The Division of Environmental Services applied research projects seek innovative solutions for the water management and environmental challenges faced by DWR. Projects are conducted in coordination with partners to optimize resources and expertise.
We aim to improve our understanding of the ecological interactions between key species and their habitats; food webs; contaminants; and the advancement of new scientific tools. Applied research findings also help improve approaches for the division’s monitoring, assessment, compliance, and restoration responsibilities.
Contaminants and harmful algal blooms pose serious concerns for both human and ecosystem health in the Delta. Contaminants in the system originate from various sources, including wastewater effluent, historic mining byproducts and agricultural and urban runoff. Harmful algal blooms, abbreviated “HABs”, occur when colonies of certain species of aquatic algae proliferate and produce toxins harmful to animals, including humans. Contaminants and HABs may have direct visible impacts to organisms (e.g. tumors, lesions, death) or indirect impacts (e.g. behavioral changes, depressed reproduction, decreased growth). Both have important effects on the Delta ecosystem and the people that recreate and live within it.
Contaminant and HAB applied research in the Division of Environmental Services seeks to understand the causes and consequences of these constituents to organisms and ecosystems in the Delta. Specific areas of investigation include:
• What conditions cause and affect blooms of the cyanobacterium, Microsystis in the Delta
• Local sources and movement of mercury in the system
• Impacts of contaminants and HABs on zooplankton and fishes
The Mercury Monitoring and Evaluation Section was created in 2012, after the Delta Mercury Control Program was adopted by the Central Valley Regional Water Quality Control Board. This section ensures DWR's compliance with mercury and methylmercury related regulations in California. This includes designing and implementing water quality studies, aggregating and analyzing data, and serving as an information resource for DWR staff working on projects with a mercury component.
The Mercury Open Water Final Report was submitted by DWR in compliance with the Delta Mercury Control Program, promulgated by the Central Valley Regional Water Quality Control Board. The report consists of an Executive Summary and seven individual chapters. The report summarizes the results of a combination of modeling and scientific studies, in the Delta and Yolo Bypass, to evaluate open water mercury and methylmercury sources and possible management practices (Yolo Bypass only) to reduce methylmercury loads. Mercury Open Water Final Report for Compliance with the Delta Mercury Control Program
Technical Appendices providing details associated with the modeling and scientific studies are available upon request. Send Technical Appendix enquiries to David.Bosworth@water.ca.gov or Petra.Lee@water.ca.gov.
For information regarding modeling studies or for questions on downloading and running the Delta Mercury Model (DSM2-Hg), send modeling enquires to Prabhjot.Sandhu@water.ca.gov.
1. Lee, P. and Manning, J. 2020. Mercury Imports and Exports of Four Tidal Wetlands in the Sacramento-San Joaquin Delta, Yolo Bypass, and Suisun Marsh for Delta Mercury Control Program Compliance. California Department of Water Resources. April 2020.
2. Lehman P, T Kurobe, S Lesmeister, M Mizel, D Baxa, A Tung, S Teh (2017) Impacts of the 2014 severe drought on Microcystis blooms in the San Francisco Estuary. Harmful Algae 63: 94-108.
3. Lehman PW, C Kendall, MA Guerin, MB Young, SR Silva, GL Boyer, SJ Teh (2015) Characterization of the Microcystis bloom and its nitrogen supply in San Francisco Estuary using stable isotopes. Estuaries and Coasts Estuaries and Coasts (2015) 38:165-178
4. Lehman PW, K Marr, GL Boyer, S Acuna, SJ Teh (2013) Long-term trends and causal factors associated with Microcystis abundance and toxicity in San Francisco Estuary and implications for climate change impacts. Hydrobiologia 718:141-158
5. Acuna S, DF Deng, P Lehman, S Teh (2012) Sublethal dietary effects of Microcystis on Sacramento splittail, Pogonichthys macrolepidotus. Aquatic Toxicology 110-111 (2012) 1-8
6. Baxa DV, T Kurobe, K Ger, PW Lehman, SJ Teh (2010) Estimating the abundance of toxic Microcystis spp in the San Francisco Estuary using quantitative real-time PCR. Harmful Algae 9:342-349
7. Deng, DF, K Zheng, FC Teh, PW Lehman, SJ Teh (2010) Toxic Threshold of Dietary Microcystin (-LR) for Quart Medaka. Toxicon 55:787-794
8. Henery RE, TR Sommer, CR Goldman (2010) Growth and Methylmercury Accumulation in Juvenile Chinook Salmon in the Sacramento river and Its Floodplain, the Yolo Bypass. Transactions of the American Fisheries Society, 139: 550-563
9. Lehman PW, SJ Teh, GL Boyer, ML Nobriga, E Bass, C Hogle (2009) Initial impacts of Microcystis aeruginosablooms on the aquatic food web in the San Francisco Estuary. Hydrobiologia DOI 101007/s10750-009-9999-y
10. Moisander PH, PW Lehman, M Ochiai, S Corum (2009) Diversity of Microcystis aeruginosa in the Klamath River and San Francisco Bay delta, California. Aquatic Microbial Ecology 57:19-31
11. Lehman PW, G Boyer, M Satchwell, S Waller (2008) The influence of environmental conditions on the seasonal variation of Microcystis cell density and microcystins concentration in San Francisco Estuary. Hydrobiologia 600:187-204.
