Brian S. Anderson

Relationships between sediment contamination and toxicity in San Francisco Bay

Sediment contamination and toxicity were monitored at 14 sites in San Francisco Bay between 1991 and 1996. Sediment contamination patterns were diAerent in the major reaches of the Bay, and at each site. Several contaminants were consistently above concentrations previously associated with toxicity at most sites. Bulk sediment bioassays using the amphipod Eohaustorius estuarius and sediment elutriate bioassays using larval bivalves (Mytilus spp., Crassostrea gigas) also indicated diAerent patterns of sediment toxicity in space and time. Sediments were most toxic to the amphipods at Redwood Creek (90% of the tests), and were toxic in at least half the tests conducted at five other sites. Sediment elutriates severely reduced normal bivalve larval development at the San Joaquin and Sacramento Rivers in all samples, but toxicity occurred in less than a third of the tests in the Central and South Bays. Toxicity could not be statistically related to seasonal freshwater flow or rainfall in the Bay, but seasonal variation in contaminant concentrations and toxicity was observed. Amphipod toxicity was inversely and significantly related to the mean eAects range-median quotient, suggesting that cumulative concentrations of several contaminants were related to toxicity. Further analysis identified suites of specific contaminants at each site that were variably related to amphipod toxicity at each site. Chlordanes, cadmium, and silver were significantly related to amphipod survival in the North Bay. Seasonal patterns in low, and high molecular weight polycyclic aromatic hydrocarbons (PAHs) were related to toxicity at Alameda, and metals and PAHs were related to toxicity at Castro Cove. Larval bivalve toxicity was associated with metals in bulk sediments, but elutriate chemistry was not measured, and relationships with toxicity could not be examined. Hypotheses about eAective concentrations of several

AMBIENT TOXICITY DUE TO CHLORPYRIFOS AND DIAZINON IN A CENTRAL CALIFORNIA COASTAL WATERSHED

The Salinas River watershed along the central coast of California, U.S.A., supports rapidly growing urban areas and intensive agricultural operations. The river drains to an estuarine National Wildlife Refuge and a National Marine Sanctuary. The occurrence, spatial patterns, sources and causesof aquatic toxicity in the watershed were investigated by sampling four sites in the main river and four sites in representative tributaries during 15 surveys between September1998 and January 2000. In 96 hr toxicity tests, significant Ceriodaphnia dubia mortality was observed in 11% of the mainriver samples, 87% of the samples from a channel draining anurban/agricultural watershed, 13% of the samples fromchannels conveying agricultural tile drain runoff, and in 100% of the samples from a channel conveying agricultural surface furrow runoff. In six of nine toxicity identificationevaluations (TIEs), the organophosphate pesticides diazinon and/or chlorpyrifos were implicated as causes of observed toxicity, and these compounds were the most probable causes oftoxicity in two of the other three TIEs. Every sample collectedin the watershed that exhibited greater than 50% C. dubia mortality (n = 31) had sufficient diazinon and/or chlorpyrifos concentrations to account for the observed effects.Results are interpreted with respect to potential effects on other ecologically important species.

Solid‐phase sediment toxicity identification evaluation in an agricultural stream

The lower Santa Maria River watershed provides important aquatic habitat on the central California coast and is influenced heavily by agricultural runoff. As part of a recently completed water quality assessment, we conducted a series of water column and sediment toxicity tests throughout this watershed. Sediment from Orcutt Creek, a tributary that drains agricultural land, consistently was toxic to the amphipod Hyalella azteca, which is a resident genus in this river. Toxicity identification evaluations (TIEs) were conducted to determine cause(s) of toxicity. We observed no toxicity in sediment interstitial water even though concentrations of chlorpyrifos exceeded published aqueous toxicity thresholds for H. azteca. In contrast to interstitial water, bulk sediment was toxic to H. azteca. In bulk-phase sediment TIEs, the addition of 20% (by volume) coconut charcoal increased survival by 41%, implicating organic chemical(s). Addition of 5% (by volume) of the carbonaceous resin Ambersorb 563 increased survival by 88%, again suggesting toxicity due to organic chemicals. Toxicity was confirmed by isolating Ambersorb from the sediment, eluting the resin with methanol, and observing significant toxicity in control water spiked with the methanol eluate. A carboxylesterase enzyme that hydrolyzes synthetic pyrethroids was added to overlying water, and this significantly reduced toxicity to amphipods. Although the pesticides chlorpyrifos, DDT, permethrin, esfenvalerate, and fenvalerate were detected in this sediment, and their concentrations were below published toxicity thresholds for H. azteca, additivity or synergism may have occurred. The weight-of-evidence suggests toxicity of this sediment was caused by an organic contaminant, most likely a synthetic pyrethroid.

