Aquatic Invasive Species

Aquatic ecologists are constantly fretting over invasive species, an issue which requires billions of dollars of spending. Any species that enters a non native area and causes negative effects qualifies as invasive. One of the most notorious aquatic invasive species is the Myriophyllum spicatum, a freshwater plant native to Asia more commonly known as milfoil. The plant is often transported in the hull water of ships, and currently exists in nearly every U.S. state. Attention is currently centered on the Great Lakes where milfoil poses a particularly strong threat.

This study examined the impact of the milfoil invasion from multiple aspects, and the results have shown that there is much more to milfoil invasions than meets the eye. The plant poses hazards to boaters and swimmers by clogging waterways, and it threatens plant species native to the area. The milfoil invasion has also caused shoreline property values to sink. It is imperative that milfoil populations are controlled or irreparable damage may be done.

Land Economics 85: 391-409 (2009)

Mar Ecol Prog Ser doi: 10.3354/meps07620

Invasive species often oust indigenous species from their native locations. Experiments on the movement of the Indo-Pacific lionfish (Pterois volitans) and the recruitment of native fishes suggest that the lionfish is already having substantial negative effect on the coral reefs in the Atlantic Ocean.

Mark Albins and Mark Hixon of Oregon State University used concrete constructed artificial reefs to study the difference of native fish recruitment between reefs that the authors transplanted a single lionfish, from control reefs where there was no lionfish transplantation. The results were that there was a significant decrease (average 79%) in native fish population at reefs with the lionfish from reefs that did not. According to the authors, stomach content analysis showed that the reduction in recruitment was definitely the result of lionfish predation on native species and that strategic control of lionfish need to be implemented quickly.

Biological Control on Snails

Biological Invasions. doi 10.1007/s10530-008-9378-z (2009)

Indigenous to South America, the golden apple snail (Pomacea canaliculata) has invaded the agricultural and wild areas of several Asian countries.  As an invasive species, the golden apple snail is a pest in the agricultural wetlands of Asia, causing major damage to rice production.  Due to the gold apple snail’s rapid growth and reproduction, they have posed a great threat to the Asian population.

In response to this growing threat, Pak Ki Wong and his colleagues of Hong Kong Baptist University have experimented on the use of common carp (Cyprinus Carpio) as a biological control agent against the invading snail.  Throughout a two month experiment, Wong “quantified the impact of common carp” on several species of snails as well as noting the impacts of the carp on non-targeted aquatic plants and animals.  The common carp was shown to be an effective biological control agent against the golden apple snail, however, necessary precautions should be carried out due to the potential of the common carp “to reduce wetland floral and faunal diversity.”

Jeremy Joven

Invasion By Distribution

BioScience doi: 10.1641/0006-3568(2004)

Zebra mussels have been a devastating problem with the expansion and economic problems in six continents on Earth. Experiments on the zebra mussel, considered one of the most detrimental invasive species, suggest that the potential of the distribution is very high except for the western United States.

John M. Drake and Jonathan M. Bossenbroek measured eleven environmental factors that determine the distribution of the zebra mussels. These are average annual temperature, frost frequency, annual precipitation, solar radiation, minimum temperature, and maximum temperature, bedrock and surface geology, elevation, flow accumulation, and slope. The team then inputted these variables into a genetic algorithm to find potential growth with the zebra mussels’ current distribution. Drake and Bossenbroek state that even though the probability of the transfer in the west is lower than the rest of the states, there is still a good risk due to recreational boaters, which is a focus that should be prevented.

Opportunistic Invaders

Crustaceana 82, 703-720 (2009)

One of the deciding factors of whether an exotic species will thrive in a given environment is its ability to find sufficient nutrients. The killer shrimp, (Dikerogammarus villosus), a species that originated in the Ponto-Caspian region, is currently invading areas of Europe. This species shows all the signs of a generalist feeder and may be able to invade the United States if given the opportunity. Dirk Platvoet of the University of Amsterdam and his colleagues from around the world have analyzed the feeding behavior of the killer shrimp. They have found that the shrimp is able to gain nutrition from a multitude of sources, including “detritus feeding, grazing, particle feeding, coprophagy, predation on benthic and free swimming invertebrates, predation on fish eggs and larvae and feeding on byssus threads of zebra mussels.” This ability makes the shrimp a threat to bodies of water everywhere.

Nile tilapia, originally from Eurasia and Africa, is a very dangerous invasive species according to Cleber C. Figueredo and Alessandra Giani of the Federal University of Minas Gerais in Brazil because of its significant impact on ecosystems that it invades. Furthermore, it has tremendous potential to spread even further throughout the United States and the rest of the world.

Their goal was to determine what impact that the tilapia had on several ecosystems in Brazil terms of water condition and the phytoplankton community. In their study, the researchers discovered that Nile tilapia have increased the quantity of nitrogen and phosphorus in the water. Furthermore, they have changed algal composition, biomass, as well as water quality. Most importantly, Figueredo and Giani urge caution when tilapia are used in aquaculture so as to prevent extreme environmental problems for native species.