Aquatic Invasive Species

Increasing concern over the invasive threat of the red lionfish (Pterois volitans) has become ever present. The species has been observed to have spread ubiquitously throughout the Bahamas and along the east coast of North America. They disrupt coral reef by reducing indigenous Bahamian fish recruitment by over 79%. And because of the lionfish’s poisonous fins, there have been concern about whether its growth can be contained.

Maljkovic and Leeuwen (2008) of Simon Fraser University however reported anecdotal incidences of finding native Bahamian groupers (tiger grouper, Mycteroperca tigris and five other Nassau groupers) with partially digested red lionfish in their stomaches. This provides hope that there is a potential native biocontrol for the invasion of lionfish, and that the species will be safely integrated into Bahamian ecology without significant damage to the current ecological structure. However, the anecdotal evidence in this paper still needs to be empirically confirmed.

Coral Reefs (2008) 27:501 DOI 10.1007/s00338-008-0372-9

Lake Taihu in Jiangsu Province of China has been overrun by huge algae blooms and poisoned with cyanobacteria. Chen et al 2001 of Nanjing Institute of Geography and Limnology conducted a study to determine the relationship between algal biomass and the following environmental factors: water temperature, suspended solids, Secci depth, and Alkalinity. This statistical study calculated the relationship between algal chlorophyll a, total algal biomass, and Microcystis biomass with said environmental factors. The study concluded that water temperature was one of the most significant factors contributing to total biomass while Alkalinity affected Microcystis biomass the most. This study tracks the progression of blue green algal bloom throughout Lake Taihu and formulates the first steps to end this problem.

Chen, Yuwei et al. 2001. Journal of Lake Science. Prediction of Blue-green Algae Bloom Using Stepwise Multiple Regression Between Algae & Related Environmental Factors in Meiliang Bay, Lake Taihu. http://en.cnki.com.cn/Article_en/CJFDTOTAL-FLKX200101009.htm.

Understanding how lampreys use pheromones to navigate and find suitable spawning grounds is an important step in understanding their migration patterns and what steps to use in order to control their spread and reproduction. Fine, Vrieze, and Sorensen (2004) found that lampreys were attracted to pheromones given off by larvae of the same species, implying that migratory pheromones are species specific. This makes sense, they argue, because each species has different requirements for spawning and larval habitat requirements. In areas where lampreys are a problem, isolating the pheromone can be useful in more effectively controlling the spread of the species: since the lampreys will migrate to areas with the greatest concentration of pheromone, artificial pheromones could be introduced to theoretically control and decrease spawning runs, thus decreasing the overall concentration of the lamprey population. In areas where lampreys are at risk (in coastal areas), the opposite could be true: using the pheromones to direct lampreys to favorable streams could help increase spawning runs and population growth for threatened species.

Fine J, Vrieze L, Sorensen P. Evidence that Pteromyzontid lampreys employ a common migratory pheromone that is partially composed of bile acids. Journal of Chemical Ecology, Volume 30, Number 11, November 2004.

A collaboration between  the Monterey Bay Aquarium Research Institute in California, and Sumitomo Heavy Industries in Japan report on a new, cost-effective method for treating ballast water. The method, deoxygenation, involves the removal of oxygen water from ballast water using nitrogen gas. Oxygen levels can be reduced to levels less than 0.5%. While deoxygenation prevents the spread of aquatic invasive species by killing oxygen-dependent organisms, the low oxygen levels also reduce ship corrosion, providing an economic benefit to the shipping industry.

Taburri M, Wasson K, Matsuda M. Ballast water deoxygenation can prevent aquatic introductions while reducing ship corrosion. Biological Conservation, Volume 103, Issue 3,  March 2002.

Marine and Freshwater Research doi: 10.1071/MF08011 (2008)

Didymosphenia geminata, an invasive freshwater diatom, forms thick mats in riverbeds.  Riverbeds are home to trout redds, gravel nests in which eggs are laid.  According to a recent study, didymo may impede the flow of water to redds, decreasing the amount of oxygen received by eggs and causing a decline in trout populations.

A study by the Clutha Fisheries Trust, led by Drs. Tobias Bickel and Gerard Closs, investigated the effect of didymo on hydraulic conditions in trout redds.  The team collected data from rivers with varying didymo presence, measuring in each the oxygen concentration, hydraulic conductivity, substrate water flow, and surface water – groundwater exchange rate.  They found that the amount of didymo had no effect on the first three variables, but that there was significant indication that didymo diminishes surface water – groundwater exchange.  This water transfer is critical to trout egg development, and the authors recommend that further research be done.