Integrated assessment of the impacts of agricultural drainwater in the Salinas River (California, USA)

The Salinas River is the largest of the three rivers that drain into the Monterey Bay National Marine Sanctuary in central California. Large areas of this watershed are cultivated year-round in row crops and previous laboratory studies have demonstrated that acute toxicity of agricultural drainwater to Ceriodaphnia dubia is caused by the organophosphate (OP) pesticides chlorpyrifos and diazinon. In the current study, we used a combination of ecotoxicologic tools to investigate incidence of chemical contamination and toxicity in waters and sediments in the river downstream of a previously uncharacterized agricultural drainage creek system. Water column toxicity was investigated using a cladoceran C. dubia while sediment toxicity was investigated using an amphipod Hyalella azteca. Ecological impacts of drainwater were investigated using bioassessments of macroinvertebrate community structure. The results indicated that Salinas River water downstream of the agricultural drain is acutely toxic to Ceriodaphnia, and toxicity to this species was highly correlated with combined toxic units (TUs) of chlorpyrifos and diazinon. Laboratory tests were used to demonstrate that sediments in this system were acutely toxic to H. azteca, which is a resident genus. Macroinvertebrate community structure was moderately impacted downstream of the agricultural drain input. While the lowest macroinvertebrate abundances were measured at the station demonstrating the greatest water column and sediment toxicity and the highest concentrations of pesticides, macroinvertebrate metrics were more significantly correlated with bank vegetation cover than any other variable. Results of this study suggest that pesticide pollution is the likely cause of laboratory-measured toxicity in the Salinas River samples and that this factor may interact with other factors to impact the macroinvertebrate community in the system.

Evidence of pesticide impacts in the santa maria river watershed, California, USA

The Santa Maria River provides significant freshwater and coastal habitat in a semiarid region of central California, USA. We conducted a water and sediment quality assessment consisting of chemical analyses, toxicity tests, toxicity identification evaluations, and macroinvertebrate bioassessments of samples from six stations collected during four surveys conducted between July 2002 and May 2003. Santa Maria River water samples collected downstream of Orcutt Creek (Santa Maria, Santa Barbara County, CA, USA), which conveys agriculture drain water, were acutely toxic to cladocera (Ceriodaphnia dubia), as were samples from Orcutt Creek. Toxicity identification evaluations (TIEs) suggested that toxicity to C. dubia in Orcutt Creek and the Santa Maria River was due to chlorpyrifos. Sediments from these two stations also were acutely toxic to the amphipod Hyalella azteca, a resident invertebrate. The TIEs conducted on sediment suggested that toxicity to amphipods, in part, was due to organophosphate pesticides. Concentrations of chlorpyrifos in pore water sometimes exceeded the 10-d median lethal concentration for H. azteca. Additional TIE and chemical evidence suggested sediment toxicity also partly could be due to pyrethroid pesticides. Relative to an upstream reference station, macroinvertebrate community structure was impacted in Orcutt Creek and in the Santa Maria River downstream of the Creek input. This study suggests that pesticide pollution likely is the cause of ecological damage in the Santa Maria River.

Copper toxicity to sperm, embryos and larvae of topsmelt atherinops affinis, with notes on induced spawning

Abstract Topsmelt, Atherinops affinis, were induced to spawn repeatedly in the laboratory using a combination of environmental cues. Temperature ‘spikes’ appeared to be the most important factor to induce spawning. Egg production peaked four days after a 2°C increase in water temperature, and declined thereafter. A series of static toxicity tests compared the relative sensitivity of topsmelt sperm, embryos, and larvae to copper chloride. Of the three developmental stages compared, sperm were more sensitive than embryos, and embryos were more sensitive than larvae. The mean EC50 from four separate 48-h fertilization experiments was 109 μg copper liter−1. The mean EC50 from three, 12-day embryo development tests was 142–147 μg copper liter−1, depending on the endpoint used. The mean LC50 from three, 96-h larval mortality tests was 238 μg copper liter−1. Topsmelt are amenable to laboratory culture and are a promising eastern Pacific toxicity test species.

