Archive of Spotlight Feature Articles

Assessment of Transoceanic NOBOB Vessels as Vectors for Nonindigenous Species Introductions to the Great Lakes

Project Managers: Thomas Johengen, CILER-University of Michigan and David Reid, NOAA-Great Lakes Environmental Research Laboratory.

Bythotrephes, Cercopagis, Gobies, Quagga Mussels... foreign sounding names that have become all too common to managers and users of the Great Lakes. These are but a few of the more than 180 aquatic nonindigenous species (ANS) documented in the Great Lakes. The first questions usually asked are, "where do they come from?" and "how did they get here?".

We know from previous studies that as many as 2/3 of the ANS now found in the Great Lakes were likely introduced via ships' ballast tank discharges. During the 1990s much attention was therefore focused on ballast water as a vector for nonindigenous species introductions to our Great Lakes and marine coastal ecosystems, and open-ocean ballast exchange was implemented as a defense against new introductions. However, on average, less than 20% of ocean vessels entering the Great Lakes over the last two decades contained declarable ballast water on board. The issue of NOBOB (no-ballast-on-board) vessel operations in the Great Lakes has risen from a position of relative obscurity to become a major concern in the Great Lakes basin today. NOBOB vessels escape scrutiny under existing U.S. and Canadian federal, state, and provincial regulations, yet their ballast tanks contain residual volumes of unpumpable ballast water and sediment which contain live aquatic organisms and resting stages - eggs, spores, and cysts - accumulated over numerous previous ballasting operations.

A scientist scoops ballast tank sediment into a bucket

A student prepares one of several resting egg emergence trap experiements

(Left) CILER scientist, Ying Hong, collecting residual sediment from a NOBOB ballast tank.

(Right) University of Windsor Ph.D student, Sarah Bailey, as she prepares one of the resting egg emergence trap experiments in the ballast tank of a commercial vessel.

While operating in the Great Lakes, NOBOB vessels take on water to maintain their trim and stability as they off load cargo. This new ballast water mixes with the residual ballast water, mud, and associated organisms in these tanks and is later discharged as the vessels take on new cargo at various ports along their routes. An assessment of the risks posed by NOBOB vessel ballasting operations while in the Great Lakes, and a study of the efficacy of ballast water exchange in protecting the Great Lakes from ANS introductions, are the focus of a major program led by the CILER-University of Michigan and OAR's Great Lakes Environmental Research Lab (GLERL). CILER and GLERL assembled an international team of invasive species experts from the University of Michigan, Old Dominion University, University of Windsor, the Smithsonian Environmental Research Center, and a commercial vessel operations expert (P.T. Jenkins and Associates) to address these questions.

Our multidisciplinary research program is built around the following three objectives:

Characterization and risk assessment of biological communities (invertebrates, phytoplankton, microbes, including resting stages) in residual ballast water and sediment in NOBOB tanks and their relationship to ballast management procedures. This task involved entry and direct sampling in ballast tanks, so the scientific teams were given extensive confined space entry training.
Ballast tank mesocosm experiments. This task is to look for evidence of in situ hatching of resting stages in ballast tanks while ballasted with Great Lakes water during operations in the Great Lakes, and also to look for evidence that residual biota in NOBOB ballast tanks may be discharged to the Great Lakes under actual ship operating conditions.
Experimentally determine the effectiveness of open-ocean ballast water exchange in transoceanic vessels carrying fresh or low-salinity ballast water.

RESULTS

More than 100 oceanic ships that entered the Great Lakes during the two year field study were surveyed and 82 ballast tanks were entered and sampled. Each residual water and residual sediment sample was dispersed among our team for analyses of microbial community and enteric pathogens, phytoplankton composition and viability, invertebrate composition, resting egg density and viability, and physical/chemical conditions.

The photo show two resting eggs and the organisms that later hatched from them.

Example of invertebrate resting eggs (top row) and the organisms that hatched from them (bottom row) in lab cultures.

Our ongoing assessment of results-to-date suggests that bacterial levels generally mimic what is found in the natural environment and only about 10% of the samples tested positive for potentially pathogenic microbes. Viable phytoplankton and dinoflagellate cysts were present in all samples and 25 nonindigenous marine and freshwater Diatom species have been identified to date. Of the 38 species of copepods and cladocerans identified, six of them were nonindigenous to the Great Lakes. Densities of resting eggs within the tanks we sampled ranged from 10 6 -109 and the viability of those eggs varied from 0 - 90% under laboratory testing conditions. Three on-board experiments to assess ballast water exchange efficacy were completed.

As we continue to finalize our data analyses we hope to document ballast management procedures that appear to be effective at reducing ANS risk related to NOBOB vessels. The results of the ballast water exchange experiments will be combined with a larger set of similar experiments conducted by our Smithsonian research partner to provide a scientifically-based evaluation of ballast water exchange as a preventive management practice.

Our research indicates that the risk associated with NOBOB vessels operating on the Great Lakes cannot be ignored, and management solutions to reduce that risk must be sought as we move forward to minimize the spread and impact of aquatic invasive species. To this end the U.S. Coast Guard is planning a public meeting and technical workshop in 2005 to examine the NOBOB issue in light of our research findings.

This research was supported by multiple sponsors including Great Lakes Protection Fund, NOAA, US EPA, and the U.S. Coast Guard.

The Cooperative Institute for Limnology and Ecosystems Research (CILER) is a cooperative institute between NOAA and the University of Michigan. The Institute was conceived to have a regional focus and fosters research collaborations between NOAA and academic scientists throughout the Great Lakes basin. CILER's research themes cover a diverse area of disciplines focused around the overall goal of improving our understanding and management of the Great Lakes through ecosystem based research. Research themes cover Climate and Large Lake Dynamics, Coastal and Nearshore Processes, Large Lake Ecosystem Structure and Function, Remote Sensing of Large Lake and Coastal Ocean Dynamics, and Marine Environmental Engineering.

[11/29/04]

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