Ballast Water Management and Its Implications Regarding Invasive Species Introduction

By Casey Dresbach, SRC intern

Ballast water, either fresh or salt water, and sometimes containing sediments, are held in tanks and cargo holds of ships to increase stability and maneuverability during transit. It’s advantageous in its means to stabilize, increase propeller immersion to improve steering, and to control trim and draft. Often times, cons outweigh the pros in the ballast water process. In regards to the marine ecosystem, ballast water discharge contains many plants, animals, viruses, and microorganisms some of which can be invasive or exotic species that can lead to detrimental ecological and economical effects, as shown in Figure 1.

Figure 1. Depiction of how Ballast Water Management can instigate water pollution of the seas from untreated ballast water discharges

Figure 1. Depiction of how Ballast Water Management can instigate water pollution of the seas from untreated ballast water discharges

Invasive species are a major threat to biodiversity in the marine ecosystem. Once integrated, they become predators, parasites, and diseases of native organisms. Unfortunately, many of these nonindigenous species (NIS) are spreading across the seaboard. These invasive species are making their way into ballast water of ships globally. These ships are picking up water in one location, carrying their said cargo across the seas (ranging from far to close distances), and then discharging that water at their acquired destination. By doing so, the ships transport a subset of native species from one ecosystem into another, to which they may not be native.

In the 15th century, the shipping industry expanded exponentially and led to an increase in the number of vessels. By the 18th century, the expansion was furthered in steam technology, with the addition of more complex vessels that required more stability efforts. Ballast water was issued to these vessels, consequently increasing opportunities for nonindigenous species to spread.

At the global scale, initial efforts have been underway in the past twenty five years to control unwanted nonindigenous species with the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990, and later the National Invasive Species Act of 1996. Such policy instigation focused on aspects from mid-ocean ballast exchange to quantitative standards of permitted organism density upon ballast water discharge. Among all, there have been exemptions or exceptions to the proposed policies, including crude oil tankers engaged in coastwise trade.

A study in Alaska was initiated in regards to questionable effects of exemptions. The study focused on determining the “effectiveness of existing shore-side ballast water facilities used by crude oil tankers in the coastwise trade off Alaska.” The results indicated a high risk of NIS transport from ballast water discharged in Prince William Sound, Alaska. Much of the ballast water was discharged along intra-coastal shipping routes that originate on the Pacific Coast of North America from invaded source ports. Prince William’s largest port, Valdez, may serve as a designated area for the secondary transfer of nonindigenous species.

The initial BWM policy was not enforced it was voluntary; the nonbinding guidelines were insufficient and continued invasion and warranted stronger action. With that in mind, the initial efforts of BWM were more of a reactionary process because the invasions had since occurred. On November 21, 2001, the United States Coast Guard (USCG) published its final ruling. Since participation in the voluntary program was insufficient to the success of the program; BWM was now going to become mandatory. With this mandate, vessels (other than those exempted: crude oil tankers engaged in coastwise trade, Department of Defense of USCG vessels, and vessels operating within one USCG Captain of the Port Zone) would be fined or issued a monetary civil penalty up to $35,000.

With growing concern, the IMO (International Marine Organization) developed “The International Convention for the Control and Management of Ships Ballast Water and Sediments,” in 2004, to further protect the marine ecosystem from the transport of detrimental nonindigenous species in ballast water carried by vessels.

In 2005 policy initiatives were furthered, and BWM was mandatory for all vessels in the United States, with the same exemptions as before. By 2008, management and recordkeeping requirements went into place with the hopes of decreasing these risks. However, many of those exempted from the BWM such as the crude oil tanker traffic had their transports undocumented and under-reported. As seen in Figures 2 and 3, exemptions from management have negated these efforts to reduce invasion risk. Studies found a 440% increase in ballast water discharge to Alaska in the following year. In a review of ballast water discharge to Alaska (Danielle E. Verna, Bradley P. Harris), a suggestion was made that a precautionary approach to exemptions was of dire need, as well as consistent assessments of the vessels expeditions to reduce the risks of increased invasion.

Figure 2A. Valdez, Alaska water ballast water sources from 2005-2008.

Figure 2A. Valdez, Alaska water ballast water sources from 2005-2008.

Figure 2B. Valdez, Alaska water ballast water sources from 2009-2012 shows an exponential increase in source volume, primarily due to consequence of exempting a sector.

Figure 2B. Valdez, Alaska water ballast water sources from 2009-2012 shows an exponential increase in source volume, primarily due to consequence of exempting a sector.

