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Date Permissions Signed


Date of Award

Fall 2015

Document Type

Masters Thesis

Degree Name

Master of Science (MS)


Environmental Sciences

First Advisor

Love, Brooke

Second Advisor

Strom, Suzanne L., 1959-

Third Advisor

Olson, M. Brady (Michael Brady)


To date few studies have explored indirect effects of OA on microzooplankton. Microzooplankton grazing behavior is acutely sensitive to prey cell size, physiology, and nutritional state, which may all be influenced by OA in phytoplankton. Therefore, microzooplankton may be indirectly affected by OA through their prey. Due to undersaturation of CO2 for the carboxylating enzyme, RuBisCO, increasing availability of CO2 through acidification could affect algal cellular processes, physiological states, and the nutritional value for their primary consumers. In this study I tested for indirect effects of OA on three microzooplankton species, representing two ecologically significant functional groups of microzooplankton, tintinnid ciliates (Favella taraikaensis and Eutintinnus sp.) and heterotrophic dinoflagellates (Oxyrrhis marina). I characterized the direct effects of OA on the physiology and biochemistry of two phytoplankton, Emiliania huxleyi CCMP 2668 and Rhodomonas sp. CCMP 755 under three pCO2 treatments (400ppmv, 750ppmv, and 1000ppmv). I quantitatively assessed cell size, C:N, growth rate, photosynthetic capacity, cellular carbohydrate and chlorophyll a concentrations. Phytoplankton cell size increased significantly under 750 ppmv and 1000 ppmv with no other consistent changes under elevated pCO2. To test for indirect effects on microzooplankton, the grazers were fed a diet of pCO2-acclimated cells. All three microzooplankton species showed increased short-term ingestion rates and increased population feeding on prey grown in elevated pCO2. Multiple Linear Regression models revealed that that OA indirectly affects microzooplankton through direct effects on the size of their phytoplankton prey. This pathway for OA effects has the potential for widespread impacts within marine food webs.





Western Washington University

OCLC Number


Subject – LCSH

Phytoplankton--Effect of water acidification on; Marine zooplankton--Food; Predation (Biology); Ocean acidification




masters theses




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