Model setup

The focus of the assessment was on potential long-term impacts on abundance of populations and potential resultant impacts on community structure and function within a hypothetical shallow water body (e.g., a flooded marsh) following the aerial application of permethrin in Mastic Shirley, Long Island, New York.

The fate portion of the model, which especially applies to organic toxicants, includes the following: partitioning among organisms, suspended and sedimented detritus, suspended and sedimented inorganic sediments, and water; volatilization; hydrolysis; photolysis; ionization; and microbial degradation. The effects portion of the model includes the following: toxicity to the various organisms modeled and indirect effects such as release of grazing and predation pressure; increase in detritus and recycling of nutrients from killed organisms; dissolved oxygen sag due to increased decomposition; and loss of food base for animals.

The modeled shallow surface water body represented a freshwater mixed brackish environment. Both a shallow water body receiving indirect drift of permethrin and an untreated (i.e., control) shallow water body were evaluated for comparative purposes. Aquatic species incorporated into the modeling included the following:

• benthic organisms (amphipods, chironomids);

• suspended feeders (Daphnia, copepods);

• predatory invertebrate (Odonata);

Population dynamics Deterministic Malthusian growth

rn—rn—rn—i—rn—i—n—i i i i i—i i i

Probabilistic Malthusian growth

Probabilistic Malthusian growth

Logistic growth (density dependence)

Spawner-recruit relationships

Number of spawners

Beverton-Holt

Hockey stick Depensation

Number of spawners

Logistic growth (density dependence)

Figure 7 Forms of commonly used population models.

• small forage fish (silverside);

Periphyhton and aquatic plants (e.g., diatoms, blue green algae) were also included as primary producers in the simulation.

The total modeling period for both treated and control simulations was May 2005 through April 2006. Postprocessing of AQUATOX results were performed using Statistica v7.1 statistical software. Observed differences between treatment and control shallow water body results were marked significant at a probability of error of 5% (p < 0.05).

N = population density K = carrying capacity r = intrinsic rate of population growth t = time

Results

The results of the fate and transport component of AQUATOX were compared to an independent fate and transport model. Figure 8 depicts AQUATOX's predicted surface water concentration following two aerial applications spaced 7 days apart. Based on the predicted aquatic persistence of permethrin, two peak concentrations were observed on the dates of applications followed by subsequent rapid dropoffs to nominal concentrations comparable to control conditions. No long-term persistence of permethrin was predicted. Good agreement was reached between the AQUATOX-predicted 14 day average concentration of 0.018 mgl_1 and the independent model-predicted 14 day average concentration of 0.016 mgl"1.

With respect to population-level impacts, no long-term significant differences in abundance were observed among treated and control organisms. Box and whisker

Predicted permethrin shallow surface water concentrations based on Aquatox 3.14 Two aerial applications spaced 7 days apart - Mastic-Shirley

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1-ni.ni.ni.ni.ni.ni.ni.ni.ni.ni.ni.ni.ni.ni.ni.ni.ni.ncDcDcDcDcDcDcDcDcD ooooooooooooooooooooooooooo ooooooooooooooooooooooooooo

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Figure 8 AQUATOX-predicted concentrations of permethrin in a shallow open surface water body.

plots are presented here to provide comparisons of predicted average annual abundances for treated (organisms denoted with 'P') and control (organisms denoted with 'C') simulations.

Figure 9 depicts the predicted annual abundances of Daphnia and copepods under treated and control simulations. No long-term differences in abundances were observed. Some short-term reductions were predicted for Daphnia in the treated simulation, with recovery to pre-treatment levels occurring within 1-2 months.

Figure 10 depicts the predicted annual abundances of chironomids and amphipods under treated and control

Daphnia and copepods present in shallow surface water body Predicted annual abundance estimates following two permethrin aerial applications - Mastic-Shirley 0.016

0.014 0.012 0.010 0.008 0.006 0.004 0.002 0.000 -0.002 -0.004 -0.006 -0.008 -0.010

Ol CS

CS Q

Figure 9 AQUATOX-predicted annual abundances for daphnia and copepods in treated and control simulations.

Chironomids and amphipods present in shallow surface water body Predicted annual abundance estimates following two permethrin aerial applications - Mastic-Shirley a ~o

"U

SE o

Figure 10 AQUATOX-predicted annual abundances for chironomids and amphipods in treated and control simulations.

simulations. No significant long-term differences in abundances were observed for chironomids. Amphipods under treated conditions had a slightly lower average annual abundance than that predicted for the control (i.e., 1.0 vs. 1.7 gm~ ); however, this difference was not statistically significant. Some short-term reductions were predicted for both chironomids and amphipods in the treated simulation, with recovery to pretreatment levels occurring within 2-2.5 months.

Figure 11 depicts the predicted annual abundances of mussels, gastropods, and dragonflies (Odonata) under treated and control simulations. No long-term significant differences in abundances were observed for any of these organism populations. Some short-term reductions were predicted for Odonata in the treated simulation, with recovery to pretreatment levels occurring within 2-3 months, possibly due to the inclusion of modeled immigration.

Figure 12 depicts the predicted annual abundances of fish (i.e., silversides, white perch, catfish, largemouth bass) under treated and control simulations. No long-term significant differences in abundances were observed for any of these fish populations.

Conclusions

The AQUATOX model was used to evaluate potential long-term impacts to aquatic life populations and communities in shallow water bodies receiving indirect deposition of permethrin following aerial application in Long Island, New York. Based on this modeled scenario, no long-term impacts were predicted for a variety of aquatic life populations, including those for aquatic plants, benthic organisms (amphipods, chironomids), suspended feeders (Daphnia, copepods), predatory invertebrates (Odonata), mollusks (mussel), gastropods (snail), and fish. Some short-term decreases were observed for some aquatic invertebrates, such as chirono-mids, amphipods, and Odonata, though recovery to pretreatment abundance levels was predicted to occur within 3 months.

The results of the AQUATOX modeling indicate that although some short-term impacts to individual invertebrates may be possible, longer-term populationlevel impacts are not predicted. If population-level impacts are not predicted, then commensurate community-level impacts are, by proxy, also not predicted. Further, if no impacts are observed within 1 year, impacts attributable to application across years are unlikely. The absence of longer-term population and community-level impacts for aquatic invertebrates predicted using AQUATOX was judged to be consistent with the findings previously reported in the open literature for Minnesota wetlands, seasonal wetlands in California, and wetlands and marshes Long Island exposed to vector control pesticides.

Mussel, gastropod, and Odonata present in shallow surface water body Predicted annual abundance estimates following two permethrin aerial applications - Mastic-Shirley

m m o el s s d o p o a o o d o p ro st a o ta at n o d O

Figure 11 AQUATOX-predicted annual abundances for mussel, gastropod, and odonata in treated and control simulations.

Fish present in shallow surface water body Predicted annual abundance estimates following two permethrin aerial applications - Mastic-Shirley

12 10

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Figure 12 AQUATOX-predicted annual abundances for fish in treated and control simulations.

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