Eelgrass Habitat Studies
In 2009, we collected additional data from select sites including information on shoot density, shoot length,
epiphytic load, and sediments.
A 0.25 x 0.25 m quadrat was used to estimate shoot density. At all sites, shoot density increase during the growing season.
Shoot length varied significantly among sites. Shoot length was greatest at the eelgrass site in Plymouth.
At the sites on the Eastham Flats and Jeremy Point, shoots
along the edge were on average half the length of those
collected from the inside of the beds.
Organisms that settle and grow on eelgrass blades are called epiphytes. Epiphytes of eelgrasses include algae,
bacteria, fungi, sponges, bryozoans, tunicates, protozoa, hydroids, crustaceans and mollusks. Epiphytes
provide food for many marine organisms. However, if epiphytic growth becomes too dense on eelgrass blades,
it negatively affects the eelgrass by shading and competition for nutrients.
Blades from each site (inside the eelgrass bed and along the edge) were collected, length and width of each
blade were measured to calculate surface area, and the epiphytes were scraped off of the blades. These
epiphytes were dried for 24 hours at 60oC and weighed. Epiphytic load was calculated by dividing the dry
weight by the surface area of the blades.
At each site, the epiphytic community differed in both the biomass and the species composition. At the
eelgrass bed on the Eastham Flats, the epiphytic load was much greater along the edges of the bed. At
the Jeremy Point eelgrass bed, eelgrass blades along the edges had less epiphytic growth than the blades
inside the bed. The Plymouth site had less epiphytic growth on average than the other two sites.
Sediment samples were collected from the surface by grab
sampling. Each sample was rinsed with DI water, dried for 24
hours at 60oC , and weighed. Samples were then sorted with a
sediment shaker using sieves with mesh sizes ranging from 0.053
to 2.0 mm. The sediment retained in each sieve was weighed to
determine the percent composition of each sediment sample by
Grain size was finest at Plymouth with sediments mostly < 0.25 mm
and coarsest at Jeremy Point with the majority of sediments ranging
between 1.0 - 0.5 mm. At the Eastham Flats eelgrass bed most
sediments were medium grain size, ranging between 0.25 - 0.5 mm.