To minimize the dispersal of aquatic nuisance species through shipping, ballast water can be treated to kill, remove, or inactivate organisms. Ultraviolet (UV) radiation is used in some ballast water management systems to address this goal. Because UV treatment renders cells non-viable (by sterilizing them, preventing reproduction) and does not necessarily kill organisms instantaneously, the efficacy of UV treatment has been verified historically by regrowth assays in which microorganisms are cultured (and thus, reproduce) under optimal growth conditions. Although regrowth assays are definitive, they are time consuming—lasting for days or weeks—and, importantly, are applicable only to organisms amenable to culturing. Furthermore, these estimates of cell concentrations are often accompanied by large error estimates. In this paper, several rapid alternatives to regrowth assays are described and evaluated. An ideal approach would shorten or simplify the analysis burden and, potentially, could be used for shipboard testing to determine compliance with national and international ballast water standards. Complicating this task is the requirement that compliance with the ballast water standards will be determined by quantifying the number of living organisms in ships’ ballast water, and while organisms may be living following UV treatment, they may not be viable (i.e., they may not reproduce). To address this dichotomy, alternatives to regrowth assays were categorized based upon the complexity of the analysis and the means used to determine the status of microorganisms (either as viable or living): 1. Instantaneous growth and cell replication, 2. Cell activity and metabolic rates, 3. Cell structural integrity, and 4. Biomolecule presence and status. With the suite of approaches currently available, it is not possible to determine the viability of organisms rapidly, that is, within minutes of collecting a ballast water sample. Measurements of the photosystem integrity via variable fluorescence and the presence of adenosine triphosphate (ATP) are currently the most promising for rapidly estimating concentrations of living cells in compliance testing of ballast water discharges; however, extensive validation is required to verify the applicability of these approaches for the complexity of real-world samples.

Two field experiments were carried out using a custom built flow-through laboratory to test the effect of elevated pH on dreissenid mussels as a potential control method. Both experiments tested the ability of dreissenid pediveligers to settle under conditions of elevated pH and the long-term survival of adult dreissenids under the same conditions. The two experimental sites had different water quality and different species of dreissenids present. The settlement of quagga mussel pediveligers at the lower Colorado River was inhibited with increasing pH. At the maximum achieved pH of 9.1, there was approximately 90% reduction compared to the maximum settlement observed in the controls. Since the settlement was almost as low in pH 8.9 as at pH 9.1, the inhibition in settlement may have been due to the presence of a precipitate formed under high pH conditions rather than the increase in background pH. No mortality of quagga mussel adults was observed in the experimental pH levels at the lower Colorado River. At San Justo Reservoir, zebra mussel settlement decreased with increasing pH. New settlement was almost entirely absent at the highest pH tested (pH 9.6). The observed mortality of adult zebra mussels was low, but did tend to increase with increasing pH. We also tested the response of adult zebra mussels to short-term exposure to very high pH levels (i.e. pH 10, 11, and 12). Adult mussels in poor physical condition experienced 90% mortality after 12 hours at pH 12. For unstressed adult zebra mussels, 90% mortality was reached after 120 hours at pH 12. Significant mortalities were also observed both at pH 10 and pH 11. From this study, we conclude that pH elevation could be used both as a preventative treatment to eliminate settlement by dreissenid mussels and as an end of season treatment to eliminate adults. The high pH treatment would have to be tailored to the site water quality to prevent formation of precipitate during treatment and to minimize corrosive action on materials of construction.

