It is a very long and thin line that separates the terrestrial
wonders of British Columbia from the wonders hidden beneath the
sea. And just as on land, there are a myriad of forces at work
there. The edge of the continent slips below the sea's surface,
in a gentle slope called the continental shelf. At the edge of
this shelf, the sea floor plummets from about 200 meters below
the surface to the ocean depths. Most marine life exists in the
relatively shallow water of the continental have gouged long
narrow fiords into British Columbia's coastline, the sea floor
may be three times deeper than on the continental shelf. In many
cases, the glaciers left large mounds of gravel and rock at the
mouths of these fiords, called sills. The currents moving over
these sills force nutrients upward, making the fiord mouths
productive feeding areas. Behind the sills, the water often lies
stagnant and almost lifeless. The key to survival in the ocean
is light. Below about 40 meters, there is too little light for
plant life to