The inclusion of intra-coastal vessel traffic as well as a better understanding of the NIS risks at stake may reduce the risk of further invasions. The most beneficial impact to the Alaskan industry practices was when BWM became mandatory to all vessels. However, the exemption factor is what threatened to negate the initiative. With continued assessment of vessel behavior and transport as well as documentation and data recordings can help trace back to where this exemption may take their turn in increasing the risk of NIS introduction. Moving forward, policy makers will continue to do their job, but further education among communities will only benefit their obligatory feats.

International Marine Organization. (n.d.). Ballast Water Management. Retrieved October 24, 2016, from IMO :
MaxxL, & Hartmann, T. (2014, June 24). Ballast Water. Retrieved October 24, 2016, from Wikimedia Commons:
Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., & Minorsky, P. V. (2014). Campbell Biology . Boston: Pearson.
Verna, D. E., & Harris, B. P. (11, April 2016). Review of Ballast Water Management Policy and Associated Implications for Alaska. Elsevier Journal .

Active and passive environmental DNA surveillance of aquatic invasive species

By Jake Jerome, SRC graduate student

Species that are not typically found in a certain environment or geographical location are known as invasive species. Invasive species can be harmful to the natural ecosystem and the organisms that typically reside there. Monitoring the introduction or spread of invasive species is important to environmental managers so they can control their populations and attempt to retain balance in an ecosystem. One way that researchers can monitor invasive species is through the surveillance of environmental DNA (eDNA).

In the Muskingum River Watershed (MRW) in Ohio, Simmons et al 2015 looked for signs of the invasive Asian bighead carp (Hypophthalmichthys nobilis) and silver carp (Hypophthalmichthys molitrix) through both active and passive eDNA surveillance. Active eDNA surveillance is used to detect specific species within a sample. Passive surveillance, however, looks for all species present in a sample, potentially leading to species that were not known in that location. Because the MRW has intermittent water passages that lead to Lake Erie, it is important to survey the area to see if these two highly invasive carp species are present.

Bighead carp (Hypophthalmichthys nobilis). (Wikimedia Commons)

Bighead carp (Hypophthalmichthys nobilis). (Wikimedia Commons)

In October 2013, 211 water samples were collected from 7 sites found within the MRW. They were analyzed for eDNA both actively and passively to determine species that were present. The active surveillance of the two Asian carp species found eDNA of bighead carp in 10 samples from four locations while no detections were found of the silver carp. Besides showing the naturally occurring species, the passive surveillance of the water samples did not find eDNA from either of the Asian carp species. It did, however, detect the eDNA from a different invasive, the snakehead.

Environmental DNA water sample locations within the Muskingum River Watershed in eastern Ohio and surrounding bighead carp capture locations (bighead carp coordinates provided by Midwest Invasive Species Information Network, March 2015). (Simmons et al 2015)

Environmental DNA water sample locations within the Muskingum River Watershed in eastern Ohio and surrounding bighead carp capture locations (bighead carp coordinates provided by Midwest Invasive Species Information Network, March 2015). (Simmons et al 2015)

The authors note that the discrepancy between the two methods for detecting the bighead carp are likely due to the sensitivity of active surveillance and the more broad approach used for passive surveillance.  Despite this, it is clear that both techniques prove useful for managing aquatic invasive species. Used alone, active surveillance is useful for immediate, known threats but may miss unknown species or invaders that are not targeted. Together, active and passive surveillance of aquatic invasive species can give managers a holistic view of the area they are studying and hopefully further their conservation efforts in response.


Simmons, M., Tucker, A., Chadderton, L.W., Jerde, C.L., Mahon, A.R. (2015). Active and passive environmental DNA surveillance of aquatic invasive species. Can. J. Fish. Aquat. Sci. 73: 1-8.

Summary of “Competitive interactions for shelter between invasive Pacific red lionfish and native Nassau grouper”

Hannah Armstrong, RJD Intern

Invasive species have the potential to negatively effect normal ecological function in any environment. Marine biological invasions are increasingly common, most notably that of the Pacific red lionfish (Pterois volitans).  While the lionfish invasion and its direct effects on native fish communities has been well researched, there has been little documented evidence regarding non-predatory interactions.  In a 2014 study by Raymond, Albins and Pusack, they observed whether Pacific red lionfish and Nassau grouper, two species that occupy similar habitats, compete for shelter and whether or not the competition is size-dependent.

Pacific red lionfish (Pterois volitans) have been reported in the Atlantic Ocean since the mid-1980s and now pose a threat to the western Atlantic and Caribbean coral reef systems.  As small-bodied predators, they are capable of significantly reducing the abundance and diversity of native fishes via predation. Nassau groupers (Epinephelus striatus), despite being regionally endangered, are a larger predator found throughout the lionfish’s invasive range. Because these two species use similar resources and compete for similar habitats, it is important to understand how they interact and what may result from their competition.


