Primary and Bacterial Secondary Production in a Southwestern Reservoir

Abstract

Rates of primary and bacterial secondary production in Lake Arlington, Texas, were determined. The lake is a warm (annual temperature range, 7 to 32 degrees C), shallow, monomictic reservoir with limited macrophyte development in the littoral zone. Samples were collected from six depths within the photic zone from a site located over the deepest portion of the lake. Primary production and bacterial production were calculated from NaHCO(3) and [methyl-H]thymidine incorporation, respectively. Peak instantaneous production ranged between 14.8 and 220.5 mug of C liter h. There were two distinct periods of high rates of production. From May through July, production near the metalimnion exceeded 100 mug of C liter h. During holomixis, production throughout the water column was in excess of 100 mug of C liter h and above 150 mug of C liter h near the surface. Annual areal primary production was 588 g of C m. Bacterial production was markedly seasonal. Growth rates during late fall through spring were typically around 0.002 h, and production rates were typically 5 mug of C liter h. Growth rates were higher during warmer parts of the year and reached 0.03 h by August. The maximum instantaneous rate of bacterial production was approximately 45 mug of C liter h. Annual areal bacterial production was 125 g of C m. Temporal and spatial distributions of bacterial numbers and activities coincided with temporal and spatial distributions of primary production. Areal primary and bacterial secondary production were highly correlated (r = 0.77, n = 15, P < 0.002).