Aquatic Invasive Species

Options for Refining Ballast Water Treatment Protocols Will Arise Pending the Results of a Proposed Study:
Ship ballast water used to maintain the stability and structural integrity of the vessel has long since been linked to the spread of non-native species across the globe. When a ship takes cargo, its ballast water is discharged to offset the additional weight of the cargo. An unintended consequence of this discharge is the subsequent release of non-native species into the port where the ship is docked. Invasive species have been associated with health risks and ecological and economic effects. The estimated cost of invasive species damages exceeds 138 billion dollars in the United States (Tsolaki et, al., 2009). Rapid growth of the shipping industry has further facilitated the exchange of not only consumer goods but also species “stowed away” in ships’ ballast water. Over 80% of the world’s goods are moved by shipping accounting for the transfer of 10 billion tons of ballast water annually (Boldor et. al., 2008). As the shipping industry cannot be expected to reduce its’ scale or operations, steps must be taken to ensure that ballast water is not carrying potentially harmful invasives.

Several methods exist for the elimination of species taken in with ballast water thereby eliminating the risk that these species are introduced into foreign environments. Port-based treatment involves treating the ballast water in portside treatment facilities requireing that the ballast water be pumped out of a ship’s tanks before it is treated. Shipboard treatment involves treating the ballast water onboard the ship using physical methods (filtration), mechanical treatments (microwave heating or ultraviolet light), or chemicals (biocides, chlorine, ozone, and hydrogen peroxide) (Tsolaki et. al., 2009). All of these methods vary both in removal efficiencies and cost. To determine the best option for ballast water treatment, Kevin Shia has proposed a study to evaluate the best method of ballast water treatment. Working under the research questions “can ballast water treatments reduce a significant number of foreign species while being environmentally safe and inexpensive? Will port-based or shipboard treatment be the most successful at removing the majority of foreign species?” (Shia, in production), Shia hopes to determine a protocol for the effective and cost-efficient treatment of ballast water. Shia expects that both port-based and shipboard treatments will significantly reduce the number of invasive species in ballast water further asserting his conviction that shipboard treatments utilizing mechanical separation will be the safest, most economical, and efficient. In order to test this hypothesis, Shia proposed a study of species populations in ballast water on one trade route. After taking initial tallies of species found in ballast water, Shia will test 5 port-based treatments, and 9 shipboard treatments’ (3 mechanical, 3 chemical, and three combined) effects on species populations in ballast water. Shia will utilize DNA testing to indicate the presence of species in ballast water. A main goal of the study is the establishment of an effective ballast water treatment protocol to reduce the number of species found in ballast water. The study should provide information on the economic and environmental cost of each treatment method with respect to its effectiveness for removing invasives. The results of this study will also be directly applied to industrial engineering. Better information on ballast water treatment methods allows engineers to make decisions when designing both ships and ports. In this way, the negative effects of invasive species can be mitigated through the installation of efficient, inexpensive, and environmentally safe ballast water treatment systems in ports and on ships.

DURHAM, N.C. – Invasive species have become a large problem worldwide. They cause environmental as well as economic problems. Scientists have been studying numerous invasive species looking at their breeding patterns, suitable habitats for them, and many other aspects of their existence. However, researchers are still having difficulty discovering effective methods to control their current spread as well as to prevent their future spread. Every invasive species is different, and rarely is any control method completely effective.

There are several current methods in use by scientists including chemical, physical, and genetic methods (that prevent reproduction). One popular method in use since the late 19^th century is biological control. Biological control is the intentional use of one organism to control the population size of another organism. Biological control has had many disasters throughout its practice. The problem with biological control is that many times, organisms introduced to control one alien species problem, actually cause further negative environmental impacts.

The important questions about biological control is what do you think? What do your friends and neighbors think? Depending on what you say, biological control may soon be coming to your nearest invasive species if you and your neighbors say it is socially acceptable. Jeremy Joven, a student at Duke University, is searching for the answers to these questions that many researchers have ignored for years.

Scientists do not always fully explain scientific processes such as biological control and ask for the average layman’s opinion. However, Joven is about to change all that. Joven is in the process of researching invasive species control methods and their popularity in random samples of people across all dimensions of knowledge in society including representatives of aquatic conservation groups, local, state, and national aquatic managers, international scientists, and average citizens like you and me. He says the current methods of control that are publicly acceptable are largely ineffective and cost inefficient. He speaks of rare success stories with all methods including biological control.

Knowing that the government is unlikely to fund programs and projects containing control methods unpopular with taxpayers, Joven’s goal is to find the “perfect solution” to alien species being both effective as well as socially acceptable. He wants to educate people and differentiate between the actual effectiveness of biological control and its social acceptability. He does not want a repeat of the public relations’ disasters of recent years regarding inhumane killing methods of invasive species.

