Using spatial and temporal variability data to optimize sediment toxicity identification evaluation (TIE) study designs

Toxicity tests are an important aspect of sediment quality assessments, but knowledge of the cause of toxicity is needed to determine effective management actions. Toxicity identification evaluation (TIE) methods were developed to meet this need. While TIE method manuals provide information on the procedures, little information on study design is presented. The level of variability associated with performing TIEs and how to account for it is also not addressed. The goal of this study was to collect data on both the spatial and temporal variability associated with sediment TIEs by use of the amphipod Eohaustorius estuarius 10-day survival test and then apply that information to make recommendations for designing future TIE studies. Ten stations were sampled at Consolidated Slip in Los Angeles Harbor, California, with samples collected 2 months apart. In the first stage, TIEs were conducted on whole sediment and pore water from 3 of the most toxic stations. In the second stage, focused TIEs were conducted on whole sediment from all stations. Chemical analysis for metals and organic contaminants was also performed. With a weight of evidence approach, it was determined that pyrethroid pesticides were the likely cause of toxicity, with a lesser contribution from polycyclic aromatic hydrocarbons (PAHs). Results of the individual TIEs fell into 3 broad categories: TIEs in which treatments for organic chemicals and pyrethroids were effective; TIEs in which the treatment for pyrethroids was not effective but the treatment for organic contaminants was effective; and TIEs in which the treatment for pyrethroids was effective but the treatment for organic contaminants was not. This variability was used to calculate that at least 3 TIEs were necessary to make a confident assessment of the cause of toxicity. There was not substantial temporal variability in the TIE outcomes. Other recommendations are made regarding effective TIE study design. Integr Environ Assess Manag 2019;15:248-258. © 2018 SETAC.

The use of sediment toxicity identification evaluation methods to evaluate clean up targets in an urban estuary

The Ballona Creek Estuary (BCE) in Los Angeles, California, is in a highly urbanized watershed, is contaminated by a variety of chemicals, and has prevalent sediment toxicity. Sediment cleanup targets for BCE have been established for Cu, Cd, Pb, Zn, chlordane, DDTs, PCBs, and PAHs, based on sediment quality guidelines. A sediment toxicity identification evaluation (TIE) was conducted to examine how these targets corresponded to toxicity observed with the estuarine amphipod Eohaustorius estuarius. Whole sediment and porewater TIEs were used to identify the cause of toxicity. Passive samplers were deployed to determine the bioavailable fraction of contaminants. Spiked sediment tests were conducted to determine the thresholds of toxicity for selected constituents. Toxicity was found to be widespread but temporally and spatially variable. Whole sediment and porewater TIEs both indicated pyrethroid pesticides were the most likely contaminant group contributing to the toxicity. Concentrations of the chemicals listed for cleanup were found to often exceed target values but were not observed at concentrations likely to cause toxicity. Bioavailable fractions of the target chemicals quantified using passive samplers did not exceed toxicity thresholds. Spiked sediment tests established 10 day LC50s for 4,4' DDE, 4, 4' DDT, α-chlordane, and cyfluthrin at >3050 μg/g, 266 μg/g, >2120 μg/g, and 0.33 μg/g organic carbon (OC), respectively. The cyfluthrin LC50 was within the range of concentrations observed in the estuary sediments, but LC50s for the other 3 chemicals were orders of magnitude greater than observed levels. The combination of TIE, sediment chemistry and the results from spiked sediment exposures indicate pyrethroid pesticides are more likely the cause of the observed toxicity than any of the contaminants targeted for cleanup. The results of this study indicate the importance of using a TIE approach to determine chemicals of concern and dose-response information to set cleanup targets, rather than using sediment quality guidelines. Integr Environ Assess Manag 2014;10:260-268. © 2013 SETAC.

Biological responses of marine flatfish exposed to municipal wastewater effluent

There is increasing concern over the presence of pharmaceutical compounds, personal care products, and other chemicals collectively known as contaminants of emerging concern (CECs) in municipal effluents, yet knowledge of potential environmental impacts related to these compounds is still limited. The present study used laboratory exposures to examine estrogenic, androgenic, and thyroid-related endocrine responses in marine hornyhead turbot (Pleuronichthys verticalis) exposed to CECs from municipal effluents with 2 degrees of treatment. Fish were exposed for 14 d to environmentally realistic concentrations of effluent (0.5%) and to a higher concentration (5%) to investigate dose responses. Plasma concentrations of estradiol (E2), vitellogenin (VTG), 11-keto testosterone, and thyroxine were measured to assess endocrine responses. Contaminants of emerging concern were analyzed to characterize the effluents. Diverse types of effluent CECs were detected. Statistically significant responses were not observed in fish exposed to environmentally realistic concentrations of effluent. Elevated plasma E2 concentrations were observed in males exposed to ammonia concentrations similar to those found in effluents. However, exposure to ammonia did not induce VTG production in male fish. The results of the present study highlight the importance of conducting research with sentinel organisms in laboratory studies to understand the environmental significance of the presence of CECs in aquatic systems.

