Susceptibility of quagga mussels (Dreissena rostriformis bugensis) to hot-water sprays as a means of watercraft decontamination

Watercraft decontamination practices to reduce the viability of aquatic invasive species implicated in overland transport

Recreational boating activities enable aquatic invasive species (AIS) dispersal among disconnected lakes, as invertebrates and plants caught on or contained within watercraft and equipment used in invaded waterbodies can survive overland transport. Besides simple preventive measures such as "clean, drain, dry", resource management agencies recommend decontaminating watercraft and equipment using high water pressure, rinsing with hot water, or air-drying to inhibit this mode of secondary spread. There is a lack of studies assessing the efficacy of these methods under realistic conditions and their feasibility for recreational boaters. Hence, we addressed this knowledge gap via experiments on six invertebrate and plant AIS present in Ontario. Washing at high pressures of 900-1200 psi removed the most biological material (90%) from surfaces. Brief (< 10 s) exposure to water at ≥ 60 °C caused nearly 100% mortality among all species tested, except banded mystery snails. Acclimation to temperatures from 15 to 30 °C before hot water exposure had little effect on the minimum temperature required for no survival. Air-drying durations producing complete mortality were ≥ 60 h for zebra mussels and spiny waterfleas, and ≥ 6 days among plants, whereas survival remained high among snails after a week of air-drying. Hot water exposure followed by air-drying was more effective than either method separately against all species tested.

What we know and don't know about the invasive zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis bugensis) mussels

We summarized existing knowledge on Dreissena polymorpha (the zebra mussel) and D. r. bugensis (the quagga mussel), including data on their taxonomy, systematics, evolution, life cycle, reproduction, feeding, growth and longevity, population dynamics, interspecific competition, habitat requirements, and distribution within and among waterbodies. We analyzed the history of spread of both species and the major pathways and vectors of their spread in Europe and North America. Special consideration was given to their ecological and economic impacts and their natural enemies, like waterfowl, fishes, and parasites, as well as the prevention of their introduction, early detection, control, and containment. We also outlined the most salient ecosystem services provided by zebra and quagga mussels, including water purification, nutrient recycling, culling the effects of eutrophication, biomonitoring, and their role as a food resource for fish and waterfowl. Finally, we identified major knowledge gaps and key studies needed to better understand the biology, ecology, and impacts of these aggressive freshwater invaders. Our review indicates that much crucial information on the quagga mussel is still missing, including key life history parameters, like spawning cues, fecundity, and longevity, particularly for the profundal zone of deep lakes.

Toxicity of Potassium Chloride Compared to Sodium Chloride for Zebra Mussel Decontamination

The use of chemicals to decontaminate watercraft and/or equipment after exposure to zebra mussels Dreissena polymorpha is one method of decontamination that has been recommended by multiple government agencies in the United States. The ideal chemical to be used for decontamination would be inexpensive and easily obtained, would have no or limited effect on nontarget species, and would be relatively environmentally friendly. Two chemicals that have been tested are potassium chloride (KCl) and sodium chloride (NaCl). The toxicity of each chemical to both adult zebra mussels and veliger larvae was examined. Sodium chloride was less effective at causing mortality than KCl within the exposure periods tested. Adult mussels required a 4× longer exposure period to exhibit complete mortality when exposed to NaCl at 30,000 mg/L (24 h) compared to KCl (6 h). At 10,000 mg/L, NaCl took 8× longer (96 h) than KCl (12 h) to cause 100% mortality of adult mussels. Veligers that were exposed to KCl at 1,250 mg/L required a 12-h exposure to attain complete mortality, while those exposed to NaCl at 10,000 mg/L required an 18-h exposure to exhibit the same result. To determine whether KCl is more advantageous as a decontamination chemical, the cost and chemical availability must be researched.