Joven believes that biological control will be deemed socially unacceptable because of its low success rate and high costs. People want consistent positive results, and biological control is just too unreliable for people to accept as the best method for widespread use. However, Joven believes that his research will lead to further research into determining a publicly approved program with better results. Most importantly, Joven believes his work will lead to an established order for the use of the various control methods on invasive species in the future and bring greater success to invasive species prevention.

Bernard Jiang

A common trait of an invasive species is the ability to out-compete a native one. This superiority can be attributed to a multitude of causes, one of which is predation by native species. In some situations, a native predator will not prey on the invasive species, worsening the situation for the native species. A recent study shows, however, that native predators can actually prevent invasion. A recent study by Steven A. Juliano from the School of Biological Sciences in Illinois and his colleagues supports this idea. They compared the populations of the native mosquito (Aedes triseriatrus) and an invasive mosquito (Aedes albopictus) with and without the presence of the native predatory midge (Corethrella appendiculata). What they found was that in the environments where the two mosquitoes only competed with each other, the amount of A. albopictus skyrocketed. When the presence of C. appendiculata was introduced, the proportion of one mosquito to the other greatly shrank. This may be evidence that species native to a certain area benefit from a kind of biological synergy. There may be also behavioral cues the native species are aware of that prolong their lifespans and help them escape their predators. The invader, unaware of these nuances, are easier prey.

Oecologia. 162: 709-718

Is Habitat Conservation the Solution to Nile Tilapia Invasion?

Nile tilapia are a widespread invasive species that is able to survive in diverse environments making it very difficult to control them and prevent them from invading new habitats. Linde, Izquierdo, Moreira, and Vasquez (2008) performed a recent study in Brazil in which they studied juvenile Nile tilapia and their invading habits along with the native pearl cichlid. They used molecular markers to identify between the two species for their study. The researchers looked at four distinct habitats with different levels of degradation. They compared the populations of Nile tilapia and pearl cichlid at each location. They found that there was a higher proportion of Nile tilapia in the degraded parts of the river than less polluted areas. The researchers suggest that Nile tilapia are more able to invade and adapt than native fish in degraded ecosystems. Thus, habitat conservation and restoration may be a deterrent if not a solution to Nile tilapia invasion.

Aquatic Conserv: Mar. Freshw. Ecosyst. 18: 891–895 (2008)

Oxygen Needed

By: David Lung

Giant salvinia is an invasive aquatic fern that quickly covers the water surface, outcompetes native aquatic plants, and kills other aquatic organisms due to a decrease of dissolved oxygen. Flores and Carlson (2006) worked with the salvinia weevil to figure out if there was a correlation between the control effects of the weevils on giant salvinia and also dissolved oxygen levels after the release of the weevils. Flores and Carlson (2006) reared the salvinia weevil in tanks with giant salvinia and released the weevils at 6 sites in Texas waterways. Insect population densities were sampled monthly to make sure that the insects were dispersing. Dissolved oxygen levels were then measured after a little over a year. Flores and Carlson (2006) observed a significant increase in dissolved oxygen levels following successful control. More research is needed to understand the relationship between the weevil and the fern in order to understand the difference in the amount of time needed for complete control.

Journal of Aquatic Plants Management. 44: 115-121

The northern snakehead has become a widespread invader in the United States. Due to this species’ ability to survive and thrive in many different environments, control efforts for this species must implemented. Poison is one of the various methods being explored. In laboratory testing, several different concentrations proved lethal to the snakehead . Lazur et. al determined that the smallest lethal dose was 0.075mg/L of rotenone, a commonly used aquatic poison. Such a dose killed all test subjects within 1 hour of administration, and proved incredibly effective in a pond setting in Crofton, MD as 8 adult and 834 juvenile snakeheads were recovered. These results demonstrate a susceptibility of this species to known control methods. However, all other aquatic fauna in the affected region succumbed to the poison as well. Additionally, the affected area remained toxic for at least one week after treatment. It is suggested that this method only be utilized in clearly defined and isolated areas.

(North American Journal of Fisheries Management 2006; 26: 628-630)

Much like in healthcare, preventative action for invasive species is typically much cheaper and simpler than palliative action. Preventing the establishment of a problem is crucial in the management of invasive species. Currently, much of the regulation concerning invasive species deals with specific species. This is something that policy-makers have to work on. Given the sheer volume of species that are moved from area to area that have the potential to become invasive, more regulation needs to be established about the vectors of transportation rather than targeting individual species themselves. While policy that deals with one specific species may be  better suited to be dealing with that species, the other potential invasive species are essentially ignored. Spending so much time on one species, no matter how problematic it may become is baffling when one thinks about the broader policies that could be enacted which would cover both the species in question as well as others. In imposing a broad set of regulation to the various vectors of species transport, whether it be through ballast water, live bait, aquaculture or other anthropogenic factors, one ultimately protects the environment better than they would through individual species policy.

