Aquatic Invasive Species

Recent studies have discovered a higher alien richness in the Curonian lagoon than in the benthic zones of the Baltic Sea.  Through their research, scientists have postulated what allows an ecosystem to be invaded, and for that matter, why is the invader invading?

There are two general hypotheses concerning species diversity and the “invisibility” of a habitat. Stachowicz et al.(1999) argues that the diversity of an ecosystem  increases is resistance, amd protects it from foreign invasion Stohlgren et al.(2003), on the other hand, believes that invasive species are “invisible” and undetectable under such a huge lens of a marine ecosystem.

Research concluded that systems have already been modified by man, through dams or embankments, or have already been invaded by a species, such as the zebra mussel, are high susceptible to further invasion. For instance, when a concrete construction is made in the Klaipeda strait, it provides the zebra mussel a hard substrate to bind to. The mussels then provide foreign invaders with nutrients and thus create a positive feedback system that may never be stopped.  The correlation between debth range and inasice species richness is explained by the decline in oxygen and thus yielding more vigorous conditions (Leppakoski and Olenin 2000). Species tend to approach less diverse ecosystems that have less competition and more of their particular nutrients of interest. It’s important for biological control to focus on these hot spots of lagoons and swamps, even if they aren’t directly related to the fishing trade; an abundance of invasive species can clog or poison entire water channels that deposit  into our water reserves.

http://www.glerl.noaa.gov/pubs/fulltext/2006/20060037.pdf

Biol Invasions- DOI 10.1007

Tilapia is a group of hardy and fast reproducing fishes which are widely used in aquaculture. Yet the same qualities that make tilapias ideal for fish farming also make it a potential invasive species.

In Nicaragua, non-native tilapia were repeatedly introduced into lakes and rivers for aquaculture. Tilapia were repeatedly introduced in 1960s and approved by the government in the 1980s. Its establishment in Nicaraguan waterways have, instead of increasing biomass and fishery resources, has corresponded with a reduction of native chichlid species.

To better understand the effect tilapia has on native chichlids, McCrary et. Al sampled lakes and fish markets. They found that the invasive tilapia not only consumes much of the native chichlid’s food, they also carry pathogens that can switch host, causing blindness in the indigenous population. Although there has not been enough evidence to link tilapia introduction with the reduction of native fish species, McCrary et Al advised that the spread of tilapia should be prevented as much as possible.

http://www.springerlink.com/content/c7961346242m66kq/fulltext.pdf

Environ Biol Fish (2007) 78:107–114

A recent study of Sea Lamprey (Petromyzon marinus) control methods was conducted by L.A. Velez-Espino and R.L. McLaughlin of the Department of Integrative Biology at the University of Guelph and T.C. Pratt of the Great Lakes Laboratory for Fisheries and Aquatic Sciences.

The invasion of Sea Lamprey into the Laurentian Great Lakes has had a profound impact on the local ecology. The lamprey has a parasitic stage during which it feeds on the blood and flesh of large fish, sometimes killing them. This along with habitat destruction and overfishing has led to declines in population and endangering of local host fish such as Lake Trout (Salvelinus namaycush).

The study employed matrix models to show that Sea Lamprey populations can continue to be controlled by decreasing use of chemical pesticides that specifically target the lamprey when it is in its parasitic stage and increasing use of alternative control methods that target the adults in their reproductive stages.

NRC Research Press Website: cjfas.nrc.ca, 2008

Ballast water is a major vector for transporting aquatic alien species and The International Marine Organization (IMO) has implemented new international regulations to treat ship’s ballast water (BW) before discharge. One potential treatment is electrolysis; however electrolysis can corrode the interior of ballast tanks. Dr. Guangzhou Lui et al from Zhejiang University, Chemistry Department, China are analyzing the effects of electrolysis on Q235 steel.

Using four different concentrations of total residual chlorine (TRC) (0,5,10,20 mg/L) on Q235 steel, the group analyzed TRC’s effect on Q235 to determine which concentration will remain effective at treating ballast water without corroding the metal. The TRC was analyzed using electrochemical impedance spectroscopy. Concentration levels of 5 and 10 mg/L enhanced the corrosion of steel while 20mg/L TRC inhibited the corrosion

Dr Lui et al concluded that electrolysis which result in TRC levels greater than 10 mg/L is more efficient on alien species and these TRC levels are not detrimental to the ship’s structural integrity.

 Source: Acta Metall Sin 2010, 46(09) 1093-1097 DOI:   10.3724/SP.J.1037.2010.00239

It is without a doubt that ballast water is the primary cause of the introduction of nonindigenous species within the Great Lakes. In order to prevent the rate of invasive species from increasing over the years, the United States decided to implement an environmental policy in which ships were required to exchange their foreign ballast water within the ocean before entering the Great Lakes.

Although the United States attempt in decreasing invasive species by enforcing policies may be perceived as a potentially ideal solution, Christopher Costello, from the University of California, Santa Barbara, has speculated whether these policies have contributed to the decline of invasive species within the Great Lakes.

