Zebra Mussel Mortality Research Articles

Influence of Environmental Stressors on the Microbiota of Zebra Mussels (Dreissena polymorpha)

Host-associated microbiota play a critical role in host fitness by providing nutrition, enhancing digestion capabilities, and by providing protection from pathogens. Here, we investigated the effects of two environmental stressors, temperature, and salinity, on the microbiota associated with zebra mussels (ZMs), a highly invasive bivalve in North America. To examine this in detail, lake-collected ZMs were acclimated to laboratory conditions, and subjected to temperature and salinity stress conditions. The impact of these stressors on the diversity, composition, and dynamics of ZM-associated microbiota were assessed by using amplicon- and shotgun-based sequencing, and qPCR-based approaches. Elevated temperature was found to be the primary driver of ZM mortality, although salinity alone also increased its likelihood. Stressor-induced ZM mortality, which ranged between 53 and 100%, was concomitant with significant increases in the relative abundance of several genera of putative opportunistic pathogens including Aeromonas. These genera were only present in low relative abundance in ZMs obtained from the control tank with 0% mortality. Shotgun sequencing and qPCR analyses indicated that the relative and absolute abundances of pathogenic Aeromonas species (particularly A. veronii) were significantly greater in temperature-induced dead ZMs. Taken together, our results show that environmental stress, especially elevated temperature (> 25 °C), is associated with the rapid mortality of ZMs as well as the proliferation of putative opportunistic bacterial pathogens.

Environmental conditions increase growth rates and mortality of zebra mussels (Dreissena polymorpha) along the southern invasion front in North America

Environmental conditions found along an invasion front can mediate spread dynamics of an invasive species. Conditions that affect survival and individual growth rates of founder propagules and the first young-of-year generation can have a profound effect on establishment dynamics. Responses of younger, more sensitive individuals to these novel conditions, in part, determine establishment success. The southern invasion front of zebra mussels in North America expanded into Texas in 2009. To determine mechanisms that could affect establishment of zebra mussel populations at low latitudes in North America, an in situ study was conducted in Lake Texoma, on the Texas-Oklahoma border. Survival and growth were measured of young-of-year juveniles at multiple sites within the reservoir. Age-specific mortality was significantly positively correlated with temperature at all sites and no mortality occurred when temperatures were <26 °C. Shell-length growth rates were the highest ever reported for lentic environments. A decrease in shell-length growth rates was associated with an increase in soft tissue mass, possibly resulting from flexible energy allocation from shell development to gametogenesis after maturation. Overall, survivorship and growth were related to water temperatures and chlorophyll-a concentrations. Warm waters found at lower latitudes along the invasion front could facilitate establishment of populations by increasing growth rates and decreasing time to maturity. However, due to extreme climate events (e.g. drought and flooding) and a strong temperature-mortality relationship, mortality likely will also be high beyond the southern invasion front, resulting in highly dynamic boom and bust cycles.

An evaluation Zequanox® efficacy and application strategies for targeted control of zebra mussels in shallow-water habitats in lakes

An evaluation of Zequanox ® (a naturally derived biopesticide that is non-toxic to humans and other aquatic life and selectively kills dreissenid mussels) for controlling zebra mussel infestations in shallow-water habitats in lakes was conducted at Deep Quarry Lake in DuPage County, Illinois during summer 2012 and 2013. During the 2012 trial, three sets of paired 24-m² treatment and control sites were established within the lake, while a single 324-m² treatment site was established for the 2013 trial. Zequanox was applied to treatment plots, contained using PVC barrier curtains, and barriers were removed during the morning following application. Zebra mussel mortality and size distributions on natural substrates were assessed one day and one week post-treatment for 2012 trials and one day and two weeks posttreatment for 2013 trials; percent mortality of zebra mussels in mesh containers in treatment and control sites was also monitored up to 14 days and 48 days post-treatment in 2012 and 2013, respectively. Several water quality parameters were measured in control and treatment plots before and during application and up to 14 d post-treatment. Mean percent mortality for adult zebra mussels on natural and artificial substrates in treatment locations 7–48 d following Zequanox application ranged from 92–98% during both years, while mortality was consistently ≤10% in control locations. Mean percent mortality ranged from 15–76% in locations > 5 m from and in water shallower than Zequanox application points (<0.6 m depth) during the 2013 trial likely due to limited product dispersal into these areas. There was no significant difference in the size distribution of live and dead zebra mussels in treatment plots. Mean veliger mortality was 94.4% 20-h after the start of the 6-h Zequanox treatment period in the treatment area compared to 15.1% in untreated locations during the 2013 trial. Temporary but substantial reductions in dissolved oxygen were observed in treatment locations during the morning following Zequanox treatment in both 2012 and 2013 trials, likely due to the presence of the barriers that prevented well-oxygenated water from circulating into treatment zones from adjacent areas in the lake. Dissolved oxygen concentrations quickly rebounded to levels consistent with control sites upon removal of barriers. No effects of Zequanox treatment on ammonia, total nitrogen, total phosphorus, biochemical oxygen demand, chlorophyll a, pH, or conductivity were observed. Results suggest that Zequanox has potential as a tool for controlling zebra mussels in shallow-water habitats in lakes without significant long-term effects on water quality.