All organisms need enough food in order to survive and reproduce. Thus, understanding the Delta food web is critical to support the foundation of the ecosystem. In the Division of Environmental Services, applied food web research seeks to understand how the complicated, interconnected and changing Delta food web functions, how it is affected by the surrounding environment, and how science-based management may alleviate human impacts.
Specific research includes:
• How the productivity and species composition of phytoplankton (microscopic aquatic plants), zooplankton (near-microscopic aquatic animals), clams and other invertebrates vary in different habitats and under different water conditions (e.g. flow, chemistry, salinity, tides, organic content)
• How management actions may influence food web productivity
• The effects that one species or species group has on another population by grazing or predating on them.
• How food availability and predation affect vulnerable and listed species, including Delta smelt and Chinook salmon.
This project is a multi-agency collaboration lead by DWR as part of the Resources Agency’s Delta Smelt Resiliency Strategy. Loss of plankton in the Delta is a major factor responsible for the decline of many fishes, including the endangered Delta Smelt, whose status affects water supply reliability in the state. This study seeks to understand if sending a pulse of water through the plankton-rich Yolo Bypass and Cache Slough Complex areas can transport a productivity “seed” to the downstream Delta that increases food production for Delta Smelt.
Corline NJ, Sommer T, Jeffres CA, Katz J (2017) Zooplankton ecology and trophic resources for rearing native fish on an agricultural floodplain in the Yolo Bypass California, USA. Wetlands Ecology and Management doi:101007/s11273-017-9534-2
Brown, LR, W Kimmerer, JL Conrad, S Lesmeister, and A Mueller–Solger 2016 Food Webs of the Delta, Suisun Bay, and Suisun Marsh: An Update on Current Understanding and Possibilities for Management San Francisco Estuary and Watershed Science 14(3)
Lehman PW, S Mayr, L Leiji and A Tang (2015) Tidal day organic and inorganic material flux of ponds in the Liberty Island freshwater tidal wetland. SpringerPlus 4:273
Loboschefsky E, G Benigno, T Sommer, K Rose, T Ginn, A Massoudieh, et al (2012) Individual-level and Population-level Historical Prey Demand of San Francisco Estuary Striped Bass Using a Bioenergetics Model. San Francisco Estuary and Watershed Science 10(1)
Lehman PW, S Mayr, L Mecum, C Enright (2010) The freshwater tidal wetland Liberty Island, CA was both a source and sink of inorganic and organic material to the San Francisco Estuary. Aquatic Ecology 44:359-372
Lehman PW (2007) The influence of phytoplankton community composition on primary productivity along the riverine to freshwater tidal continuum in the San Joaquin River, California. Estuaries and Coasts 30: 82-93.
Lehman PW, T Sommer, L Rivard (2007) The influence of floodplain habitat on the quantity and quality of riverine phytoplankton carbon produced during the flood season in San Francisco Estuary. Aquatic Ecology 42: 363-378
Nobriga M, F Feyrer (2007) Shallow-water piscivore-prey dynamics in the Sacramento-San Joaquin Delta. San Francisco Estuary and Watershed Science. 5(2)
Lehman PW (2004) the influence of climate on mechanistic pathways that affect lower food web production in northern San Fransicso Bay estuary. Estuaries 27:311-324.
