Date of Award

Fall 2010

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

Alexander B. Bochdansky

Committee Member

Fred C. Dobbs

Committee Member

Margaret R. Mulholland

Call Number for Print

Special Collections LD4331.O35 P25 2010

Abstract

Phosphorus is a key element in important biochemical compounds, such as RNA and phospholipids, and can become limiting in a variety of marine systems. The uptake of phosphorus into biochemical fractions (protein, low molecular weight (LMW) compounds, lipid, polysaccharide and nucleic acid) in Acartia tonsa fed 33P -labeled Rhodomonas salina was examined. R. salina was cultured on two variations of one media that in one case contained phosphorus in balance and the other out of balance with relation to other standard f/2 components. The P-balanced (PB) media had a N:P ratio of 24.5, which is higher than that found in the Redfield N:P ratio of 16. The P-imbalanced (Pl) media, on the other hand, had an N:P of 245.3. PB R. salina incorporated more 33P into their cells than did the PI R. salina in all but the LMW compounds fraction. 33P was incorporated faster into all biochemical fractions in the tissue of A. tonsa when fed PB R. salina. The 33P uptake kinetics of A. tonsa were rapid in both treatments, but always higher when the copepods were fed PB R. salina during the standard uptake experiment and variable among biochemical fractions in the modified uptake experiment. The elimination of the 33P signal from biochemical fractions was investigated, with prelabeled A. tonsa, during exposure to different feeding environments (i.e., artificial seawater without phosphorus, R. salina, Thalassiosira weissflogii). 33P was released more rapidly in the fed rather than in the unfed treatments, indicating that phosphorus turnover in copepods is directly dependent on the quantity of assimilated phosphorus. However, the feeding history of A. tonsa, initially fed on food of different elemental composition, did not affect elimination rates in any food environment. This study provides insights into how the physiology and homeostatic control of algae and copepods dampen fluctuating concentrations of inorganic nutrients for higher trophic levels.

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DOI

10.25777/2ak5-t463

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