Ecotoxicological impact of Zequanox®, a novel biocide, on selected non-target Irish aquatic species

Effective, species-specific zebra mussel control is needed urgently for Ireland׳s freshwater bodies, which became infested with non-native zebra mussels in the 1990s. Zequanox®, a newly commercialized product for zebra and quagga mussel control, is composed of dead Pseudomonas fluorescens CL 145A cells. This paper describes ecotoxicology tests on three representative native Irish freshwater species: Anodonta (duck mussel), Chironomus plumosus (non-biting midge), and Austropotamobius pallipes (white-clawed crayfish). The species were exposed to Zequanox in a 72-h static renewal toxicity test at concentrations of 100–750mg active ingredient per liter (mga.i./L). Water quality parameters were measured every 12–24h before and after water and product renewal. After 72h, endpoints were reported as LC10, LC50, and LC100. The LC50 values derived were (1) Anodonta: ≥500mga.i./L (2) C. plumosus: 1075mga.i./L, and (3) A. pallipes: ≥750mga.i./L. These results demonstrate that Zequanox does not negatively affect these organisms at the concentration required for >80percent zebra mussel mortality (150mg a.i/L) and the maximum allowable treatment concentration in the United Sates (200mga.i./L). They also show the overall species-specificity of Zequanox, and support its use in commercial facilities and open waters.

Biotic resistance on the increase: native predators structure invasive zebra mussel populations

SUMMARY 1. Abundant native predators, parasites and pathogens that switch to consuming a hypersuccessful exotic species may be able to control the invasive population. Native predators may, however, need time to adapt to feed effectively on an exotic resource. In this case, mortality on an exotic population from native predators could increase over time even without a numerical increase in the predator population. 2. We measured mortality of zebra mussels (Dreissena polymorpha) in the Hudson River both in controls open to predation and in exclosures that excluded large predators to estimate mortality of zebra mussels from large predators and other causes. 3. We found that predation by the blue crab (Callinectes sapidus), and perhaps other predators, causes high mortality on zebra mussels in the Hudson River estuary. This predation apparently led to increased mortality and altered population structure in the invader over time. 4. Long-term data from the Hudson River suggest that components of the invaded ecosystem, like rotifers, are recovering through predator-caused release from zebra mussel grazing. Increased mortality on hyper-successful exotic populations over time may be a common phenomenon with both ecological and management implications.

Strong effects of predation by fishes on an invasive macroinvertebrate in a large floodplain river

We assessed the effects of fish predation on zebra mussels (Dreissena polymorpha) in Navigation Pool 8 of the Upper Mississippi River from 13 May to 5 October, 1998. Concrete-block samplers were deployed at 18 randomly chosen sites in the main-channel border, with 6 sites in the upper, middle, and lower segments of the pool. Two blocks, 1 of which was enclosed in a cage to exclude large predatory fishes, were deployed at each site. After 145 d, blocks were retrieved from 12 of the 18 sites, and zebra mussels were found on all blocks. Densities of zebra mussels were higher on caged blocks than uncaged blocks, and the magnitudes of the differences varied spatially. Mean mussel densities on uncaged blocks were reduced by 66%, 86%, and 20% compared to caged blocks in the upper, middle, and lower pool segments, respectively, over the 145-d interval. Mean daily instantaneous zebra mussel mortality rates from large predators ranged from 0.0016 to 0.0138. Similarly, biomass of zebra mussels was higher on caged than uncaged blocks. Mean mussel biomass on uncaged blocks was reduced by 64% pool-wide, relative to biomass on caged blocks. Zebra mussels were consumed by at least 6 fish taxa including redhorse suckers (Moxostoma spp.), common carp (Cyprinus carpio), bluegill (Lepomis macrochirus), quillback carpsucker (Carpiodes cyprinus), flathead catfish (Pylodictis olivaris), and freshwater drum (Aplodinotus grunniens). Fish predation had an important moderating effect on zebra mussel demography in Pool 8.

