Sources, spatial variability and uptake of Polychlorinated biphenyls (PCBs) in Southern Resident killer whales

Chemical contaminants, particularly Polychlorinated Biphenyls (PCBs), have been identified as one of three major threats to the health of Southern Resident killer whales (SRKWs)(Grant & Ross, 2002). The SRKW population has been listed as Endangered under Canada’s Species at Risk Act, 2002 (SARA) and under the US Endangered Species Act. Recent monitoring has shown that the concentration of PCBs in SRKW tissue hasn’t significantly declined from 1996 to 2015 as would be expected for a chemical that was banned in the 1970’s (Guy, unpublished Master Thesis). This observation suggests that there continue to be inputs of PCBs into the marine environment that supports the SRKW food chain. This is important to address because PCBs have been linked to adverse health effects in marine mammals(Ross, Ellis, Ikonomou, Barrett-Lennard, & Addison, 2000). To reduce risks of PCBs to SRKWs, it is critical to identify the sources of PCBs to killer whales and to develop measures to reduce these sources. We will use GIS spatial analysis tools to estimate spatially averaged concentration of PCBs in sediments within killer whale habitat. A previously developed bioaccumulation model (Alava, Ross, & Gobas, 2016; Lachmuth et al., 2010) will be used to estimate the uptake of PCBs by male, female and juvenile SRKW. This spatially explicit approach has been used in recent bioaccumulation modeling studies of migratory species that inhabit areas with spatially varying contaminant concentrations (Kim et al., 2016; von Stackelberg, Williams, Clough, & Johnson, 2017). The research aims to support a recovery plan for the SRKW by (i) compiling information on sediment PCB concentrations and PCB sources in the Salish Sea and visually displaying the information on maps; and (ii) identifying PCB sources and recommending actions that may reduce the exposure of SRKWs to local sources of PCBs.