Research ProjectShipping Transports Aquatic Invaders

The transport of aquatic organisms through shipping: the role of ballast water and hull fouling

  • Ship entering the Panama Canal

    A Panamax ship entering the Miraflores Locks of the Panama Canal. Photo by Kristen Larson

  • Dr. Gail Ashton surveys a ship in California

    Dr. Gail Ashton surveys a ship in California. Photo by Ian Davidson.

  • Ships docked at the Port of Busan, Korea

    Ships at the Port of Busan, Korea. Photo by Monaca Noble

Affiliated Labs

Project Goal

We are assessing the role of commercial shipping in the transport of aquatic organisms and examining the composition of the communities being transported in the two major shipping vectors, ballast water and hull fouling.


Commercial shipping is the dominant method of transporting goods for trade, making it a vital and ever growing global industry. Yet, in addition to transporting commodities, vessels are also transporting and introducing aquatic organisms to new environments. While not all of these introductions cause noticeable harm, many can have significant impacts on the environment, economy, and even human and animal health. 

Ballast water* and hull fouling* are the primary ways that marine organisms are transported by commercial shipping. Many harmful organisms have been introduced through ballast water discharge, with the introduction of zebra mussels to the Great Lakes being an infamous example. As a result, the International Maritime Organization (IMO) has created an international ballast water management policy to minimize the possibility of future ballast water introductions.

Our researchers board ships to collect water and plankton* samples from ballast tanks to determine what species are being transported, assess the efficacy of management on species in ballast water, and much more.  Our hull fouling research program investigates organism communities attached to the outside of vessels, often concentrated in niche areas such as propeller shafts. We use SCUBA diver surveys and a submersible Remotely Operated Vehicle (ROV) to visually identify and measure the abundance of organisms on recreational and commercial vessels. 

For both ballast water and hull fouling studies we use a combination of microscope examination and genetic tools, including metabarcoding* techniques using high throughput sequencing technology*, to identify and assess the diversity of the organisms collected. With this information we can evaluate whether current management is likely to reduce the risk of new introductions, or if alternate strategies are required.  


Jenny Carney

Darling, J., Martinson, J., Gong, Y., Okum, S., Pilgrim, E., Lohan, K., Carney, K.J., and Ruiz, G. (2018). Ballast water exchange and invasion risk posed by intra-coastal vessel traffic: An evaluation using high throughput sequencing. Environmental Science & Technology DOI: 10.1021/acs.est.8b02108 

Davidson, Ian C., Minton, Mark S., Carney, Katharine J., Miller, A. W. and Ruiz, Gregory M. (2017). Pioneering patterns of ballast treatment in the emerging era of marine vector management. Marine Policy, 78 , 158-162.

Ricciardi, Anthony, Blackburn, Tim M., Carlton, James T., Dick, Jaimie T. A., Hulme, Philip E., Iacarella, Josephine C., Jeschke, Jonathan M., Liebhold, Andrew M., Lockwood, Julie L., MacIsaac, Hugh J., Pysek, Petr, Richardson, David M., Ruiz, Gregory M., Simberloff, Daniel, Sutherland, William J., Wardle, David A. and Aldridge, David C. (2017). Invasion Science: A Horizon Scan of Emerging Challenges and Opportunities. Trends in Ecology & Evolution, 32 (6) , 464-474.

Ricciardi, Anthony, Blackburn, Tim M., Carlton, James T., Dick, Jaimie T. A., Hulme, Philip E., Iacarella, Josephine C., Jeschke, Jonathan M., Liebhold, Andrew M., Lockwood, Julie L., MacIsaac, Hugh J., Pysek, Petr, Richardson, David M., Ruiz, Gregory M., Simberloff, Daniel, Sutherland, William J., Wardle, David A. and Aldridge, David C. (2017). Invasion Science: Looking Forward Rather Than Revisiting Old Ground - A Reply to Zenni et al.. Trends in Ecology & Evolution, 32 (11) , 809-810.

Carney, Katharine J., Minton, Mark S., Holzer, Kimberly K., Miller, A. W., McCann, Linda D. and Ruiz, Gregory M. (2017). Evaluating the combined effects of ballast water management and trade dynamics on transfers of marine organisms by ships. PloS One, 12 (3) , 1-20.

Ashton GV, Davidson IC, Geller J, and Ruiz GM (2016). Disentangling the biogeography of ship biofouling: barnacles in the Northeast Pacific. Global Ecology and Biogeography DOI: 10.1111/geb.12450

Davidson I, Scianni C, Hewitt C, Everett R, Holm E, Tamburri M, and Ruiz G (2016). Mini-review: Assessing the drivers of ship biofouling management -- aligning industry and biosecurity goals. Biofouling 32(4): 411-428. 

