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2018
Jabusch, T.; Trowbridge, P.; Wong, A.; Heberger, M. 2018. Assessment of Nutrient Status and Trends in the Delta in 2001–2016: Effects of drought on ambient concentrations and trends. SFEI Contribution No. 865. Aquatic Science Center: Richmond, CA.

Nutrients and the effects of nutrients on water quality in the Sacramento-San Joaquin Delta is a priority focus area for the Delta Regional Monitoring Program (Delta RMP). The Program’s first assessment question regarding nutrients is: “How do concentrations of nutrients (and nutrient-associated parameters) vary spatially and temporally?” In this analysis, we confirmed previously reported declining trends in the San Joaquin River for nutrient concentrations at Vernalis and chlorophyll-a concentrations at Buckley Cove and Disappointment Slough. A slight increasing trend for dissolved oxygen at Buckley Cove was also detected which could be confirmation that management actions for the San Joaquin River Dissolved Control Program are having the desired effect. Finally, at stations in Suisun Bay, the Confluence region, and Franks Tract, chlorophyll-a showed modest increasing trends, which were not evident in previous analyses. The new analyses presented in this report and the findings from earlier reports constitute encouraging early progress toward answering the Delta RMP’s assessment questions. Specifically, due to the existence of long-term data sets and synthesis efforts, spatial and temporal trends in the concentrations of nutrients and nutrient-related parameters are reasonably well understood and so are the magnitudes of the most important sources of nutrients from outside the Delta. However, additional synthesis work could be done to understand the factors behind these trends. Large knowledge gaps remain about nutrient sinks, sources, and processes within the Delta. The mechanistic, water quality-hydrodynamic models being developed for the Delta may be able to address these questions in the future.

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Jabusch, T.; Trowbridge, P.; Heberger, M.; Orlando, J.; De Parsia, M.; Stillway, M. 2018. Delta Regional Monitoring Program Annual Monitoring Report for Fiscal Year 2015–16: Pesticides and Toxicity. SFEI Contribution No. 864. Aquatic Science Center: Richmond, CA.

The primary purpose of this report is to document the first year (FY15/16) of pesticide monitoring by the Delta Regional Monitoring Program (Delta RMP). This document reports the results from samples collected monthly from July 2015 through June 2016. The data described in this report are available for download via the California Environmental Data Exchange Network (CEDEN) website.

Pesticide monitoring of the Delta RMP includes chemical analysis and toxicity testing of surface water samples. The parameters analyzed include 154 current use pesticides, dissolved copper, field parameters, and “conventional” parameters (ancillary parameters measured in the laboratory, such as dissolved/particulate organic carbon and hardness). Toxicity tests included an algal species (Selenastrum capricornutum, also known as Raphidocelis subcapitata), an invertebrate (Ceriodaphnia dubia, a daphnid or water flea), and a fish species (Pimephales promelas, fathead minnow). Toxicity testing included the evaluation of acute (survival) and chronic (growth, reproduction, biomass) toxicity endpoints. The surface water samples were collected from 5 fixed sites representing key inflows to the Delta that were visited monthly: Mokelumne River at New Hope Road, Sacramento River at Hood, San Joaquin River at Buckley Cove, San Joaquin River at Vernalis, and Ulatis Creek at Brown Road.

A total of 52 pesticides were detected above method detection limits (MDLs) in water samples (19 fungicides, 17 herbicides, 9 insecticides, 6 degradates, and 1 synergist). A total of 9 pesticides (5 herbicides, 3 insecticides, and 1 degradate) were detected in suspended sediments in 10 of a total of 60 samples collected during the study period. All collected samples contained mixtures of pesticides ranging from 2 to 26 pesticides per sample. From a total of 154 target parameters, 100 compounds were never detected in any of the samples.

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Jabusch, T.; Trowbridge, P.; Heberger, M.; Guerin, M. 2018. Delta Regional Monitoring Program Nutrients Synthesis: Modeling to Assist Identification of Temporal and Spatial Data Gaps for Nutrient Monitoring. SFEI Contribution No. 866. Aquatic Science Center: Richmond, CA.

