It Takes a Village: Life on the Bottom at Cashes Ledge

If you’re reading this post, you are probably a vertebrate. Those of us with spines and bones may find it hard to empathize with invertebrates (animals without spines), with their radically alien ways of being, frequent radial symmetry and general facelessness! But in many ways, invertebrates are the heart of ocean ecosystems, so for those of us interested in the fascinating universe of the sea it is important to understand them. And there are few better places to study invertebrate communities than one unique and now threatened special area in the Gulf of Maine.

Off the New England coast, about 80 miles due east from Cape Ann, lies Cashes Ledge: an undersea mountain range that is one of the most dynamic, and ecologically productive areas in the entire North Atlantic. Although only the most intrepid divers have seen Cashes Ledge with their own eyes, you can imagine the undersea terrain by thinking of mountains that you already know: as a multifaceted terrain of rocky peaks, banks, and channels, with a valley floor of mud, gravel, sand, boulders, and rock. This terrain supports a vibrant bottom-dwelling community of bright orange, red, and yellow sponges, sea stars, brittle and feather stars, sea squirts, sea pens, anemones, tube worms, northern shrimp, horse mussels, and sea mosses, technically known as “bryozoans.”

This colorful community is one of Cashes Ledge’s treasures, and one that is ever more in peril.

Invertebrates of Cashes Ledge. Photo by Jon Witman.
Invertebrates of Cashes Ledge. Photo by Jon Witman.

 

The variety of terrain at Cashes Ledge makes it an ideal living laboratory for studying the structure of the vibrant communities that grow along its slopes and hills. The enhanced water flow created by the topographic “ramp” of the Ledge encourages a high growth rate of invertebrates, both mobile and encrusted to their home rocks—varieties of sponges that are as yet uncatalogued, including a rare species of blue sponge that has only ever been sighted in the rock wall communities of Cashes Ledge.

Unique communities form at each depth, creating a complex and rich diversity of species. Metridum anemones gather at the tops of the ridges, sheltered by waving groves of laminarian kelp. Large urticina anemones and orange sea stars flourish in the mid-depth areas, as well as brachiopods, crinoids, ascidians, and yellow mounding sponges the size of footballs. The soft bottom is home to tube worms, pink northern shrimp, and thickets of mud anemones. Ammen Rock, the highest peak in the Cashes Ledge range, hosts large, sensitive beds of horse mussels: a “foundation species” because they provide habitat and refuge for other species.

Phakelia sponge and brittle stars. Photo by Jon Witman.
Phakelia sponge and brittle stars. Photo by Jon Witman.

The biological richness which makes Cashes Ledge so compelling for scientists to study has also drawn the attention of industrial fishing interests, which are currently lobbying to remove long-standing protections for Cashes Ledge.  Allowing bottom trawling at Cashes Ledge would rapidly deplete the remaining populations of large cod and other groundfish who are the most prolific spawners. The kelp forests, slopes and rocky terrain serve as excellent habitat and the best chance for restoring Gulf of Maine cod populations, which are now at historically low numbers.

Cod and anemones. Photo by Stellwagen Bank National Marine Sanctuary.
Cod and invertebrates. Photo by Stellwagen Bank National Marine Sanctuary.

New bottom trawling would be bad news for bottom-dwelling sea life at Cashes Ledge, because a number of the invertebrate species that grow there are particularly vulnerable to human disturbance. These invertebrates move slowly (if at all), and often have specialized reproductive cycles. If their habitat is harmed and breeding adults removed, species could take many years to recover, even longer for rarer species. Scientific estimates predict that the large, solitary sea anemone Urticina crassicornis would take 268 years to return to the community if it were removed by fishing gear.

Trawling Cashes Ledge could deplete or endanger many species that we do not yet fully know about. Cashes Ledge should be left intact as a resource for scientists, as well as a replenishment zone whose presence will sustain a recovering ocean ecosystem that will be of benefit to fishermen in the future. Trawling at Cashes Ledge is a short-term economic gamble that would cause long-term economic and environmental damage.

Cashes Ledge is a “wild offshore place that helps us understand how marine ecosystems tick,” says marine ecologist Jon Witman, who has been studying it for 35 years. “Cashes Ledge provides an opportunity to understand why biodiversity matters in an ecological sense. Unfortunately,” he continues, “we are losing marine biodiversity in the world’s oceans faster than we can study it.”

As an offshore haven far from the polluted waters of coastal habitats, Cashes Ledge warrants full and permanent protection to ensure that its intricately connected habitats and unique ecosystem can continue to serve as a reservoir of diverse ocean wildlife, a replenishment zone for sustainable fish stocks, and an open ocean laboratory for scientific research. Please add your voice to those calling for the protection of Cashes Ledge.

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.

Feature image credit: Josh Cummings