or even diseases is hard to distinguish. In addition to the ambiguous cause of SSWD, it is a widespread and sporadic challenge. “For geographically expansive events like SSW, a coordinated, collaborative effort among scientists, resource managers, and community science groups is essential for documenting the extent of impact,” says Miner. This means collecting data that can be compiled into long-term data sets, which are crucial in identifying ecological regime shifts and predicting changes in ecosystem dynamics.

Sea Star Wasting Disease highlights the inadequacies of funding systems and the deficiencies in disease research approaches. Gehman and her graduate student Grace Crandall point out the need for new frameworks for studying diseases that may have multiple causes because, at the moment, “governing bodies overseeing the ecology and evolution of disease want to know that you’re studying an infectious disease before giving funding” says Gehmen. However, she explains that past techniques of using controlled infection studies aren’t applicable in cases where there might be many different factors working in tandem to trigger an immune response or in cases where stress responses in the organism are limited. According to her, “ it can take about 10 years to find the cause of marine diseases” due to a lack of a “baseline for what’s normal in marine invertebrates.” Gehmen and Crandall emphasize the continued need for research into the physiological and ecological consequences of SSWD despite a lack of clear cause because, as Crandall puts it, “there’s more to every organism than just the organism itself.”