Toxic and excitatory effects of the molluscicide metaldehyde on the biofouling bivalveDreissena polymorpha Pallas

The zebra mussel, Dreissena polymorpha Pallas, is a biofouling freshwater pest for which alternative control methods to the use of chlorine are sought. Metaldehyde, a molluscicide used primarily for control of terrestrial slugs, has also been shown to have efficacy and specificity in the control of aquatic snails. To test its potential for zebra mussel control, we investigated its effects on zebra mussel viability and on contractility of siphon/mantle muscle preparations in vitro. Metaldehyde caused zebra mussel mortality within 48 h at concentrations of approximately 0.1 and 0.2 g litre−1. The same concentrations of metaldehyde activated a complex, excitatory response in previously quiescent siphon/mantle preparations but did not modify the contractile responses of the preparations to acetylcholine. The relatively low level of toxicity of metaldehyde to zebra mussels, compared to its toxicity to snails and slugs, and the difficulty of applying this relatively insoluble molluscicide in the aqueous environment suggest that metaldehyde would not be an effective zebra mussel control agent. © 2000 Society of Chemical Industry

Survivorship of Aerially-Exposed Zebra Mussels (Dreissena polymorpha) under Laboratory Conditions

ABSTRACT Zebra mussels (Dreissena polymorpha) were aerially exposed at temperatures of 5 C and 20 C for 12, 24, 36, and 60 h. Survivorship was nearly 100% in all control containers and for the 5 C replicates but declined substantially in the 20 C replicates after 36 and 60 h. Additional zebra mussels were aerially exposed at 5 C and 20 C on both wet and dry substrates for 60 h. Those aerially exposed on a wet substrate at 5 C had greater survivorship than did mussels on a dry substrate at 20 C. Larger zebra mussels (shell length > 16 mm) were significantly more likely to survive exposure for 36 or 60 h at 20 C than were smaller individuals. These results show that survivorship of freshly-collected zebra mussels under controlled, biologically-relevant conditions is strongly affected by length of aerial exposure, ambient temperature, substrate moisture, and mussel size. Our findings largely confirm results of companion field experiments, implying that temperature and moisture conditions caused the observed zebra mussel mortality in nature. Taken together, these studies suggest that aerial exposure at warm temperatures (≥ 20 C) may be an effective control for zebra mussels in regulated waters where water levels can be lowered for more than 24 h.

Effects of pH, calcium, alkalinity, hardness, and chlorophyll on the survival, growth, and reproductive success of zebra mussel (Dreissena polymorpha) in Ontario lakes

In 1991, field studies were conducted to determine the effects of pH, calcium, alkalinity, hardness, and chlorophyll on the survival, growth, and reproduction of zebra mussel (Dreissena polymorpha). Water from 16 south-central lakes in Ontario was collected and supplied to zebra mussels in a flow-through system. Adult zebra mussel mortality was significantly correlated with calcium and pH. Growth rates of juvenile mussels ranged from -83.3 to 200 µm ·week-1. Water buffer variables (calcium, alkalinity, and total hardness) explained 60-66% of the variation observed in the change in shell length of juvenile zebra mussel (p = 0.001-0.003). There was negative growth at calcium levels less than 8.5 mg Ca · L-1, alkalinity levels less than 17.1 mg CaCO3 · L-1 and total hardness levels less than 31 mg CaCO3 · L-1. Maximum growth occurred at calcium levels of 32 mg Ca ·L-1, alkalinity of 65 mg CaCO3 · L-1, and total hardness of 100 mg CaCO3 · L-1. Positive growth of juvenile zebra mussel only occurred at pH levels greater than 8.3. Only one veliger survived to the settling stage.

Zebra mussel mortality with chlorine

A kinetic model allows prediction of the mortality of zebra mussels as a function of chlorine concentration, temperature, and contact time.The rate of mortality of the zebra mussel in response to chlorine is described by a kinetic model that combines a statistical characterization of mussel mortality with a disinfection‐type modeling approach. Parameter estimates were made with nine sets of data from experiments conducted in Niagara River water. From the kinetic model, an operational diagram was constructed that describes the time to 95 percent mortality as a function of chlorine concentration and temperature. Either the model or the diagram can be used to assist utilities in planning chlorination treatments for controlling zebra mussels.