Schemel LE, TR Sommer, AB Muller-Solger, WC Harrell (2004) Hydrologic variability, water chemistry, and phytoplankton biomass in a large floodplain of the Sacramento River, CA, USA. Hydrobiologia 513:129-139
Quality habitat is a critical component of the Delta ecosystem, and key for the survival and long-term persistence of species living within the estuary. Understanding how organisms interact with and depend upon their surroundings for rearing, feeding, shelter, and reproduction is therefore essential to create sustainable landscapes. Applied research in the Division of Envrionmental Services focuses on understanding how organisms utilize habitats, and how changes to those habitats affect populations. This research helps DWR meet its habitat restoration mandates by informing project design with the best available science. Findings also help the department craft innovative management solutions that may avoid or alleviate negative impacts from human activities.
Research projects include:
How listed and vulnerable species, such as Delta smelt, Chinook salmon and green sturgeon use different habitats (e.g. open water, riverine, floodplain, tidal wetlands).
The impacts of of droughts and floods, anticipated to occur more frequently with climate change, on key habitats and the organisms that use them.
How to improve management of tidal wetlands and floodplain agricultural land to balance both species (e.g. waterfowl, fishes, plankton) and human uses.
Suisun Marsh is the largest contiguous brackish marsh remaining on the west coast of North America. Habitat research at the marsh seeks to gain a better understanding how to maintain and increase the value of the Suisun Marsh habitat for waterfowl and other waterbirds. This work aims to better understand the factors affecting waterfowl production, winter habitat use, and food production for waterfowl, particularly as they relate to wetland management techniques.
1. Takata, L, TR Sommer, JL Conrad, and BM Schreier (2017) Rearing and migration of juvenile Chinook salmon (Oncorhynchus tshawytscha) in a large river floodplain. Environmental Biology of Fishes. 100(9), 1105-1120. 10.1007/s10641-017-0631-0
2. Conrad JL, E Holmes, C Jeffres, L Takata, N Ikemiyagi (2016) Application of passive integrated transponder technology to juvenile salmon habitat use on an experimental agricultural floodplain. North American Journal of Fisheries Management. 36:30-39
3. Jeffries KM, Connon RE, Bjelde BE, Komoroske LM, Britton MT, Sommer T, Todgham AE, Fangue N (2016) Effects of high temperatures on threatened estuarine fishes during periods of extreme drought. Journal of Experimental Biology 2019: 1705-1716
4. Tsao, DC, RE Meicer Jr, M Bradbury (2015) Distribution and habitat associations of California black rail (Laterallus jamaicensis cortuniculus) in the Sacramento-San Joaquin Delta. San Francisco Estuary and Watersched Science 13(4)
5. B Herbold, DM Baltz, L Brown, R Grossinger, W Kimmerer, P Lehman, PB Moyle, M Nobriga, CA Simenstad (2014) The Role of Tidal Marsh Restoration in Fish Management in the San Francisco Estuary. San Francisco Estuary and Watershed Science 12(1)
6. Seesholtz AM, MJ Manuel, JP Van Eenennaam (2014) First documented spawning and associated habitat conditions for Green Sturgeon in the Feather River, California. Environmental Biology of Fishes 98(3):905–912.
7. Sommer T, F Mejia (2013) A place to Call Home: A Synthesis of Delta Smelt Habitat in the Upper San Francisco Estuary. San Francisco Estuary and Watershed Science 11(2), 27 p
8. Feyer F, M Nobriga, T Sommer (2007) Multi-decadal trends for three declining fish species: habitat patterns and mechanisms in the San Francisco Estuary, California, USA. Canadian Journal of Fisheries and Aquatic Sciences 64:723-734
9. Sommer, T, C Armor, R Baxter, R Breuer, L Brown, M Chotkowski, S Culberson, F Feyrer, M Gingras, B Herbold, W Kimmerer, A Mueller-Solger, M Nobriga, K Souza (2007) The collapse of pelagic fishes in the upper San Francisco Estuary. Fisheries 32:270-277
10. Sommer T, B Harrell, M Nobriga, R Brown, P Moyle, W Kimmerer, L Schemel (2001) California's Yolo Bypass: evidence that flood control can be compatible with fisheries, wetlands, wildlife, and agriculture. Fisheries 26:6-16
Non-native or “invasive” species are organisms that are transported by humans to a region where they do not naturally occur. Once in a new location, invasive species can change the new environment, altering food webs, structural habitat, and the ecological community. Moreover, the Bay-Delta is perhaps the most invaded estuary in the world. In the Delta, invasive species often negatively impact native organisms and can cause serious problems for human use and water operations.
