Sunday, February 28, 2010

Rockweed - A "keystone species" of Quoddy's spectacular productivity?

No videos or pictures in your ILQW email? See them at

Excerpt from:

What isn't known is whether or how animal populations, including commercially important species, are negatively affected in the long-term by these changes.

Jill Fegley, a marine biologist for the North Carolina Coastal Reserve, has studied rockweed since conducting her Ph.D research under Vadas in the late 1990s. She found a temporary decrease in some species (and an increase in dog whelk) immediately after experimental harvest, with all species recovering to their original abundances within two years. Tom Trott, working with the Bigelow Lab's Peter Larsen, also did not find any changes in assemblages of species or the abundance of periwinkle snails.

Heightened attention to rockweed has prompted claims that rockweed is a "keystone species" in the Gulf of Maine. While used casually as a synonym for "important," the term has a scientific meaning, defined by University of Washington zoologist Robert Paine in 1969: A keystone species is one whose impacts on its community or ecosystem are large and greater than would be expected from its relative abundance or total biomass. In other words, keystones are only those species having a large, disproportionate effect, with respect to their biomass or abundance, on their community. According to Jill Fegley, rockweed does not meet this definition. "I personally would not call rockweed a keystone species. I would consider rockweed to be an ecosystem engineer because of its three-dimensional structure," she said.

Common eiders, black ducks, and mallards feed in rockweed beds; a study by Diana Hamilton at the University of Guelph in Ontario found that while rockweed harvest had no overall effect on the invertebrate community, it did reduce the effectiveness of ducklings feeding at the top of the rockweed canopy.

The fact that none of these studies focused on community-scale effects or long-term impacts has some calling for the establishment of long-term monitoring at harvested and protected sites in Maine, as has been done in New Brunswick.

Photo credit: Art MacKay

No comments:

Post a Comment