New Englanders are familiar with the mountains that mark their landscape: the Green or White Mountains in Vermont and New Hampshire, the Berkshires and Holyoke ranges in Western Massachusetts. But mountain ranges also lie beneath New England’s North Atlantic waters, and are equally diverse havens for wildlife as their terrestrial counterparts.
Cashes Ledge is one of New England’s most spectacular mountains, but it happens to be lying 80 miles southeast of Portland. This submerged mountain, known as a seamount, is composed of widely spaced peaks, pinnacles, and knolls with average depths of about 100 feet and its highest peak, Ammen Rock, rises within 40 feet of the surface.
This topography is one of the contributors to Cashes’ ecological richness; the steep angle of the slopes causes an oceanographic phenomenon called internal waves. As currents bring water against the abrupt topographic “high” of the ridge, the layers of plankton in the warmer overlying waters are driven to the bottom, as frequently as 20 times a day. These down-welling plankton layers are pulses of concentrated food that sustain bottom-dwelling organisms and fuel the entire food web.
Along with the constant circulation of nutrients by internal waves, the variety of terrains at Cashes Ledge—rocky banks and granite outcroppings, peaks, and channels, cobble and boulder fields, sand-and-gravel-covered seafloor, and soft bottom areas of mud and silt in the basins—also contributes to its intense complexity of life.
Having so many different spaces for organisms to inhabit increases species diversity. The hard, rocky substrate on Ammen Rock and other pinnacles along Cashes Ledge is home to a variety of plants and animals that vary by depth along the slopes, creating identifiable shallow, intermediate, and deep water zones.
In the shallow zone, which extends from the top of each pinnacle down to a depth of approximately 130 feet, grow forests of laminarian kelp up to 30 feet tall, shifting to shotgun kelp as the depth increases. At this depth, kelp groves alternate with aggregations of sea anemones, and both encrusting and mobile invertebrates proliferate in the profuse protection of the kelp.
In the intermediate zone, suspension-feeding invertebrates begin to predominate, and continue to the bottom of the rock slope at approximately 200-230 feet. As the slope begins to level off between 230-250 feet, the muddy bottom of the deep zone supports a biogenic habitat structure for tube worms, mud anemones, and northern shrimp.
The teeming diversity of seamount ecosystems makes them tempting to deep-sea fishing trawlers, which would drag weighted nets across the mountainous terrain in order to catch the schools of fish which congregate there to breed, lay their eggs, and grow to maturity among the sheltering crags. The rocky cobble and gravel substrates of Cashes Ledge are critical nurseries for juvenile Atlantic cod; its sandy and algal dominated areas serve as habitat for pollock eggs, larvae, and young, and its deep muddy areas are essential habitat for white hake.
The kelp forest that is a signature of Cashes Ledge is quite susceptible to human-induced harm. If stripped by mobile fishing gear or shredded by repeated impact from lines, hooks, traps, or other human influences, the tall kelp forests that grow on the Cashes Ledge pinnacles would take many years to re-achieve their former stature. The diverse ecosystem that depends upon these kelp forests could be completely altered, if not eliminated, during that period of regrowth.
Bottom trawling to catch a few groundfish is “like clear cutting a forest to catch a squirrel,” says New England Ocean Odyssey partner and renowned marine wildlife photographer Brian Skerry, who has witnessed bottom-trawled environments firsthand on his dives.
It is such a unique, valuable, and interdependent ecosystem, Cashes Ledge requires permanent protection from human impingement. As a large area comprising many different types of habitat, Cashes Ledge has much to contribute toward keeping our oceans healthy.
Laura Marjorie Miller writes about travel, ocean conservation, Yoga, magic, myth, fairy tales, photography, and other soulful subjects. She is a regular columnist at elephantjournal, a writer at UMass Amherst, and a travel correspondent for the Boston Globe. Her writing has appeared in Parabola and she has features forthcoming in Yankee Magazine and Seven Miles of Steel Thistles. She is based in Massachusetts, where she lives with a cat named Huck.