Responses to Salinity of Color Polymorphs in Two Populations of the Sea Star, Pisaster ochraceus.

Click here to open his Thesis (pdf)

Reports

Perumal, V. and Dunbar, S. G. 2005. Roatan Rapid Assessment Project for the Queen Conch, Strombus gigas, Roatan, Bay Islands, Honduras (RRAP-L). USAID/MIRA.La Ceiba, Honduras. Pp.26. Link to PDF

I began my interest in Marine Biology while taking a summer course at the Walla Walla College Marine Station at Rosario Beach. I fell in love with the beauty of the area and the many interesting organisms found between the tide marks of the frigid waters.

When trying to decide on what project to do for my master’s thesis, I decided to figure out a project that would get me back up to Rosario Beach. One of the intertidal organisms that had jumped out at me was the colorful ochre sea stars, Pisaster ochraceus. I was fascinated with these creatures, and began looking into the literature on these organisms. I was delighted to find so many unanswered questions and mysteries about these common and well studied creatures.

I narrowed down my searching to a question about the color polymorphism that is seen in this species, and began to design an experiment that would examine one environmental factor (salinity) and see if it affected the different colors differently. The reason for choosing salinity was due to the fact that across a longitudinal gradient in Washington State, a change in frequencies of color morphs of these sea stars can be observed.

There are many more orange and brown individuals on the open coast of Olympic National Park, and in the Inland Straits near Rosario Beach, the sea stars tend to be larger, and mostly purple. Salinity is also very different between the two locations, which provided me with a reason to choose it as my environmental variable to consider.

I examined three responses of P. ochraceus to various salinities, and found that there was no difference in responses between orange and purple color morphs with respect to aerobic respiration and ammonia excretion, however I found that there was a significant difference between self righting times among the factors of location, color, and salinity.