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Cyanobacterial phytoplankton blooms are more prevalent in the freshwater Sacramento-San Joaquin Delta (Delta) since the late 1990s, including blooms driven by overgrowths of potentially toxigenic organisms of the genus Microcystis. Data from 2014 to 2021 were used to show how flow dynamics, water temperature, and water clarity drive occurrence of Microcystis. We used a Microcystis bloom in the central Delta from 2021 as a case study for how novel monitoring tools can track blooms in real-time and be used post hoc to evaluate the effects of management actions.Microcystis was detected throughout the Delta in all but the highest-flow years, and bloom incidence and severity increased during drier years. In the South Delta, Franks Tract, lower San Joaquin River, and Old River regions, where blooms are most prevalent, higher water temperatures and clarities combined with lower exports from state and federal water projects were the best explanatory factors for the occurrence of Microcystis blooms. Nutrient concentrations were lower in summer than in winter, but only became limiting at high phytoplankton concentrations.We used satellite data and in situ continuous monitoring of flow, phytoplankton communities, and water quality to track hydro-biogeochemical conditions during the 2021 case study Microcystis bloom in the Central Delta. We did not find evidence that changes to Delta outflow regulatory standards contributed to this bloom, but changes in flow caused by a salinity barrier placed in west False River may have exacerbated the bloom. The frequency and severity of droughts are expected to increase in the future as a result of climate change, and our study demonstrates how continued monitoring of cyanotoxins, water quality, and phytoplankton communities could help improve management of cyanobacterial blooms in the Delta and other estuaries.

The competition between sulfate-reducing bacteria and methane-producing archaea has a major influence on organic matter removal, as well as the success of sulfidogenic systems. This study investigated the performance of six batch sulfidogenic reactors in response to different COD/sulfate ratios (1.0 and 2.0) and electron donors (cheese whey, ethanol, and sodium lactate) by evaluating the biochemical mechanisms of sulfate reduction, organic matter oxidation, and microbial structure modification. A COD/sulfate ratio of 1.0 resulted in high sulfidogenic activity for all electron donors, thereby achieving a nearly 80% sulfate removal. Lactate provided high sulfate removal rates at COD/sulfate ratios of 1.0 (80%) and 2.0 (90%). A COD/sulfate ratio of 2.0 decreased the sulfate removal rates by 25 and 28% when ethanol and cheese whey were used as substrates. The sulfate-reducing bacteria populations increased using ethanol and lactate at a COD/sulfate ratio of 1.0. Particularly, Desulfovibrio, Clostridium, and Syntrophobacter were predominant. Influent composition and COD/sulfate ratio influenced the relative abundance of the microbial communities. Therefore, controlling these parameters may facilitate the wastewater treatment with high sulfate levels through bacterial activity. [ABSTRACT FROM AUTHOR]