Dynamics of bacterioplankton abundance and production in seagrass communities of a hypersaline lagoon

Abstract

In the upper Laguna Madre, Texas annual estimates of bacterial production were 25.24 g C m-2 yr-1 (based on thymidine) and 25.12 g C m-2 yr-1 (based on leucine). Assuming a 30% growth efficiency, the annual bacterioplankton growth could be supported by 15% of the total primary production (seagrasses and phytoplankton), 17% of the above-ground production of the dominant seagrass, Halodule wrightii, or 103% of the phytoplankton production. Bacterial abundance was high throughout the year, often exceeding 1 × 1010 cells l-1. Bacterioplankton production varied seasonally and over the diel cycle, with maximal values during warmer months and during daytime. Although changes in water temperature could account for some of this variation, shifts in the quantity and quality of the organic substrates supporting bacterial growth appeared to be the major factors. -from Authors