There seem to be some misconceptions about the Chesapeake Bay.
There are those who believe that at one time there were great expanses of submerged aquatic vegetation in the Bay. But SAV will not grow in water that is too shallow or too deep. As water gets deeper, less light reaches the plant, and it can’t perform photosynthesis.
This has always been the case; the bottom of the Bay has never been covered with SAV, as some might have thought. Is there too little SAV in the Bay today? Yes. Can we get more to grow? Yes.
There are those who would like to think that at one time the bottom of the Bay was covered with oysters. It was not. The oysters like water a little deeper than the SAV.
Oysters do not like and will not grow if the water is too shallow and in some cases, too deep. Nor will they grow on a muddy or silted bottom.
Oyster spat (baby oysters, larvae) like to adhere to hard surfaces; oyster shells themselves are ideal substratum. Oyster bars do not make good grass beds and grass beds do not make good oyster bars. Therefore, throughout the evolution of the Bay they have competed somewhat for space, although they do not occupy the same space.
I cannot count the number of times I have read or heard that years ago, the oysters in the Bay years ago could filter all of its water in three days. This did never happened and never will. There are no oysters in shallow water, so they never filtered that water. There are no oysters in muddy or silted bottoms, so they did not filter that water. Some of the deeper parts of the Bay (more today than years ago) contain little oxygen, so the oysters can’t live there and do not filter the water that water, either.
Oysters live on the bottom and don’t move. They can only feed and filter the water that tides and currents bring to them. As tides roll in and out, the oysters are basically filtering the same water except for some churn. In the water column, starting a short distance above the oysters and all the way to the surface, is water never filtered by the oysters.
This misconception arose when sometime in the past, someone calculated that an oyster could filter so many gallons of water a day. They then took the number oysters once in the Bay along the amount of water in the Bay and with some simple math came to the conclusion that the oysters could filter the amount of water in the Bay in three days. This does not mean they could filter all of the water in the Bay, as many people like to quote.
Are the oysters important to an environmentally sound Bay? Yes. Will the oyster save the Bay? No.
One of the real water filterers, menhaden, gets little attention. From the time these fish are microscopic larvae till they are full-grown, menhaden continue to feed and filter the water. And, they move around to where the food is throughout the water column.
The reason little respect is given to these fish is that we don’t eat them directly. Indirectly, we consume when we eat meat or poultry, because the fish is often dried, made into fish meal and fed to livestock.
There are some very small plants in the water, algae, that are often discussed in a derogatory manner. We mostly hear about these plants when they multiply into enormous numbers and turn the water into various colors. We even name the phenomenon a “red tide” or a “mahogany tide” to correspond to the particular alga that caused it.
When this mass of cells dies and deteriorates, it uses up a lot of oxygen in the water and makes it unfit habitat for many sea creatures. Bad algae? No, they are not bad algae. Algae are the very basis of the food chain for almost all sea animals. Without algae there would be very few creatures in our water.
Problems occur, though, when algae get too much food; especially nitrogen.
We are the main cause of the overabundance of nitrogen in the Bay. Consider the millions of people who live in the Chesapeake watershed and one can start to see the problem. Our urine is 10–14 percent nitrogen. Add to this all of the waste from farm animals, wild animals and pets as well as the fertilizer applied to farmland and lawns. All of this washes into streams and eventually the Bay when it rains.
Sometimes we have to think a little deeper about what we hear and read. Things are not always as they appear to be.