Moser, Cameron S., Wier, Timothy P., Grant, Jonathan F., First, Matthew R., Tamburri, Mario N., Ruiz, Gregory M., Miller, A. Whitman and Drake, Lisa A. 2016. Quantifying the total wetted surface area of the world fleet: a first step in determining the potential extent of ships' biofouling. Biological Invasions, 18(1): 265-277.

Holzer, Kimberly K., Jim R. Muirhead, Mark S. Minton, Katharine J. Carney, A. Whitman Miller, Gregory M. Ruiz. (2016). Potential effects of LNG trade shift on transfer of ballast water and biota by ships. Science of The Total Environment. Online December 2016, 

Hughes, Kevin A. and Ashton, Gail V. (2016). Breaking the ice: the introduction of biofouling organisms to Antarctica on vessel hulls. Aquatic Conservation: Marine and Freshwater Ecosystems, DOI: 10.1002/aqc.2625.

KM Pagenkopp Lohan, RC Fleischer, KJ Carney, KK Holzer, GM Ruiz. (2016). Amplicon-based pyrosequencing reveals high diversity of protistan parasites iships’ ballast water: implications for biogeography and infectious diseases. Microbial Ecology, 71 (3): 530-542.

Verna, Danielle E., Harris, Bradley P., Holzer, Kimberly K. and Minton, Mark S. (2016). Ballast-borne marine invasive species: exploring the risk to coastal Alaska, USA. Management of Biological Invasions, 7 , 199-211.

Muirhead, Jim R., Minton, Mark S., Miller, A. Whitman and Ruiz, Gregory M. (2015). Projected effects of the Panama Canal expansion on shipping traffic and biological invasions. Diversity and Distributions, 21(1): 75-87. doi:10.1111/ddi.12260

Ashton, Gail, Davidson, Ian C. and Ruiz, Gregory M. (2014). Transient small boats as a long-distance coastal vector for dispersal of biofouling organisms. Estuaries and Coasts, 37(6): 1572-1581. doi:10.1007/s12237-014-9782-9

Miller, A. W. and Ruiz, Gregory M. (2014). Arctic shipping and marine invaders. Nature Climate Change, 4(6): 413-416. doi:10.1038/nclimate2244

Ros, Macarena, Ashton, Gail V., Lacerda, Mariana B., Carlton, James T., Vázquez-Luis, Maite, Guerra-García, José M. and Ruiz, Gregory M. (2014). The Panama Canal and the transoceanic dispersal of marine invertebrates: Evaluation of the introduced amphipod Paracaprella pusilla Mayer, 1890 in the Pacific Ocean. Marine Environmental Research, 99: 204-211. doi:10.1016/j.marenvres.2014.07.001

First, Matthew R., Robbins-Wamsley, Stephanie, Riley, Scott C., Moser, Cameron S., Smith, George E., Tamburri, Mario N. and Drake, Lisa A. (2013). Stratification of Living Organisms in Ballast Tanks: How Do Organism Concentrations Vary as Ballast Water Is Discharged? Environmental Science & Technology, 47(9): 4442-4448.doi:10.1021/es400033z

Frazier, Melanie, Miller, A. Whitman, Lee, Henry, II and Reusser, Deborah Ann. (2013). Counting at low concentrations: the statistical challenges of verifying ballast water discharge standards. Ecological Applications, 23(2): 339 doi:10.1890/11-1639.1

Reusser, Deborah A., Lee, Henry, II, Frazier, Melanie, Ruiz, Gregory M., Fofonoff, Paul W., Minton, Mark S. and Miller, A. Whitman. (2013). Per capita invasion probabilities: an empirical model to predict rates of invasion via ballast water. Ecological Applications, 23(2): 321-330. doi:10.1890/11-1637.1

Term  Definition
Ballast water Ballast water is carried by ships to provide balance, stability, and trim during sailing and to keep them upright during loading and offloading operations. Ballast water is typically held in dedicated ballast tanks located around cargo holds and near the bow and stern of the ship.
Hull fouling Organisms like barnacles, mussels, sponges, algae and sea squirts attach themselves to the hulls of ships, fouling them. These organisms then colonize the hull and "hitch a ride" from one port to the next. Invasions can occur when these fouling organisms release their larvae into its waters adjacent to structures in a new port. Under the right conditions, these invaders may establish themselves in the new port and spread to nearby areas within that region.
Plankton  A diverse group of aquatic organisms that are too small to swim so they drift in the current. They provide a crucial source of food to many aquatic organisms. Examples include algae, bacteria, protozoans, crustaceans, mollusks, and many more. They could be adults or the larval stages of larger animals (larval crabs for example). 
Metabarcoding A rapid method of biodiversity assessment that combines two technologies: DNA based identification and high-throughput DNA sequencing. Visit this blogpost for more details. 
High throughput sequencing technology Faster and less expensive methods of sequencing and analyzing large genomes.