1. Investigations of the Acute Effects of Mosquito Control Activities on Water Quality, Fish, and Shrimp in the Salt Marshes of Suffolk County, NY
R. Turner1, A. McElroy2, C. Gobler2, B. Brownawell2, R. Barnes2, S. Terriciano3, and B. Gibbins1
1 – Long Island University 2 – Stony Brook University 3 – U.S. Geological Survey

2. A study funded by Suffolk County as part of the
Suffolk County Vector Control and Wetlands Management Long Term Plan & Generic Environmental Impact Statement
see

3. Background
1930s
Ditches were dug in salt marshes throughout the U.S. to reduce standing water and decrease mosquito populations.
Over 90% of Suffolk County’s 17,000 acres of salt marsh are “grid-ditched.“ That amounts to over 4,000,000 feet of ditches that are maintained by the county.1
1 -

4. Background
1940s – 1960s
DDT and other pesticides are applied in marshes and wetlands to combat mosquitoes.
1995
Suffolk County Vector Control Program begins spraying Altosid® (methoprene) as a larvicide and Scourge® (resmethrin) as an adulticide.

5. Background
Pesticides are applied via helicopter, truck, and backpack spraying, mostly from late spring through September.
Altosid
Larvicide
Helicopter application at 1 ounce/acre, feet above ground level1
20% Methoprene1
Juvenile hormone mimic, growth regulator
Tightly sorbed to soil
Slightly soluble in water
Half-life in water ~ 30 hours Half-life in soil < 10 days1, 2
These are the three pesticides we looked at, and all of these have been used in NY for mosquito control. Pyrethroids are highly toxic to aquatic organisms with LC50s in the ng/L range. Malathion is generally less toxic in the ug/L range, and methoprene is the least toxic since it functions more as a growth inhibitor than lethal toxicant with LC50s generally exceeding 100s of ug/L.
1 – 2 – ECOTOXNET

6. Background Scourge Resmethrin Piperonyl Butoxide Adulticide
Helicopter application at 0.6 ounces/acre.
Application between 7-10pm, from 150 feet above ground level.1
Mix of Resmethrin (18%) and piperonyl butoxide (54%).1
Resmethrin
Pyrethroid
Neurotoxic: sodium channel modulator leading to insect paralysis1
Half-life in water < 1 hour Half-life in soil < 30 days2
Piperonyl Butoxide
Synergist, microsomal enzyme inhibitor slows chemical metabolism1, 2
EPA acute toxicity category IV compound (low toxicity)2
These are the three pesticides we looked at, and all of these have been used in NY for mosquito control. Pyrethroids are highly toxic to aquatic organisms with LC50s in the ng/L range. Malathion is generally less toxic in the ug/L range, and methoprene is the least toxic since it functions more as a growth inhibitor than lethal toxicant with LC50s generally exceeding 100s of ug/L.
1 –
2 – ECOTOXNET

7. Background
(hydrophobic)
(hydrophobic)

8. Background
1999
West Nile Virus, carried by mosquitoes, infects at least 62 people in the New York metropolitan area, resulting in 7 fatalities.1
present
West Nile Virus spreads across the nation. Cumulatively, 19,707 cases have been reported and 785 people have died.1
1 – Center for Disease Control web site

9. Background
2003
Suffolk County begins work on the Suffolk County Vector Control and Wetlands Management Long Term Plan & Generic Environmental Impact Statement, as required by the Council on Environmental Quality.
Comments received in the scoping process underscore the need to study the potential impacts of mosquito spraying on salt marsh and estuarine organisms.

10. Background
2003
Matthew Vilbas, working on a fellowship with the Southampton College Estuarine Research Program,
conducts a caged fish study in marshes subject to mosquito spraying.

11. Background 2003 The Vilbas study finds:
Growth and survival of sheepshead minnows in a mosquito ditch subjected to aerial application of larvicide in Oakdale were significantly lower relative to control sites.
Growth rates of sheepshead minnows in a mosquito ditch subjected to aerial application of adulticide in Mastic Beach were significantly lower relative to control sites.

12. Background
2003
However!
There was minimal analysis of environmental parameters…
No continuous monitoring of temperature, dissolved oxygen, or water depth.
No analysis of water and sediment samples for pesticide concentrations.
And fish growth and survival was only monitored during one larvicide event and one adulticide event. No replication.

13. Which leads us to…
The 2004 Caged Fish Study

14. Hypotheses of Caged Fish 2004
The null hypothesis is that there will be no statistically significant difference in:
the mortality rate of caged fish or shrimp;
the growth rate of caged fish;
the prey capture ability of caged shrimp; or
the fecundity of caged shrimp;
that have been exposed to an aerial application of larvicide (Altosid) or adulticide (Scourge) while in a salt marsh mosquito ditch compared to organisms that have been placed in a “control” marsh not subjected to mosquito pesticide application.

