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Effectiveness of a copper based molluscicide for controlling: Dreissena adults
Abstract
Pilot scale experiments were conducted to test the copper-based EarthTec QZ molluscicide for killing adult quagga mussels. The work was done in Lake Ontario water with average water temperatures ranging between 10.4-6.7°C. Trials consisted of eight copper concentrations varying between 30-500 μg/L in triplicate under continuous and cyclical flow regimes. A 1 mg/L total chlorine trial was used to provide a comparative standard. Complete control was achieved in all test groups ranging within 7 to 28 days for the copper trials, while the chlorination group required 41 days. The efficacy of the copper product was not impacted by continuous versus cyclical flow regime. Results from this study indicate that the copper based product is a viable molluscicide option for adult control with possible advantages over chlorine in cyclical flow regimes and at colder water temperatures.
... Freshwater species are particularly vulnerable to Cu pollution, which is lethal at low environmental concentrations in benthic invertebrates, fish, amphibians, and zooplankton [17,18]. More specifically, Cu exposure can cause direct mortality in a variety of organisms, including mollusks [19], decrease the reproductive success of copepods [20], induce behavioral changes and stunted growth in larval amphibians [21], and alter community structure and trophic interactions [22]. Understanding the effects of Cu contamination and exploring ways to advance mitigation efforts are essential for managing human impacts on freshwater ecosystems in human dominated landscapes. ...
Freshwater ecosystems face numerous threats from human populations, including heavy metal contamination. Phytoremediation, the use of plants to remediate contaminated soils and sediments, is an effective and low-cost means of removing chemical contaminants, including heavy metals, from polluted environments. However, key questions remain unanswered in the application of this technology in aquatic environments, such as the long-term fate of pollutants following plant uptake. In this study, using two common wetland plant species (duckweed and tape grass), we first examined the capacity of plants to remove copper (Cu) from polluted water. Next, we evaluated the leaching potential of plant tissues following decomposition and how it is affected by a simulated freeze-thaw cycle. Using phytoremediated water and leachates from senescent plants we assessed phytoremediation success and Cu leaching potential by conducting standard toxicity assays using pond snails (Physa acuta), a species with known Cu sensitivity. We found that duckweed outperformed tape grass as a phytoremediator at low Cu concentrations. In addition, for plants grown in low concentrations of Cu, leaching from decaying plant material did not negatively impact snail survival, while at high concentrations of Cu, leaching did result in toxicity. Lastly, we found that a simulated freeze-thaw cycle increased the release of Cu from plant tissue in the presence of high Cu concentrations only, resulting in reduced snail survival. Our results indicate that in moderately Cu-polluted environments, some aquatic plants can remove contaminants without a long-term risk of leaching. In contrast, phytoremediation in highly polluted environments will likely require removal of plant tissue to prevent leaching of previously accumulated metals. Land managers must not only consider plant species and degree of contamination, but also geographic location, as freeze-thaw cycles may enhance plant decomposition and increase the likelihood of contaminant leaching following phytoremediation efforts in aquatic ecosystems.
... Nanomaterials and heavy metals can often interrupt or alter the ion channel receptors form the gastropod neuronal membranes and lead them to reduce the ability to assess predation risk, such as reported for Ag NPs (Bernot and Brandenburg, 2013;Justice and Bernot, 2014). The behavioral alterations induced by both iron forms, such as SWS and WA, have been reported for several compounds with potential molluscicidal activity (Lake- Thompson and Hofmann, 2019;Sarquis et al., 1997;Schüder et al., 2004), and may lead to increased predation risk. On the other hand, the SR behavior consists of a defensive response of the snail by decreasing the surface area of exposure with the medium. ...
In Latin America and in Asian countries, the apple snail Pomacea canaliculata is one of the most destructive pests present in rice plantations, which is why it is considered among the 100 invasive species in the world. The present work is an experimental laboratory test where different doses of copper and ozone chelate for the control of apple snail are applied with 4 treatments, 1 control and 6 repetitions. For the evaluation of the applied molluscicides, the WHO method (1965) was used. The percentage of mortality of T4, which corresponds to the dose of 2 L / ha of copper chelate mixed with ozonized water with 2 ppm concentration, was the treatment that best controls apple snail, resulting in 97.67% of mortality, however, in T5 (control) a 6.33% of mortality was obtained. The results suggest that the copper chelate mixed with ozonated water can be used in the effective control of the apple snail.
