I. Contact Information
Program Manager: Rich Breuer
Lead Contact: Karen Gehrts
Department of Water Resources
Division of Environmental Services,
901 "P" Street, Sacramento, CA 95814
(916) 651-0190
email Karen Gehrts
II. Study Mandate and Objectives
The State Water Resources Control Board (SWRCB) sets water quality objectives to protect beneficial uses of water in the Sacramento-San Joaquin Delta and Suisun Bay. These objectives are met by establishing standards mandated in water right permits issued to the Department of Water Resources and U.S. Bureau of Reclamation by the SWRCB. The standards include minimum Delta outflows, limits to Delta water export by the State Water Project (SWP) and the Central Valley Project (CVP), and maximum allowable salinity levels.
In 1971, the State Water Resources Control Board (SWRCB) established Water Right Decision 1379 (D-1379). This Decision contained new water quality requirements for the San Francisco Bay-Delta Estuary. D-1379 was also the first water right decision to provide terms and conditions for a comprehensive monitoring program to routinely determine water quality conditions and changes in environmental conditions within the estuary. The monitoring program described in D-1379 was developed by the Stanford Research Institute through a contract with the SWRCB. Implementation of the monitoring program began in 1972, as SWRCB, DWR, and USBR met to define their individual responsibilities for various elements of the monitoring program. In 1978, amendments to water quality standards were implemented and resulted in Water Right Decision 1485 (D-1485). More recently these standards were again amended under the 1995 Water Quality Control Plan and Water Right Decision 1641 (D-1641) established in 1999. The SWP and CVP are currently operated to comply with the monitoring and reporting requirements described in D-1641. D-1641 requires DWR and USBR to conduct a comprehensive environmental monitoring program to determine compliance with the water quality standards and also to submit an annual report to SWRCB discussing data collected.
The benthic monitoring program is one element of DWR’s and USBR’s Environmental Monitoring Program (EMP) conducted under the Interagency Ecological Program (IEP) umbrella. The EMP also includes monitoring of water quality, zooplankton, and phytoplankton. The overall objective of the benthic monitoring program is to determine the impacts of water project operations on the estuary. These impacts are interpreted by changes in benthic fauna presence, abundance, and distribution associated physical factors in the estuary. Data collected from the benthic monitoring program is also used to detect newly introduced species in the estuary. To date, 266 species in nine phyla (cnidaria, platyhelminthes, nemertea, nematoda, annelida, arthropoda, mollusca, chordata, and echinodermata) have been collected from the study area. Sediment composition data are also collected as part of the benthic monitoring program to document general trends in sediment composition for all sites where benthic samples are collected.
III. Study Area and Sample Sites
A.General Information
Geographic coverage of the sampling sites ranges from San Pablo Bay east through the upper Estuary to the mouths of the Sacramento, Mokelumne, and San Joaquin rivers. The study area currently comprises ten sites that are sampled monthly. These sites represent a wide variety of habitats that vary in size and physical make-up as well as water quality and sediment composition. The aquatic habitats sampled range from narrow, freshwater channels in the Delta to broad, estuarine bays. The mixing of river water with tidal water creates a wide range of water quality conditions. For example, salinity ranges from freshwater to around 19 psu in the most western sites.
B. Name and Location Information for Benthos Sampling Sites
IV. Period of Record
Benthic monitoring began in 1975. From 1975 through 1979 the program collected samples biannually from 18 to 35 stations, for a total of 48 stations over the period. In reviewing data collected between 1975 and 1979, it became evident that semi annual monitoring was insufficient to reveal long term ecological changes as mandated by Water Right Decision 1485. In 1980, DWR revised the benthic monitoring program and began monthly sampling at nine stations. In 1995, major program revisions were implemented to the program. A review of the data collected from 1980 to 1990 recommended that across-channel sampling be reduced to a single station per location in the Delta so that the geographic coverage could be widened. These revisions included increasing the number of sites sampled each month from nine to ten and increasing the number of grab sample replicates from three to four. Detailed information about location, number of and characteristics of the historical sites can be found in IEP Technical Report 12 (Markmann, 1986) and IEP Technical Report 38 (Hymanson, et al., 1994).
A programmatic review of the EMP in 2001-2002 found that the benthos monitoring element was particularly in need of fundamental and comprehensive consideration through intense special studies and study design examination. Reviewers recommended a temporary reduction in sampling frequency to free up EMP resources to conduct the more spatially intense sampling without requiring additional resources. October 2003 was the last of the monthly sampling events and sampling will continue quarterly (in October, January, April, July) at the stations sampled since 1996 until a new sampling plan is put in place.
