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The Decline of Seagrass Meadows

Zostera! 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?

Bay Scallop on Eelgrass

Argopecten on Zostera! Bay Scallops, Argopecten irradians , have developed a very close relationship with eelgrass, Zostera marina. As larvae, they are passively transported, and tend to settle in eelgrass meadows when the current is dampened by the 3D structure of the seagrass. This same 3D structure provides post-set juvenile scallops a spatial refuge from predation. Even as larger juveniles and adults, scallops are capable of, and have been shown to, actively select eelgrass habitats.

Other species also use eelgrass

grass shrimp A number of other species utilize eelgrass as a habitat. Included are grass shrimp, like the Palaemonetes pugio, other decapods such as blue crabs, bivalves such as hard clams, gastropods (snails), and numerous fish species, including winter flounder, tautog and cod.

Tropical Marine Ecology 2011…

Each year my adviser Bradley Peterson and fellow professor Joe Warren take a group of undergraduate students to Jamaica to participate in a course called Tropical Marine Ecology.  This year is no different, although they ended up there a day late due to the most recent snow storm.  That said, they all got there safe and appear to be settled in nicely.  The idea behind the course is to get the students to learn about tropical marine environments by actually seeing them first hand – many of the upper level marine classes at Stony Brook are experiential in that students get hands on experiences in the field.  Tropical is no different.  The first few days will consist of lectures and snorkeling around to learn about the species in Discovery Bay, where the group stays.  Once they take their practical, the students need to conduct a research project which they then write up for their grade in the course.

It is a short course (only ~2.5 weeks), so it is hard to accomplish very rigorous scientific experiments (also, any equipment they use needs to be brought with them, which also makes things difficult), however, the students undertake a variety of projects, investigating mangroves and seagrasses, coral cover, sponge communities, fish territories, etc.  Some of the research under taken is of high quality and warrants publication.  One such publication came from a group of students when the trip still went to the South Pacific where they investigated how Stegastes damselfish controlled algal assemblages, and the interplay between herbivory and nutrient addition. (Gobler, C. J., Thibault, D.B., Davis, T.W., Curran, P.B., Peterson, B.J., Liddle, L.B. 2006. Algal assemblages associated with Stegastes sp. territories on Indo-Pacific coral reefs: Characterization of diversity and controls on growth.  Journal of Experimental Marine Biology and Ecology 336: 135–145).

More recently, a colleague of mine investigated the difference in growth rate and grazing of Thalassia between groundwater influenced and non-groundwater sites in Discovery Bay, Jamaica, with some interesting and unexpected results.  That manuscript is currently submitted.  In addition, thanks to her undergraduate visit to Jamaica, Amber developed her dissertation project investigating sponge community dynamics and recruitment on reefs impacted by sedimentation due to the creation of mega-resorts and those with no impact.  She visits Jamaica frequently to collect data (I have tried to get her to blog about this stuff, maybe one day she will).

Anyway, back to the course.  For many students, it is their first time in a tropical environment, their first time SCUBA diving, or both.  It is also the first time a lot of them are expected to independently do a research project and write up/present the results.  It is a great experience, and one the students truly enjoy.  You can read about their excitement and adventures on the trip’s blog Tropical Blogs.  You should definitely check it out.

2 comments to Tropical Marine Ecology 2011…

  • I love when we actually get the chance to take students to far flung field sites. Even if they don’t have enough time to get a publication out of two weeks in the field, they come back with a real appreciation for how field science is done, and the end result is better scientists.

    My personal favorite though is a publication that came out of a Hawaiian University about the collapse of a brachiopod population in one bay due to continuous harvesting. About halfway through the methods it became apparent that the harvesting was being conducted by an Invert Class that had been going on the same field trip for 20 years.

  • Yeah I have worked extensively with a class called Experimental Marine Biology here at Stony Brook, and, while the weather is nice, labs are field trips to learn different field techniques. We do trawling, hydrocasts in the ocean, salt marsh surveys, explore the mud flats, etc.

    The class actually visits the same marsh every year since I took the class back in 2003, and it does the same measurments every year. Wouldn’t it be great if we had been collecting all that data somewhere to notice any long term trends in marsh plant species distributions? Ah well. We are starting to do that this year, so maybe we’ll have that kind of data set someday too.

    Classes that get you dirty are the best!

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