La plaga que más problemas ha causado en los últimos años en el arroz (Oryza sativa L.) es el Caracol manzana (Pomacea canaliculata Lamarck), esta plaga está considerada entre las 100 peores especies invasoras del mundo. El presente trabajo es un ensayo experimental a nivel de campo donde se aplicaron diferentes dosis de quelato de cobre y agua ozonizada para el control del caracol manzana en el cultivo de arroz, para lo cual se utilizó un diseño de bloque completo al azar (DBCA), con cinco tratamientos incluido el testigo y cuatro repeticiones. El sitio experimental se ubicó en una finca del cantón Salitre, provincia del Guayas, Ecuador con clima tropical. Se evaluó el índice de mortalidad de los caracoles frente a los tratamientos propuestos. El tratamiento T4, que correspondía a la dosis de 2 L ha-1 de quelato de cobre mezclado con agua ozonizada con 2 ppm de concentración, fue el tratamiento que mejor control de caracol manzana se observó, dando como resultado 94% de mortalidad.
Prechlorination is the most common strategy for zebra and quagga mussel control in drinking water treatment plant intakes in the Great Lakes region. Although effective and inexpensive, chlorine can form regulated disinfection byproducts. Two potential alternatives to prechlorination were evaluated for mussel control: peracetic acid (PAA) and EarthTec QZ, a copper-based product. Pilot-scale experiments were conducted to test EarthTec QZ for veliger control and to evaluate the efficiency of PAA and EarthTec QZ for adult mussel control. EarthTec QZ doses of 30, 60, and 120 μg/L as copper ions demonstrated dose-dependent veliger control at 12 C. PAA doses of 5, 10, and 25 mg/L were effective for adult mussel control at the low water temperatures tested (4 C). Results from this study indicate that PAA and EarthTec QZ may be an alternative to prechlorination.
The management and control of dreissenid mussels (zebra mussels, Dreissena polymorpha, and quagga mussels, Dreissena rostriformis bugensis) that have infested various components (e.g., intake structure, pipes) of drinking water treatment plant is a priority for facility managers. Mussel infested waterbodies are often used as source water for water treatment. Mussels can cause clogging of water intakes and pipes, along with the formation of disinfection byproducts. Capital costs and the operations and maintenance (O&M) costs are presented using ten case studies from drinking water facilities that are contending with ongoing mussel infestations. The O&M-based unit cost of mussel control vary from 12.63 for 2,640 MGD capacity. The capital cost and O&M-based equivalent annual unit cost for treatment vary from 13.41 for 2,640 MGD capacity. Cost for larger water treatment plants (i.e., >10 MGD) vary between 14.00/MG.
Hydrotrope-combined copper (HCC) is a copper (Cu2+)-based algicide, which is combined with a hydrotrope that keeps copper ion in solution to improve performance. This study assessed the growth inhibition effect of HCC against Microcystis aeruginosa which is one of the most common toxic cyanobacterium in eutrophic freshwater environment. Various HCC doses, ranging from 5.5 to 550 μg/L as Cu2+, were applied to either BG-11 or 1/4 diluted medium with low- or high-inoculum density of M. aeruginosa. Growth inhibition was monitored based on a decrease in chlorophyll-a content in culture medium during the incubation. Results showed that HCC significantly inhibited the growth of M. aeruginosa in a dose-dependent manner. In case of 1/4 diluted BG-11 medium, HCC dose as low as 5.5 μg Cu2+/L completely inhibited the production of chlorophyll-a by M. aeruginosa. It was found that HCC did not induce any significant release of microcystin-LR from M. aeruginosa. Acute toxicity of HCC was tested using Daphnia magna, and the 24-h EC50 value was 0.30 mg/L as Cu2+ which was much higher than the actual inhibition dose. Ames test was performed using Salmonella enterica serovar Typhimurium TA100, and HCC showed no increase in the number of revertant colonies. The result suggested that HCC does not have any mutagenic potential in the aquatic environment. In addition, no genotoxic effect of HCC was also confirmed based on the SOS ChromoTest using Escherichia coli PQ37. Therefore, HCC could be used as a relatively safe and effective pre- and post-treatment agent to control hazardous algal blooming in aquatic environments.
