Effects of Selective Grazing by Microzooplankton on Phytoplankton Composition in a Subtropical Estuary

<p>Rates of phytoplankton growth and microzooplankton grazing were measured at two locations within the Bay of St. Louis, MS, over the course of three months to explore the dynamics of the phytoplankton community. Community growth rates were estimated based on the changes in chlorophyll a (chl a) concentration using the dilution technique, (Landry and Hassett, 1982) and a C-specific rate was obtained using chl a labeling (Redalje and Laws, 1981). Concentrations of chl a were determined using high performance liquid chromatography (HPLC) and fluorometry. HPLC was also employed to obtain class specific growth and grazing rates, using either marker pigments or the program CHEMTAX. Intrinsic phytoplankton community growth rates (μ_o) ranged from -0.11 d_-1 to 0.49 d_-1 and varied based on how chl a was measured. C-specific growth rates ranged from 0.24 d_-1 to 0.88 d_-1 and were not significantly different (p<0.05) from the nutrient replete community growth rates (μn). Class specific growth rates (μo) ranged from -0.46 d_-1 to 0.73 d_-1 and varied for all phytoplankton classes. During all samplings, μ_o was less than μ_n indicating persistent nutrient limitation of all phytoplankton classes during the incubations. Grazing by microzooplankton accounted for <50% of daily standing stock removal, and grazing rates were often 0 d_-1, indicating no significant grazing, and highly variable. The results of this study demonstrate that environmental conditions and microzooplankton grazing both play an important role in controlling phytoplankton composition in the Bay of St. Louis, MS.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Masters Thesis

Discipline thesis:degree_discipline

Marine Science

Year dc:date.available

2014

Author dc:creator

• McGehee, Amanda Marie

Contributors dc:contributor

• Donald Redalje
• Scott Milroy
• William Graham

• phytoplankton
• estuary
• microzooplankton
• grazing
• pigments
• pigment labeling
• Oceanography
• Oceanography and Atmospheric Sciences and Meteorology

Repository record dc:identifier

https://aquila.usm.edu/masters_theses/43

OAI identifier oai:identifier

oai:aquila.usm.edu:masters_theses-1046