One interesting idea brought up in the article that was proposed in 1999 by Reeves was that any person or corporation wanting to introduce a species must first prove that it will not cause ecological or economic harm. This policy would hold that entity accountable for the actions of the introduced species. I think that this would be a highly effective policy as it would add a more prominent economic incentive to those companies who would want to establish a species. It would be crucial to have an opposing point-of-view do their own research into the potential damage of the species though, as statisticians can create misleading data. Only if the two sides are in concordance with the results could the species be introduced.

In his article, Brendon Larson discusses the use of “militaristic” rhetoric to describe the issue of invasive species. Larson argues that the use of metaphor misleads the public, and even scientists, into a false perception of the invasive species issue and how to effectively deal with it.

For example, a recent article in Time – entitled “Asian Carp in the Great Lakes? This Means War!” – proves Larson’s point. In addition to the title, language such as “infiltrating a new home,” or “eradicate them after the fact” (Walsh, 2010) compares the idea of invasive species to an enemy that must be defeated in war. I agree with Larson that this kind of rhetoric leads us to think that a “brute force” approach is the only way to deal with the invasive species problem – which is problematic because this kind of approach is usually the least cost-effective and successful. However, I think that there is some use to this kind of rhetoric. The metaphor is necessary for the public to understand the issue of invasive species. Especially in a popular magazine such as Time, overly scientific language would not be of any use to the general reader.

Larson, 2005. The war of the roses: demilitarizing invasion biology. Frontiers in Ecology and the Environment.

Walsh, 2010. “Asian Carp in the Great Lakes? This Means War!”. Time Magazine. http://www.time.com/time/health/article/0,8599,1962108,00.html

SW6

By: David Lung

Larson criticizes the militaristic language that biologists use in order to inform the public. Doing so would ultimately describe invasive species wrongly, cause a backlash from the people because we were at fault to begin with for bringing in these invasive species and create a fear of these plants that might be counterproductive to conservation. He argues that waging war is not a good description for controlling invasive species because they are a part of our lives now and we were the ones that gave them the opportunity to live in foreign environments. Also, he states that it is impossible to completely get rid of these species from ecosystems they have already invaded and the methods to restore a particular ecosystem might cause further problems. Larson states that the rhetoric should be toned down considerably and we should work on preventing the spread of invasive species and accept that they are a part of the ecosystems they now inhabit based on our own actions

“Cyrtobagous Salviniae destroyed terminal and lateral buds on the parent plant which partially compensated for this loss by producing new buds of higher order rank, some of which were also attacked by adults and larvae.” (Forno and Semple 1987)

I saw this quote on a study of the salvinia weevil as a potential biocontrol agent of giant salvinia (salvinia molesta). Using terms like “destroyed” and “attacked” gave this sentence a militaristic tone. The authors could have stated that the salvinia weevil ate the terminal and lateral buds or simply that the insect controlled the giant salvinia by doing so. I somewhat disagree with Larson’s argument though. In my opinion it is obvious that we were the main agents that brought invasive species, but to allow these invasive species to live with us when they already do so much damage to the ecological services native organisms provide, it does not make sense to live peacefully with them. The damage these invasive species do is not overexaggerated for the most part. They are essentially parasites, outcompeting native species that have already reached an equilibrium with their ecosystem and also disrupting the overall balance of the ecosystems they now inhabit. The backlash he talks is somewhat probably because these invasive species such as the Sitka black-tailed deer that help people with a lower socioeconomic status. Overall, I do believe the militaristic tone is necessary and effective for preserving what is left of pristine ecosystems from invasive species, but also to restore invaded ecosystems to the best of our ability because we are at fault for disrupting those ecosystems and should be reminded in the urgency of the problem we’re responsible for.

References:

Larson, B.M.H. 2005. “The war of the roses: demilitarizing invasion biology.” Frontiers in Ecology and the Environment 3: 495-500.

Forno, I.W. and J.L. Semple. 1987. “Response to Salvinia Molesta to insect damage: changes in nitrogen, phosphorus, and potassium content.” Oecologia. 73: 71-74.

Proc. R. Soc. Vol. 276, 2813 – 2818, (2009)

A study done on Australian death adders shows how certain adaptations have become liabilities in reference to the invasion of cane toads. These snakes have adapted to their environments by developing lures on their tails, allowing them to attract more agile prey, and they have a delayed ingestion process, which allows them to circumvent the dangers of natural toxins.

Cane toads, however, pose a threat to these reptiles. Listed as a “top-ten global invader”, they are slowly decreasing Australian adder populations. Cane toads are typically bigger than native frogs, making it more attractive for adders to lure them in. They also move in slower, shorter hops, increasing their availability as prey. However, their toxins remain active for a long time after their death, increasing adder fatalities. More than half of the adders who tried to eat the toads died as a consequence. Cane toads are not only harming adders, but other Australian wildlife that typically prey on toads as well.

Chris Rzeznik