The Bayesian network’s graph structure accommodates conditional independence between domain elements. It is not necessary to specify the relationship between every variable (and every hypothesis H that describes a possible state of each variable) in an exhaustive joint probability matrix. Instead, each variable in a Bayesian network requires only a local joint probability distribution that reflects the possible configurations of its immediate parents, if any, in the graph. A node with no parents is said to be marginally independent. The marginal probabilities used to describe the states of such a node may depend on observed data or expert estimates, but are not directly influenced by other nodes in the network. By contrast, conditional probabilities are used to describe the various states of a node with parents, where each state of such a node is described in terms of the various combinations of its parents’ states. These probabilities are conditional on the knowledge of the parents’ states. The Bayesian approach thus limits the number of quantitative parameters needed to describe the probabilistic influence of domain elements on each other; conditional probabilities are described locally, but, through propagation of probabilities from one node to the next, and hence have global influence. The WEBWEAVR-IV Toolkit (Xiang 2006) will be employed to model a Bayesian network that utilizes the concentration levels of raw water parameters to predict levels of TTHM.
Environmental factors that can affect the settlement rate of quagga mussel veligers include flow velocity, water temperature, pH,dissolved oxygen (DO), conductivity, total organic carbon (TOC), and the surface roughness of monitoring substrates. In thepresent study, six artificial substrates, Acrylonitrile Butadiene Styrene (ABS) plastic, High Density Polyethylene (HDPE) plastic,Concrete Underlayment Board (CUB), aluminum, stainless steel and fiberglass, were used to monitor the settlement of quagga mussel veligers at different water depths in Lake Mead, Nevada-Arizona, USA. Considering the hierarchical data structure of observed mussel densities, we investigated the relationship between mussel settlement on monitoring substrates and the surrounding environmental variables by applying the Linear Mixed Effects (LME) model. After normalization, the above six environmental variables were considered as independent factors in fixed-effect calculation, while water depth and substrate
roughness acted as the group variable and the random term, respectively. The results indicated that flow velocity, water temperature, and DO were significant factors in determining the mussel settlement on substrates. TOC was barely significant while conductivity and pH had no impact on settlement of quagga mussel veligers. As to the random effect, no preference for substrate type could be found, while water depth caused considerably more variation in modeling since it might correlate with most environmental variables. There is need to emphasize the critical role of flow velocity which is often ignored by biologists - higher flow velocities significantly decreased the settlement of quagga mussel veligers on substrates. Therefore, to more efficiently monitor quagga mussel colonization in water bodies, artificial substrates should be deployed in areas without strong flow.
Quagga mussels (Dreissena rostriformis bugensis) have created economic and ecological impacts in the western United States since their discovery in 2007. This study focuses on chemical control for preventing the spread of these mussels. The effectiveness of EarthTec® in killing quagga mussels (adults, juveniles, and veligers) in Lake Mead, Nevada-Arizona, was evaluated over time across six concentrations: 0, 1, 5, 10, 17, and 83 ppm. One hundred percent mortality of adult and juvenile mussels was achieved after 96 h with 17 ppm and 5 ppm (respectively), and 100% veliger mortality occurred within 30 min at 3 ppm. From December 2010 to February 2011, the effectiveness of EarthTec® in preventing veliger colonization was also evaluated and the results showed that 2.8 ppm was effective in preventing veliger colonization on fiberglass panels. This study indicates that EarthTec® has the potential to be an effective control agent against the invasive quagga mussel, and more specifically, in preventing the colonization of veligers.
Small adult zebra mussels (Dreissena polymorpha), 2–8 mm valve length, collected from Lake St. Clair were exposed to a range of concentrations of three biocides in static, acute toxicity tests in the laboratory. Laboratory conditions (22C; pH 7.8; water hardness 100 mg/L) were representative of midsummer conditions in the nearshore of Lakes Erie and St. Clair. Mussels actively colonized styrene test substrates which were transferred to three replicate, 1-L test vessels. Sodium hypochlorite was an effective biocide at concentrations exceeding 1.00 mg/L and resulted in complete mortality of mussels by 157 and 264 h at concentrations of 5.00 and 2.50 mg/L, respectively. Poly [oxyethylene (dimethylimino) ethylene (dimethylimino) ethylene dichloride] at 1,2,4 and 8 mg/l and (2-(thiocyanomethylthio) benzothiazole) at 0.5,1,2 and 4 mg/L resulted in 100% mortality at all concentrations in times ranging from 144 to 250 h and 110 to 192 h, respectively. Biocide concentration significantly affected the mean time of death for all three of the compounds tested. Mussel valve length had a significant positive effect on time of death in (2-(thiocyanomethylthio) benzothiazole) but only explained a maximum 18% of the variance. Resistance of these actively colonizing mussels to biocides was greater than that found by other laboratory studies, perhaps because of lowered handling stress in our experimental manipulations.
