Paul Monfils wrote,
 
If salinity in excess of 6 parts per thousand kills them, I wonder if
they could be controlled by seeding the beds with rock salt??
Theoretically the large, heavy rock salt crystals should sink
quickly, with minimal dissolving on the way down; then dissolve on
the bottom, creating a dense bottom layer with salinity well over 6
parts per thousand; then gradually diffuse into the overlying water,
causing negligible increase in salinity to the main water mass??
What do you think?
 
++++++++++++
 
Well, Paul, for starters, the zebra mussels wouldn't die right away. After
all, they are adapted to live in fluctuating conditions at the mouths of
rivers. They would probably just clamp their valves shut until the salty
water was diluted or flushed away.
 
Also, what else are you willing to kill just to control the zebra mussel?
Six parts per thousand is equivalent to brackish water, which would
assuredly kill most species of native freshwater mussels, and just about
everything else adapted to fresh water, including plants. If you killed off
the zebras' (admittedly feeble) competition, the prolific zebras would soon
bounce back with higher populations than ever. In Alabama, when drillers
for coalbed methane proposed to dump very slightly salty (but drinkable)
water into the Cahaba River, environmentalists landed on them like a ton of
bricks.
 
But please don't stop posting your ideas. They are always stimulating.
 
Andrew K. Rindsberg
Geological Survey of Alabama