Georgia Ward-Fear of the University of Sydney (Australia) and her colleagues have found that Cane Toads (bufo marinus) are in fact quite vulnerable to a native species of Australian ant. Although cane toads are poisonous to most of their predators, these ants are immune to the toxins secreted by the amphibians.

To measure the toad’s response to attack, they placed toads in a shallow plastic dish and tapped on it until it had completed five hops. They also measured the toads’ activity in the wild vs. the ants’ activity.

They concluded that because the toads have shorter, slower hops than other native frog species and share similar activity patterns with the ants, they are far more vulnerable to meat ant attack. As toads mature, they are active diurnally, which increases their encounters with meat ants. The experiment also showed that many toads failed to detect and evade approaching ants.

Functional Ecology Vol 23, Pages 559-568 (2009)

Biological Invasions 6: 295–300, (2004)

Aquatic and marine invasive species are a great threat to biodiversity and industries located by bodies of water.  They cost governments and industries millions of dollars a year in destruction.  However, efforts have gone underway to “contain, if not eradicate” these invasive species.  Ronald Thresher and Armand Kuris of CSIRO Marine Research and the University of California in Santa Barbara believe that current methods are low risk and publicly acceptable, but have low rates of success.  They propose methods that may be more socially and politically contentious, but more effective at maintaining invasive species.  The researchers discovered through workshops that genetic modification of invasive species to reduce its viability had the most potential to be acceptable.  Biological control was also a strong, accepted option.   However, when considering this method, specificity should be considered so that other species are not targeted along with invasive pest by the biological control species.

Jeremy Joven

Vol. 210: 139–148, 2001

Ballast water is a leading vector for the spread of invasive species across the world. Thousands of species are transported across the globe daily. There are many different treatment options that are always being evaluated for efficacy and new ones are being developed.

T.F. Sutherland and colleagues at the Fisheries and Oceans Canada Institute conducted a field study that measured the survivorship of plankton in ballast water based on the type of treatment used. They tested one filtration system, with the sample being pretreated with ultraviolet rate and one without being exposed to UV. They then compared the growth rate of phytoplankton during the different situations. They found that the growth of phytoplankton in UV-treated samples was stopped, while those in other treatments still exhibited growth. They concluded that UV has potential to stop growth in ballast water and that future studies should be done on UV treatments.

Emilia Rybak

The determination of larval trajectories of crab species is an important factor in understanding population dynamics and migration patterns of these organisms. In a study conducted by Cecily C. Natunewicz, Charles E. Epifanio, and Richard W. Garvine, three researchers from the University of Delaware, satellite-tracking devices were used to examine larval transport patterns of the blue crab (Callinectes sapidusemploys) in the Delaware Bay. The researchers tagged eight larval patches and followed their movement for 1 to 11 days.

To assess the crab’s larval trajectories, they took this data, along with physical data on winds and river discharge, and compared it to predicted trajectories from a 2-D mathematical model. They discovered that larval patches initially tagged in the bay’s plume water moved farther south than patches in shelf water. The main factor driving this movement was wind patterns. Thus, the determination of the blue crab’s larval trajectories shows that applying this method to the Chinese mitten crab may also be successful.

Natunewicz et al., 2001 C.C. Natunewicz, R.W. Garvine and C.E. Epifanio, Transport of crab larvae patches in the coastal ocean, Mar. Ecol. Prog. Ser. 222 (2001), pp. 143–154.

Ben Berg

Gene Expression Patterns, July 2008
The fight against cane toads has been waged since shortly after their introduction to the Australian continent in 1935. Many different strategies have been tried to limit population growth, but none deterred the poisonous toads’ invasion. New research led by Damian Halliday et al., however, attempts to find a weakness in the toad’s life cycle by examining changes in toad gene expression during metamorphosis.

Funded by the Australian Government’s Department of Environment and Heritage, the study identified changes in gene expression that occur during the somewhat miraculous metamorphosis from tadpole to toad. Transformations such as changing hemoglobin structures and creation of different digestive enzymes are known to occur between the stages. Halliday et al. were able to isolate the specific genes used in these transitions through the use of microarray analysis of toad DNA. Pending further research, the authors hope to find a method of preventing these genes from being expressed, inhibiting metamorphosis and thus eliminating the toad problem.