After gathering data on the population size of invasive species prior and after 1993, he discovered that the rate of invasive species has increased. However, he states that this does not necessarily mean that policy has not been effective. Instead, we must account for factors such as a ships ability to travel faster prior than 1993 and the increase traffic rate of ships within the Great Lakes, resulting in more invasive species being introduced in overwhelming rates.  Ultimately he suggests that further experiments take account for these several factors before determining the effectiveness of environmental policy.

Reference: Evaluating an Invasive Species Policy: Ballast Water exchange in the Great Lakes. Ecological Society of America.  Vol. 17(3), 2007, pp. 655-662

Melaleuca Quinquenervia, an invasive tree, has overrun much of South Florida’s wetlands.  The plant has incited and withstood multiple attempts at biological control from both animals and fungi.  A team from the Fort Lauderdale Research Center, headed by Dr. Rayachhetry, tested the effect of the fungus B. Ribis, a Florida native, on the invader.  Rayachhetry injected six strains of the fungus into foliated trees, defoliated trees, and tree stumps.  The fungus eats the tree from the inside, but the plant often forms cankers around infected areas and drives it out.  The foliated Melaleuca showed no increase in mortality, and only the fifth strain of fungus significantly increased mortality in the defoliated trees.  The Ribis infected tree stumps regrew at a slower rate, but not as slowly as those treated with the common herbicide imazapyr.  Given these results, B. Ribis unfortunately seems unable to control the Melaleuca infestation.

Weed Technology Vol 13: 59-64, 1999

An evaluation of the effects of rusty crayfish on a stream ecosystem showed that the crayfish have not been found further downstream than they had been found in a previous study of crayfish distribution and expansion.

Bobeldyk and Lamberti of the Department of Biological Sciences at the University of Notre Dame conducted a longitudinal survey of the spread, density, and effects of an invasive crayfish species downstream of Bond Falls in the Middle Branch of the Ontonagon River and compared the results to a similar study completed in 1992. Using a 28 day leaf breakdown experiment, Bobeldyk and Lamberti sampled benthic substrates in three areas of different expected crayfish density. The study’s findings demonstrate that the crayfish have not expanded downriver and have in fact been found less far downriver than in 1992.

Bobeldyk and Lamberti concluded based on the leaf breakdown experiment that while the crayfish did not spread, they significantly reduced available stream resources wherever they were found.

J. Great Lakes Res. doi: 10.3394/0380-1330(2008)34[265:ADAIET]2.0.CO;2 (2008).

Researchers from the Ciências da Universidade de Lisboa, Portugal led by Maria Cruz and Rui Rebelo

have found that Procambarus clarkii, or the red swamp crayfish, introduced in the 1970′s to the Iberian peninsula is still well established today. Originally from the southern United States of America, the red swamp crayfish has been found to establish itself on every continent except Antarctica and Australia and has been noted for its severe detrimental effects on rice production on the Iberian Peninsula.

Cruz and Rebelo found that with the red swamp crayfish, its range was mostly determined by geographical features. However, they also found that the red swamp crayfish frequently experiences overland transfer between bodies of water, making it an extremely mobile aquatic species. With this said, Cruz and Rebelo both predict a continued spread to red swamp crayfish to currently unpopulated bodies of water in the region.

Reference: Hydrobiologia, Volume 575, Pages 191-201, Published OCT 2006, DOI: 10.1007/s10750-006-0376-9

Aquarium and ornamental fish trade is one of the most dangerous and rapidly growing vectors for invasive species. Andrew Chang and his team from the Department of Environmental Science and Policy at the University of California examined the invasion risk posed by aquarium fish in the San Francisco Bay-Delta region by identifying potentially invasive species sold in local stores.

Chang’s team identified freshwater and saltwater fish species in pet stores around the Bay-Delta area and compared their temperature and salinity requirements to local environmental data. Under conservative estimates, the pet stores sold three potentially invasive freshwater species and two saltwater species. However, under less conservative estimates, which allowed more realistic temperature variations, they found nine freshwater and eighteen saltwater invaders. Additionally, in the researcher’s survey, most pet store employees agreed the potential invaders represent a serious threat to the Bay-Delta ecosystem. This study represents a step towards identifying species with high invasion risk and taking action against their introduction.

Biological Invasions. doi: 10.1007/s10530-008-9292-4 (2009).

Commercial ships’ ballast waters are one of the main vectors in transporting aquatic invasive organisms. Ballast water is necessary to maintain a ship’s stability. The ballast tanks are filled at the ship’s starting port with coastal water accompanied by organisms. Throughout the trip, when needed, the water , along with the organisms, are released or exchanged.

Emma Verling et al., of the Smithsonian Environmental Research Center in Maryland, was interested in the affect of various commercial ships’ ballast water operations and  how they affected the transport of invasive organisms. She started by looking at the quality and quantity of propagule supply via ballast water. Using this information, she measured the frequency and amount of ballast water of various vessels coming from various regions. She then tested the survival rate of zooplankton coming from three different routes ending in the US.

Verling et al. prove that ships’ propagule supply aren’t equal. Therefore, different vessels do affect the establishment of invasive organisms differently.

Reference: Proceedings: Biological Sciences, Vol. 272, No. 1569 (Jun. 22, 2005), pp. 1249-1256