Elser from Arizona State University and his team conducted a study examining the distribution and competitive effects of the invasive zooplankton Daphnia lumholtzi in Arizona. First detected in Texas in 1990, this species indigenous to Africa, Australia, and India has spread throughout the midwestern and southern United States.
Elser conducted a field sampling of 12 reservoirs in central Arizona and a competition experiment involving water from Canyon Lake. The samplings demonstrated that D lumholtzi was dispersed across central Arizona in various watersheds, some with a greater percentage of the exotic zooplankton than others (ranging from none to more than the native species). This proves the persistence of this specie’s invasion in Arizona. The competition experiments found that the production of both species (D lumholtzi and native D pulex) decreased when both were present at the lake. Also, D lumholtzi reduced total zooplankton production. Therefore, communities dominated by D lumholtzi are expected to be less fertile and retain lower biomass.
Research on this detrimental species will continue because it impacts plankton communities and fish production since their spination renders them inedible.
Resource: Journal of the Arizona-Nevada Academy of Science Vol. 34(2): pp 89-94. (2002)
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A study on Daphnia species competition demonstrated that Daphnia lumholtzi only out-competed native Daphnia species in the presence of a predator.
Katharine Engel and Ralph Tollrian, of Ludwig-Maximilians-University Munich and Ruhr-University Bochum respectively, explored the Daphnia lumholtzi‘s growth in environments with native Daphnia pulicaria with and without predators. They found that in an environment with predators, Daphnia pulicaria was dominant over the invasive Daphnia lumholtzi, but in the presence of a predator, Daphnia lumholtzi became more dominant.
From the results of the study, Engel and Tollrian concluded that the ability of Daphnia lumholtzi to grow head and tale spines in the presence of fish predators may be a key adaptation for the success of the species in North American invasions.
Proc. R. Soc. B. 276: 1865–1873, 2009. doi:10.1098/rspb.2008.1861
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It’s quite ironic as always, when dealing with invasive species, that human pleasures can bring about the downfall of an ecosystem. In this case, its none other than the highly profitable and yet highly expendable industry of aquarium and ornamental trade, which has been the villain behind hundreds of introduced non-native invasive species worldwide, and the aquatic ecosystem of the Florida Keys.
Caitlin Finn, an undergraduate researcher at Duke University, believes aquarium species have many advantages that will allow them to thrive in the Florida Keys. Unlike other invasive species or plants, the aquarium species have an exceptionally high rate of survival, mainly because they are sold as adults and need to be large enough to survive the transportation process. A previous risk analysis in 2005 of the San Francisco Bay-Area determined that the cold temperature of the bay was the limiting factor of an introduced species’ invasion success. Finn believes, however, that the moderately warm and tropical waters of the Florida Keys are optimal conditions for an introduced species to invade.
Two aquarium species that pose a dire threat to aquatic environments are the lionfish (Pterois volitans) and the Hydrilla verticillate, which have invaded most of the western Atlantic through the fishing trade. Lionfish are carnivores that can eat other fish up to two-thirds their own length, while they are protected from other predators by long, poisonous spines. Because of their incredible defense mechanisms, it’s nearly impossible to eradicate their presence using predators.
Why then, are non-native aquarium species introduced into native ecosystems? Research has shown that insufficient transportation methods have resulted in significant amounts escaped organisms. In addition, there have been numerous reports of owners dumping their fish-tanks into local waters, instead of handling them more delicately, given their invasive capabilities. This, Finn says, is due to insufficient knowledge amongst the public of the potential threat their “prized fish” can have on nearby coral reefs.
Finn’s main research objective is to determine, firstly, which species pose the most ecological risks , and then, secondly, to adapt the necessary preventative measures to keep such aquarium species from overpopulating the Florida Keys.
In order to determine the threat level of a particular species, Finn and her colleagues will conduct a wide scale risk analysis surveys in which, she says “are different than ones past in that we are testing warm waters, which are more favorable to aquarium species.” Finn will assess the invasion potential of a particular species by its range of temperature and salinity tolerance, as well as previous invasion history in other ecosystems. Also taken into consideration will be the popularity of a given species, which is directly correlated to the amount of species present and their potential for harm.
