Proposed Abstract Title

Biomagnification, oceanographic processes, and the distribution of toxic contaminants in Puget Sound’s pelagic food web

Type of Presentation

Oral

Session Title

General Pollution Topics

Location

2016SSEC

Description

Long-term monitoring of toxic contaminants in fish has shown that Puget Sound’s pelagic food web is a regional hot spot of persistent, bioaccumulative, and toxic chemicals. Chemicals such as polychlorinated biphenyls (PCBs) are accumulated in and magnified by the pelagic food web, resulting in high concentrations in resident piscivorous fishes, salmon, and apex predators including killer whales. In this talk we underscore the importance of biomagnification of PCBs in the lowest trophic levels of the pelagic food web, and compare PCB biomagnification patterns across four of Puget Sound’s oceanographic basins. PCB data from phytoplankton, primary consumers, and resident fish predators lend credence to the hypothesis that PCBs concentrate in the pelagic food web as they enter surface waters, challenging the paradigm of preferential accumulation in sediments. Four potentially contributing factors are considered:

  • Puget Sound’s microbial food web and abundant micro-grazers promote remineralization and recycling of organic material in surface waters, reducing the intensity of the benthic-pelagic coupling,

  • Puget Sound’s fjord-like basins are deep enough to support vertically migrating zooplankton such as krill, which intercept and feed on sinking particles; krill feeding behavior mechanically breaks up particles and reduces their sinking rate, promoting retention of particle-bound PCBs in mid- and surface waters,

  • a long pelagic food chain including vertically migrating zooplankton and a complex microbial community increases biomagnification potential, and

  • sinking particles aggregate at the pycnocline in stratified waters, where they are processed by micro-grazers, and particulate PCBs are recycled by micro-grazers into the pelagic food web.

These factors are discussed, using Elliott Bay as an example representing one of Puget Sound’s greatest sources of PCB contamination. Elliott Bay also has a history of large blooms of micro-grazers (Noctiluca sp.), it is deep enough to support vertically migrating zooplankton such as krill (Euphausia pacifica), and its waters can be strongly stratified.

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Biomagnification, oceanographic processes, and the distribution of toxic contaminants in Puget Sound’s pelagic food web

2016SSEC

Long-term monitoring of toxic contaminants in fish has shown that Puget Sound’s pelagic food web is a regional hot spot of persistent, bioaccumulative, and toxic chemicals. Chemicals such as polychlorinated biphenyls (PCBs) are accumulated in and magnified by the pelagic food web, resulting in high concentrations in resident piscivorous fishes, salmon, and apex predators including killer whales. In this talk we underscore the importance of biomagnification of PCBs in the lowest trophic levels of the pelagic food web, and compare PCB biomagnification patterns across four of Puget Sound’s oceanographic basins. PCB data from phytoplankton, primary consumers, and resident fish predators lend credence to the hypothesis that PCBs concentrate in the pelagic food web as they enter surface waters, challenging the paradigm of preferential accumulation in sediments. Four potentially contributing factors are considered:

  • Puget Sound’s microbial food web and abundant micro-grazers promote remineralization and recycling of organic material in surface waters, reducing the intensity of the benthic-pelagic coupling,

  • Puget Sound’s fjord-like basins are deep enough to support vertically migrating zooplankton such as krill, which intercept and feed on sinking particles; krill feeding behavior mechanically breaks up particles and reduces their sinking rate, promoting retention of particle-bound PCBs in mid- and surface waters,

  • a long pelagic food chain including vertically migrating zooplankton and a complex microbial community increases biomagnification potential, and

  • sinking particles aggregate at the pycnocline in stratified waters, where they are processed by micro-grazers, and particulate PCBs are recycled by micro-grazers into the pelagic food web.

These factors are discussed, using Elliott Bay as an example representing one of Puget Sound’s greatest sources of PCB contamination. Elliott Bay also has a history of large blooms of micro-grazers (Noctiluca sp.), it is deep enough to support vertically migrating zooplankton such as krill (Euphausia pacifica), and its waters can be strongly stratified.