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, July 29, 2010
We're not hunting tommy-cod...
Although there are a lot of them associating with eelgrass beds in Shinnecock Bay, NY. Nope, I am hunting for baby scallops. Shinnecock Bay has some of the healthiest eelgrass meadows in Long Island, and in some places within the bay, new meadows are forming. This is great, as many species depend on seagrasses as predation refuges and nursery grounds, including my model organism, bay scallops. Why then are there apparently no scallops in Shinnecock Bay? Well, its not exactly that there aren't any, of course, but that there are so few, they might essentially be ecologically extinct. However, restoration efforts in the Peconics and larval monitoring have turned up some pretty exciting results. And, Shinnecock Bay is connected to the Peconics through a canal, whose gates are left open when there is a high tide in the Peconics, allowing water to flow into Shinnecock Bay. This is a potential source of scallop larvae. While the spawner sanctuaries are quite distant from the canal, there is a growing scallop population around Robin's Island in Great Peconic, not far from the canal. And either way, scallop larvae spend up to 2 weeks in the water column, so it is possible for fairly long distance dispersal. So I thought we might see some scallops in Shinnecock Bay. I certainly saw some juveniles last summer, but didn't see any adults, so their survival is likely very low. One reason is probably predation. The same eelgrass meadows that are valuable for scallops is also a valuable habitat for blue crabs and mud crabs, both of which eat scallops like popcorn (or at least I imagine that's how they eat them). And yet, no one has investigate either scallop or blue crab recruitment in Shinnecock Bay, so that's what I am currently doing. My scallop monitoring has already started, and surprisingly (or maybe not surprisingly), I didn't get the results I was anticipating. Instead of the highest numbers of scallops at the site closest to the canal and diminishing numbers with distance, I had two relatively high spat numbers sites, on either side of the Shinnecock Inlet, opening up to the ocean. Could this mean a possible oceanic transport of scallop larvae into Shinnecock Bay? Is this supply-side ecology? There are clearly not large numbers of larvae, but there is a supply, and it's coming from somewhere, but to be honest, I have no idea where. Soon I plan on sampling for blue crabs, whose larval origin I know is oceanic. If they display a similar settlement pattern, perhaps my question will be answered. On a side note, we did collect a lot of other organisms. All together, over 20 different species of organisms came up on the collectors. The most abundant were scallops, mud crabs, blue mussels, jingle shells and slipper shells. But we also saw 2 types of sea squirts, bryozoans, rock crabs, 4 different species of snails, sea stars, urchins, other bivalves (arcs, angel wings and cockles), scaled worms and other polychaetes. Oh yeah, and a few of these things that I have as yet been unable to identify, although my guess is some sort of nudibranch. So yeah, exciting stuff indeed. (scaled worm)
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.