The biggest goal of Finn’s project is to ensure that adequate knowledge is known about the aquarium species being bought. In the past, storeowners have accidentally put incorrect taxonomical labels on many of the fish species, which has greatly influenced the way that fish enthusiasts dispose of their aquarium pets. By surveying fish aquarium stores around the Florida Keys and relabeling the species correctly, Finn hopes to increase public awareness of the invasive abilities of many aquarium species and thereby reduce the risk of further invasions.
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Every year, invasive animals, plants, and every type of living organism find ways to infiltrate across borders to infect exotic ecosystems. These invaders have caused devastating losses in biodiversity, radical changes in environment, and fluctuations in ecosystem makeup. In nearly every case these effects have been traced to problems in agriculture, the economy, and human interaction around the world. Scientific studies have discovered these invasive species’ transportation by the hulls of tanker ships, by farmers looking to increase their output, and even by the waders of unknowing fishermen. Many efforts have already been enacted to slow the flow of invasive species. However, it may be surprising to learn that local nurseries could very well harbor invasive aliens. Due too a lack of government restrictions on the trade of horticultural plants, many invasive species such as the Brazilian pepper, melaleuca, Java plum, and Gold Coast jasmine have all been bought and sold in nurseries across the state of Florida. These invaders threaten Florida’s many unique ecosystems. Places such as the Everglades or the Keys harbor life unlike anywhere in the world and invasive species are one of their major threats.
This is by no means the final word on the matter. Efforts around the world are taking place to stem the flow of invasive species through horticultural trade. Nikki Rigl, a researcher from Duke University in Durham, North Carolina hopes to address this problem in a study. “When people think about invasive species, they do not think about their plants,” said Rigl in an interview. She plans to decrease the knowledge gap between Florida citizens while determining the threat posed by the horticultural trade as a vector for invasive species. She proposes a state-wide survey of random nursery owners and other horticultural traders about invasive plants and their views on selling this volatile species.
The survey will ask a variety of questions ranging from typical “age?” “sex?” “location?” questions to more specific questions on horticultural trade in Florida. Each respondent will be asked to identify certain invasive species from a photograph, their opinion on the “invasive” status of a plant, and about the likelihood for them stocking invasive plants. Rigl hopes that the information obtained from these questions will help shed some light on the issue of invasive horticultural plants in Florida.
A similar study conducted in Minnesota was published in 2006. The researchers, Peters, Meyer, and Anderson, found that horticultural professionals in the state for the most part supported efforts to curb invasive species expansion. However, the study also found that many of these experts were unable to identify certain invasive species and that more than half of them reported that they would sell known invaders if faced with economic competition. It is this lack of information about invasive species that Rigl sees as the main problem. “The main problem is the knowledge gap…. If people knew the detrimental effects of certain species they would be less likely to deal with them.”
Whatever the results of the study indicate, Rigl believes the survey will ultimately create a better understanding about invasive species in the horticultural industry. Nurseries and other aspects of the horticultural industry are often a direct link between people and nature, and she feels that educating the professionals here will spread to the rest of the community. Rigl believes that this survey will provide a cheap way to stimulate education efforts throughout the state of Florida, and through this provide the foundation for future efforts to slow and perhaps even stop the flow of invasive horticultural plants once and for all.
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Look out United States, there’s a new invasive species in town, and if you don’t look close enough, you just might not be able to see it. The New Zealand Mudsnail ( Potamopyrgus antipodarum) is only 4-6 mm in length and is considered to be one of the tiniest aquatic invasive species visible to the human naked eye.
Discovered in Idaho in 1987, these small, yet destructive mudsnails have established their presence throughout the western region of America except New Mexico. These devious species are thought to have been introduced through the little cracks of fishermen’s boots, fishing equipment and ballast water. Although they may seem to be insignificant in individual size, they are present in massive numbers and can be so large that entire ecosystems can become disrupted.
They have become a successful invader because they are asexual and reproduce in large quantities. They are also able to thrive in a wide range of ecological settings, except cold temperatures and are not preyed upon as much because they are indigestible. Several attempts to eradicate these nuisances have proven to be successful, such as freezing the gears, but many argue that damages incurred by the gears are not worth implementing this eradication method. Thus, Ms. Thomas, a student at the prestigious Duke University, has proposed that the best eradication method is through the use of chemicals.