Three potential chemical controls (sodium hypochlorite, hydrogen peroxide, and poly[oxyethylene (dimethylimino) ethylene (dimethylimino) ethylene dichloride] (commercial trade name BULAB 6002)) were evaluated for acute toxicity to small adult zebra mussels (Dreissena polymorpha) in chronic and pulsed-dose laboratory trials at two temperatures. All three control agents tested effected greater mortality ofD. polymorpha at 22C than at 12C. In most cases the mortality level at 12C was one half or less that incurred at the higher temperature. Analysis of variance showed significant effects of temperature in the case of BULAB 6002 and for hydrogen peroxide; plots of cumulative mortality through time show this trend as well. The relationship between mussel valve length and time-of-death is consistently positive but is significant in few individual treatments, however, when treatments (all concentrations and temperatures) for a single biocide are pooled, the relationship is significant and explains 16–26% of the variance. This suggests that control programs might be more effective if they are initiated whenD. polymorpha are small. Pulsed-dose control programs also are affected by temperature but generally are likely to be more cost-effective than continuous application control programs and would result in lower overall discharge of biocides to surface waters. Hydrogen peroxide at concentrations of 12.0, 20.0, or 30.0 mg/L is a quick acting control agent that probably will have fewer long-term consequences for nontarget organisms in discharge areas or for municipal water users than either BULAB 6002 or, especially, sodium hypochlorite.
The Dreissena-Monitor is a biological early warning system for the aquatic environment. It is based on the valve movements
of up to 2 × 42 specimens of the zebra mussel Dreissena polymorpha, exposed in a flow-through system of 2 experimental channels connected to the water to be tested. A computer records whether
a mussel is open or closed. After an analysis period of 5min, the percentage of open mussels and the number of valve movements
are computed as running averages for each experimental channel. With consideration being given to the normal behaviour of
the mussels and the response of the system during several toxicity tests, reliable alarm-thresholds were established which
are based on dynamic limits. In addition to these alarm functions (including the automatically safekeeping of a water sample)
and the primary measurements, the computer fulfils every function necessary for an early warning system, e.g., complete storage
and documentation of all data, validity-check of the primary measurements, and graphical presentation of all results. Together
with more than 20 biological early warning systems, the Dreissena-Monitor was tested and evaluated by a joint federal government/federal
states project group in Germany. As one of three systems, the Dreissena-Monitor is now recommended for implementation at the
measuring stations of the ‘German Commission for the Protection of the Rhine Against Pollution.’ Starting in 1992, the Dreissena-Monitor
is now applied at 13 water control stations in Germany (Rhine, Elbe, Danube, several tributaries). The experience of the users
at the different stations have revealed that the Dreissena-Monitor complies quite well with the main functional requirements
of an early warning system: (1) reliable, unattended operation for at least 1week, (2) ease of handling, (3) an average of
less than 3h of maintenance per week, and (4) automatic detection of alarm situations within 30min. In particular, the Dreissena-Monitor
detected some water alarms at different rivers that give first clues on the sources of emission.
Mortality pattern of different size groups (5-20 mm shell lengths) of the zebra mussel Dreissena polymorpha (Pallas), was studied in the laboratory under different chlorine concentrations (0.25-3.0 mgl(-1)). Results showed that exposure time for 100% mortality of mussels significantly decreased with increasing chlorine concentration. For example, mussels in the 10mm size group exposed to 0.25mg l(-1) chlorine residual took 1080h to reach 100% mortality whereas those exposed to 3 mg l(-1) chlorine took 252 h. All size groups (between 5 and 20 mm shell length) took identical exposure time to reach 100% mortality at given chlorine concentration (between 1 and 3mg l(-1)). The effect of acclimation temperature on D. polymorpha mortality in the presence of chlorine was significant. For example, 1026 h is required to reach 95% mortality using 0.5mg l(-1) residual chlorine at 10 degrees C, compared to 456h at 0.50 mg l(-1) chlorine and 25 degrees C. Resistance of D. polymorpha to chlorine appeared to be lower than that for other mussel species in The Netherlands viz., Mytilus edulis L. and Mytilopsis leucophaeata (Conrad). The present study also suggests that 100% mortality data for European populations of D. polymorpha at different chlorine concentrations are similar to those for the North American populations.
