Zostera marina is a seagrass species, commonly known as eelgrass, that is found on both coasts of the United States, as well as in Europe. Unfortunately, Zostera is disappearing all over the place, including right here in New York. This could have devastating impacts on animals that rely on eelgrass as foraging grounds, or, as is the case with scallops, use it as a refuge from predation. This is its story, as seen through the eyes of an aspiring graduate student...
Thursday, January 15, 2009
Most bay scallops live less than 2 years, and so a concentric growth ring is usually only laid down once. Typically seed scallops reach a size threshold, 35-55mm by the end of their first growing season. However, some scallops are less than 20mm when the growth ring is set. These could be the product of fall spawns, and there is some thought that these scallops don't spawn before they are large enough for their first harvest, that is, they are likely to live into and spawn in a 2nd year. Some populations consist of more than 50% of these "nub" scallops. This has been a particular problem in places like Nantucket, where large portions of scallops have small growth rings. In order to harvest a bay scallop, it must have a clear growth ring, however, "nub" scallops have such small rings, they often appear as ringless adults. This has drastically shrunk the harvest of scallops in this area. That is, until this year, when an emergency regulation was passed to save the harvest. The legislation stated that now scallops could be harvested if they were greater than 2.5 inches in shell height OR if they had a 10mm growth ring - this means that ringless adults (nub scallops) can be harvested if they are greater than 2.5 inches. I don't know if I agree about this legislation, mostly because very little is known about nub scallops and their potential importance for spawning in the 2nd year. I did think it was interesting that bay scallops have been in the news recently. The photos were taken by Steve Tettelbach and borrowed from a poster presented at last year's 100th annual National Shellfish Association meeting.
I am a marine biologist that is currently attending graduate school at the School of Marine and Atmospheric Sciences, Marine Sciences Research Center, of Stony Brook University, New York. I am very interested in marine ecology and have been focusing my studies on bay scallop interactions with their habitats. I plan to investigate various anthropogenic impacts on bay scallop populations for my PhD dissertation. This blog will highlight the details of my graduate research, from bay scallop-eelgrass interactions as previously mentioned, to alternative habitats for scallops, such as Codium, to trophic cascades, and more. Enjoy!
Eelgrass is an important habitat for multiple marine species, including the bay scallop
Scallop on Artificial Eelgrass
This tethered juvenile bay scallop attached itself to my artificial eelgrass...
The decline of eelgrass meadows
Eelgrass, Zostera marina, is a flowering, marine vascular plant that remains submerged all the time. This is quite a feat for vascular flowering plants, and only a few dozen species world wide are capable of growing completely submerged in a marine environment. Eelgrass creates and extremely important habitat, its upright structures and complex root system create a 3-D living space for many different types of animals. It is (or was) the dominant habitat forming SAV (submerged aquatic vegetation) throughout much of the coastal waters in the northeastern United States. Unfortunately, for various reasons, eelgrass meadows have seen drastic declines, and in many locations eelgrass only exists in a mosaic of small patches. This is extremely bad news as many of the important, and formerly important, commercial and recreational fisheries of the northeast US are dependent on Zostera at some part of their life cycle as a nursery and foraging ground. Some of the species are finfish like tautog, bluefish, fluke, winter flounder, porgies, while others are shellfish such as blue mussels, hard clams, oysters, bay scallops, and blue crabs. Many of the aforementioned species support or once supported vibrant fisheries. Many of those fisheries have collapsed, also for various reasons. However, is it possible there is a link between the crash of the fisheries, the decline of Zostera and the failure for recovery on both ends?
Eelgrass, Zostera marina, a temperate seagrass species, providing a vital habitat for numerous marine species
Scallops in eelgrass
Some adult bay scallops we planted in eelgrass for a free release survival experiment we conducted
If you live in coastal zones, urge your local and state representatives to push for environmental issues that you are concerned about. Ask for more stringent rules regarding the destruction of existing eelgrass. Encourage restoration programs to be set-up. Call your state and national representatives and ask them what they are doing to protect our precious resources. Practice safer boating and know the undersea terrain - i.e., don't drive your boat in very shallow water. Avoid clamming in eelgrass meadows.