[1] US EPA, Off Res & Dev, Off Sci Policy, Washington, DC 20007 USA
[2] Simon Fraser Univ, Sch Resource & Environm Management, Burnaby, BC V5A 1S6, Canada
[3] Univ Maryland, Chesapeake Biol Lab, Ctr Environm Sci, Univ Syst Maryland, Solomons, MD 20688 USA
[4] Univ Toronto, Dept Geog, Mississauga, ON L5L 1C6, Canada
[5] Geol Survey Canada, Bedford Inst Oceanog, Nat Resources Canada, Dartmouth, NS B2Y 4A2, Canada