Carbon Flux between Sediment and Water Column of a Shallow, Subtropical, Hypereutrophic Lake

Field and laboratory experiments were conducted to measure forms, storages, and flux of C in the water-sediment colunm of a shallow, subtropical, hypereutrophic lake. High gross primary productivity in the lake (1.4 ± 0.3 kg C m^-2 yr^-1 ) was not significantly correlated with any water chemistry parameters measured. This suggested that the phytoplankton community was functioning at maximum levels and under nutrient nonlimiting conditions. Major C input to the lake is through gross primary productivity, of which 90% is lost through heterotrophic and microbial respiration processes within the water column. Resuspension of the bottom sediments was a major input of C into the water column, contributing 720 g C m^-2 yr^-1 . In comparison, diffusive flux of dissolved organic C from the sediment was minimal (1.2 g C m^-2 yr^-1 ), as were external inputs into the water column (20 g C m^-2 yr^-1 ). High productivity of this system has resulted in a net accumulation of C (as sediments) of 118 g C m^-2 yr^-1 .