Event Title

Low concentrations and short durations of road runoff are lethal to coho salmon

Streaming Media

Presentation Abstract

Urban stormwater runoff contains a complex mixture of toxicants that is acutely lethal to coho salmon (Oncorhynchus kisutch). Although it is unknown what chemicals in the mixture are responsible for the toxicity, the land use most strongly related to rates of mortality in the field is roads — particularly busy arterials. Juvenile and adult coho salmon experimentally exposed to 100% collected road runoff die within a few hours of exposure. In field studies, dead coho spawners are observed following rain events, but it is unknown how dilute are the chemicals causing the mortality, nor how quickly these mortalities occur after exposure to runoff. To better understand the lethality of road runoff to coho salmon, we experimentally exposed juvenile coho salmon to dilutions of road runoff collected from a busy arterial in Seattle, Washington, USA, varying the concentration and exposure duration. Runoff collected from three storm events showed 24-h median lethal concentrations (LC50) that were remarkably similar (6-10%). Runoff from an additional storm event (24-h LC50 = 4%) was used to determine minimum exposure durations to cause mortality. Factorial exposures of 1, 2, 4, and 8 h were conducted for runoff concentrations of 5%, 11.2%, and 25% and survival monitored up to 24 h. Nearly all mortality occurred after fish were transferred to clean water. Mortality (24-h) occurred for exposures as brief as 1 h at 25%, 2 h at 11.2%, and 8 h at 5%. No mortality occurred following 1-h exposure to 11.2% and following ≦4-h exposures to 5%. All other combinations of exposure time and concentration caused mortality for at least some individuals. By linking these results to water chemistry and observed rates of mortality in urban creeks, we may begin to estimate the amount of treatment required for runoff entering streams where coho salmon spawn.

Session Title

Session 1.1B: The Environmental Toxicology and Chemistry of the Salish Sea Ecosystem

Conference Track

Contaminants, Plastics, Microplastics, Toxicology & Stormwater

Conference Name

Salish Sea Ecosystem Conference (2020 : Online)

Document Type

Event

SSEC Identifier

2020_abstractID_5837

Start Date

21-4-2020 10:30 AM

End Date

21-4-2020 12:00 PM

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

Language

English

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Apr 21st, 10:30 AM Apr 21st, 12:00 PM

Low concentrations and short durations of road runoff are lethal to coho salmon

Urban stormwater runoff contains a complex mixture of toxicants that is acutely lethal to coho salmon (Oncorhynchus kisutch). Although it is unknown what chemicals in the mixture are responsible for the toxicity, the land use most strongly related to rates of mortality in the field is roads — particularly busy arterials. Juvenile and adult coho salmon experimentally exposed to 100% collected road runoff die within a few hours of exposure. In field studies, dead coho spawners are observed following rain events, but it is unknown how dilute are the chemicals causing the mortality, nor how quickly these mortalities occur after exposure to runoff. To better understand the lethality of road runoff to coho salmon, we experimentally exposed juvenile coho salmon to dilutions of road runoff collected from a busy arterial in Seattle, Washington, USA, varying the concentration and exposure duration. Runoff collected from three storm events showed 24-h median lethal concentrations (LC50) that were remarkably similar (6-10%). Runoff from an additional storm event (24-h LC50 = 4%) was used to determine minimum exposure durations to cause mortality. Factorial exposures of 1, 2, 4, and 8 h were conducted for runoff concentrations of 5%, 11.2%, and 25% and survival monitored up to 24 h. Nearly all mortality occurred after fish were transferred to clean water. Mortality (24-h) occurred for exposures as brief as 1 h at 25%, 2 h at 11.2%, and 8 h at 5%. No mortality occurred following 1-h exposure to 11.2% and following ≦4-h exposures to 5%. All other combinations of exposure time and concentration caused mortality for at least some individuals. By linking these results to water chemistry and observed rates of mortality in urban creeks, we may begin to estimate the amount of treatment required for runoff entering streams where coho salmon spawn.