I was both encouraged and disappointed in the tone and content of articles and letters in the November 1999 Bay Journal regarding the next iteration of the Bay agreement.
I am encouraged by the many excellent articles on TMDLs, and the renewed and continuing efforts at cleaning up the Bay. I am encouraged by the suggestion that Delaware, New York and West Virginia may be brought into the Bay Program. I am also encouraged by the discussion of air deposition and other nonpoint sources as important sources of nutrient pollution and acid rain. The recently announced lawsuit by the EPA against seven large electric power utilities in the Midwest is a good start on the air deposition issue.
I am disappointed, though, that relatively little attention is being paid to the decline of filter feeders (oysters, other shellfish and certain finfish, particularly menhaden). Before the colonial era, water was clear, nutrient levels were a fraction of what they are today, and most sediment was trapped in dense forests that surrounded the Bay and occupied most of its watershed. The Bay’s food chain though complex, was in balance so that the great amount of phytoplankton that was produced was quickly consumed by grazing zooplankton and filter feeders. This kept the water clear, allowing light to reach the bottom, supporting lush “meadows” of submerged aquatic vegetation.
Human influences, however, have upset this balance. Nutrient pollution has increased plankton production, while diseases and the overharvesting of filter feeders have reduced the Bay’s ability to keep itself clean.
The result of this combination of assaults is very predictable. Large plankton populations and sediment loads have reduced water transparency, leading to the loss of SAV, while the decomposition of large plankton populations has led to anoxic bottom water.
We have all heard the oft-quoted statement that in pre-colonial and colonial times, oysters processed enough water to filter the entire volume of the Bay in a few days while today this phenomenon takes months. We have also heard many reports, both historical and from lifelong watermen, that the water’s clarity is nothing compared with what it was even 50 or 60 years ago.
The importance of filter feeders cannot be overemphasized, as they directly remove particulate matter from the water column. This results in improvements in water clarity, giving SAV the light necessary for growth and reproduction.
In addition, removing these organic particles before they settle to the bottom reduces the oxygen demand as they decompose. This oxygen demand is a major factor contributing to anoxic conditions in bottom waters.
An example of the potential that filter feeders hold for improvement in the Bay’s water quality is Lake Champlain, situated between upstate New York and northern Vermont. Although I am not for a second suggesting that we import zebra mussels (or any other foreign, filter-feeding organism, for that matter) into the Bay, local residents in Vermont report that since the zebra mussel invaded Lake Champlain, water transparency has improved dramatically. The same would be true for the Bay if we had our filter feeders back.
I believe that much more emphasis in the Bay restoration effort should be placed on increasing the populations of filter feeders, because trying to “starve” phytoplankton to significantly reduce their standing crop simply will not work. Too many nutrients will continue to leak into the Bay through nonpoint sources so that phytoplankton populations will never decline to desired levels. Nutrient reduction is only half the game. We must also increase the populations of filter feeders if we expect to see real progress in the coming decades.
Regarding the restoration of the oyster population, I am aware that progress is being made through the use of seeding, sanctuaries and limits on harvesting.
Little, however, is being done to manage filter feeders, specifically menhaden. (See Jim Price’s letter, Bay Journal, November 1999.)
I have personally witnessed the scale of menhaden harvesting done by large purse seiners operating out of Reedville, VA.
Although harvesting has been greatly reduced compared with its heyday, these fish are still being taken in great numbers using high-tech methods. Spotter planes locate schools of menhaden, which are then surrounded with a large net. The bottom of the net is then cinched and the hapless fish are pumped aboard.
If the Bay’s menhaden has truly declined 79 percent since 1991, as stated in Mr. Price’s letter, this fishery needs to be managed to increase its numbers, and it needs to be done immediately. Menhaden are vital to the Bay both as filter feeders and as forage species for the Bay’s favorite fish, striped bass.
I heartily endorse the Bay Program and its restoration efforts but feel that the subject of filter feeders should receive greater attention