Illustration showing the transport of copepods through the water column

The Great South Channel is an undersea canyon between shallower Nantucket Shoals and Georges Bank. A relatively fresh coastal current flows south along the New England coast, bringing copepods along with it. In the channel, the coastal current collides with saltier, denser water to form an ocean front. Denser, saltier water sinks beneath the lighter, fresher water. Copepods sinking with the water swim back toward the surface, aggregating in dense patches along the front. (Illustration by Amy Caracappa-Qubeck, © Woods Hole Oceanographic Institution)