Research ArticleECOLOGY

Common insecticide disrupts aquatic communities: A mesocosm-to-field ecological risk assessment of fipronil and its degradates in U.S. streams

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Science Advances  23 Oct 2020:
Vol. 6, no. 43, eabc1299
DOI: 10.1126/sciadv.abc1299
  • Fig. 1 Response of larval aquatic macroinvertebrates to fipronil and fipronil degradates in a mesocosm experiment.

    Taxa richness (larvae) as a function of (A) fipronil, (B) desulfinyl, (C) sulfone, and (D) sulfide concentration fitted with a three-parameter logistic function. Each data point represents larvae from an individual stream mesocosm at the end of the 30-day mesocosm experiment. Taxa richness is a count of unique taxa within each stream. Concentration values are time-weighted averages of observed concentrations in each stream mesocosm measured at the end of the 30-day experiment. Fipronil amide (not shown) did not have a relation with taxa richness. Note that the x axes are on the log scale. EC20 and EC50 with SEs are reported in table S1.

  • Fig. 2 Cumulative emergence of adult aquatic insects (Chironomidae) from mesocosm experimental treatments.

    Cumulative emergence is the mean cumulative daily insect emergence from each treatment minus the mean cumulative daily emergence from control stream mesocosms for (A) fipronil, (B) desulfinyl, (C) sulfone, (D) sulfide, and (E) amide. n = 1 except for control (n = 6). Concentration values are time-weighted averages of observed concentrations in each stream mesocosm.

  • Fig. 3 Structural equation models for indirect effects of fipronil, sulfide, desulfinyl, and sulfone on scraper and chlorophyll a (Chl a) biomass.

    Fipronil(s) significantly reduced the biomass of grazing (scraper taxa as larvae) taxa (direct effect) but had no direct effect on the biomass of chlorophyll a. However, a strong indirect effect of fipronil(s) was that the biomass of chlorophyll a increased in response to less grazing. Arrows indicate standardized path coefficients, and negative signs (−) indicate direction of association. * indicates level of significance.

  • Fig. 4 Species sensitivity distributions for larval macroinvertebrates exposed to fipronil and fipronil degradates in a mesocosm experiment.

    Species sensitivity is depicted as taxa EC50 values when exposed to (A) fipronil, (B) desulfinyl fipronil, (C) fipronil sulfone, (D) fipronil sulfide for 30-days in a mesocosm experiment. Blue dashed lines indicate 95% CIs. Horizontal dashed lines indicate the HC5. HC5 values in nanograms per liter derived for each compound were as follows: fipronil, 4.56 ng/liter (95% CI, 2.59 to 10.2); sulfide, 3.52 ng/liter (1.36 to 9.20); sulfone, 2.86 ng/liter (1.93 to 5.29); and desulfinyl, 3.55 ng/liter (0.35 to 28.4). Note that the x axes are on the log scale.

  • Fig. 5 Species at Risk pesticides metric (SPEARpesticides) versus the sum of toxic units for fipronil(s) (ΣTUFipronils) at streams sampled in five regional studies (3640).

    Fipronil toxic units are the measured fipronil(s) concentrations divided by compound-specific HC5 values determined from SSDs (see Fig. 4) derived from the mesocosm experiment. Black lines, generalized additive model (GAM). Red dashed lines, 95% CIs of GAM. ΣTUFipronils are transformed as log10(ΣTUFipronils + 1).

  • Table 1 Characteristics (90th percentile concentration, detection frequency, and potential toxicity) of fipronil compounds detected in 444 wadeable streams across the continental United States by region (35).

    *Compounds used in the mesocosm experiment. †ΣTUFipronils, median of the sum of toxic units [observed field concentrations for four fipronil compounds/hazard concentration for the fifth percentile of affected species from the SSDs (Fig. 4) for each compound] for fipronil(s) calculated for weekly samples from the last 4 weeks of pesticide samples collected at each site. ‡Number of sites where pesticides were measured. §The 90th percentile was derived from the site maximum observed concentration during the last 4 weeks of pesticide sampling. ║Percentage of samples with detections. ¶The 95% CIs for HC5 values (Fig. 4 and table S3, mesocosm-only) were used to calculate CIs. Dechlorofipronil was analyzed in all regions and never detected. ND, not detected.

    Fipronil*Desulfinyl
    fipronil*
    Fipronil
    sulfide*
    Fipronil
    sulfone*
    Fipronil
    amide*
    Desulfinyl
    fipronil
    amide
    Fipronil
    sulfonate
    Mean ΣTUFipronils% Sites >
    ΣTUFipronils = 1
    Number of
    sites
    All regions,
    90th
    percentile
    concentration
    (ng/liter)§
    6.32.22.04.210.8NDND
    All regions
    (year)
    22%11%13%20%18%1%0.1%0.62 (0.27–1.62)16% (9–20%)444
    Midwest
    (2013)
    14%9%6%9%5%1%0.3%0.32 (0.14–0.96)5% (4–9%)100
    Southeast
    (2014)
    51%30%40%57%56%3%ND1.82 (0.80–4.92)51% (32–55%)77
    Northwest
    (2015)
    9%3%4%14%2%NDND0.13 (0.06–0.28)6% (0–9%)87
    Northeast
    (2016)
    19%10%11%17%21%0.3%ND0.62 (0.27–1.56)14% (8–16%)95
    Coastal
    California
    (2017)
    19%4%8%11%14%NDND0.40 (0.18–0.85)12% (6–18%)85

Supplementary Materials

  • Supplementary Materials

    Common insecticide disrupts aquatic communities: A mesocosm-to-field ecological risk assessment of fipronil and its degradates in U.S. streams

    Janet L. Miller, Travis S. Schmidt, Peter C. Van Metre, Barbara J. Mahler, Mark W. Sandstrom, Lisa H. Nowell, Daren M. Carlisle, Patrick W. Moran

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    • Supplementary Materials and Methods
    • Figs. S1 to S7
    • Tables S1 to S5
    • References

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