Presentation Abstract

River otters (Lontra canadensis) are apex predators that play an important role in aquatic ecosystems. They accumulate contaminants via their diet of fish and invertebrates, potentially serving as biomonitors of watershed health. In summer and fall 2016, we collected 33 otter scats from sites along the Green-Duwamish River, ranging from river miles 0-54. River miles 0-5 represent the Lower Duwamish Waterway (LDW), a U.S. Superfund site slated for a 17-year remediation. Concentrations of polychlorinated biphenyls (PCBs) at sites in the LDW were 9.1 and 19.3 mg/kg (geometric means, lipid weight) - above the reported threshold value of 9 mg/kg associated with adverse effects for river otters. By river mile 10, mean concentrations of PCBs decreased to 2.6 mg/kg, with remaining upriver sites ranging from 0.4-1.9 mg/kg. Polycyclic aromatic hydrocarbon (PAH) concentrations showed a similar pattern. The highest PAH levels (140 and 91 mg/kg, geometric means, wet weight) were measured in the LDW whereas levels upriver were 9.7-25 mg/kg. Based on preliminary genetics data from several sampling locations, we infer that otters remain in local river reaches, so scat contaminant levels reflect local environmental concentrations. These are the only empirical contaminant data available for a mammal or apex predator in the Green-Duwamish, and they reveal: 1) otters may be impacted by contaminant loads in the LDW; 2) the contamination gradient along the Green-Duwamish is reflected in otters, indicating they may be useful biomonitors; and 3) a baseline level of contamination in otters that may be of great value for assessing ecological impacts of long-term cleanup efforts. Scat collected in 2017 and analyses for brominated flame retardants, organochlorine pesticides, stable isotopes, and genetics will provide additional depth and breadth to these results. Significant questions remain as to the potential individual health and population impacts of environmental contaminants in this top-level aquatic predator.

Session Title

Contaminants in Marine Mammals of the Salish Sea and Their Food Web

Keywords

River otters, Green-Duwamish, Biomonitors of ecological health

Conference Track

SSE3: Fate, Transport, and Toxicity of Chemicals

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE3-334

Start Date

4-4-2018 1:45 PM

End Date

4-4-2018 2:00 PM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 4th, 1:45 PM Apr 4th, 2:00 PM

River otters of the Green-Duwamish: biomonitors of ecological health

River otters (Lontra canadensis) are apex predators that play an important role in aquatic ecosystems. They accumulate contaminants via their diet of fish and invertebrates, potentially serving as biomonitors of watershed health. In summer and fall 2016, we collected 33 otter scats from sites along the Green-Duwamish River, ranging from river miles 0-54. River miles 0-5 represent the Lower Duwamish Waterway (LDW), a U.S. Superfund site slated for a 17-year remediation. Concentrations of polychlorinated biphenyls (PCBs) at sites in the LDW were 9.1 and 19.3 mg/kg (geometric means, lipid weight) - above the reported threshold value of 9 mg/kg associated with adverse effects for river otters. By river mile 10, mean concentrations of PCBs decreased to 2.6 mg/kg, with remaining upriver sites ranging from 0.4-1.9 mg/kg. Polycyclic aromatic hydrocarbon (PAH) concentrations showed a similar pattern. The highest PAH levels (140 and 91 mg/kg, geometric means, wet weight) were measured in the LDW whereas levels upriver were 9.7-25 mg/kg. Based on preliminary genetics data from several sampling locations, we infer that otters remain in local river reaches, so scat contaminant levels reflect local environmental concentrations. These are the only empirical contaminant data available for a mammal or apex predator in the Green-Duwamish, and they reveal: 1) otters may be impacted by contaminant loads in the LDW; 2) the contamination gradient along the Green-Duwamish is reflected in otters, indicating they may be useful biomonitors; and 3) a baseline level of contamination in otters that may be of great value for assessing ecological impacts of long-term cleanup efforts. Scat collected in 2017 and analyses for brominated flame retardants, organochlorine pesticides, stable isotopes, and genetics will provide additional depth and breadth to these results. Significant questions remain as to the potential individual health and population impacts of environmental contaminants in this top-level aquatic predator.