Healthy ecosystems are resilient. They can handle change up to certain point until they crash in a devastating loss of biodiversity. That is precisely what happened to the Chesapeake Bay about a hundred years ago, when one species was over-harvested: Chesapeake Gold. Crassostrea virginia. The Eastern Oyster.
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| Chesapeake Blue Crab |
People, being a terrestrial species, don't often think about the other 70% of the Earth. When people talk about biodiversity loss, it's usually described in land-centric terms like "desertification". What they don't realize is that the same process is happening on a massive scale in the water world. The Chesapeake Bay, where we have been actively studying this process, is an estuary. Estuaries are the most biodiverse aquatic biomes in the world. They are the rainforests of the water - and in a world that is mostly water, estuaries hold a significant place in the web of life. In just the few days that we've been camping on the beach here in Maryland, we've come across herons, egrets, ospreys, geese, mallards, shad, perch, rockfish, gobies, blue crabs, horseshoe crabs, mud crabs, eels, water snakes, deer, fox, rabbits, diamondback turtles, muskrats, mussels, clams, oysters, and feral Berea College students.
The Chesapeake is the largest estuary in the United States, and it's vast biological wealth lives primarily in three habitats: sea grasses, emergent wetlands, and oyster reefs. Losing those critical habitats is altering the ecology of the bay drastically. Said in land-centric terms, the bay is going from rainforest to desert within a few generations.
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| A new sign marking the oyster reef. |
To stop the desertification of the Chesapeake, the government, NGO's, and regular people are actively attempting to restore those habitats, beginning with the oyster reefs. We got a taste of what it takes to restore an oyster reef today when staff from the Chesapeake Bay Foundation took us canoeing on Black Walnut Creek. Paddling to the headwaters of the stream, we first took measurements for salinity and dissolved oxygen to determine if it provided suitable conditions for the oysters. They prefer brackish water, but can tolerate conditions ranging from 5 ppt salinity in tidal creeks to 35 ppt salinity in the ocean.
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Becca Shaw pulls oyster clusters
from the reef for closer study. |
An oyster reef had previously been planted in the creek, but it's location was uncertain and took some searching for by the class. Once we found the reef we installed a sign to mark it and took a few samples of oyster clusters to measure their growth. Closer to the shore, oysters in cages were growing in a "nursery," waiting to be transported to the reef. As we pulled these cages from creek, signs were already starting to appear of other creatures like mud crabs, eels, and barnacles using the oysters for habitat. After cleaning off the shells a little bit, the oysters were canoed out to the reef and dumped along the edges, expanding the reef and adding new generations of oysters.
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