Fouled ship hulls not a big risk to freshwater systems

So with all the depressing studies about maritime vessels as a vector for invasive species, new research in the journal Diversity and Distributions offers up some relatively good news about transport in the Great Lakes. A new study found that boat hulls appear to pose a low risk of introduction of exotic species capable of surviving in the lakes.

This contrasts with maritime and coastal areas where the attachment of creatures to the hulls of ships (otherwise known as hull fouling) has been responsible for widespread introduction of invasive species.To test whether a similar phenomenon is occurring in the Great Lakes, researchers Francisco Sylvester and Hugh MacIsaac conducted the first ever comprehensive study of ship hull fouling in a freshwater environment.

They utilized dive teams to collect scrapings from exterior surfaces of 20 vessels shortly after their arrival in port. The also used underwater video-transects to calculate species abundance.

They found that 72% of the taxa encountered were freshwater species already present in the Great Lakes.  They did find some invasive freshwater species but they were already present in the area. They did find one freshwater species new to the Great Lakes, the oligochaete Arthonia onegensis. However, given the numbers and condition - they found only one individual and it was dead - they concluded that the invasion risk was low.

The remaining species were either marine or estuarine and not expected to survive in a lake environment. The researchers conclude that hull fouling does not appear to pose strong risk to species invasion for freshwater environments. This contrasts with ship ballast water which is much more problematic. They state,

"The presence of non-indigenous freshwater species on the hull of a transoceanic ship is probably limited by the stresses of transit across the ocean. In addition to the sheer forces from the ship’s movement and scarcity of food, organisms attached to the exterior surfaces of ships have to endure high salinity and wide temperature fluctuations. Nevertheless, there are species that can tolerate a wide range of salinities."

--Reviewed by Rob Goldstein

Sylvester, F., & MacIsaac, H. (2009). Is vessel hull fouling an invasion threat to the Great Lakes? Diversity and Distributions DOI: 10.1111/j.1472-4642.2009.00622.x