Review Panel: Brandon Braxton, Andrew Van Orden, Shane Stone,Katherine Ferguson

Rand proposes to study the potential toxicity of lionfish meat to humans. His view is that since no viable control options have been found, it is best to embrace the potential of lionfish as a food source and the possibility of taking enough to slow population growth. Because of the risk of toxic chemicals such as PCBs accumulating in the fat of the lionfish, the study proposes to collect samples of fish from several areas and test for the presence of these chemicals to determine if lionfish is safe for consumption according to FDA standards.

Reinsvold proposes to study the potential of grouper predation to control the lionfish population in the Caribbean. If this is successful, it will open the possibility of augmentative biocontrol for the lionfish. The study will take place in several microcosm environments within a lab that manipulate the presence of groupers, lionfish, and native species. The results of the study are expected to provide a further direction for study in regards to lionfish control, either towards augmentative biocontrol or in a new direction.

Blaser also proposes to study the potential of augmentative biocontrol using groupers. The study will include observation of the natural dynamics of lionfish and grouper populations on a reef and also manipulate the proportion of lionfish and grouper on a separate reef. He expects to be able to provide insight on the potential of augmentative biocontrol for controlling the lionfish.

From studies lionfish, it was been concluded that the lionfish population is not going to be decreasing anytime soon. Therefore, a proposal that suggests methods to try and reduce the population is important. Our panel recommends that a full proposal be solicited from Reinsvold to study the potential of grouper predation on lionfish. This study seems to be the most worthwhile option for combating the lionfish and is also well structured. While Blaser proposes to study the same option of augmentative biocontrol, is not as simple and has potential for error since it is taking place on an actual coral reef where it would be nearly impossible to control the amount of fish in the area. Our panel also feels that augmentative biocontrol has a greater chance of success to control the lionfish than commercial fishing and consumption if the fish in Rand’s study prove to be safe to eat.  Furthermore, Reinsvold’s suggestion to utilize augmentative biocontrol makes his study more favorable to fund. Through augmentative biocontrol, a native species is increased rather than introducing a new species into an already invaded ecosystem.

Unfortunately, we would not accept the study as it is now because it is in need of improvement. In terms of the prose, Reinsvold’s need to emphasize the beauty of the reefs is not really necessary plus most scientists want to preserve reef ecosystems not because of aesthetic beauty, but because of its scientific usefulness. Also, the question could be worded clearer. It is concise and to the point, but adding a little to it could improve the clarity of the paper as a whole. In addition, an explanation of why this method of eliminating the lionfish is plausible would be better in persuading readers to give funds to the effort. Lastly, we are not convinced that if the biocontrol was unsuccessful simply increasing fishing permits could have a serious impact on reversing the introduction of the groupers. For the actual study, we suggest a change of the methods. We suggest two additional treatments. One treatment will have Tiger groupers, lionfish, and native fish, and one that will have Nassau groupers, lionfish, and native fish. This way, he will be able to compare feeding rates when the biocontrol agents have a choice in feeding. The first four treatments do not reflect actual scenarios, but do provide important data. The two suggested treatments, in addition to current “Treatment 4”, reflect real life. These changes would improve Reinsvold’s proposal and improve his chances of receiving funding.

Biological Control 44, 235-241 (2008)

Biological control is one of the most widely used methods of controlling populations of invasive species. Melaleuca quinquenervia, or the melaleuca tree, is one such species. A native of Australia, this tree has invaded the Florida Everglades and had enormous effects on the ecosystem. Several biological control agents have been used in an attempt to reduce melaleuca populations.

Philip Tipping and his colleauges at the UDSA-ARS and University of Florida examined the efficacy of two biological control agents, Oxyops vitiosa (weevil) and Boreioglycapsis melaleucae (psyllid). Over a two year period, these agents were added to trees, some of which were protected by an insecticide. The researchers found that trees without insecticide had much lower biomass and produced less seeds. They also discovered that trees receiving irrigation had slightly higher growth than those without, which presents a potential problem for control. The wetlands are thus not the ideal environment for the weevil and psyllid. The authors wrote that these biological control agents have the potential to suppress melaleuca growth in the Everglades in conditions where they are favored.

Biol Invasions Vol 11:2223–2232, 2009.

The golden apple snail (Pomacea canaliculata), is native to South America, but has invaded many Asian countries. As its numbers have increased, the golden apple snail has heavily grazed upon plant life. Limited methods have been found to control the snail population, but biocontrol may be a viable option. Some researchers have suggested that the Common carp (Cyprinus carpio) could efficiently control the population, but the side effects of its usage are unknown.

