Have canals like the Panama or Suez resulted in any noticeable “contamination” of species from one body of water into another? I know from my experience in the Navy that both the above canals are quite long and have numerous barriers between the two ends at any given time, but I would imagine that at least some fish (or other life) have managed to cross them, so I wonder if this has had any measurable effect on the ecology of the vicinity of the mouths of these and other canals.
There has been extensive migration through the [Suez Canal](Cloudesley Shovell), which is entirely salt water, mostly from the Red Sea into the Mediterranean. From the link:
The impact of the Panama Canal, on the other hand, has been pretty small. The central section, Lake Gatun, is a man-made freshwater lake about 85 feet above sea level and reached by locks. This freshwater barrier prevents the migration of most saltwater fauna through the canal, although some have gotten through. Such migration would be a major environmental issue should a sea level canal ever be built.
A more significant issue for the transfer of marine life globally has been the venting of ballast water and the transport of organisms on hulls.
The ballast of the ships are a big contaminator. We’ve gotten lake devastating species in the Great Lakes through the boat ballast that used the canal systems. We are trying to keep out the high flying Asian Carp right now which have come up the Mississippi river. There is a double electric barrier on the Shipping Canal from the Illinois river to the Great Lakes. Unfortunately everyone seems to have forgotten Wisconsin. It would be easy enough during flooding near Portage for them to migrate from the Wisconsin to the Fox river when they eventually make make it up the Wisconsin. There are so many scenarios were they could break into the Great lakes that they will be there eventually. Maybe they’ll eat Zebra Muscles.
Well, if I recall correctly the GLMRIS study (Great Lakes Mississippi River Interconnectivity Something) didn’t find the Portage to the Fox connection that likely. But there are other natural intermittent connections that are potential problems, most notably the Wabash- Maumee connection through Eagle Marsh. (Maumee drains to L. Erie, Wabash to the Ohio, and it already has carp.) They’ve, believe it or not, erected a chain link fence to keep the carp from swimming through the marsh if it floods. There is some reason to believe that juvenile carp are not likely to be found in this area, at least yet, so it is not as dumb as it sounds. But still, I think risky.
The Chicago Ship and Sanitary Canal that HD mentions connects the Chicago River (used to drain to L. Michigan, now it runs the other way because of the canal) to the DesPlaines->IL River->Mississippi River, and of course the carp are swimming up the river and some unknown number, probably a small number, seem to be on the wrong side of the electric barrier now. Only one has actually been caught there, on the wrong side of the barrier. But the first electric barrier was built to keep the round goby (which entered the great Lakes from Europe via ballast water) out of the Mississippi Basin. But it got built too late, and the goby was already through. And zebra mussels already got through downstream too, into the IL and Mississippi Rivers. Also some nasty zooplankton we don’t really want, and some other things. Some people think that gizzard shad invaded the Lakes through the canal going north many years ago.
Oh, and HD, bighead and silver carp WILL eat zebra and quagga mussels - but not the adults, just the veligers. Zebra mussel veligers are a big part of the silver carp and bighead carp diet in some other places where they have been introduced together. But don’t expect it to make any difference for the zeebs. I have not seen any evidence that such predation reduces the zebra infestation any.
Black carp might eat the zeebs, but they probably are not close to invading to the lakes. Even though black carp are probably the world’s most efficient freshwater molluscivore, some say they won’t be able to feed effectively on zeebs because they need to engulf the mussels to eat them, and the zeebs’ bissal threads may tie them to the substrate too strongly.
Today, Judge Dow ruled in favor of the defendents in a case in which Michigan and other GL states were suing Chicago to close the locks and the canal.