Gaging Downstream Transport of Cyanobacteria in the Raritan River Basin

Cyanobacteria dominated Harmful Algal Blooms (HABs) have the potential to release toxic compounds harmful to human health. Few studies have examined the potential for cyanobacteria travelling from lacustrine HAB sources through fluvial systems used for potable water supply. The Raritan Basin Water Supply Complex (RBWSC) sources potable water for several utilities serving more than 1.5 million people in central New Jersey. The RBWSC features three lentic waterbodies with persistent HABs; discharges from these waterbodies all reach the downstream drinking water intakes. The objectives of this study were to 1) review the persistence of cyanobacteria during fluvial transport from upstream, cyanobacteria-dominated lakes and reservoirs to downstream drinking water intakes in the RBWSC, and 2) find which physiological parameters influence the downstream transport of cyanobacteria. This study found cyanobacteria persistence downstream was primarily influenced by discharge, with periods of higher discharge resulting in greater persistence of cyanobacteria travelling downstream. Factors frequently associated with lentic cyanobacteria growth—such as higher concentrations of nitrogen and phosphorous, warm water temperatures, and lower turbidity—did not show evidence of aiding lotic cyanobacteria travel. It is unclear why some cyanobacteria genera showed greater persistence than others. Drinking water managers in the RBWSC should know that an increased, but diluted, amount of cyanobacteria may reach their intakes during periods of increased discharge. Downstream transport of cyanobacteria from HABs should be investigated on a sitespecific basis, as transport mechanisms, impoundments, trappings, and phytoplankton composition are specific to each water basin