Pak Ki Wong, King Lun Kwong, and Jian-Wen Qiu, of the Department of Biology at Hong Kong Baptist University, decided to engage in an 8-week study to determine whether the common carp could be used. They studied the carps’ effect on 3 aquatic macrophytes and 9 snails (including the golden apple snail). Results indicated the carp removed juvenile golden apple snails, but did not significantly affect the adult population. They concluded that it could be used to reduce the golden apple snail population, but hat caution be taken because if can affect other species too.

Although the highly invasive water hyacinth was introduced into Florida over 30 years ago, the aquatic plant hasn’t been nearly as successful as it has been in other places such as Lake Victoria, South Africa. Despite this, Florida’s weather and conditions are optimal for sufficient growth of water hyacinth. The warm climate, high nutrient and light environment is very conducive to water hyacinth growth. Researchers Volin and Soti from the University of Connecticut and Florida Atlantic University sought to test various nutrient and herbivory levels  versus water hyacinth growth to see if the specific amount of nutrients and plant removal found in Florida had a negative impact on the water hyacinth. Soti and Volin found that water hyacinth are able to survive under low amounts of plant removal no matter the nutrient level. This suggests the most effective method of removal of the plant is a high level of herbivory. This research gives great insight into future control of the highly invasive plant.

Biological Control Vol. 54 Issue:1 35-40 July 2010

Journal of Applied Ecology, Volume 47, 273-280 (2010).

Biocontrol is often seen as an effective way to fight invasive species but there is always potential for reduced biodiversity.  Therefore, it seems to cause more of a problem than a solution.  Since the occurrence of catastrophic biocontrol attempts, it has been rejected as a reliable process.  However, Georgia Ward-Fear, Gregory P. Brown, and Richard Shine have proposed a way to utilize all the positive effects of biocontrol without its major flaw.  In response to the cane toad invasion to tropical areas of Australia, the researches used a native predator, the meat ant, to control the invasion.  They observed that the ants were fatal to the toads and simply increased the density of ant populations.  The researchers successfully reduced the numbers of the cane toads without introducing a new invasive species, and just as importantly, without spending too much money.

Biological Control 53, 1-8 (2010)

Biological control is a widely used method of controlling invasive species. The melaleuca tree (Melaleuca quinquenervia), an Australian native currently populating the Florida Everglades, has had devastating effects on the ecosystem. Several biological control agents have been used in an attempt to reduce melaleuca populations.

Min Rayamajhi and his colleagues at the USDA investigated the effectiveness of three biological control agents, herbivorous insects Oxyops vitiosa (weevil) and Boreioglycaspis melaleucae (psyllid) as well as rust fungus Puccinia psidii individually and together. 120 trees were felled, harvested and measured for damage, height, branching, mortality, and biomass for each of the groups. The team found that when used in conjunction, these three control agents caused more damage to the melaleuca than when used separately. Because of their interspecies competition, the insects and fungi each feed on different parts of the tree, resulting in more widespread control. The authors concluded that these species have great potential to suppress melaleuca growth in the Everglades.

The purple loosestrife have gotten out of control in the continental US, and are taking over and choking out native species and altering the habitats.  Blossey et al. argues that the impacts of the purple loosestrife upon the environment are of great enough magnitude where it would be worth it to release another nonnative species, an insect, as a biocontrol method to attempt to reduce the population of the loosestrife and keep it under control.  The loosestrife have risen in both number and extent to which they alter the habitat they live in, and though it might seem that they would only impact other competing native plant species, they also have become enough of a problem where they also are hurting animal species, especially specialized wetland birds.  Though the introduction of other nonnative species may have unforeseen negative impacts, with so much potential in danger as a result of the loosestrife, the prospective benefits would outweigh the possible dangers.

Blossey, Bernd, Luke C. Skinner, and Janith Taylor. “Impact and Management of
Purple Loosestrife.” Biodiversity and Conservation 10 (2001): 1787 – 1807.
Web of Science. Web. 25 Sept. 2010.