Ms. Thomas believes that the use of certain chemicals has yet to be properly and thoroughly studied. Ms. Thomas expects that the most suitable and effective chemicals to use are Formula 409 Disinfectant diluted to a 50% solution and undiluted, 100% solution, Copper sulfate pentahydrate, and industrial Sparquat 256. When asked if these chemicals can be harmful to the environment she claims that “these chemicals are the most effective and most environmentally friendly. Any chemical introduced into an environment is not always a good thing, but we need to take measures to prevent the spread of these mudsnails.”
Ms. Thomas is positive that by spraying the equipment and gears with these chemicals, that several mudsnails will die. “Best of all, we are certain that these chemicals will not erode or bring damage upon the gears.” Not only does Ms. Thomas intend to spray the gears, but she also plans to spray current paths that the New Zealand mudsnails are present in. “ Within 6 months to a year, after spraying the path of mudsnails with chemicals, volunteers can go back and measure the population density and observe whether these chemicals are effective.”
When asked if this eradication method is realistic, Ms. Thomas optimistically replied “ Of course, but then again we are also focusing on preventing the spread of these species as well, not necessarily bringing eradication.”
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Native to the Ohio River Valley, the rusty crayfish (Orconectes rusticus ) is an aquatic invasive species that has spread outside its native habitat into other freshwater sources ranging from Minnesota to Maine. Detrimental to invaded ecosystems, rusty crayfish out-compete native crayfish and tend to replace the native crayfish population rather than just displace them. This out competition is mainly a result of the rusty crayfish’s larger body mass and greater reproductive abilities (Klocker and Strayer 2004). As rusty crayfish becomes more dominant with in an invaded environment, they can significantly reduce the amount of benthic invertebrates in an ecosystem resulting in the removal of much of the available nutrient resources in the water (Bobeldyk and Lamberti 2008). In addition the fish and bivalve population suffer under the invasion as rusty crayfish preys on small fish and the eggs of many species (Klocker and Strayer 2004).
Bait buckets are the main transport vector for rusty crayfish across state lines. As the aquatic invasive species becomes a greater problem, programs have been developed to educate fishermen about the dangers of bait bucket transfer. However, this is not enough and the gravity of this problem has led Michael Potts of Duke University to investigate widespread control methods for rusty crayfish. A native of Pennsylvania, Potts became interested in rusty crayfish after discovering “a research article on the effect of the aquatic invasive species in [his] home state.” As a result of this discovery, Potts proposes to study the effect of trapping and predation on rusty crayfish populations. Potts’ methodology draws upon a previous study conducted by Hein et al.(2006) in Wisconsin’s Sparkling Lake, however while both his and Hein et al.’s methodology are similar, Potts decided to focus his research on rusty crayfish population within dynamic water bodies, mainly rivers and streams, versus closed water bodies such as lakes. According to Potts, he took this focus “because not a lot of work has been done in moving waters (rivers) as far as trying to control rusty crayfish.”For the predation aspect of his proposal, he will use small mouth bass, a predator of rusty crayfish, and set up a control mechanism to maintain the bass’s population. He will then implement wire minnow traps along the river section in distances approximately 15 meters apart and bait it with frozen smelt and the sex, weight and length of captured specimen will be recorded.
While Hein et al.’s study differs from Potts. He stated in his proposal that “due to the similarities in lake and river ecosystems… it is hypothesized that the experiment will result in a significant decrease in rusty crayfish population.” Furthermore when asked about his believe in the future implication of his project, Potts stated that “ [the] methods in the proposal and the Hein et al (2006) study are very sound and could be easily replicated across different types of water systems such as rivers, lakes, and steams and would significantly decrease the population of rusty crayfish.”
Sources: Bobeldyk AM and Lamberti GA, Journal of Great Lakes Research. 34:265-275; Hein CL, Roth BM, Ives RA, Vander Zanden MJ. Can. J. Fish. Aquat. Sci. 63:383-389.
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Many are familiar with the red lionfish (Pterois volitans) as an inhabitant of aquariums, but few know of its invasive nature. Native to the Pacific and Indian oceans, they were first introduced into the Atlantic ocean in 1992. Since then, they have spread far and wide, now establishing themselves as far south as the Bahamas.