Applied research on invasive species in the Division of Environmental Services seeks to understand the life history of non-native organisms in the Delta, how they impact important native organisms and ecosystems, and how these impacts might be alleviated or avoided through management and restoration.
- Mahardja B, Farruggia MJ, Schreier B, Sommer T (2017) Evidence of a Shift in the Littoral Fish Community of the Sacramento-San Joaquin Delta. PLoS ONE 12(1): e0170683 doi:101371/journalpone0170683
- Mahardja B, JL Conrad, L Lusher, B Schreier (2016) Abundance trends, distribution, and habitat associations of the invasive Mississippi Silverside (Menidia audens) in the Sacramento-San Joaquin Delta, California, USA. San Francisco Estuary and Watershed Science 14(1): Article 2
- Schreier, BM, MR Baerwald, JL Conrad, G Schumer, and B May (2016) Examination of predation on early life stage Delta Smelt in the San Francisco Estuary using DNA diet analysis. Transactions of the American Fisheries Society 145: 723-733
- Brown T, KA Hieb (2013) Status of the Siberian Prawn, Exopalaemon modestus, in the San Francisco Estuary. San Francisco Estuary & Watershed Science. 12(1)
- Ferrari, MCO, L Ranåker, KL Weinersmith, MJ Young, A Sih, JL Conrad (2013) Effects of turbidity and an invasive waterweed on predation by introduced largemouth bass. Environmental Biology of Fishes Published online March 2013
- Feyrer F, T Sommer, S Slater (2009) Old School vs New School: Status of Threadfin Shad Five Decades after its Introduction to the Sacramento-San Joaquin Delta. San Francisco Estuary and Watershed Science 7(1).
- Feyrer F (2004) Ecological segregation of native and alien larval fish assemblages in the southern Sacramento-San Joaquin Delta. Pages 67-79 in F Feyrer, LR Brown, RL Brown, and JJ Orsi, editors Early Life History of Fishes in the San Francisco Estuary and Watershed. American Fisheries Society, Symposium 39, Bethesda, Maryland
- Feyrer F, B Herbold, SA Matern, PB Moyle (2003) Dietary shifts in a stressed fish assemblage: Consequences of a bivalve invasion in the San Francisco Estuary. Environmental Biology of Fishes 67:277-288
- Toft JD, CA Simenstad, JA Cordell, LF Grimaldo (2003) The effects of introduced water hyacinth on habitat structure, invertebrate assemblages, and fish diets. Estuaries 26:746-758
Technology and Tool Development
New scientific technologies and analytical tools enable researchers to improve the quality and quantity of environmental data collected in the Delta. These can allow for the collection of field data on species that are difficult to find, or sensitive to traditional methods of capture, such as Delta smelt. Hence, new tools and technologies can provide new insights that were not feasible with traditional techniques. In some cases, new technologies allow for the collection of more information using the similar amounts of resources and manpower.
Applied research on new technologies and tools in the Division of Environmental Services seeks to find novel ways to maximize resources and allow DWR to address its environmental responsibilities while meeting human needs in the Delta. Research topics include:
• Genetics: Testing and refining genetic techniques to: 1) Detect very rare species in the wild; 2) Identification what races of Chinook salmon are present and; 3) Identify what species are eaten by predators.
• Observation: Evaluating and refining new camera and sonar technologies to quantify and identify fishes and plankton quickly and often without the need for capture or handling.
• Modeling: Developing and testing computer models to anticipate how organisms may distribute themselves under different environmental and flow conditions in the Delta
- California Department of Fish and Wildlife, Bay-Delta Region
- San Francisco State University, Romberg Tiburon Center for Environmental Studies
- UC Davis, Research
- U.S. Bureau of Reclamation, Bay-Delta Office
- U.S. Fish and Wildlife Services, Delta Juvenile Fish Monitoring Program
- U.S. Geological Survey, California Water Science Center
- U.S. Geological Survey, Western Ecological Research Center