Aquatic Sciences Meeting, Albuquerque 2001

SS01 Submerged Aquatic Vegetation and the Water Column (Environmental Connections)

Date: Tuesday, February 13, 2001, Time: 3:45:00 PM

Location: Galisteo

Nietch, C, T, Oak Ridge Institute for Science and Education/US Environmental Protection Agency/NRMRL, Edison, USA, nietch.christopher@epa.gov

Morris, J, T, University of South Carolina, Columbia, USA, morris@biol.sc.edu

CARBON BALANCE MEASUREMENTS FOR TWO TIDAL MARSH MACROPHYTES GROWN UNDER DIFFERENT NUTRIENT REGIMES

Peltandra virginica and Typha domingensis were grown alone and mixed in mesocosms under nutrient-limited and -enriched conditions for three years. Carbon exchange measurements made in the spring, summer, and fall of the third year at different light intensities were integrated using a canopy-level net exchange model and summed over the season to estimate net production. Greater biomass under nutrient-enriched compared to nutrient-limited conditions translated to higher instantaneous photosynthesis and respiration rates; Typha generally had higher photosynthesis rates compared to Peltandra. Net production was slightly higher in Typha but similar between nutrient treatments, which was explained by the constraint of a dense canopy on photosynthesis and differences in carbon allocation (root:shoot ratios generally higher under nutrient limitation). In Peltandra, up to 40% of net production accumulated in the surface substrate as organic sediment compared to Typha, at less than 3%. This explained the higher soil carbon efflux from Peltandra mesocosms. The data suggest that differences in turnover rather than production between these species may be more important to carbon and nutrient source/sink relationships with adjacent environments.

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Aquatic Sciences Meeting, Albuquerque 2001

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