A need exists for an environmentally friendly mussel control method to replace chlorine and other traditional control methods currently utilised in drinking water plants and other infested facilities. Zequanox® is a newly commercialised microbial biocide for zebra and quagga mussels comprised of killed Pseudomonas fluorescens CL145A cells. The objective of this study was to compare the efficacy of a developmental formulation of Zequanox (referred to as MBI 401 FDP) and chlorine treatments on adult and juvenile zebra mussels by running a biobox trial in conjunction with chlorine treatments at an infested Irish drinking water treatment plant. Since 2009, the plant management has used a residual chlorine concentration of 2 mg/L in autumn to control both adult zebra mussels and juvenile settlement in their three concrete raw water chambers. Juvenile mussel settlement was monitored in three bioboxes as well as in three treatment chambers in the plant for three months prior to treatment. Adult mussels were seeded into the chambers and bioboxes four days before treatment. In October 2011, the bioboxes were treated with MBI 401 FDP at 200 mg active substance/L, while chlorine treatment took place in the water chambers. The MBI 401 FDP treatment lasted only 8 hours while chlorine treatment lasted seven days. Juvenile numbers were reduced to zero in both the bioboxes and treated chambers within seven days. Adult mussel mortality reached 80% for both the chlorine and MBI 401 FDP treatment; however, mortality was achieved faster in the chlorine treatment. These results provided important insights into zebra mussel control alternatives to chlorine and supported further development of the now commercial product, Zequanox.

Nonnative invasive mollusks degrade aquatic ecosystems and induce economic losses worldwide. Extended air exposure through water body drawdown is one management action used for control. In North America, the Chinese mystery snail (Bellamya chinensis) is an invasive aquatic snail with an expanding range, but eradication methods for this species are not well documented. We assessed the ability of B. chinensis to survive different durations of air exposure, and observed behavioral responses prior to, during, and following desiccation events. Individual B. chinensis specimens survived air exposure in a laboratory setting for > 9 weeks, and survivorship was greater among adults than juveniles. Several B. chinensis specimens responded to desiccation by sealing their opercula and/or burrowing in mud substrate. Our results indicate that drawdowns alone may not be an effective means of eliminating B. chinensis. This study lays the groundwork for future management research that may determine the effectiveness of drawdowns when combined with factors such as extreme temperatures, predation, or molluscicides.

Invasive quagga and zebra mussels (Dreissena rostriformis bugensis and Dreissena polymorpha, respectively) pose a great threat to US waters. Recreational boats constitute a significant risk for spreading the organisms. Recreational boats circulate large amounts of raw water when in use, and if not drained and dried correctly can transport many mussel larvae, called veligers. Veligers experience very high mortality rates; however, the number of potentially transported veligers can be a serious risk to non-infested bodies of water, especially if multiple boats are involved. The risk of veliger transport was calculated for Lake Mead and Lake Michigan using boat capacities for water circulation and specific veliger density data. Results illustrate the importance of draining, drying, and/or decontaminating recreational boats after use.

In the western United States, federal, state, and local agencies have engaged in extensive efforts to detect the presence of larval dreissenid mussels (veligers) in water bodies before such a presence becomes a full-scale infestation. Cross-polarized light microscopy (CPLM) is commonly used to detect the veliger’s specific birefringence pattern, but the effect of sample preservation on dreissenid birefringence has not yet been determined. This study examined the effects of solution pH, ethanol concentration, and storage temperature on veliger birefringence loss. Birefringence loss was determined by examining veligers under CPLM at regular intervals over a 30 day period. Veliger birefringence loss was below five percent in all basic solutions, regardless of holding temperature or ethanol concentration. Veliger birefringence loss was also below five percent in acidic solutions that were refrigerated or contained 50–70 percent ethanol. Veligers in acidic solutions that were held at 25°C and 34°C with 0–25 percent ethanol had 7–25 percent veliger birefringence loss over a 30 day period. While ethanol addition and refrigeration are both important preservation methods, the results of this study indicate that samples collected for dreissenid veliger detection by CPLM must also be maintained at a basic pH in order to preserve veliger shell integrity and birefringence. Determining the best conditions for long-term preservation of veliger shells requires further investigation, and these results should not be assumed best for analyses other than CPLM.