Gene expression of fathead minnows (Pimephales promelas) exposed to two types of treated municipal wastewater effluents

Contaminants of emerging concern (CECs) in treated municipal effluents have the potential to adversely impact exposed organisms prompting elevated public concern. Using transcriptomic tools, we investigated changes in gene expression and cellular pathways in the liver of male fathead minnows (Pimephales promelas) exposed to 5% concentrations of full secondary-treated (HTP) or advanced primary-treated (PL) municipal wastewater effluents containing CECs. Gene expression changes were associated with apical end points (plasma vitellogenin and changes in secondary sexual characteristics). Of 32 effluent CECs analyzed, 28 were detected including pharmaceuticals, personal care products, hormones, and industrial compounds. Exposure to both effluents produced significantly higher levels of plasma VTG and changes in secondary sexual characteristics (e.g., ovipositor development). Transcript patterns differed between effluents, with <10% agreement in the detected response (e.g., altered production of transcripts involved in xenobiotic detoxification, oxidative stress, and apoptosis were observed following exposure to both effluents). Exposure to PL effluent caused changes in transcription of genes involved in metabolic pathways (e.g., lipid transport and steroid metabolism). Exposure to HTP effluent affected transcripts involved in signaling pathways (e.g., focal adhesion assembly and extracellular matrix). The results suggest a potential association between some transcriptomic changes and physiological responses following effluent exposure. This study identified responses in pathways not previously implicated in exposure to complex chemical mixtures containing CECs, which are consistent with effluent exposure (e.g., oxidative stress) in addition to other pathway responses specific to the effluent type.

Genomic and phenotypic response of hornyhead turbot exposed to municipal wastewater effluents

Laboratory tests with marine flatfish were conducted to investigate associations among gene expression, higher biological responses and wastewater effluent exposure. In the present study, male hornyhead turbot (Pleuronichthys verticalis) were exposed to environmentally realistic (0.5%) and higher (5%) concentrations of chemically enhanced advanced-primary (PL) and full-secondary treated (HTP) effluents from two southern California wastewater treatment plants (WWTP). Hepatic gene expression was examined using a custom low-density microarray. Alterations in gene expression (vs. controls) were observed in fish exposed to both effluent types. Fish exposed to 0.5% PL effluent showed changes in genes involved in the metabolism of xenobiotics, steroids, and lipids, among other processes. Fish exposed to 5% PL effluent showed expression changes in genes involved in carbohydrate metabolism, stress responses, xenobiotic metabolism, and steroid synthesis, among others. Exposure to 5% HTP effluent changed the expression of genes involved in lipid, glutathione and xenobiotic metabolism, as well as immune responses. Although no concentration-dependent patterns of response to effluent exposure were found, significant Spearman correlations were observed between the expression of 22 genes and molecular and/or higher biological responses. These results indicate that microarray gene expression data correspond to higher biological responses and should be incorporated in studies assessing fish health after exposure to complex environmental mixtures.

Selection of methods for assessing sediment toxicity in California bays and estuaries

Toxicity tests are often used in sediment assessment programs. However, the choice of methods has been largely limited to acute tests. Where sublethal methods have been used, there has been little consistency among programs in the types of the sublethal tests used. The goal of this study was to develop a method for choosing a suite of acute and sublethal tests for use in a California statewide assessment program, and to develop a set of method-specific thresholds for classifying the degree of toxicity within a multiple line of evidence framework consisting of sediment chemistry, benthic community structure, and sediment toxicity. A group of candidate methods was evaluated using feasibility and performance criteria. Toxicity thresholds were calculated based on test variability and sensitivity. As a result of the evaluation, 3 acute toxicity methods using amphipods (Eohaustorius estuarius, Rhepoxynius abronius, and Leptocheirus plumulosus), and 2 sublethal methods using a polychaete and mussel embryos (Neanthes arenaceodentata growth and Mytilus galloprovincialis embryo development at the sediment-water interface) were selected for recommendation. Thresholds for toxicity categories corresponding to Nontoxic, Low Toxicity, Moderate Toxicity, and High Toxicity were developed for each test method. Although these toxicity categories and thresholds provide a consistent framework for the interpretation of test results among different methods, additional research is needed to determine their effectiveness for predicting impacts to benthic communities.