Invaders in hot water: a simple decontamination method to prevent the accidental spread of aquatic invasive non-native species

Watersports equipment can act as a vector for the introduction and spread of invasive non native species (INNS) in freshwater environments. To support advice given to recreational water users under the UK Government’s Check Clean Dry biosecurity campaign and ensure its effectiveness at killing a range of aquatic INNS, we conducted a survival experiment on seven INNS which pose a high risk to UK freshwaters. The efficacy of exposure to hot water (45 °C, 15 min) was tested as a method by which waters users could ‘clean’ their equipment and was compared to drying and a control group (no treatment). Hot water had caused 99 % mortality across all species 1 h after treatment and was more effective than drying at all time points (1 h: χ² = 117.24, p < 0.001; 1 day χ² = 95.68, p < 0.001; 8 days χ² = 12.16, p < 0.001 and 16 days χ² = 7.58, p < 0.001). Drying caused significantly higher mortality than the control (no action) from day 4 (χ² = 8.49, p < 0.01) onwards. In the absence of hot water or drying, 6/7 of these species survived for 16 days, highlighting the importance of good biosecurity practice to reduce the risk of accidental spread. In an additional experiment the minimum lethal temperature and exposure time in hot water to cause 100 % mortality in American signal crayfish (Pacifastacus leniusculus), was determined to be 5 min at 40 °C. Hot water provides a simple, rapid and effective method to clean equipment. We recommend that it is advocated in future biosecurity awareness campaigns.

Potential antifouling strategies for marine finfish aquaculture: the effects of physical and chemical treatments on the settlement and survival of the hydroid Ectopleura larynx

The hydroid Ectopleura larynx is a common fouling organism on aquaculture nets. To contribute to the development of novel cleaning methods, laboratory and field studies determined the effects of heat (30, 40, 50 and 60°C for immersion times of 1 and 3 s) and acetic acid (0.2 and 2.0% for immersion times of 1, 3 and 10 s, 1 and 5 min) on the settlement of actinulae and the survival of juvenile and adult E. larynx. Laboratory studies showed that, regardless of immersion time, a temperature of 50°C was effective in preventing the settlement of actinulae and the survival of juveniles, while ≤12% of adult hydroids could survive. A temperature of 60°C killed all adult hydroids. For an acetic acid concentration of 0.2%, an immersion time of 1 min substantially reduced the settlement of actinulae and the survival of juvenile and adult hydroids, and none of the juvenile and adult hydroids survived after 5 min. For an acetic acid concentration of 2.0%, all immersion times were effective and reduced the mean settlement of actinulae and the survival of juvenile and adult hydroids to ≤10%. Field studies with fouled net panels exposed to selected heat or acetic acid treatments showed small reductions in mean wet weight and net aperture occlusion of the net panels 2 and 5 days after treatment. Visual inspections of the net panels showed that hydranths of the hydroids were shed, but the dead stolons of the hydroids remained on the treated net panels. Novel cleaning methods and devices may utilise these results to effectively kill E. larynx on aquaculture nets, while further studies are needed to determine the necessity of removing the dead hydroids before further biofouling accumulates on the nets.

Thermal tolerance of Limnoperna fortunei to gradual temperature increase and its applications for biofouling control in industrial and power plants

The acute upper lethal temperature (AULT) at different rates of increase was evaluated as a tool for the design of cheaper and environmentally friendlier control strategies for the invasive bivalve Limnoperna fortunei. Survivorship of 6 ± 2 mm and 20 ± 2 mm mussels acclimated to 12, 23 and 28 ° C and subjected to different heating rates (1 ° C per 5, 15 and 30 min) was estimated in the laboratory. The temperatures required to kill 50% (LT(50)) and 100% (SM(100)) of the mussels, and the mean death temperature (MDT) varied between 42.2 and 51 ° C over 54 experiments. Heating rates significantly (p < 0.001) affected LT(50), SM(100), and MDT. AULT was not affected by mussel size and acclimation temperatures. Limnoperna appears to be more resistant to high temperatures than Dreissena polymorpha, a mussel invasive in the USA and Europe. Lethal temperatures of L. fortunei are within the current thermal operational industrial capacities, suggesting that heat treatment is a viable alternative for controlling its fouling in utility systems.