Quantifying potential benefits to Microcystic aeruginosa through disentrainment by buoyancy within an embayment of a freshwater river

Abstract

Vertical profiles of Microcystis aeruginosa and other phytoplankton were measured on several occasions within the main channel and an embayment of a freshwater tidal river. The cyanobacteria M. aeruginosa and Anabaena circinalis were able to migrate to surface waters within the embayment but not within the main channel. Using a quantitative estimate of primary productivity (over a 24 hour period), the potential benefits through disentrainment by buoyancy were determined for M. aeruginosa within the embayment and compared to the main channel. The population within the embayment had a daily integral of photosynthesis of 603.13 mmol of O2m-2, nine times greater than the evenly distributed main channel population with a daily integral of 62.08 mmol of O2m-2. It is likely that embayments along the tidally mixed reaches of the Hawkesbury River may be areas where M. aeruginosa can disentrain through buoyancy and enhance primary productivity rates.