Water use, Pollution, and Invasive species

In todays blog I will address the issues of Water use, and pollution and their effects on invasive species.  Invasive species are often brought in through human activity.  Some species cling to boats or can be found in ballast tanks, others were released through sheer human stupidity.  Our Great Lakes are connected to the ocean through the St. Laurence Seaway, a series of man-made locks that allow ships to gain access to the Great Lakes from the Atlantic Ocean.  Shipping is a form of water use, and the locks use a lot of water to raise or lower a ship to the level of the next lock to allow movement up or down the system.  What does this have to do with invasive species?  The ships traveling this canal are ocean going ships that carry ocean water in their ballast tanks.  When emptied, any animals that may have been trapped in the tanks are dumped into the Great Lakes.  Zebra mussels, Sea Lamprey, and other small invasive species may have been introduced to the Great Lakes in this manner.

Pollution represents a significant problem to our Great Lakes.  The Great Lakes hold a vast amount of drinkable fresh water.  If this water becomes polluted, this has consequences for human life near the Great Lakes.  On the invasive species front, pollution is more a problem for native species than the hordes of invasive species on the rise.  Raw sewage dumped into the lake may sound like a bad thing, and for human health and the health of many native species it is, however there is one species that was introduced to the United States to combat that very thing.  Asian carp are bottom feeders, consuming plankton, detritus, and quite possibly raw sewage.  They reproduce in vast numbers and consume large amounts of food.  Wherever these fish go they choke out all other competition by growing large, breeding fast, and consuming anything and everything.  If these fish are not bad enough let us add a small invasive species called the zebra mussel.  This little filter feeder also reproduces fast and in large numbers, spreading like a plague.  These mussels suck up water, remove any particles from it and release clean water.  While you might ask is this a bad thing to have clean water, the answer is yes it is bad.  Those small particles, ditritus, and plankton represent the lowest level of the food chain.  These mussels muscle in on the lowest level of the food chain, wiping out all other compitition by out competing them for food.  These nasty little critters can steralize a lake if left unchecked.  Pollution is more likely to feed these critters than hurt them.

To conclude, Pollution and human water use cause many problems for native species, but for at least two of the invasive species threatening the Great Lakes, pollution may prove to fuel the fire.  Animals that can consume raw sewage and spread like a plague in vast numbers are a larger threat than the pollution they themselves can consume.

Sources:
http://www.greatlakes-seaway.com/en/
http://www.oar.noaa.gov/spotlite/archive/spot_zebramussels.html
http://eattheinvaders.org/asian-carp/