Everything on the lionfish from its colorful red stripes to its ominously long dorsal fins seems to scream “poisonous”, and poisonous it is. The sharp spines sticking out of its back contain a venom that causes nausea, extreme pain and difficulties breathing in humans, but is rarely fatal. Because the lionfish’s venomous spines prevent it from becoming prey to larger fish, it is considered an apex predator. Because it has no natural enemies in the Atlantic ocean, the lionfish population has since then exploded. Recently, organizations have expressed interest in adding lionfish onto restaurant menues, but this is still an initiative in progress.
Though the lionfish has been established in the Atlantic ocean for almost 20 years, very little is known about it outside of its natural habitat. This is something that Hannah Naughton of Duke University hopes to change. Naughton describes her project as ‘a citizen science approach tacked onto a project already in place’. The project that she will be working with is currently implemented by th Reef Environmental Education Foundation (REEF). REEF holds lionfish “hunt-a-thons” in Florida. These hunt-a-thons, or lionfish derbies, involves teams that go out with scuba diving equipment and compete to see who can capture the most lionfish. In a recent lionfish derby, 26 registered teams brought in a total of 1,408 lionfish and over $5,000 in prize money was awarded!
After the competition, REEF sells the lionfish to local restaurants for human consumption. What Naughton is proposing is that instead of selling the fish right away, they will first be brought to a team of volunteers who will record various information about the lionfish including size, mass, and gender. A genetic sample will also be taken from a portion of the fish for later lab analysis. Because each lionfish derby can bring in so many fish, data collected from just one of two of them should be enough to detect important patterns and trends.
In an interview, Naughton emphasized that it is crucial to gather for data regarding the invasive lionfish population if we are to fully undertand the effects it is having on local ecosystems. An important part of what the study will be trying to achieve is to discover any differences in the way lionfish affect the tropical ecosystems of the Bahamas as opposed to more temperate ones further north.
The integration of citizen science into the data gathering project will also raise public awareness regarding the dangers of continued proliferation of lionfish. And because it is already established in the Atlantic ocean, researchers are also trying to determine if lionfish meat is safe for human consumption so that comercialization can be employed as a method of control. Who knows? Maybe one day in the near future, lionfish will be something we can all order at T.G.I. Fridays.
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The Red Lionfish, Pterois volitans, is a venomous fish native to the Indo-Pacific that was imported to the U.S. as an aquarium attraction and accidentally released into the wild. By now, it has invaded the Carribeans and the southern Atlantic Coast.
To reduce the Red Lionfish’s damage on the ecosystem, there have been many attempts to limit its spread. However, Lionfish’s habitat, the sea, makes chemical control ineffective and its poisonous spines leave the Lionfish with no predators. Currently, the only method to slow the lionfish’s spread so far is commercial fishing by popularizing lionfish as a food choice.
Recently, there has been a fish found that could tolerate the Red Lionfish’s poisonous spines. The Blue-Spotted Cornetfish, Fistularia commersonii, has been seen to prey on a similar lionfish, Pterois miles, by eating the fish tail first to avoid its poisonous spines. It may be possible to use the Blue-Spotted Cornetfish to prey on the Red Lionfish as a form of bio-control.
However, the Blue-Spotted Cornetfish has a voracious and varied appetite. In the Mediterranean, the Blue-Spotted Cornetfish is an invasive species, eating fishes from 41 different taxa (Bariche et al). If it were to be released in the Atlantic, there is a possibility that the Cornetfish would preferentially eat native fish, which would damage the native ecosystem further.
Thus, Michael Motro proposes to use two aquariums to study the feeding habits of the cornetfish. In one tank, Michael will put the Cornetfish, several native fishes of the Carribean and Atlantic, and the Red Lionfish. This will test whether the Blue-Spotted Cornetfish dietary preferences.
In the second, he will mix the Blue Cornetfish with a species which it is known to often feed on, as a control method. Since the Blue-Spotted Cornetfish uses many different tactics to prey on fish, such as ambushing P. Miles from behind to avoid its poisonous spines, Michael Mojo believes that the size and shape of the aquarium can have unexpected effects on its diet.
1. Bariche et al. Diet composition of the Lessepsian bluespotted cornetfish Fistularia commersonii in the eastern Mediterranean. DOI: 10.1111/j.1439-0426.2008.01202.x
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There are over 20 million aquatic like rodents running around Louisiana’s wetlands causing havoc. These aquatic invasive species are known as Nutrias (Myocastor copus) and were first introduced in the early 1900s as a stimulant for the US fur trade. However, the fur trade died down and farmers were no longer able to take care of the nutrias. Therefore, the farmers opted to release the nutrias into the wild causing devastating consequences to not only Louisiana, but the 22 other Southern states nutrias now invade.
