Looking at three options to eventually replace the 7 kilometre stretch of underwater pipeline.
Overload has fed harmful algae blooms that have fouled drinking water and killed fish.
US-Canadian agency urges designating them resources held in public trust.
Ten leaders will work together to expand a regional maritime strategy.
Scientists say smaller bits attract dangerous chemicals such as pesticides.
Shipping logjam caused weeklong shutdown at largest steel mill in the US.
Studies are underway to determine the impact of microplastics along the food chain.