Toni Ignoffo | Geology Reports

USGS2023

Sacramento River nutrient change study

The Sacramento River Nutrient Change Study (SRiNCS) was developed with input from multiple stakeholders in the Delta Regional Monitoring Program, as well as the State Water Contractors. We tracked the effects of changes in nutrient loading resulting from a short-term wastewater hold at the Sacramento River Wastewater Treatment Plant (SRWTP). In the summer of 2019, scheduled wastewater effluent holds occurred during the Effluent Valve Replacement (EVR) project, part of the EchoWater Project upgrade at the SRWTP. During an EVR hold in early September 2019, no treated effluent entered the Sacramento River for 48 hours, creating a parcel of “without-wastewater” river water approximately 20 miles (32 km) long. We observed the magnitudes and impacts of short-term changes in nutrient loading in water with wastewater (WW+, September 10) and without wastewater (WW-, September 11 and 12) in the Sacramento River and three downstream channels: Georgiana Slough, the North Fork Mokelumne River, and the South Fork Mokelumne River

California↗

USGS2020

Production of the copepod Pseudodiaptomus forbesi is not enhanced by ingestion of the diatom Aulacoseira granulata during a bloom

In 2016, a massive bloom of the chain-forming diatom Aulacoseira granulata occurred in the upper San Francisco Estuary, California, with chlorophyll concentrations up to 75 μg Chl L −1 . In this study, quantitative PCR was used to investigate consumption of the bloom organism by the numerically dominant zooplankter Pseudodiaptomus forbesi (Copepoda: Calanoida) and to estimate the contribution of the bloom to egg production. Copepods were collected on four transects during May and June 2016; egg production rates were somewhat elevated above previous rates measured in the estuary. Ingestion of A. granulata was highest on the first sampling day, just after the peak of the bloom, ranging from 175 to 945 cells copepod −1 day −1 . One month later ingestion rates dropped to 0–130 cells copepod −1 day −1 , despite continued dominance of A. granulata in the plankton. Ingestion of A. granulata provided from 0 to 21% (median 1%) of the estimated daily carbon required for growth and reproduction of P. forbesi . Although the copepods probably obtained nutrition from a microbial food web stimulated by the bloom, monitoring data showed little demographic response to this bloom. Thus, a massive diatom bloom in an unproductive estuary provided only a minor stimulus through an abundant consumer to the pelagic food web.

California↗