Nutrias cause six million dollars of agricultural damage each year. Their main food source are the high grasses of wetlands, which now are dwindling in number due to the appetites of the nutria. As a result, less tall grasses leave wetlands vulnerable to flooding and limits the diversity of species present. Over the years, these diverse species have become a spectacle for tourists. Yet, nutrias interference have caused a decrease in the 15 million dollar ecotourism industry and in return affect the economy of numerous southern states.
Unfortunately for those trying to control the nutrias, they are adaptable to numerous climates and are immune to various aquatic pollutants and toxics. These animals can have up to 13 off spring in one litter. “They can have up to 3 litters in one year,” says Ulises Munoz of Duke University. “The nutrias are multiplying at a faster rate then we can eradicate them.” The effects of this has created a crucial problem for southern states that is in route to become lethal.
Therefore, Munoz proposes to set up an after school program that will help eradicate the nutrias by taking advantage of the rich hunting culture in southern states.”Other eradication methods are in place, yet hunting has been the most effective when incentives are involved.” By providing a gun, hunting clothing, and waiving the hunting license fee, Munoz is enthusiastic that his program will greatly contribute to the decline in nutria.
In addition, Munoz is comparing his program to other extracurricular activities such as soccer or dance. Like these activities, Munoz’s program would promote afterschool activity, stimulate exercise activity, and potentially keep teenagers out of trouble on the streets. Munoz has not only created an incentive for participating in the extracurricular program, but also to get good grades. “Of course, good academics would be necessary. You can’t just hand any one a gun.” Further, Munoz comments that an added bonus will be a healthier economy.
To test the effectiveness of this eradication method, Munoz plans to set up an extracurricular hunting program in Louisiana, where the hunting age is 16. He then plans to compare the results in this region to a region that is similar to Louisiana’s climate, hunting culture, and nutria problem. Munoz will measure and record the population trends of both regions and survey the participating teenagers in their knowledge of aquatic invasive species compared to those who aren’t in the program.
Munoz is very optimistic about his eradication program. In fact, he feels that within a matter of years the nutria population will drastically decrease. Only time will tell, yet in the meantime Munoz is satisfied with the amount of awareness his program will raise. “The most important part of my program will be that students will know about aquatic invasive species. It is crucial to know how damaging aquatic invasive species can be to an economy and environment. My program will bring awareness.”
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The Northern Snakehead Trout is one of the most famous invasive species of Northern America. A fish that can survive on land would gain press coverage any day, and this one happens to be spreading through our nation’s river system at an incredible rate, eating all native fish in its way. However, all the media and government concern has done nothing to stop the snakehead’s expansion.
Part of the problem is that the snakehead’s movements are nearly impossible to predict. The fish can survive in a wide range of temperatures and environments, and its land-travelling abilities allow it to jump across rivers in ways no other fish can. As such, humans generally do not become aware of the snakehead’s presence in an ecosystem until it is firmly entrenched there. At that point, there is no means of removing the invader short of poisoning the entire lake.
Fortunately, there may be a way to detect the next environment that the snakehead invades. It has been provided not by ecologists or environmental agencies but by genetic researchers, who have discovered that water contains trace amounts of DNA from the creatures that live in it. These traces have been dubbed environmental DNA or eDNA, and can be analyzed to determine the species of fish present. If there are any snakeheads in the water, their eDNA will be detected and preventive measures can begin before their population increases.
Of course, this is not quite as easy as it sounds. “Fish share a lot of the same DNA, so you have to know what part is different,” says Ming Leung of Duke University. “On the other hand, one species can have many different genotypes [genetic variations among individuals].” Leung is currently gathering snakehead DNA and comparing it to other similar fish to find the unique genes. Once those genes are known, the information can be stored on a microchip and used by scientists to check gathered eDNA.
This genetic screening has already been used to gather information on Asian carp, another invasive fish that threatens to spread to the Great Lakes. Government agencies have managed to keep large numbers of carp out, thanks in part to speedy eDNA warnings in nearby areas. Leung hopes that it will be just as useful against snakeheads.
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