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

Abstract

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. C 2018 SETAC

Seasonal Toxicity Observed with Amphipods (Eohaustorius estuarius) at Paleta Creek, San Diego Bay, USA

“…Our results are similar to others in Southern California, including San Diego Bay, suggesting that pyrethroids may be the cause of seasonal toxicity (Holmes et al ; Anderson et al ; Greenstein et al , ). Pyrethroids may be especially relevant in highly urbanized watersheds, such as Paleta Creek, because they have replaced organophosphates as a common household insecticide (Amweg et al ; Weston and Lydy ; Tang et al ) and are becoming increasingly relevant in agricultural settings as well.…”

“…It is noteworthy, however, that H. azteca has been reported to be somewhat more sensitive than E. estuarius to pyrethroids (Lao et al ). Regardless, several studies have incorporated H. azteca LC50 values when no E. estuarius data were available (e.g., Greenstein et al , ), so the results we present are comparable. The LC50 values used in our study are shown in Table .…”

“…In addition, toxicity unit analyses were performed for pyrethroids and PAHs, summing them to understand bulk sediment concentrations in terms of toxicity (Holmes et al 2008;Greenstein et al 2019). Similar to these studies, relevant pyrethroid literature LC50 values from a similar freshwater amphipod Hyalella azteca (when not available for E. estuarius) were used to calculate toxicity units by dividing the concentrations of each constituent by literature LC50 values (Table 1).…”

“…To assess whether pyrethroids might result in significant toxicity to E. estuarius, a sum toxicity unit approach was used that has been used previously for evaluating pyrethroid toxicity (Holmes et al 2008;Lao et al 2010;Greenstein et al 2014Greenstein et al , 2019. Organic carbon normalized LC50 values from sediment spiking studies were used to determine toxicity units.…”

“…At this site, copper (Cu) and polycyclic aromatic hydrocarbons (PAHs) have been traditionally assumed to be the cause of the observed toxicity (SWRCB 1999;Southern California Coastal Water Research Project and Space and Naval Warfare Systems Center 2005). However, several studies in southern California have attributed this seasonal toxicity of sediments to pyrethroids, using the standard 10-d amphipod acute toxicity test (US Environmental Protection Agency 1994, rather than either Cu or PAHs (e.g., Holmes et al 2008;Anderson et al 2010;Lao et al 2012;Greenstein et al 2014Greenstein et al , 2019. Pyrethroids are commonly used insecticides for residential uses because organophosphates were phased out of household use in the United States (Amweg et al 2006).…”