Aquatic Invasive Species

In the never-ending battle to prevent blood-sucking sea lamprey from wiping out some of the most popular fish species in the Great Lakes, experts are developing a new method of control that uses the invader’s dead body.

The sea lamprey releases some sort of chemical “repellent” when there is mechanical damage done to the skin due to events such as predation. This repellent acts as a warning to other fish in the area to stay away from the potential danger in that direction. Area avoidance as a result of injury-released chemical alarm cues has not been sufficiently studied. Therefore, Xiangyu Wang and his team of scientists are investigating the effects of dead lamprey on migrating lamprey. “It may be possible to counter the lampreys during their mating season by neutralizing the hormones that attract them to their mating grounds by releasing some sort of lamprey repellent at the mouth of particular streams and tributaries,” says Wang.

Wang had done previous work on lamprey larval release of hormones. His interest in sea lampreys came from the fact that they are an ancient species of fish that has been unchanged for millions of years. “This is what makes them so successful,” says Wang. Therefore, he and his team of scientists decided to investigate the species further.

His study will use a Y-shaped water maze with dead lamprey extract continuously injected into one end. The lamprey will have a choice to either swim up the passage in which dead lamprey extract is present or to swim up the passage in which nothing was added. According to Wang, “There is a good chance that the lampreys will respond to the dead fish extract.” If this proves to be true, the team’s next step would be to specifically isolate the chemical that is causing this response and determine an effective method at spreading it. If distributed around spawning grounds, reproduction could be severely reduced and the problems associated with these leech-like creatures would hopefully be alleviated. If lampreys can not find suitable habitats to breed, then their populations will be brought under control.

Complete eradication may not be possible, but the goal is to keep the lamprey numbers low enough to prevent significant harm to the 7 billion dollar Great Lakes fishing industry. Although native to the Atlantic, they can live in fresh water and migrated to the Great Lakes through shipping canals. By the late 1940s, the prolific invaders had decimated trout, whitefish and other sport and commercial species across the lakes. They have dramatically decreased the populations of many  other species of local game fish and hurt the livelihoods of many fishermen.

“They are parasites that feed on the blood and flesh of fish. With their destructive ways they have had a large impact on fish population,” states Wang. This is why research on the sea lamprey has continued to grow; a need for an effective method of control is imminent.

“The results of this study will pave the way for a method to be developed that is effective and has a low impact on the environment,” says Wang. In addition, he expects that his method will improve previous protocols. By using a maze with flowing water instead of a tank, Wang and his team will be able to more accurately model the reaction a lamprey would have in the wild.

Despite their damage to the environment, invasive species often grow unchecked, smothering the natural community with unbridled proliferation. Such is the case for the water hyacinth (Eichhorinia crassipes), an aquatic plant that has taken over waterways in North America, Asia, and Africa. The plant has plagued Lake Victoria, one of the hardest hit water bodies, since its introduction in the 1980s. Water hyacinth is a particularly successful invader because it can withstand great variations in salinity and temperature, allowing it to inhabit a variety of locations. Furthermore, it can reproduce asexually at an astounding rate. Though it quickly becomes invasive, the negative effects of the water hyacinth can be long lasting and irreparable.

Water hyacinth spreads across the surface of a water body, blocking light to species below. This creates a cascade of effects because decreased photosynthesis causes dissolved oxygen levels to decrease, harming other members of the ecosystem. Furthermore, the plant’s large biomass hinders boating, a problem that has been particularly devastating to the community of fishermen surrounding Lake Victoria. Indeed, their catch was reduced by as much as 45% at the peak of the invasion.

Past methods to control the spread of the water hyacinth have yielded only temporary reductions in the plant population. Both biocontrol and herbicides have provided temporary relief from the water hyacinth, but these control methods are expensive, and they come with other environmental effects. As a result, they do not always garner support in the community, which makes their implementation less effective. Given the water hyacinth’s damage to both the environment and the surrounding community, how can we incentivize companies to implement water hyacinth control methods?

Sammy Brunell has been researching the most effective methods to eradicate the water hyacinth while appealing to the greater financial interests of the regions surrounding Lake Victoria. A control method that contains the water hyacinth with an additional financial incentive for the community could create lasting environmental and financial benefits for the region. Brunell proposes a containment method that entails harvesting the plant then using its biomass to produce ethanol, which can then be burned for energy.

The process requires the plant to be fermented using various yeasts. Brunell’s experiment will test the effectiveness of several strains of genetically modified yeasts and enzymes in efficiently fermenting water hyacinth. He sees this genetic modification to be the key to making the process a viable solution. Though past experiments have only used naturally occurring yeasts and enzymes, genetically modified designs could improve the process substantially. Brunell also plans to test the application of warm and cold temperatures to examine their effects on the project’s efficiency. He believes his control method will “make [the] public aware that hyacinth can serve a good purpose if utilized the right way.”

Brunell expects this technology to have wide-reaching effects throughout the community surrounding Lake Victoria. Not only will fishermen be able to use the lake, but the surrounding community will have an additional source of income. Brunell says, “My results will hopefully revamp the infrastructure of African nations around Lake Victoria; they can use hyacinth to produce ethanol and fuels to power houses, cities, cars, etc., while also hopefully controlling the advancement of water hyacinth through human consumption.” In the future, he foresees on-shore generators to easily turn the water hyacinth into a necessary fuel source. Brunell’s control methods could be a permanent and self-sustaining solution for the water hyacinth problem on Lake Victoria.