Chesapeake Bay Grasses

Yeah, time to celebrate! Chesapeake Bay grass beds expanded by 27% in the last year. Then again, maybe not as we will see. The grass beds had been expanding until 2011 when two storms, Irene and Lee devastated the beds.

The increase in the last year has brought the grass beds back to 76,000 acres, nearly where they were before 2011. But it is still less than half the 185,000 acre goal targeted by the restoration effort. The effort is one part of a larger effort to bring back the health of the Bay. Even so, the target is still far less than the historic area covered by grass beds and subaquatic vegetation (SAV).

Why should you Care about Grasses in the Bay?

They are also known as seaweed. If you like oysters and crabs and rockfish, you should care about the grass beds. They provide sanctuary and breeding grounds for crabs and fish. They are also a safe place for crabs to molt when they are most vulnerable.

Helping Clean the Water

The grasses also filter nutrients out of the water and help keep the water clear. They need sunlight just like plants on land, so they grow better if the water is clear. Beds of seaweed have an amazing damping effect on waves and can greatly decrease shore erosion as well which will also help clear the water. Plus, they absorb nutrients which helps prevent algae blooms which are caused by excess nutrients.

There could also be a synergistic effect between grasses and oysters. Oysters are filter feeders and also help clear the water and also do better in clear water.  If we can succeed in getting both the oysters and the grasses to thrive, we might once again have clear waters in the Chesapeake like it was before the 1950s.

If there is too much sediment in the water, such as after a storm, the sediment not only shades out light, it can settle on the grasses’ leaves and further block the sunlight. Algae blooms also block the light getting to the plants.

Temperature has an affect as well. Hot summers in 2005 and 2010 killed a lot of eel grass int the southern part of the Bay. They bounced back somewhat this past year as well. The hope is that the summer won’t be too hot and the eel grass will continue to recover.

Short Term or Long Term Gain?

The big worry is that this gain may be ephemeral. In the past, grass beds have been a mix of species. If conditions weren’t good for one species, the others would fill in.

The large gains in the last year are worrisome because it is almost entirely due to widgeon grass. This particular grass can disappear as rapidly as it appears. So, if the conditions change and the widgeon grass dies back, all of this last year’s gains could be lost.

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