V. Sampling Frequency
Biannually, in late spring and fall, from 1975 to 1979; monthly starting in June 1980 and ending in October 2003. Currently samples are collected quarterly.
VI. Data availability in EMP's benthic database
A. Sampling events
B. Grabs
VII. Field Collection Methods
A. Benthos
The benthic macroinvertebrate sampling methodology used in this program is described in Standard Methods for the Examination of Water And Wastewater, 20th ed. 1998 American Public Health Association, Washington D.C. (See pages 10-60 through 10-74.)
B. Sediment
VIII. Lab Processing Methods
A. Benthos
At the laboratory, the volume of settleable substrate in each sample jar is estimated and recorded. The formalin fixative is poured off and the sample is thoroughly washed on a 30-mesh (0.6 mm) screen. The composition of the substrate is estimated and recorded noting the relative percentages of peat, sand, mica, organic detritus, and other materials. The substrate is hand picked for organisms under a three diopter illuminated magnifier.
Organisms are placed in 70% ethyl alcohol for subsequent identification. A stereoscopic dissecting microscope (70-120x) is used to identify most organisms. When taxonomic features are too small for identification under the dissecting scope, the organism is permanently mounted on a slide and examined under a compound microscope.
If more than four hours of picking is required, and a sample contains many organisms but few species, a one-fourth subsample is chosen at random. The subsample is picked and the results are multiplied by four to represent the total sample. The remainder of the sample is inspected to make sure no other taxa were overlooked.
Laboratory identification and enumeration of macro-benthic organisms in each sample is performed under contract by Hydrozoology Laboratory, P.O. Box 682 Newcastle, CA 95658. Analysis has been done by Hydrozoology for the program's entire period of record.
The list of all species of macro-benthic organisms identified and the total number of individuals counted can be found in the Benthic Dictionary. In the dictionary, the "Total counted" column is the total number or individuals counted since the beginning of the program; the "Reference#" columns refer to the list of taxonomic references.
B. Sediment
All sediment samples are analyzed by the DWR Soils Laboratory, Bryte, CA. Analysis of a sediment sample involveses determining the percent size fractions with the use of a mechanical sieve. The sieves sizes are as follow: 76.2, 38.1, 19, 9.5, 4.76, 2.38, 1.19, 0.6, 0.3, 0.15 and 0.074 mm. All particle sizes are found on a regular basis in the samples with the exception of gravel (particles greater than 4.76 mm in diameter).
The percent organic content of each sediment sample is also determined from the loss in weight of an oven-dried sample burned at 440 degrees Celsius for 8 hours. All laboratory analysis procedures follow the American Society for Testing Methods, D-2974, "Moisture, Ash, and Organic Matter of Peat and Other Organic Soils" and D-422-63, "Particle-Size Analysis of Soil".
IX. Data Management and Summarization
A. Benthos
EMP benthic data fields available via BDAT include important program internet links, geographical sampling station information, sampling date and time, organism information, measured organism sizes, and enumeration results for each sample.
Specifically, the fields available via BDAT are:
Counts of individuals per grab can be expanded to abundance per unit area by averaging the individual species counts over the number replicate grabs and multiplying by a constant k to obtain a number of individuals per m2 for a given sampling event. The value of the constant k is computed as follow k = 1 / sample area of the ponar dredge in m2, and provided in the "multiplication factor" field in BDAT.
Note on lost & empty grabs: To correctly expand counts of individuals per grab to abundance per unit area, the data user must be careful to distinguish between a) sheduled sampling events that were missed entirely, b) grabs that were acquired in the field but were lost or were unusable for lack of correct preservation and c) grabs that, although successfully acquired in the field and correctly preserved, did not contain any macro-invertebrate organisms. This 3 cases are distinguished in the benthic database as follow:
B. Sediment
Sediment composition data is provided to the program by the DWR Soils Laboratory in the form of monthly written reports. These data are then entered monthly by DWR Personnel into EMP's Benthic database. After reviewing of the results for accuracy and completeness, data are exported electronically to the Bay-Delta and Tributaries Database (BDAT). All data are not yet available for download through BDAT Web Interface. For more information regarding the sediment data please contact the person listed at the beginning of this document.
X. Reference
A. Taxonomic References
The list of taxonomic references contains all references used for species identification. The "Reference Code" column in this list is used in the "Reference#" columns in the Benthic Dictionary to establish species-reference relationships.
B. Program Reports, Publications, and Other Pertinent Literature.