15. Methods Biological Effects of Mosquito Spray
Monitor survival of caged organisms in sprayed vs. non-sprayed marshes.
Monitor growth of caged fish.
Monitor prey capture ability and fecundity of surviving shrimp.
96 hr static renewal shrimp toxicity tests using water collected 30 min. post spray.
Comparative survey of benthic organisms in sprayed vs. non-sprayed marshes.

16. Methods – Shrimp Lab Tests
Test Type:
Method Summary:
Why Studied?
Static Tests:
-water taken after spray
-replenished daily in lab
-independent measure of toxicity without environmental variables
Prey Capture Tests:
-1 or 2 h in duration
-5 brine shrimp prey
-replenished every 15 m
-assessment of non-lethal effects of pesticide exposure on shrimp
Dosing Experiments:
-3 or 4 replicates
-dosed 1 time/day for 4 d
-water & acetone controls
-measure acute toxicity of LI pesticides on shrimp
Generally supposed to be a caged fish study. Lab studies were based on additional measures of crustaceans…

17. Prey Capture Experiments
Static & Dosing Experiments
--static & dosing experiments… performed in small bowls with a single shrimp per bowl
--prey cap studies performed in 20cm diameter bowls
--5 brine shrimp were used as prey items at the beginning of each experiment
--The number of brine eaten per 15 minutes was assessed for 1 or 2 hrs.
--the prey capture rate was calculated for all shrimp at the end of each experiment.

18. Methods Efficacy of Mosquito Spray
Monitor survival of caged mosquitoes in sprayed vs. non-sprayed marshes.
Monitor “fly-up” of field collected mosquito pupae.
Confirmation of surface deposition.
Modeling of air dispersion and deposition.

19. Methods Water and Sediment Chemistry
Continuous monitoring of dissolved Oxygen concentrations and temperature (data stored every 30 minutes).
Analysis of water samples for pesticide concentrations before a spray event and 30 min to 96 hrs post spray.
Analysis of sediment samples for pesticide concentrations before and after a spray event.

20. Methods Water and Sediment Chemistry
Surface water (upper 6”) was sampled both including the air-water interface and excluding it.
USGS measured filtered water employing GC/MS methods (reporting limits of 5 ng/L for 6 target chemicals.
USB measured unfiltered water and splits of above using HPLC-time-of-flight-MS methods with method detection limits of 0.5 ng/L in water.
Composite sediment samples (0-1 cm) were collected at ditch bottoms, intertidal locations, and selected high marsh locations; analysis based on GC-MS.

21. Methods Caged Organism Logistics
Deployment of at least 168 adult grass shrimp and 240 juvenile sheepshead minnows one day before a spray event in flow-through cages in marsh ditches or small tidal creeks.
Simultaneous deployment in two sprayed and two reference marshes.
3 cages of shrimp and 3 cages of fish per site.
Length of fish measured immediately prior to deployment.
Monitoring of caged fish and shrimp mortality on a daily basis for 5 days.

22. Juvenile Sheepshead minnows Cyprinodon variegatus
20 fish per cage
3 cages per site

23. Grass shrimp Paleomonetes pugio, 14 per cage, 3 cages per site

24. Methods

25. Blue = reference site
Red = spray site

26. Field Sites
Finding suitable salt marsh locations for the study was more difficult than anticipated. Unacceptable mortality of caged fish and/or shrimp occurred in marshes at the following locations.
Beaverdam Creek, Captree Island, Fireplace Neck (3 sites), Gilgo State Park, Stokes/Podges, Tanners Neck, Timber Point, West Gilgo, West Shinnecock.
Reconnaissance done at several other marshes as well.
Most ditches in most marshes are too shallow at low tide for use in the study.

27. Field Sites
Johns Neck – Spray Site

28. Field Sites
Havens Point - Control

29. Field Sites
Havens Point Control Site
Johns Neck Spray Site

30. Field Sites
Timber Creek – Spray Site

31. Field Sites
Flax Pond – Control

32. What was done… where and when
Field Activities
What was done… where and when

33. Results Survival of Fish Over Time
Blue squares = sprayed sites
DO data not available
Results from first larvicide experiment

34. Results Survival of Fish Over Time
Results from second larvicide experiment
Timber Point survival significantly lower than Flax and Haven’s

35. Fish and Shrimp Survival for 8/3/04
Percent Survival L

36. Results Survival of Fish Over Time
Results from third larvicide experiment
DO data not available for JN or HP after 12 Aug
Timber significantly higher DO than all other sites.

