Sea star (Pisaster orchraceus) is a keystone species in the rocky intertidal habitat along the California coast. Keystone species are species which have an impact on population dynamics within an ecosystem. Ochre stars vary in colorization. They can be found being pink, purple, and orange. Sea stars are an amazing group of organisms that belong to the phyla Encinodermata, meaning spiny skin. They have a water vascular system which means they are able to maintain internal fluid balance. What some people call suction cups on the underside of a sea star are actually tiny tube feet that work like a vacuum, pushing and pulling the internal water which is how they move!
Along the California coast these beautiful resilient species are being harmed by a wasting disease known as withering syndrome. This disease will cause sea stars to have lesions (sores), which is then followed by tissue decay, ending in death within a few days. The studies that have been conducted on the cause of this disease discovered that a bacterium is normally found; it is correlated with an increase in water temperatures. This rapid die off has happened in the past in southern California from 1983-84 and yet again in 1997-98. Ochre stars being a keystone species can have a large influence of population dynamics of other species. For instance, California mussels are a delicacy for these animals and with a massive sea star die off these mussels can increase in population taking up more space.
Create a Sea Star Activity
- sand paper or sand
- tongue depressors
Step one: Glue 3 tongue depressors together to form a star.
Step two: Glue sand or sand paper to the tongue depressors. (Hint: cover tongue depressors with glue and sprinkle sand over it.
Step three: Let Dry
You can add string or other crafty items to hang them up on the wall.
For a more in depth explanation for creating your own sea star click the picture below