Photosythesis/respiration ratios in aquatic microcosms under arsenic stress
The ratio of net photosynthesis (P) to total ecosystem respiration (R) usually declines when an aquatic ecosystem is subjected to various types of stress. P/R ratios were measured in 12 80-1 microcosms containing water, sediment, and entire biotic communities (dominated by Elodea sp.) from a shallow pond. P and R were estimated from changes in dissolved O/sub 2/ concentrations during the day and night, respectively. After 10 weeks, the microcosms were stressed by the addition of sodium arsenate at concentrations of 0, 0.066, 11.5, and 143 ppM (as As). P/R ranged from 1.0 to 1.4 in all microcosms before arsenate was added. Under stress, both P and R declined in the 11.5 and 143 ppM microcosms, with negative net photosynthesis (i.e., decreases in dissolved O/sub 2/ during the day) observed on several occasions. P/R in these microcosms fell to zero or below, returning to 1.0 after three weeks. P/R remained above 1.0 in the 0.006 ppM and control microcosms. The P/R response could be used for screening suspected hazardoud substances in microcosms, as well as for monitoring natural ecosystems.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- OSTI ID:
- 6272857
- Journal Information:
- Water, Air, Soil Pollut.; (United States), Vol. 9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AQUATIC ECOSYSTEMS
DOSE-RESPONSE RELATIONSHIPS
PHOTOSYNTHESIS
RESPIRATION
ARSENIC
BIOLOGICAL STRESS
METABOLISM
OXYGEN
PLANTS
PONDS
SODIUM COMPOUNDS
WATER POLLUTION
ALKALI METAL COMPOUNDS
CHEMICAL REACTIONS
CRYOGENIC FLUIDS
ECOSYSTEMS
ELEMENTS
FLUIDS
NONMETALS
PHOTOCHEMICAL REACTIONS
POLLUTION
SEMIMETALS
SYNTHESIS
560300* - Chemicals Metabolism & Toxicology