Pyrethroids in Southern California coastal sediments

Little is known about pyrethroid fate and effects in estuarine and marine environments. In the present study, the extent and magnitude of pyrethroids in coastal embayments of the Southern California Bight (SCB), USA, were assessed. Using a stratified probabilistic design, 155 sediment samples were collected from four embayment habitats (estuaries, marinas, open bays, and ports) and analyzed for eight common-use pyrethroids. Total pyrethroid concentrations ranged from less than 0.5 to 230 µg/kg dry weight (area-weighted mean concentration=5.1 ± 3.1 µg/kg) and were detected in 35% of the total SCB embayment area. Estuaries and marinas had the greatest areal extent of detectable concentrations (up to 65%) and the greatest area-weighted mean concentrations (22.1 ± 26.5 µg/kg). Sites with the greatest pyrethroid concentrations were located near sources of runoff from urban watersheds. Bifenthrin and cyfluthrin were detected in 32 and 15% of all samples, respectively, whereas the other six pyrethroids were detected in ≤ 5% of samples. Permethrin and bifenthrin had the highest concentrations at 132 and 65 µg/kg. Toxic units estimated for the marine amphipod Eohaustorius estuarius ranged from 0 to 5.8, exceeding unity in 9 and 32% of the total and estuary habitat areas, respectively, and were not correlated with mortality, suggesting that other factors (e.g., co-occurring contaminants, reduced bioavailability) may affect the predictive capability using a single test species.

Using gene expression to assess the status of fish from anthropogenically influenced estuarine wetlands

The diverse mixture of contaminants frequently present in estuaries complicates their assessment by routine chemical or biological analyses. We investigated the use of gene expression to assess contaminant exposure and the condition of southern California estuarine fish. Liver gene expression, plasma estradiol concentrations, and gonad histopathology were used to study biological condition in longjaw mudsuckers (Gillichthys mirabilis). Metals, legacy organochlorine pesticides, PCBs, and contaminants of emerging concern were detected in sediments and whole fish. Overall gene expression patterns were characteristic to each of four sites investigated in this study. Differentially expressed genes belonged to several functional categories including xenobiotic metabolism, detoxification, disease, and stress responses. In general, plasma estradiol concentrations were similar among fish from all areas. Some fish gonads had pathologic changes (e.g., infection, inflammation) that could indicate weakened immune systems and chronic stress. The differential expression of some genes involved in stress responses correlated with the prevalence of histologic gonad lesions. This study indicates that gene expression is a promising tool for assessing the biological condition of fish exposed to environmental contaminants.

Analysis, occurrence, and toxic potential of pyrethroids, and fipronil in sediments from an urban estuary

Eight pyrethroids and fipronil and its three major degradates were analyzed in urban estuarine sediments that exhibited a range of toxic effects to an amphipod test species. Sediments from Ballona Creek, an urban estuary in Southern California (USA), collected during three dry season events were analyzed by gas chromatography with electron capture and negative chemical ionization mass spectrometric detection (GC-ECD and GC-NCI-MS). The two detection methods were in agreement for intermediate levels of pyrethroid contamination (10-50 ng/g dry wt) but deviated for both low and high concentrations (< 5 and > 50 ng/g). Sediments contained total pyrethroids as high as 473 ng/g with permethrin, bifenthrin, and cypermethrin as the most abundant compounds. In contrast, fipronil and its desulfinyl, sulfide, and sulfone degradates were detected at much lower levels (<or= 0.18-16 ng/g). Toxic units estimated for these compounds revealed that bifenthrin and cypermethrin were likely contributors to the mortality observed in tests with the estuarine amphipod Eohaustorius estuarius. Although fipronil was not a likely contributor to the observed mortality, the concentrations detected may be of concern for more sensitive crustacean species. Furthermore, the spatial pattern of pyrethroid contamination and potential toxicity was highly correlated with fine-grained substrate, which shifted to downstream stations within a three-month period during the dry season.

Concentrations of methyl- tert-butyl ether (MTBE) in inputs and receiving waters of Southern California

The occurrence and concentration of the fuel additive methyl-tert-butyl ether (MTBE) were measured in dry weather runoff, municipal wastewater and industrial effluents, and coastal receiving waters in southern California. Combined, refineries and sewage treatment plants release approximately 214 kg day(-1) of MTBE into the marine environment, with Santa Monica Bay receiving most (98%) of this discharge. Dry weather urban runoff was analysed for samples collected from 25 streams and rivers, and accounted for less than 0.5% of the mass of MTBE discharged to coastal waters. Receiving water samples were collected from 23 stations in Santa Monica Bay, Los Angeles Harbour and Mission Bay or San Diego Bay. MTBE was detected at low concentrations near effluent discharges, however there was no evidence of baywide MTBE contamination related to these outfalls. Marinas and areas used intensively for recreational boating had the highest average MTBE concentration (8.8 microg l(-1)). Surface water contamination was most widespread in San Diego Bay and Mission Bay, areas with no refinery or sewage treatment plant inputs.