Sea stars are a common sight on the Pacific coast, you don’t even have to be a diver as you can usually find one in a tide pool. But UC Santa Cruz explained that beginning in 2013, a mysterious disease crippled sea star populations up and down the U.S. west coast. Over a matter of months, many sea star species died in record-breaking numbers and now scientists say it’s the largest disease epidemic ever observed in wild marine animals. Early signs of SSWS include lesions and tissue decay, which can spread along the sea stars’ arms, leading to limb loss and eventual death, often in a matter of days. Initially, scientists weren’t sure what caused the disease known as sea star wasting syndrome (SSWS) but a study published in the journal Science Advances is showing that climate change and warming ocean waters may be to blame for making the disease so deadly.
Joe Gaydos, the science director at the UC Davis’ SeaDoc Society and one author of a study told NPR that “What we think is that the warm water anomalies made these starfish more susceptible to the disease that was already out there.” NPR also explained that while the study did not examine why warmer water might make sea stars more susceptible to disease. The authors hypothesize that the animals’ relatively simple immune systems might be weaker when sea stars get hot.
Why This Matters: The mass die-off of sea stars has had a big impact on the Pacific marine ecosystem. As the study explained, sea stars are an important predator of sea urchins, and urchin populations who lack predators can expand and threaten kelp forests and biodiversity. In locations where sea stars are the primary predator or urchins, their decline has caused urchin populations to explode and kelp to rapidly diminish. Kelp forests are incredibly important for the Pacific coast and as UC Santa Barbara explained, can be seen as an extensive underwater solar city where the kelp forest provides food and the “building” structure for many of its inhabitants. Because seaweed is a primary producer and makes its food from the sun, many organisms feed on the kelp and then, in turn, feed other animals. Kelp can also prevent beach erosion and because of its photosynthetic properties might be a huge asset in the fight against climate change.