The word “invasion” strikes fear in the minds of many, envisioning occupation by foreign entities bent on plunder and destruction. An invasion, in fact, is the aggressive entry of an outside force to occupy the space of another. In aquatic systems of the northern United States, Eurasian watermilfoil (EWM) fits the bill of an invader to a T.
As was brought to you in our previous posting “How Dry to Die?”, Eurasian watermilfoil presents some scary survival stats when it comes to desiccation. In that posting, we discussed the findings of the study showing that plants could potentially survive even after completely drying out! Well some researchers from the University of Notre Dame have taken the science of EWM survival to the next level.
Lindsey McAlarnen, an undergraduate student at the University of Notre Dame, along with a graduate student and her professors, took a look at survival of EWM during transport from one water body to another. Using a simple fan, the team simulated the on-trailer trip of a boat from one lake to another setting the speed of travel at 55 mph. The group wasn’t simply blowing hot air, they took a look at a number of factors which may influence the survival of EWM. McAlarnen investigated a number of variables which may influence the survival of this proverbial “plant out of water” experience, including fragment length, number of nodes, and plant location of fragmentation.
Completing countless repetition and controlled testing, the group of scientists came to some interesting conclusions. Results showed that shorter stems dried more quickly than longer stems, and fragments from the apical portion (growing end) of the plant survived longer and produced roots more than basal (near sediment) cuttings. In fact, no basal cutting survived the length of the experiment. Apical portions of a plant often have more nodes than basal portions of similar length, therefore the team took their experiment further, looking at segments with the same number of nodes from both the apical and basal portions of the plant (and therefore throwing length out of the equation). Findings from this portion of the study suggested physiological differences in those fragments cut from apical and basal portions of the plant.
Why might this be a hinderance for reducing the spread of this problem invader? The study estimated that nearly two-thirds of boaters neglect to rid their boat trailers of potential hitchhikers like EWM. What is further concerning is that apical cuttings are most likely to be chopped and carried by boat propellers and trailers as they grow closer to the water’s surface. This study proves that fragments, particularly apical buds and cuttings, can easily survive overland transport to new homes where they can cause both environmental and economic damage. This study and others like it continue to confirm the fears of state and federal resource managers and funding agencies alike; that the spread of EWM and other invasive plant species are likely to continue without intervention.
To read the journal article in its entirety, click here.
For more on Eurasian watermilfoil, click here.
For more on the Aquatic Plant Management Society, visit our website at www.apms.org.The APMS Blog is prepared by Dr. Brett Hartis, NC State University