The Wonder Down Under

The January/February 2016 issue of Brown University’s Alumni Magazine includes a feature of Cashes Ledge and Dr. Jon Witman, who is a professor of biology at the university and a Cashes Ledge expert. Having dived at Cashes Ledge for more than 30 years, Witman has seen the underwater mountain range evolve from a bountiful ecological environment to a still-productive but threatened habitat. Below is an excerpt from the article by Louise Sloan. Read the full version here

It’s not exactly a trip to the Statue of Liberty or Muir Woods. To get to Cashes Ledge, part of a proposed national monument in the Atlantic Ocean’s Gulf of Maine, you have to get in a boat and head to a spot about eighty miles east of Cape Ann, Massachusetts. After the four-hour trip, you drop an anchor near Ammen Rock, the tallest pinnacle in Cashes Ledge, a twenty-five-mile-long underwater mountain chain. Ammen Rock rises from the sea floor 720 feet below to within thirty feet of the water’s surface. Once there, divers set up a buoy marking the spot, the only clue to Cashes’s underwater marvels. Then they jump into forty-degree water that’s moving at a speed of two to three knots—about as fast as a class II rapids—and “swim like hell for the buoy,” says Professor of Biology Jon D. Witman, who has been conducting research at Cashes Ledge for more than thirty years.

As you pull yourself hand-over-hand down the buoy rope, Witman says, you slowly make out what looks like the ocean floor. But, as you get closer, you realize it’s moving. What you’re looking at is the canopy of an undersea jungle, a forest of kelp exponentially thicker than any you’ll find elsewhere in the coastal Gulf of Maine. Because of the distance between Cashes Ledge and the coast, where the water is clouded by runoff and other pollutants, sunlight penetrates deeply into the clear, cold water. As a result, the kelp grows as far down as 100 feet, and it grown unusually tall—up to fifteen feet.

. . .

Ten years ago, when the Conservation Law Foundation (CLF) asked Witman, who teaches Brown undergrads the basics of ecology, to recommend an ocean area to protect, Cashes was the obvious answer. Witman describes it as a “Disneyland of biodiversity” containing every kind of ocean bottom habitat, all in a concentrated space. Combined with the food pump provided by the waves, this dense habitat contains a rare proliferation of sea creatures representing an unusual variety of species. The complexity helps create more ecosystem stability and probably greater resilience to withstand such threats as climate change. With this range of creatures filtering water, removing carbon, producing oxygen, and providing all the other “ecosystem services” that the fish we eat depend on, Witman says, Cashes is a key to the health and productivity of the entire Gulf of Maine, including areas where commercial fishermen harvest cod.

Read the full article