Nutrient loads are an important water quality management issue in the Sacramento-San Joaquin Delta (Delta) and there is consensus that the current monitoring activities do not collect all the information needed to answer important management questions. The purpose of this report is to use hydrodynamic model outputs to refine recommendations for monitoring nutrients and related conditions in the Delta. Two types of modeling approaches were applied: 1) volumetric water source analysis to evaluate the mix of source waters within each subregion; and 2) particle tracking simulations.The analysis revealed that each Delta subregion has a unique “fingerprint” in terms of how much of its water comes from different sources. Three major recommendations for a future monitoring design were derived from this analysis:

Recommendation #1: The subregions proposed for status and trends monitoring in a previous report should be redrawn to better reflect the mixtures of source waters.

Recommendation #2: Long-term water quality stations are needed in the North Delta, Eastside, and South Delta subregions.

Recommendation #3: Areas with a long-residence time and where mixing of different water sources occurs are potential for nutrient transformation hotspots. High-frequency water quality mapping of these areas has the

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Davis, J. A.; Heim, W. A.; Bonnema, A.; Jakl, B.; Yee, D. 2018. Mercury and Methylmercury in Fish and Water from the Sacramento-San Joaquin Delta: August 2016 – April 2017. SFEI Contribution No. 908. Aquatic Science Center: Richmond, CA.

Monitoring of sport fish and water was conducted by the Delta Regional Monitoring Program (Delta RMP) from August 2016 to April 2017 to begin to address the highest priority information needs related to implementation of the Sacramento–San Joaquin Delta Estuary Total Maximum Daily Load (TMDL) for Methylmercury (Wood et al. 2010). Two species of sport fish, largemouth bass (Micropterus salmoides) and spotted bass (Micropterus punctulatus), were collected at six sampling locations in August and September 2016. The length-adjusted (350 mm) mean methylmercury (measured as total mercury, which is a routinely used proxy for methylmercury in predator fish) concentration in bass ranged from 0.15 mg/kg or parts per million (ppm) wet weight at Little Potato Slough to 0.61 ppm at the Sacramento River at Freeport. Water samples were collected on four occasions from August 2016 through April 2017. Concentrations of methylmercury in unfiltered water ranged from 0.021 to 0.22 ng/L or parts per trillion. Concentrations of total mercury in unfiltered water ranged from 0.91 to 13 ng/L.

Over 99% of the lab results for this project met the requirements of the Delta RMP Quality Assurance Program Plan, and all data were reportable. This data report presents the methods and results for the first year of monitoring. Historic data from the same or nearby monitoring stations from 1998 to 2011 are also presented to provide context. Monitoring results for both sport fish and water were generally comparable to historic observations.

For the next several years, annual monitoring of sport fish will be conducted to firmly establish baseline concentrations and interannual variation in support of monitoring of long-term trends as an essential performance measure for the TMDL. Monitoring of water will solidify the linkage analysis (the quantitative relationship between methylmercury in water and methylmercury in sport fish) in the TMDL. Water monitoring will also provide data that will be useful in verifying patterns and trends predicted by numerical models of mercury transport and cycling being developed for the Delta and Yolo Bypass by the California Department of Water Resources (DWR).

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2016
Jabusch, T. W.; Trowbridge, P. 2016. Nutrient Monitoring Planning Workshop - Summary of Existing Nutrient Monitoring Programs, Data Gaps, and Potential Delta RMP “No Regrets” Monitoring Activities. Aquatic Science Center: Richmond, CA.

This report was prepared as a briefing document for a September 2016 workshop held in Sacramento by the Delta Regional Monitoring Program. The purpose of the workshop was to plan how to invest in nutrients-related studies in order to inform better management of Delta waterways. First, the report compiles information about the major existing nutrient monitoring programs in the Sacramento-San Joaquin Delta. Next, it outline options for “no regrets” actions for workshop participants to review. The report summarizes interviews with representatives of Delta monitoring and resource management programs, describes current monitoring efforts in the Delta, and presents the conclusions and recommendations from recently completed data syntheses.