37. Results Survival of Fish Over Time
Results from first adulticide experiment

38. Results Survival of Fish Over Time
Results from second adulticide experiment
DO higher at John’s Neck than Haven’s Point for full experiment

39. Results Comparison of Fish and Shrimp Survival Over Time
Corrected Percent Survival
Results from second adulticide experiment

40. Results
Summary of Mortality of Caged Organisms

41. What’s the Problem with Haven’s Point?

42. Results – Dissolved Oxygen
Problem!
Dissolved Oxygen and Temperature Time Series

43. Johns Neck
DO <20%
Diel DO - Spray Sites
Timber Point DO
TEMP

44. Channel vs. Ditch Dissolved Oxygen Saturation ebb flood photosynthesis
Time (hours)
photosynthesis
respiration
flood tide
ebb tide
Time (hours)

45. Results – Fish Growth
Fish growth was low, averaging only 0.05 to 0.5 mm/day with no differences observed between sites

46. Results Shrimp Prey Capture Ability
The ability of surviving shrimp to capture prey was highly variable, with no statistical decreases associated with pesticide exposure

47. methoprene
methoprene
resmethrin
resmethrin
methoprene
No evidence of toxicity resulting from exposure to water collected from the spray sites

48. Results Dosing Experiment
Average LC50s:
Scourge® ~ 0.58 g/L
Sumethrin: ~ 1.1 g/L
Resmethrin ~ 1.2 g/L
TOXICITY:
Scourge® > Sumethrin ~ Resmethrin
--Dosing experiment used another pyrethroid Sumethrin, which is also sometimes, but not often, sprayed on LI.
--Similar toxicities with scourge seeming to be a bit mre toxic… STATISTICS??? Not enough replication yet to do this…
--Avg. LC50s of all three pesticides less than 1.3 ug/L
--prey capture rate was possibly shown to be affected in survivors of the dosing study at 1 ug/L, however, more studies are necessary for more replication…
NOTE: no methoprene-based chemical was toxic up to 1 mg/L concentrations

49. Results Benthic Species Abundance
At diff. Sites there were both big diffs in total numbers (abundance) and species (composition) at each site, but no apparent spray differences.
Note: “Other” represents the remaining 1% of species

50. Results
Methoprene water column concentrations

51. Results
Methoprene continued

52. Results Disposition of Methoprene in marsh
Methoprene not detected in water pre spray or in reference marshes.
[Methoprene] exceeding 1,000 ng/L were observed 30 min post spray in waters after 3 of 4 sprays. Interface values not always highest.
2 hrs post spray [methoprene] < 25 ng/L with detectable levels persisting for 1 to 2 days post spray.
Methoprene in sediment was more persistent with concentrations ranging between 3-60 ng/g in samples collected within a week of spraying, but no evidence of accumulation due to repeated sprays was observed.

53. Results Scourge® water column concentrations
Johns Neck - Unchachoque Creek

54. Results Disposition of Scourge® active ingredients in marsh
Neither PBO nor Resmethrin found in pre-spray samples of water or sediment, nor in sediments after spraying
[Resmethrin] much higher at water interface (320 ng/L) than inches below water surface (60 ng/L) – highest levels found
[Resmethrin] drops rapidly in water becoming undetectable >2 hrs after spray
PBO more persistent with trace amounts detected up to two days after spray
PBO/Resmethrin in water samples >> than in Scourge® formulation (3:1) with median values of 46:1
The first spray event delivered a greater amount of Scourge® to the water than the second spray event

55. DO unknown
DO toxicity
likely

56. Non-caged fish exposure to pollutants
Related Experiments
Non-caged fish exposure to pollutants
Lab experiments to determine if fish would choose to avoid pesticides

57. Conclusions
No significant differences in fish growth rates (control sites vs. sprayed).
No significant differences in shrimp fecundity or prey capture ability (controls vs. sprayed)
No significant difference in species abundance or composition of benthic organisms (controls vs. sprayed)

58. Conclusions
Neither larvacide nor adulticide active ingredients persist at appreciable levels in marsh surface water more than a couple of hours.
New analytical methods allow for low part per trillion levels to be detected in water for up to 2 days after spraying for PBO and methoprene.
Analytical results suggest that delivery of pesticides to the marsh surface from aerial sprays can be quite variable.
Greater persistence of methoprene in sediments suggests that chronic effects on infaunal organisms should also be assessed.

59. Conclusions
Fish in lab experiments did not choose to avoid methoprene enriched water.
3 caged organism experiments exhibited decreased survival where pesticide applied.
2 experiments showed no such effect.
Low dissolved oxygen around dawn most likely cause of mortality in ditches.
Small changes in placement of cages had significant impacts on survival.

60. Conclusions
Aerial application of Altosid® and Scourge® on Suffolk County marine wetlands had no demonstrable effect on caged fish and shrimp, although field study compromised by low DO at many sites.
Data observed is consistent with the low and rapidly declining concentrations of pesticides measured in waters where cages were deployed after pesticide application, and data available on the toxicity of these compounds to fish and shrimp (LC50 of 0.5 μg/L for Scourge®, > 1mg/L for Altosid®).

61. Acknowledgements Suffolk County Legislature (funding)
Cashin Associates (coordination)
Anne McElroy – Stony Brook University (Lead P.I.)
Bruce Brownawell Lab - Stony Brook University (sampling & analysis)
Long Island University (caged fish assessment)
Suffolk County Department of Health Services
Division of Environment Quality (sampling)
Suffolk County Department of Public Works – Vector Control (spraying)
U.S. Geological Survey (sampling & analysis)
RTP Environmental Corp. (modeling)

62. Last Slide!
Thanks for listening.