Contaminants in Puget Sound Forage Fishes and Impacts to the Marine Food Web

Science Center Objects

Toxic chemical pollutants have been released into Puget Sound for decades by human activities. There’s a wide range of contaminants, from persistent compounds like polychlorinated biphenyls (PCBs) and flame retardants to contaminants of emerging concern. Aquatic species can be exposed to and accumulate contaminants, causing disease or disruption of biological processes like growth or reproduction. Forage fish, like Pacific sand lance, surf smelt, and Pacific herring, occupy a critical link in the marine food web, conveying energy from plankton up to larger fish, seabirds, and marine mammals. Understanding contaminant exposures of forage fish can provide insights into exposure routes for high profile species such as salmon, seabirds, seals, and orca. 

Despite the critical role they play, forage fish in Puget Sound are not well understood. Pacific herring have been targeted in commercial fisheries and are therefore the species most studied.  Pacific sand lance and surf smelt have received considerably less attention and there are significant knowledge gaps related to their basic life history. Potential stressors, like contaminants, are even less understood.

Pacific sand lance

Pacific sand lance. Credit: Theresa Liedtke, USGS. (Public domain.)

Through the USGS Coastal Habitats in Puget Sound (CHIPS) program, the WFRC has been investigating contaminants in forage fish. Our focus has been on Pacific sand lance and surf smelt.  These forage fish species were selected, in part to link with our previous research on their spawning and nursery habitats and movements, and in part because of the total lack of information on contaminants. Pacific herring contaminant exposure is monitored as part of the Puget Sound Ecosystem Monitoring Program, but the other forage fish species are excluded. The WFRC is working to fill this knowledge gap to help inform managers about the risk and route of contaminant exposure to high profile species such as salmon and orcas.

 Pacific sand lance in Puget Sound are contaminated with a range of toxic pollutants. A synoptic survey of juvenile and adult sand lance was conducted between 2010 and 2014 at nine Puget Sound locations ranging from South Sound (Eld Inlet and Nisqually) to North Sound (Clayton Beach, Lopez Island) and including historically contaminated urban areas (Eagle Habor, Commencement bay). Composites of whole-body fish tissue from each site were analyzed for a suite of emerging contaminants such as polybrominated diphenyl ether (PBDE) flame retardants, chlorinated paraffins, and nonylphenols, as well as legacy contaminants such as polychlorinated biphenyls (PCBs), organochlorine pesticides, and polycyclic aromatic hydrocarbons (PAHs). This study provided the first data on toxic contaminant concentrations in sand lance tissue in Puget Sound.

The WFRC CHIPS team focused on PCBs and conducted a follow-up study to the synoptic survey. An interesting finding from the survey was that PCB concentrations in sand lance tissue from Eagle Harbor (a historically contaminated area) were about ten times higher than in comparably-sized fish from Clayton Beach (in North Sound). Juvenile sand lance (recently transformed from the larval stage) had PCB concentrations similar to or higher than adult fish at both sites suggesting the potential for maternal transfer of PCBs to eggs. To investigate this potential route of exposure, we collected sexually mature male and female sand lance in two size classes (~100 mm and >130 mm fork length) from Eagle Harbor and Clayton Beach in 2016. The males and females in the small size class were estimated to be first year spawners, and fish in the larger size class were estimated to be 2nd or 3rd year spawners. PCB concentrations were determined for composites of whole body fish tissue from egg-bearing females, from the eggs removed from collected females, and from whole body fish tissue from males. Similar to the survey, PCB concentrations in fish tissue from Eagle Harbor (mean 1100 ng/g lipid) were about 10 times higher than in tissue from Clayton Beach (mean 175 ng/g lipid). There was evidence of bioaccumulation with a clear size effect for both males and females at both sites, with the larger fish having higher PCB concentrations. We concluded that sand lance demonstrate maternal transfer of PCBs to their eggs based on three findings:

  1. All egg samples (both sites and both size classes of females) contained PCBs
  2. PCB concentrations in females and their eggs were similar
  3. PCB concentrations in males were higher than comparably-sized females and eggs. (This trend was strongest in larger size class which were assumed to be 2nd or 3rd year spawners.)

The WFRC team is currently working to investigate routes of entry of PCBs into the marine food web and the potential for some complex habitats like eelgrass to trap the fine sediments that can transport PCBs, thereby concentrating contaminants in critical habitats. Microplastics are another source of contamination in Puget Sound and the WFRC team is investigating their impact to fish and other biota based on habitat complexity.  Forage fish movements need to be understood in order to mitigate the risk of contaminant exposure, and the WFRC team has monitored the movements of surf smelt using acoustic telemetry and will be evaluating sand lance movements using mark-recapture techniques.