The invasive Pacific red lionfish, Pterois volitans. (Source: Smithsonian Marine Station at Fort Pierce)

In order to investigate how Pacific red lionfish and Nassau grouper affect each other’s behavior, the three scientists set up an experiment to compare their distance from and use of shelter when in isolation versus when both species were in the presence of each other with limited shelter. The two species were first held in separate cages with partitions to allow for isolation periods lasting 24 hours, and interaction periods lasting 48 hours, with each cage containing a shelter that the scientists constructed. The trials were based on size-ratio treatments: first they observed similarly sized lionfish and Nassau grouper, then they observed a juvenile lionfish and a substantially larger juvenile Nassau grouper, and lastly they observed an adult lionfish and a much smaller juvenile grouper. Finally, to test for predation between the two species, they incorporated a prey fish in some of the trials.


The native Nassau grouper, Epinephelus striatus. (Source: IUCN Red List)

Upon statistical analyses, Raymond, Albins and Pusack eventually came to two conclusions regarding the interactions between these two species, and specifically Nassau grouper avoidance behavior: first, they found that when Nassau grouper interacted with smaller lionfish, they avoided them by moving further from the shelter occupied by lionfish, and by using the shelter less often, and second, they found that when Nassau grouper interacted with similarly sized lionfish, they avoided them by increasing their proportion of shelter use, and by avoiding the part of the experimental cage where lionfish were consistently present. The scientists ultimately found that the Nassau grouper significantly changed position relative to shelter in the presence of lionfish, however the lionfish did not change their positioning upon interacting with the Nassau grouper. This demonstrates how they have a tendency to compete for limited shelter, and the manner in which the Nassau grouper avoid lionfish is size-dependent.

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Configuration of experimental cages used in this study.

While this study highlights the competitive interactions for shelter between invasive Pacific red lionfish and Nassau grouper, it is important to note that it was performed in a laboratory setting.  For future conservation efforts, it will be critical to consider how this might apply in a natural reef habitat, and whether or not this competition could lead to lionfish being a dominant predator rather than the native Nassau grouper, a shift that may result in trophic cascades.



Raymond, WW, Albins MA, Pusack TJ.  Competitive interactions for shelter between invasive Pacific red lionfish and native Nassau grouper. Environ Biol Fish (2015) 98:57-65. 31 January 2014.


Treatment of Invasive Aquatic Species Found in Ballast Water

By Abbigail Rigdon,
Marine conservation student

As the world becomes more globalized, countries that at one time seemed distant are now easily traveled and easily contacted. Such contact does not exist only between humans, but between other species as well. Sometimes, however, these species can be detrimental to their new environment. Foreign species may be introduced to new environments accidentally (by releasing an exotic pet into the wild, for example), or purposefully (in order to manage an overabundance of a native species by increasing its competition, or by increasing the amount of predators for the species). One major method of accidental introduction is through the release of ballast water from ships.
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Photo of the Week: Invasive Lionfish

A fisherman spears an invasive lionfish in the warm, shallow waters of Nassau, Bahamas.

A fisherman spears an invasive lionfish in the warm, shallow waters of Nassau, Bahamas.

Sea Invaders: Lionfish

by Catherine MacDonald, RJD student

Sea Invaders

Anyone living in South Florida is familiar with the issue of invasive species—particularly the invasion of the Everglades by the African Rock Python (P. sebae) and the Indian Python (P. molurus) and the presence in the Florida Keys of large numbers of non-native Green or Common Iguanas (Iguana Iguana).

What you may not know, however, is that invasive marine species are also a big problem. Recent estimates by NOAA suggest that the total cost of invasive species to the U.S. economy is as much as $137 billion per year. Baltz (1991) provides a review of non-native marine fish introductions, reporting that well over 100 species have staged “invasions” worldwide, many as a result of ballast water releases in shipping, canal construction, or intentional transplantation for “fishery enhancement”. According to the U.S. Geological Survey’s Nonindigenous Aquatic Species Database, in the last 100 years more than 68 non-native species have been introduced just in Florida, the Caribbean, and the Gulf of Mexico. Once established, even intensive campaigns have failed to successfully eradicate invaders like the European Green Crab (Carcinus maenas) on the U.S. Pacific coast or a variety of ornamental fish including Siamese Fighting Fish (Betta Splendens) and the Yellow Tang (Zebrasoma flavescens) in the rivers and oceans of South Florida.

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