Reflection 187: Rockweed Perspectives

March 8, 2010

(Copyright © 2010)

There is more to rockweed than meets the eye. This is because we regard it, for the sake of clarity, from highly selective perspectives. To see anything at all clearly, we screen out much of everything else that gets in the way of what we’re trying to see from our point of view.

In the case of rockweed harvesting along the Maine coast, the two chief perspectives look at rockweed from opposite directions, from the economic-industrial side, and the research-ecological side. From a management perspective, the challenge is to find a sustainable balance between the two sides.

You can tell immediately which side people are on by the terms they use to discuss rockweed. If you hear “biomass,” “wet tons,” “weed,” “standing crop,” or “jobs,” you know you are listening to the industrial side of the discussion. On the other hand, words such as “habitat,” “primary producer,” “refuge,” “ecosystem,” or Ascophyllum nodosum (the Latin binomial by which the desirable species of rockweed is known), you are hearing the ecological side.

Rockweed harvesters dwell in the space where the two perspectives meet. Their motive for being there is primarily economic—to make a living—but to do so in that particular way they also must develop a professional understanding of what it is they are converting from a nurturing and protective habitat (as seen by one side) to so many wet tons of biomass (as seen by the other). Generally not scientists themselves, they pick up enough ecosystem talk to carry on a conversation with landowners and anyone else who engages them. But they fall short of acquiring an informed ecological perspective; their allegiance is to the industry, not the ecosystem. By way of compromise, they develop a rationale for taking so much from a given bed of rockweed—often cited as 17% of the “standing crop,” deliberately leaving the rest to carry on its ecological function. Their ultimate goal, however, is to deliver so many wet tons of biomass to a dealer at dockside.

The lobster industry in Maine is a notable example of harvesters regulating themselves to assure the sustainability of their fishery. They gave up dragging for lobsters in the 1940s, and now V-notch egg-bearing females, impose upper and lower size limits on the allowable catch, put escape vents in their parlors for undersize lobsters, limit their strings of traps, set up an apprenticeship system for those wanting to learn the craft, and generally conduct themselves in a responsible and professional manner for the sake of long-term job security. That is, beyond being harvesters, they have trained themselves to be stewards as well. Even to the point of feeding their catch by reliably filling their bait bags, which brings the wild fishery to the verge of an aquaculture operation.

The questions faced by the rockweed industry and ecologists alike include: 1) How much rockweed can be taken without disrupting the long-term structure and productivity of the ecosystems within which it function?; 2) Where can it be so taken?; 3) By what methods?; 4) At what intervals?; and 5) By harvesters with what experience and training? The challenge I see in such questions is that of asking rockweed harvesters to act as good stewards of the resource they depend on for a living. Which comes down to the issue of whose standards are they to meet—those set by the industry, or by impartial ecologists?

Harvest standards set by ecologists consider not only the biomass of the rockweed taken, but the function of that biomass if left in place. As a primary food producer—along with kelp, eelgrass, low marsh grass, and phytoplankton, among others—on which marine ecosystems depend, rockweed supports the survival of the living coast that complements upland forests in giving Maine its character and identity as a human habitat.

How does that work? Rockweed constantly feeds energy derived from photosynthesis into coastal waters from branches breaking off through wear and tear from constant motion imparted by tides and waves. As free-floating wrack, that organic material rides up and down on local currents, providing a surface habitat for amphipods and other life forms, which in turn attract birds like Bonaparte’s gulls and various species of terns—direct beneficiaries of the energy stored in bits and pieces of rockweed. That wrack either exits the bay to feed a variety of species farther along the coast or out in the Gulf of Maine. Or is perhaps deposited at the high tide line along the shore, where it provides habitat and food for shoreline scavengers—sandpipers, song sparrows, thrushes, gulls, crows, schools of small fish, among other wildlife species.

Broken into ever-finer particles, rockweed eventually decays, becomes colonized by protein-rich bacteria, and assumes a new identity as energy-rich detritus, food for filter-feeding mussels, scallops, oysters, barnacles, juvenile lobsters, and early life stages of a great many marine creatures both vertebrate and invertebrate. Because of the nutritional boost from nitrogen-rich bacteria, detritus is a value-added form of the rockweed and other primary food producers from which it derives. In supporting entire marine and estuarine ecosystems, a ton of rockweed in the form of detritus is worth far more than the $40 the rockweed harvester gets paid by the ton. In fact its value is inestimable. What is the going price of a breath of fresh air, a glimpse of sunlight, or a raindrop falling from the sky? Coastal Maine and its gulf run largely on detritus. What is that worth to a fox, eagle, harbor seal, or to you? What is the value of Cobscook Bay, Taunton Bay, or the Gulf of Maine?

The history of Maine fisheries is a tale of descent lower and lower on the food web, until now even primary producers such as rockweed and kelp have a certain market price—not as value-added detritus, but as materials in the raw. Which is the highest and best use of rockweed?—detritus to feed the entire coast, or a commodity sold as fertilizer or an additive for commercial foods and cosmetics. Perspectives have implications and ramifications which, like by-catch, often go unrecognized.

To end up, I will shift from the food-web to the habitat aspect of rockweed. Whether providing shelter; opportunity for grazing, foraging, reproducing, refuge from predation; or otherwise essential habitat, rockweed invites life to the intertidal zone, a hardscrabble habitat of extremes if ever there was one. Yet by expanding and collapsing as driven by its highly variable circumstances, rockweed offers its services to all comers with great efficiency, tide after tide, season after season, year after year. Again, what are those services worth to alewives, eels, periwinkles, crabs, copepods, amphipods, crangon shrimp, eiders, black ducks, loons, herons, kingfishers, and the likes whose lives depend on them? What are they worth to you in comparison to having a tub of industrial-grade ice cream in the freezer, or a creamy cosmetic on your lips?

The essential question is: At what harvest level do the ecological and industrial values of rockweed come into conflict so that opting for one penalizes the other? The rockweed industry aims to convert 17% of select beds of rockweed to biomass. That figure assumes a great deal about the continued functioning of local ecosystems after those beds are cut, their structure radically altered, their biomass removed.

Since the energy stored in rockweed fuels much of the Maine coast, it strikes me that removal of even 17% of select areas is excessive. Given that 100% of rockweed energy turns over every two years, distributing its wealth as wrack and detritus among species such as I have mentioned, a 17% cut on top of 50% annual turnover sounds to me more like a 34% reduction of the “standing crop” on which that natural distribution of food energy depends in the following year. In light of the habitat and energy reductions implied by that level of rockweed harvest, I propose that a 5% cut seems eminently more reasonable.

At the February 10 Rockweed Research Priorities Symposium at the University of Maine in Orono, Sea Grant joined with the Department of Marine Resources in initiating a process of discovery to find out what gaps still exist in our understanding of the ecological consequences of rockweed harvesting. On February 17, current findings were relayed to the Joint Legislative Committee on Marine Resources, which considers last year’s legislation regarding the harvest level in Cobscook Bay a done deal. That is, the state sides with industry recommendations. Which makes it all the more likely that the 17% level of harvest will spread to the rest of the coast.

It is up to resource managers in Maine to decide whether to take a short-term view for the sake of feeding biomass to the industry, or a long-term view including habitat considerations and the gradual distribution of rockweed energy as viewed from an ecological perspective. Stakes are high: Nothing less than the continued productivity and viability of the Maine coast is at issue. I have testified before the Marine Resources Committee that I consider a 17% rockweed cut to be unsustainable. From my perspective, a less risky harvest might be as high as 5% every third year in the same bed if closely monitored.

Seal Pup Amid Rockweed

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