Lake Victoria in Africa has been overrun with an invasive plant called the water hyacinth. The plant has affected the local drinking water, which has caused more sicknesses that were not previously prevalent. Water hyacinth has also affected fishing, a major income and food source. Insects called weevils have been introduced as a biocontrol method to eliminate the water hyacinth. Biologist Adrien Williams believes that although weevils did play an important role in the reduction of water hyacinth the largest destruction of water hyacinth was due to the 1997/1998 El Nino. Biologist John Wilson states that the use of weevils in destruction of water hyacinth is the main reason why the plants masses were decreasing. However, the El Nino might have propelled that process.
I agree with Wilson in that the weevils played an important part in the removal of water hyacinth from Lake Victoria and without them the plant would still be a problem. The El Nino alone would not be able to destroy the plants in the massive amount in such little time. The El Nino acted as a positive unexpected factor in the hyacinth’s removal. The change in weather also had a negative affect. Because weevils only feed and affect the water hyacinth, once its numbers lowered due to the destruction of their habitat and food there would be less weevils. Now that we know that the water hyacinth has restored itself we can say that the population decrease of the weevils after the El Nino played a huge role in its resurgence so we cannot rely on nature to come to our rescue. An El Nino only occurs every two to seven years so there needs to be something in place to control the water hyacinth.
This being said biocontrol is not a quick fix all. Recently, due to heavy rains and floods that “swept agricultural run-off and nutrient rich sediment” into the lake, there has been a rebound of water hyacinth. There aren’t going to be drastic changes within a few years but with time the weevils will help deplete the hyacinth to a manageable amount.
References:
NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria. http://earthobservatory.nasa.gov/IOTD/view.php?id=7426. Viewed 20 Jan 2010.
Williams, A. E., R. E. Hecky, and H. C. Duthie. 2007. Water hyacinth decline across Lake Victoria – Was it caused by climatic perturbation or biological control? A reply. Aquatic Botany 87:94-96.
Wilson, J. R. U., O. Ajuonu, T. D. Center, M. P. Hill, M. H. Julien, F. F. Katagira, P. Neuenschwander, S. W. Njoka, J. Ogwang, R. H. Reeder, and T. Van. 2007. The decline of water hyacinth on Lake Victoria was due to biological control by Neochetina spp. Aquatic Botany 87:90-93.

Michael Di Nunzio

09/13/2010

Water hyacinth has posed a problem for Lake Victoria since first being reported there in 1989. The plant forms dense mats of vegetation that inhibit the movements of fishermen, block sunlight to native plants, and obstruct irrigation systems.  The invasive weeds can also deplete the water’s oxygen levels, suffocating the indigenous flora and fauna of the lake and in turn disrupting the local ecosystem. To control the hyacinth populations, invasive weevils (Neochetina spp.) were introduced with the intention of suppressing the noxious weed (Williams et al. 2007).

Using satellite image samples, Wilson et al. (2007) estimated the proliferation of water hyacinth over Lake Victoria and fluctuations in the plant’s presence over time, finally presenting their data in Aquatic Botany. However, Williams et al. (2007) warned with a rebutting article that this method of gathering data is oversimplified for such a complex environment. In spite of the dispute, both parties agreed that hyacinth levels dropped after the 1998 El Niño disturbed the lake. Following the initial decline came a steady rise until 1999 when hyacinth levels again began to decrease dramatically. From 2000 until 2002 hyacinth levels remained suppressed to under 5000 hectares of biomass over the lake’s entirety (Wilson et al. 2007).

Wilson et al. (2007) reasoned that the drop in 1999 was a result of the control weevils introduced in 1995 becoming effective after four years of relative dormancy. They also noted that the weevils control the weed by lowering its buoyancy and sinking it, and El Niño could have facilitated this process with wind and wave action. Because El Niño would inevitably blow some hyacinth into new areas, Wilson et al. (2007) suspected that local reports of hyacinth resurgences might have actually been false. Valid reports of resurgence may have resulted only if weevils died due to a lack of buoyant hyacinth, leaving the plant temporarily uncontrolled. According to Wilson et al. (2007), there was no substantive evidence to link low light levels with any of the withdrawals of hyacinth as Wilson et al. (2007) surmised.

Williams et al. (2007) placed less emphasis on the importance of the weevils in regards to water hyacinth control. Rather than biocontrol being a significant factor, they claimed El Niño more likely pulled hyacinth from the shoreline and destroyed it with wave action. This theory was both plausible and agreed seamlessly with the data showing a decline in 1998. Furthermore, the 2000 to 2002 nadir in hyacinth was thought to be a fleeting product of the weevil’s efficacy after 1999 and “suboptimal light” (Williams et al. 2007). Finally, Williams et al. (2007) pointed to the River Kagera as an ideal means of future resurgence, as hyacinth from this region is untainted with weevils and can float freely into the lake. This meant that there would be a delay before biomass control could take effect.

While Wilson et al. (2007) offered the more optimistic outlook on the data set, Williams et al. (2007) were unfortunately the most realistic. Williams et al. (2007) provided the most coherent argument, and aptly paralleled the situation in Lake Victoria with that of sub-tropical climates plagued by water hyacinth. They assumed that the lack of hyacinth is a part of a cyclic process involving a balance between weevils and weeds that will invariably lead to hyacinth resurgences. Wilson et al. (2007) tended to make unlikely excuses for all reported instances of resurgence, rather than offering any real insight into the possible validity of their reasoning. The satellite images from MODIS vindicate the argument of Williams et al. (2007), as resurgence obviously took place by 2006 (NASA 2007). Thus the relationship between adequate light, the presence of weevils, and the predominance of hyacinth must be a continued subject of study at Lake Victoria if definite conclusions about the hyacinth resurgence cycle are to be drawn. However, Williams et al (2007) seems to have lead us in the right general direction.

