Semester of Graduation

Spring 2024

Degree

Master of Environmental Studies (MES)

Department

Environmental Sciences

Document Type

Thesis

Abstract

The marine cyanobacterium Synechococcus sp. CCMP 1334 was grown in a continuous culture system on a 12:12 h light:dark cycle at all combinations of low and high pCO2 (400 and 1000 ppmv, respectively), nitrate availability (nitrate-limited and nutrient-replete conditions), and temperatures of 21°C, 24°C, 28°C, 32°C, and 35°C. The maximum median nutrient-replete growth rate was ~1.15 d−1 at 32 –35°C. Median growth rates at 1000 ppmv pCO2 were higher than those at 400 ppmv at all temperatures, but most of the differences were statistically insignificant. Carbon:nitrogen ratios were independent of pCO2 at a fixed relative growth rate but decreased with increasing temperature. Nitrogen:chlorophyll a ratios also decreased with increasing temperatures. Cells produced both more chlorophyll a and more phycoerythrin per unit carbon at higher temperatures than at lower temperatures. The productivity index (photosynthetic rate normalized to the chlorophyll a concentration) was generally higher under nutrient-replete than nitrate-limited conditions. Patterns of cellular composition and growth rate are explained by a model of phytoplankton growth in which cellular carbon is allocated to structure, store, or the light or dark reactions of photosynthesis. Allocation of carbon to the light reactions was consistently higher under nutrient-replete compared to nitrate-limited conditions and was positively correlated with temperature.

Date

3-31-2024

Committee Chair

Edward Laws

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