Paul, "slime" is probably a loose translation of a French word meaning
"thin mud or slime". I read it as a euphemism for feces and pseudofeces.
Pseudofeces consist of the material that oysters and some other sessile
animals accumulate in their gills and then expel in a mucous packet; it is
not digested material.
 
Most marine sediment (and terrestrial soil, for that matter) has passed
repeatedly through the guts of worms and other organisms. For instance, the
tiny rods of clay often found in windrows on Gulf of Mexico beaches are the
feces of ghost shrimp (Callianassa and relatives), which live in deep
burrows just offshore. The shrimp are both numerous and active, and
accumulations of clay consisting of shrimp feces can be several centimeters
(inches) thick, e.g., on the Georgia coast. The accumulations of oyster
feces and pseudofeces near oyster beds can be awesomely thick (feet/meters)
in Gulf estuaries. So, no, I don't find the French Crepidula problem to be
unbelievable in this aspect.
 
I agree that the D-Day part is unbelievable; this part has the hallmarks of
an "urban legend" (something that people like to hear and will,
unfortunately, remember clearly when everything else has faded).
 
Andrew K. Rindsberg
Geological Survey of Alabama