Document Type


Date of Degree Completion

Spring 2015

Degree Name

Master of Science (MS)



Committee Chair

Alison G. Scoville

Second Committee Member

Clay Arango

Third Committee Member

Lucinda Carnell


Daphnia are a genus of freshwater zooplankton that inhabit ponds and lakes. They are commonly used as a model organism because they can reproduce clonally and are considered a foundation species in pond ecosystems. Daphnia melanica that inhabit the subalpine ponds of the Olympic National Park are exposed to high levels of ultraviolet radiation (UVR). UVR causes DNA damage that can be detrimental to the organism if not fixed. One way to avoid these harmful rays is to migrate to protected areas. In my study, I looked at two behaviors in D. melanica: diel vertical migration (DVM), which involves movement down the water column, and diel horizontal migration (DHM), which involves horizontal movement to shaded areas. I tested whether Daphnia from six populations varying in transparency differ in their DVM and DHM response to three different light conditions: cool light, low UV, and high UV. As UV increased, the Daphnia showed significantly more pronounced DVM and DHM. There were also significant differences between populations, as well as a significant interaction between population and light treatment, in DVM. I also measured a number of ecological factors for each pond, including characteristics of the surrounding vegetation and water quality. There was no significant association between any measured ecological factor and behavior of D. melanica.