The International Union for Conservation of Nature has cited Eriocheir sinensis as one of the world’s worst 100 invasive species. Outside their native range, this alien species has had adverse impacts, both ecologically and economically, on river catchments. Understanding the life cycle of the Chinese mitten crab, especially details of the migration period, is important for the potential control of this exotic species. The mitten crab has been reported from the River Thames, London, England and in this watershed the population continues to increase in numbers, disperse in a westerly direction and reports of a downstream migration date back to 1996. Recently, regular collections from a rubbish screen at a River Thames water abstraction point were used to monitor the migration of adult crabs over three years (2008–2010). Details of size, sex and condition of the crabs were recorded as were data on the abstracted flow. The main migration period runs from August to early November with peak numbers of crabs recorded in September/early October. In all years the sex ratio of captured crabs was heavily skewed towards males, which were significantly larger than females. Furthermore there is some evidence that female crabs move later in the migration period than males and that peaks in numbers of both male and female crabs are associated with full moon periods; peak numbers demonstrating significant lunar periodicity. In addition there is a weak association between crab numbers and abstraction flow rate. The key findings are used to recommend the timing of any future control measures that might be designed to reduce the population of this invasive species in the River Thames. These recommendations could also be applied to other river catchments where the species is problematic.

Crab condos are designed to sample for invasive species, which are not specifically targeted using current Australian biosecurity methodologies. Smaller crab species are often excluded, overlooked and damaged to be collected via current trapping or collection methods. An artificial habitat collector such as the ‘crab condo’ (PVC tubes 25cm long and 50mm diameter arranged in a 3×3 square matrix) aims to provide shelter among an animal’s natural environment. Twenty condos were deployed on a weekly basis for 48 hours during the months of April and July 2012 within Hillarys Boat marina, Western Australia. Condos proved to be highly successful, capturing a total of 555 specimens from five different phyla, with over half (n=332) of specimens identified as crabs. The detection of 223 other smaller non-crab individuals, covering four different phyla highlighted the versatility of condos to sample a range of other small species, not only crabs. Given the recognized importance of early detection of marine pests at their early life stages and current lack of methods targeting small and cryptogenic species, the crab condo sampling method may fill an important gap in marine pest surveillance capacity.

Marine mussels of the genus Perna include three species: P. canaliculus, P. viridis and P. perna. While P. canaliculus appears to be greatly restricted to its endemic range of New Zealand, P. perna and P. viridis introductions have been recorded outside their native ranges in several regions of the globe. Such introductions have often resulted in significant negative ecological, economic and social impacts. Perna perna and P. viridis are exotic to Australia and are listed under the Australian Government National System for the Prevention and Management of Marine Pest Incursions as high priority species. Rapid detection of marine pests such as Perna species remains fundamental to their effective containment and control. The present study reports on the development and validation of both conventional and real-time PCR assays suited to the rapid identification and discrimination of juvenile and adult specimens of P. viridis, P. canaliculus and P. perna. The development of a sensitive high-throughput real-time PCR assay offers further potential for the efficient detection of the presence of single Perna specimens in mixed populations of native mussel species, and for early detection of larval stages in ballast water and plankton samples. This assay offers considerable advantages over traditional identification methods and represents an important step in developing capacity for efficient identification and management of Perna species incursions in Australian waters.

Volunteers are increasingly involved in environmental research and their role in monitoring biological invasions is rapidly expanding in the Internet Era. On November 2012, a recreational diver reported the sighting of an unidentified and unfamiliar fish to an interactive web project ‘Seawatchers’ (http://www.observadoresdelmar.es) that aims to acquire geo-referenced observations of exotic fish species in the Mediterranean Sea. The individual was spotted on August 2009 along the coast of Tarragona, Spain and it was later identified as the sergeant major Abudefduf saxatilis (Teleost, Pomacentridae), a tropical Atlantic species previously unrecorded in the Mediterranean Sea. This finding highlights the potential of citizen scientists in revealing the occurrence of new exotic fishes in the marine environment, providing a small but concrete advancement towards early detection, which is important for management of biological invasions.