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Thesis Abstract – E. Cerny-Chipman (2009)

Title:

Assessing the Temporal and Depth Gradients in Concentrations of UV-Absorbing and Photoprotective Compounds in Zooplankton in pHake Lake in Southern California

Author and college:

Elizabeth Cerny-Chipman, Pomona College

Date:

Spring April, 2009

Degree:

Bachelor of Arts in Biology

Advisor:

Jonathan Wright, Pomona College

Abstract:

Photoprotectant compounds were assessed in zooplankton from pHake Lake at the Bernard Field Station in Claremont, CA. Ultraviolet radiation is an important factor for many aquatic organisms because it can cause physiological damage through numerous pathways including the breakdown of macromolecules, the creation of cyclobutane pyrimidine dimers in reactions with DNA, and the formation of oxygen radicals. Organisms avoid UVR through the accumulation of UV-screening compounds like mycosporine-like amino acids (MAAs) and antioxidants like carotenoids and superoxide dismutase, which were tested for in Daphnia magna and Diaptomus pallidus. For carotenoids, I looked for seasonal and depth variation in pigmentation. Using spectrophotometry and TLC confirmed the presence of carotenoids astaxanthin and beta-carotene. There was also evidence of SOD activity in zooplankton. MAAs were found in algae from the lake but not from zooplankton. No clear seasonal or depth gradients were found for carotenoid concentration, but there was significant correlation between Daphnia pigmentation and both mean solar irradiance and temperature, with copepods showing no correlation to either of these factors. Results suggest both a high ability to respond to variation in UVR over short temporal scales and a complex make-up of defensive strategies against UVR.

For more information:

Contact Jonathan Wright – jonathan.wright@pomona.edu