Photosynthesis Respiration Balance of Lakes
Abstract
Growing concern about global climate change necessitates an improved understanding of carbon cycling in aquatic systems. Aquatic ecosystems are net autotrophic and act as sinks for CO2 if photosynthesis exceeds respiration. When respiration exceeds photosynthesis they are net heterotrophic and act as sources of CO2 to the atmosphere. The relative importance of net primary productivity over community respiration in both marine and freshwater ecosystems has been a highly debated subject for many years. While some work has shown respiration to exceed photosynthesis in all but the most eutrophic ecosystems, others have found that photosynthesis is greater than respiration in even oligotrophic systems. Independent of these studies is the observation that most lakes are continually supersaturated with respect to CO2. Previous work has shown stable isotopes of oxygen are an effective means of tracing the photosynthesis respiration balance of aquatic ecosystems. In an attempt to resolve the P:R balance of lakes we have applied this stable isotope technique to twenty-one lakes in Quebec with varying physiochemical properties. The lakes were examined on a monthly basis between May and October 2003 and the metabolic balance determined. Preliminary results indicate the P:R balance of the ice-free period to be near equilibrium, despite near continual supersaturation in CO2.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSM.B14A..04D
- Keywords:
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- 0330 Geochemical cycles;
- 1845 Limnology;
- 4239 Limnology