References:

NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria. http://earthobservatory.nasa.gov/IOTD/view.php?id=7426. Viewed 12 Sep 2010.

Williams, A. E., R. E. Hecky, and H. C. Duthie. 2007. Water hyacinth decline across Lake Victoria – Was it caused by climatic perturbation or biological control? A reply. Aquatic Botany 87:94-96.

Wilson, J. R. U., O. Ajuonu, T. D. Center, M. P. Hill, M. H. Julien, F. F. Katagira, P. Neuenschwander, S. W. Njoka, J. Ogwang, R. H. Reeder, and T. Van. 2007. The decline of water hyacinth on Lake Victoria

Scholars debate the main factor of the significant decrease of water hyacinth on Lake Victoria around 1999-2000 in Wilson et al. (2007) and Williams et al. (2007). First, Wilson et al. (2007) replies to a previously published article by Williams et al. (2005) which claims that although weevils played a role in the eventual decrease of water hyacinth on Lake Victoria, the invasive species’ population was ultimately and predominately the result of the 1997/1998 El Nino. Williams et al. (2005) cites the condition of “low light availability” from El Nino and its subsequent effect on water hyacinth’s growth as the main contributor to the weed’s destruction.

Wilson et al. (2007) counters the referenced article by stating first, Neochetina bruchi and Neochetina eichhorniae (collectively Neochetina spp.) were the primary destructive agents to water hyacinth; second, El Nino caused waves and strong currents on Lake Victoria which dispersed its water hyacinth and made the weed easier to destroy by weevils; and third, water hyacinth will not reemerge in Lake Victoria unless its Neochetina spp. populations are disturbed. The authors reevaluated the light conditions around the time of El Nino, but found that by mid-1998, water hyacinth was already rebounding on Lake Victoria. Wilson et al. (2007) acknowledged that weevils took nearly four years to take effect against the invasive species in 1999 (weevils were released into the lake in 1994), but this timetable was expected and is congruent with weevil versus water hyacinth time frames from other countries with similar climates.

Lastly, in Williams et al. (2007)’s rebuttal to Wilson et al. (2007), the authors restate their aforementioned claim that weevils contributed to the reduction of water hyacinth around 1999-2000, but the invasive species would certainly still be growing strong in the absence of the 1997/1998 El Nino. Williams et al. (2007) believe Wilson et al (2007)’s arguments are oversimplified and thus erroneous because Lake Victoria is simply too vast to be considered on an individual graph of experimental results. Williams et al. (2007) maintains the diminution of water hyacinth was a result of El Nino’s flooding because it transpired “synchronously…during the second quarter of 1998”. The authors claim the hyacinth’s first reduction occurred because the floodwaters dislodged the mats that held the weed to the lake floor, and the hyacinth simply washed away into the lake. While Wilson et al. (2007) stated that Williams et al. (2005) believed low light levels caused the reduction, Williams et al. (2007) stressed that the plant mortality was due to prolonged low light, not intermittent glares, which then caused minimal growth in the plants and weak mats.

Ultimately, I believe Wilson et al. (2007) had the soundest argument, which claimed that weevils played the most significant role in reducing the population of water hyacinth on Lake Victoria. While both articles acknowledged the “lesser” cause (whether it was weevils or the effects of El Nino), I felt that Williams et al. (2007) was especially narrow-minded and barely accredited weevils as a destructive force to weevils, when they were clearly a great contributor to the hyacinth’s periodical demise. However, the fact that the water hyacinth continues to make reappearances on Lake Victoria suggests tha solely biocontrol as a method of eradication is insufficient and ultimately non-cost effective. There needs to be a more radical and long-lasting approach to ridding Lake Victoria from the ruthless water hyacinth.

NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria. http://earthobservatory.nasa.gov/IOTD/view.php?id=7426. Viewed 10 Sept 2010.

Williams, A. E., R. E. Hecky, and H. C. Duthie. 2007. Water hyacinth decline across Lake Victoria – Was it caused by climatic perturbation or biological control? A reply. Aquatic Botany 87:94-96.

Wilson, J. R. U., O. Ajuonu, T. D. Center, M. P. Hill, M. H. Julien, F. F. Katagira, P. Neuenschwander, S. W. Njoka, J. Ogwang, R. H. Reeder, and T. Van. 2007. The decline of water hyacinth on Lake Victoria was due to biological control by Neochetina spp. Aquatic Botany 87:90-93.