Eelgrass

Eelgrass (Zostera marina)

Eelgrass is marine angiosperm that grows in soft sediment in bays and estuaries in North America, Europe, and Asia. It is the most abundant seagrass species in the northern hemisphere, and it plays a critical role in forming the structural foundation for many costal communities. Eelgrass also provides ecosystem functions, including increased primary productivity, sediment stabilization, and nutrient cycling, making it of ecological and economic value.

Eelgrass is clonal species that reproduces both sexually through seeds and asexually through vegetative propagation. Eelgrass is flowering plant that produces and pollinates seeds underwater. Eelgrass can also produce new shoots off of a rhizome (a horizontal stem) that grows just below the sediment surface and allows for a single genotype or clone to spread. As a result, eelgrass populations can differ substantially in their genotypic richness, or the number of different genotypes found in a given area. Indeed, richness can range from areas in populations with many genotypes ( >10) per square meter to populations that are dominated by a single genotype that can cover hundreds of square meters. Eelgrass genotypes can be long lived with some clones that are likely 1000 years old or more.

Eelgrass typically grows in large stands where it is the dominant plant species. Because there is little species diversity at the primary producer level in eelgrass communities, genetic diversity may be particularly influential in determining population and communities properties, such as productivity, stability, and transfer of resources between trophic levels. Indeed, studies have found that eelgrass population with higher genetic diversity (measured as number of genotypes in a given area) are better able to withstand disturbances like grazing by geese, algal blooms, and heat waves.

Eelgrass community

Eelgrass beds support a wide variety of marine life. Few animals feed on the eelgrass itself because of its high cellulose content. However, some animals, including water fowl (e.g geese and ducks), sea turtles, and some invertebrates (e.g. isopods and snails), do feed directly on eelgrass, although it is not usually the their sole or even primary food source. Eelgrass also provides a substantial source of nutrients to consumers after the leaves fall of and begin to decay. This decaying material, or detritus, is broken down by bacteria and fungi into more accessible organic matter that infuanal (sediment dwelling) species, including worms and crustaceans, feed on. Clams are another important infaunal species and that live in eelgrass beds. They are suspension feeder (filtering organic matter out of the water), and are often harvested for human consumption.

Eelgrass leaves also usually host a number of epiphytes, including algal species, bacteria, fungi, sponges, bryozoans, etc. Many species of invertebrates preferentially graze the epiphtyes growing on the eelgrass.

More information coming soon!

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