Living near the coast helped Alyssa Medina develop an interest in studying marine biology, and her coursework encouraged her to pursue research into how the environment and climate change impact intertidal organisms. Her project gave her the opportunity to develop relationships with others working in her field, and she particularly appreciated the chance to work so closely with Professor Sorte and her other mentors. Alyssa credits her research experience with challenging her and improving her work ethic; she hopes to attend medical school after graduation, and she feels that these qualities have helped her prepare to meet that goal.

Increased environmental stresses, including thermal stress, resulting from anthropogenic climate change may have profound effects on the species of the intertidal zone. The effects on shellfish such as mussels are of particular interest, as they are a foundation species that support a diverse community of associated species in rocky intertidal habitats. In this study, we employed an environmental gradient approach, testing the effects of environmental stress on size at reproductive maturity of the California mussel, Mytilus californianus, across a natural gradient of temperature and feeding opportunity. Mussels were collected from low, mid, and high tide heights and length, width, depth, total weight, gonad weight, shell weight, and gonad stage were measured. We found that size at reproductive maturity differed across tide heights, with adults reaching maturity at smaller sizes at higher tide heights. This finding may represent metabolic limitations as gonadosomatic index (ratio of gonad to tissue weight) was correlated with thermal stress (90th percentile temperatures) and feeding opportunity (using submergence time as a proxy). This suggests that life history characteristics of mussels, and their ability to create habitat for species that depend on them, will be impacted by alterations in temperature and food availability resulting from climate change.

Cascade J. Sorte School of Biological Sciences

We now know from Alyssa Medina's work that shellfish living just a few meters further away from the ocean reach adulthood at smaller sizes than their wetter brethren—and that individuals of the same size can be different ages depending on where they live on the coastline. This variation is likely driven by differences in temperatures and food. Thus, Alyssa's findings tell us about physiological trade-offs and give us glimpses into what could happen as the climate warms and ocean food supply changes. These outcomes are above and beyond the benefits of undergraduate research, which include experience for the researchers and mentors at all levels.