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...
Sunday, July 11, 2010
Its that time of year again. Scallops have started spawning. Tiny larvae have drifted around and metamorphosed. And now, they are settling out of the water column onto various substrates. I have made this point many times before, but I will repeat it: typically, eelgrass is considered the main suitable substrate for bay scallops, and that their larvae settle out of the water column onto this submerged angiosperm. However, scallop spat appear to be pretty opportunistic settlers, settling on a variety of substrates - both natural and artificial. Some of my colleagues have investigated the settlement of post set on various natural substrates - comparing different abundant macroalgae to eelgrass. This past week we did some diving to look for scallop spat attached to macroalgae in the field. First, I will say it is difficult to spot 1-2mm scallops on a natural surface - they blend in very well! That said, I was able to identify ~25 scallops of the 1-2mm range attached to 3 different types of macroalgae - Codium fragile (my personal favorite and a species I am fully confident is acting as an eelgrass surrogate for many species which rely on eelgrass), Spyridea, and something I call "red puff" algae, because right now, I can't remember its genus. Anyway, we found baby scallops on these three types of algae while diving, measuring the height of attachment and collecting both the scallops (to be measure in the lab) and the algae tuft to return to the lab. We then took wet weight biomass of the algae, and sprayed it down into a sieve (800 um mesh) to see if there were any scallops we missed. All in all, it was a rewarding dive for a variety of reasons, most importantly is that if we are finding multiple scallops on relatively small algae tufts, that is an indication that this years spawning and first set have been very good. This is promising for the scallop population as a whole. Second, it further reiterates that species other than eelgrass can potentially serve as alternative habitats for scallops - and this is important for the restoration efforts along the East Coast. It will allow managers to target some potentially non-traditional areas for restoration. Good stuff!
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.