Methods
Geo-representation of pyrethroid use
Utilize current water quality, species presence, pesticide regulation, and critical habitat data to develop a geospatial representation of pyrethroid use and tidewater goby populations
Environmental modeling of pyrethroids
Implement EPA's pesticide risk assessment model, with locally accurate model inputs, to estimate the acquatic concentration of bifenthrin and the risk it poses to the tidewater gobies in Ormond Lagoon
SAmpling in Ormond lagoon
Collected water and sediment samples from Ormond Lagoon to calculate current pyrethroid levels before and after precipitation events to support environmental modeling efforts
Best Management practices
Formulate both urban and agricultural best management practices (BMPs) to reduce the off-site runoff potential in areas of pyrethroid application in the Ormond Lagoon Watershed and for the state of California
Geo-representation of pyrethroid use
Utilizing the California Department of Pesticide Regulation's Pesticide Use Reporting (PUR) data, total pyrethroid use was estimated for the coastal watersheds of California. The PUR program requires all licensed pesticide applicators- therefore excluding personal use of products sold at home improvement stores- to report their pesticide use. Agricultural use is reported to the square mile and daily level while non-agricultural use is only reported to the county and monthly level. Our team relied on population data provided by the U.S Census to estimate non-agricultural use at the watershed scale.
Total Pyrethroid Use in Coastal California
There is high spatial variability of pyrethroid use across coastal watersheds. Many areas with concentrated use (SF Bay, Salinas, LA) drain into tidewater goby critical habitat.
There is also watershed specific seasonality of pyrethroid applications which has important implications for the tidewater goby. For example, many watersheds have a spike in application loads right before the rainy season begins.
Pyrethroid Use in the Ormond Lagoon Watershed
In Oxnard, the areas with the highest rates of application are concentrated nearest Ormond Lagoon. Smaller watershed unit analysis shows the variability in location of use, and the type (Ag. or Non Ag.)
In Oxnard, the areas with the highest rates of application are concentrated nearest Ormond Lagoon. Smaller watershed unit analysis shows the variability in location of use, and the type (Ag. or Non Ag.)
Environmental Modeling of pyrethroids
The EPA Pesticide in Water Calculator (PWC) model was used to estimate bifenthrin concentration in the Ormond Lagoon under different scenarios. To inform the PWC model, detailed research was completed to collect chemical, land-use, application rate/type/extent, climate, soil, agricultural, and hydrological data.
PWC Model Results
Key Findings
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Sources of Pyrethroids
Strawberry production and pest control applications on impervious surfaces are the largest contributors of pyrethroids to the Ormond Lagoon Watershed. Bifenthrin and permethrin from these sources were identified as causing the most ecological risk to tidewater gobies. |
Potential Toxicity to the Tidewater Goby
Current pyrethroid use is likely adversely affecting tidewater gobies. Modeled results indicate both acute direct toxicity and negative indirect effects via diminished prey abundance. |
sampling in ormond Lagoon
To better understand current pyrethroid levels and populate the PWC model with the most current environmental parameters, two field sampling studies were conducted in Ormond Lagoon on October 27, 2017 and January 26, 2018. Water and sediment samples were taken from 8 sites, 6 of which were located at drainages within Ormond Lagoon (SO1, SO2, SH1, SH2, SJ1, SJ2) and 2 located within the lagoon itself (SOL1, SOL2) .
Summary of Sampling Results
• More pyrethroids were found at higher concentrations following a rain event which agrees with the model results
• The highest concentrations were found downstream of strawberry agriculture
• Results indicate that personal use of pyrethroids for home and yard pest control is a significant contributor to toxicity
• More pyrethroids were found at higher concentrations following a rain event which agrees with the model results
• The highest concentrations were found downstream of strawberry agriculture
• Results indicate that personal use of pyrethroids for home and yard pest control is a significant contributor to toxicity
Best management practices
To develop recommendations for BMPs, an extensive literature review was conducted. This review researched existing structural and behavioral BMPs that aimed to mitigate pyrethroids directly, or the means that pyrethroids enter waterways. In order to specify BMPs for Ormond Lagoon, we created two categories that matched the two types of pyrethroid application: urban, and agricultural. Within these two categories of BMPs recommendations regarding behavioral and structural approaches were made separately. The literature review into BMPs was site specific, and informed by characteristics of the Ormond watershed and the sources of pyrethroids in the watershed.
After conducting a literature review of BMPs for pyrethroids, and with our understanding of pyrethroid use in the Ormond watershed, we recommend the following BMPs for their respective category.
After conducting a literature review of BMPs for pyrethroids, and with our understanding of pyrethroid use in the Ormond watershed, we recommend the following BMPs for their respective category.