Influence of sample manipulation on contaminant flux and toxicity at the sediment–water interface

Toxicities of sediments from San Diego and San Francisco Bays were compared in laboratory experiments using sea urchin (Strongylocentrotus purpuratus) embryos exposed to pore water and at the sediment-water interface (SWI). Toxicity was consistently greater to embryos exposed at the SWI to intact (unhomogenized) sediment samples relative to homogenized samples. Measurement of selected trace metals indicated considerably greater fluxes of copper, zinc, and cadmium into overlying waters of intact sediment samples. Inhibition of sea urchin embryo development was generally greater in sediment pore waters relative to SWI exposures. Pore water toxicity may have been due to elevated unionized ammonia concentrations in some samples. The results indicate that invertebrate embryos are amenable to SWI exposures, a more ecologically relevant exposure system, and that sediment homogenization may create artifacts in laboratory toxicity experiments.

In situ water and sediment toxicity in an agricultural watershed

The Salinas River receives inputs from extensive farmlands before flowing into the Salinas River National Wildlife Refuge and the Monterey Bay National Marine Sanctuary (CA, USA). Previous monitoring using laboratory toxicity tests and chemical analyses identified toxic agricultural drain-water inputs in this system. Using caged daphnids (Ceriodaphnia dubia) and amphipods (Hyalella azteca), we investigated in situ toxicity at stations downstream from an agricultural drain relative to a reference station. A flow sensor indicated highly variable inputs from irrigation, and daily synoptic chemical analyses using enzyme-linked immunosorbent assay techniques demonstrated fluctuating concentrations of organophosphate pesticides. Test organism mortality in the field coincided with contaminant concentrations that exceeded chemical effect thresholds for the test species. Laboratory toxicity tests using C. dubia were comparable to results from field exposures, but tests with H. azteca were not. Laboratory exposures can be reasonable surrogates for field evaluations in this system, but they were less effective for assessing short-term temporal variability. Results from the field toxicity studies corroborated results of bioassessment surveys conducted as part of a concurrent study. Toxicity identification evaluations indicated that organophosphate pesticides caused toxicity to daphnids and that effects of suspended solids were negligible.

Bioassay methods for evaluating the toxicity of heavy metals, biocides and sewage effluent using microscopic stages of giant kelp Macrocystis pyrifera (Agardh): A preliminary report

Abstract Methods for using early life stages of giant kelp Macrocystis pyrifera in toxicity tests intended for evaluating the toxicity of municipal sewage effluents are given. Included are methods for both a short-term (48-h) toxicity test, and a long-term (16-day) toxicity test. Preliminary results of experiments with zinc sulfate, sodium pentachlorophenate, and a primary-treated sewage effluent showed that early life stages of Macrocystis have a variable sensitivity to these toxicants. No Observed Effect Concentrations (NOECs) for effects of zinc sulfate on germination of Macrocystis zoospores ranged from 1730 μg/liter to 5500 μg/liter in 3 separate 48-h experiments. The NOECs for zinc effects on the growth of Macrocystis zoospore germination tubes ranged from 550 to 1090 μg/liter in three 48-h experiments. The NOEC for zinc effects on sporophyte production by Macrocystis was 1070 μg/liter in a 16-day experiment. The fungicide and herbicide sodium pentachlorophenate significantly inhibited Macrocystis zoospore germination, and gametophyte reproduction at concentrations of 32 μg/liter and greater (NOEC Macrocystis pyrifera are amenable to evaluating the toxicity of a variety of toxicants, including sewage effluents, and that Macrocystis has a variable sensitivity to toxicants depending on the nature of the toxicant and the endpoint being tested.

Environmental fate of fungicides and other current-use pesticides in a central California estuary

The current study documents the fate of current-use pesticides in an agriculturally-dominated central California coastal estuary by focusing on the occurrence in water, sediment and tissue of resident aquatic organisms. Three fungicides (azoxystrobin, boscalid, and pyraclostrobin), one herbicide (propyzamide) and two organophosphate insecticides (chlorpyrifos and diazinon) were detected frequently. Dissolved pesticide concentrations in the estuary corresponded to the timing of application while bed sediment pesticide concentrations correlated with the distance from potential sources. Fungicides and insecticides were detected frequently in fish and invertebrates collected near the mouth of the estuary and the contaminant profiles differed from the sediment and water collected. This is the first study to document the occurrence of many current-use pesticides, including fungicides, in tissue. Limited information is available on the uptake, accumulation and effects of current-use pesticides on non-target organisms. Additional data are needed to understand the impacts of pesticides, especially in small agriculturally-dominated estuaries.