HRAP Online Encyclopedia

Sea Stars

Not only are sea stars beautiful animals to look at, but they are also the apex predators of Pacific Northwest tide pools. As the top of the food chain, sea stars are incredibly important to the ecosystem. They keep the population of prey species in check, which helps the ecosystem stay balanced. Sea stars are a keystone species, which means that their presence keeps certain populations under control within their habitat. In the intertidal zone, sea stars are essential for controlling California mussel populations. Without sea stars present, mussel beds would completely overtake the rocks. Having sea stars around means that many mussels get eaten, which frees up space on the rocks for other marine organisms to live (anemones, other mollusks, etc.). Although sea stars are such voracious mussel predators, they cannot eat all of the mussels on the rocks. Sea star movement is limited by the height of the tides, since they are frozen in place when out of the water. When tides are low, it is easy to see a distinct line between where the sea stars can and cannot reach mussels; the bottom halves of rocks are completely clear except for sea stars and other creatures, and the top halves are entirely crowded by mussels. Sea stars reproduce via broadcast spawning - males and females release the sperm and eggs into the water where they mix and are fertilized into planktonic larvae before settling as baby sea stars. Sea stars are also capable of regeneration! If they lose a limb (or even multiple limbs) they are able to regrow them as long as their central disc (the center part of their body where all the limbs connect) is intact. These intriguing creatures are echinoderms, which translates to “spiny skin.” They have little white bumps on the topside of their body called ossicles. These ossicles are part of a sea star’s endoskeleton and they provide rigidity and protection. On the underside of a sea star, one will find tons of little tube feet that sea stars use to move, grab prey, and cling onto rocks. The mouth is also located on the underside of the sea star.

Today it is possible to see ochre sea stars during a low tide that exposes the boulders on the north side of Haystack Rock, the north wall, and in the tide pools near The Needles on the south side. Other species of sea star are less common but can occasionally be spotted in these areas, especially during negative tides.

Sea Star Wasting Disease/Syndrome

Sea stars used to be found in incredible abundance in the Pacific Northwest of North America, until they were hit by Sea Star Wasting Syndrome in 2013. It is thought that this was one of the worst wildlife die-offs from Alaska to Mexico! Haystack Rock experienced a massive die off of 95% of our sea star population. This disease was only recently found to be caused by a bacteria, Vibrio pectenicida (Prentice et al, AP News). When infected, a sea star will suffer from lesions on their body and will lose limbs, appearing to disintegrate or waste away, ultimately resulting in death. Sea star wasting could be passed through direct contact, which is why we urge people not to touch sea stars. In the past several years we have fortunately seen increases in ochre sea star populations at Haystack Rock, and fewer cases of wasting but they are still in the process of recovering. To learn more about sea star wasting syndrome visit MARINe.

Sea Stars