| dc.description.abstract | The effects of increasing CO sub(2) concentrations on a natural phytoplankton assemblage in a tropical estuary (Godavari, India) is reported. Two short-term (5-day) bottle experiments were conducted (with and without nutrient addition) during the pre-monsoon season when the partial pressure of CO sub(2) in the surface water is quite low. The concentrations of total chlorophyll, the phytoplankton growth rate, the concentrations of particulate organic matter, the photosynthetic oxygen evolution rates, and the total bacterial count were higher under elevated CO sub(2) treatments, as compared to ambient conditions (control). delta sup(13)C of particulate organic matter (POM) varied inversely with respect to CO sub(2), indicating a clear signature of higher CO sub(2) influx under the elevated CO sub(2) levels. Whereas, delta sup(13)C sub(POM) in the controls indicated the existence of an active bicarbonate transport system under limited CO sub(2) supply. A mass balance calculation indicated that insufficient nutrients (N, P and Si) might have inhibited diatom growth compared to cyanobacteria, regardless of increased CO sub(2) supply. The present study suggests that CO sub(2) concentration and nutrient supply could have significant effects on phytoplankton physiology and community composition for natural phytoplankton communities in this region | |
