Tuesday, May 29, 2012

Crazy Plants: Eelgrass

Eelgrass (Zostera marina) at low tide
Submerged eelgrass
If you saw this plant, you might assume that it's a seaweed or other algae. However, that's far from the case. It's actually a flowering plant! Eelgrass is one of a number of marine flowering plant species that thrive while fully submerged under water. Its distribution includes just about every shallow water marine area in the Norther Hemisphere. They reproduce by having male flowers release pollen into the surrounding water, which will then float on the current to nearby female flowers. After seeds develop, the pods break off of the plant and float to the surface so that the seeds can be distributed far away from the parent plants.

Closeup of eelgrass blades
Eelgrass and other marine plants are amazingly ecologically significant, providing habitats and food sources for all sorts of living things. If you look closely at a single blade of the grass, it will frequently have a frosted look that's caused by the sheer amount of life that is living on the plant. The tiny organisms can include bacteria, algae, and invertebrates. It can get to the point where this coating of stuff can actually cause the blade to die off due to a lack of sunlight. Countless species on animal feed on the grass, and beds also act as hiding places for these and other species. Eelgrass beds also act as nurseries, with species such as herring laying their eggs in the beds.

Unfortunately, eelgrass and other seagrass beds are at risk due to a number of factors. Boat propellers and dredging operations will destroy beds directly. In contrast, runoff from land can lead to increased turbidity that can shade out beds. Also, this runoff can bring excess nutrients and lead to heavy algae growth, which will also shade out beds. The damaging and loss of beds had led to decreases in fish populations, though the exact amount of loss can't really be determined. Though these concerns do exist and eelgrass populations are decreasing, they are still considered to be of Least Concern by the IUCN.

Sources are the Maryland Department of Natural Resources, University of Delaware, Washington State Department of Ecology, and IUCN Red List. Images are from Wikimedia Commons and are under Creative Commons licenses or are copyright free: one, two, three.


  1. "If you look closely at a single blade of the grass, it will frequently have a frosted look that's caused by the sheer amount of life that is living on the plant"

    fascinating! what a cool looking plant, too.

    1. Indeed. There are a number of different species of seagrass, and this is true of them all. It's fascinating to snorkel over the beds and see the frosty appearance first hand. Unfortunately, it's more difficult to see in pictures and even worse if the plant is out of the water.

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