> > > someone wrote about introduced clams or oysters that could filter San
Francisco bay every 24 hours. How many critters would it take to do
the job? Six? Nineteen? several million?  When SF is finally cleaned
up, do they die or keep filtering? Could they do the same for
Chesapeake Bay? If it can be done, why isn't it being done?
    The Question Man< < <
 
     The Chesapeake bay used to have enough oysters to filter the entire bay
every three days. ( the SF bay is like a backyard swimming pool compared to
the Chesapeake) There are reports that there were oyster reefs that were 20
feet high in the deeper parts of the bay (the mean depth is only about 3 feet)
This is also true in the Assawoman bay by Ocean City MD and Assategue Island
MD and VA.  Since about the mid 1800's the bay's water quality has been going
down. One of the biggest problems is sedimentation from the farm land in the
Chesapeake bay watershed which covers five states. Believe it or not the water
quality has become better in the past 25 years since the passing of the Clean
Water Act in 1972 but it still is in TERRIBLE shape. Besides the declining in
oyster and blue crab populations there are serious declines in SAV (Submerged
Aquatic Vegetation)  Because of the low levels of plant life there is a
decline in dissolved oxygen which in turn causes problems for the oysters as
well as the other aquatic animals( yes including fish)
      I once heard an estimate that there were 3 BILLION oysters in the bay
before pollution and sedimentation hit it. I don't know if that is true. As
for the filtering part, I can only tell you to look at a coral reef. The water
is extremely clear yet 90% of the animal biomass are filter feeders.  I know
that the University of MD has a program where they are working of oyster
breeding and trying to release them. I have heard that they have been pretty
successful. Its not easy and trying to  restore the entire population would be
impossible because of the many peopple who make a living off the oysters and
also because the water is still to turbid and has serious sediment problems.
The sediment blocks out sunlight, clogges gills etc. I sure hope that one day
the populations of most of the the aquaic invertabrates will be restored but
it took a long time to get that way and it will take a longer time to clean it
up.
 
Sarah Watson
Silver Spring MD
http://www.geocities.com/southbeach/tidepool/8845
 
PS   we have many more lousy tasty chickens here in the Bay's watershed than
cows. Also all that chicken *$^@ is the cause of the phisteria problem. I
won't go into the chemical reactions but if you want to know the basics let me
know