Live Science: Seaweed could smother polar underwater ecosystems as melting sea ice exposes the seafloor to more sunlight, new research shows. Animals that dwell on the seafloor of the Arctic and Antarctic spend most of their lives in total darkness: Sea ice blocks rays during the spring and early summer, and the sun sets completely in the winter. Late summer and early fall when the ocean warms up enough to thaw the ice often marks the only time these critters see light. But as climate change causes sea ice...