In order to study the short-term ecotoxicity of metals to the freshwater mussel Dreissena polymorpha, the effects of Cu, Zn and Cd on the filtration rate of this mussel were determined in laboratory experiments. Filtration rate was chosen as the endpoint, because it is a sensitive sublethal parameter compared to mortality and it is an important parameter given the ecological role D. polymorpha fulfills. The filtration rate was calculated from the decrease in algal concentration, fed to mussels in aquaria, containing different metal concentrations. The EC50 for Cu (41 microg litre(-1)) was lower than for Cd (388 microg litre(-1)) and Zn (1350 microg litre(-1)). The NOEC(accumulation) for the essential metal Zn was higher than for the essential metal Cu. Cadmium, a non-essential metal, was accumulated at all elevated water concentrations, so the NOEC(accumulation) was the concentration in the control water (<0.2 microg litre(-1)). All (no) effect concentrations found in this study were above the quality criteria set for metal concentrations in Dutch surface water, suggesting that the zebra mussel is sufficiently protected by these quality criteria.
Benthic algae, much of it the green alga Cladophora, blanket the nearshore lakebed of the north shore of Lake Ontario. Nearshore field studies in Toronto, Ajax, Oshawa and Cobourg in 2012 and 2013, and Toronto in 2015 examined the distribution of Cladophora over a nutrient gradient on the north shore of the lake. Concentrations of total phosphorus, dissolved phosphorus and total inorganic nitrogen in the water column decreased from west to east over the gradient corresponding with decreasing watershed development and size. However, high surface cover and nuisance levels of Cladophora biomass were found across the gradient, including the least developed study area where total phosphorus concentrations were similar to those in the open lake. The abundance of Dreissena, high in all areas, was measured concurrently with Cladophora biomass and correlated positively at depths of 6 to 10. m. External loading of phosphorus provides a basis for abatement of Cladophora; however, the influences of enrichment along the shoreline, internal loading at the lakebed and lake trophic status in sustaining growth remain obscure. Nuisance levels of Cladophora are not isolated to locations experiencing elevated external loading and should be viewed in the context of interacting area-specific and lake-wide nutrient supplies.
Selected oxidants (chlorine, chloramines, chlorine dioxide, and ozone) and coagulants and coagulant aids (alum, ferric chloride, and polydiallyl dimethyl ammonium chloride [polyDADMAC]) were evaluated as potential molluscicides for juvenile and adult quagga mussels using bench- and pilot-scale flow-through systems supplied with Colorado River water. The efficacy of each quagga mussel control measure was evaluated in terms of mortality rate, closure response, and dose response, if applicable. Chlorine, chloramines, chlorine dioxide, and ozone were found to be effective molluscicides. Alum and ferric chloride, at the moderate dosages studied, were not effective molluscicides. Although polyDADMAC alone was shown to be an effective molluscicide, combining alum and polyDADMAC resulted in no quagga mussel mortality.
Water soluble porphyrin, α, β, γ, δ-tetraphenylporphine-trisulfonate(TPPS), was found to be very useful agent for both the direct spectrophotometric determination and the photomeric titration of copper(II). The soret bands of TPPS and Cu-TPPS complex at pH 2.5 were at the wavelength of 434 nm (e=5.0×105) and at 413 nm(e=4.76×105), respectively. For the determination of copper, the wavelength of 434 nm was used and the sensitivity of the method was 0.00013 μg Cu2+·cm-2 for A=0.001. Beer's law was followed in the range 060 ng·ml-1. Among twenty-two metal ions examined, only zinc(II) seriously interfered with the determination. The selectivity of the method seems to be largely depend on the kinetic nature of the metal incorporation reaction of TPPS.The recomended procedure is to add 2.5 ml of 1 M acetate buffer solution(pH 4.0) and 5 ml of 1×10-5 M standard TPPS solution to an about 40 ml solution containing 0.33 μg of copper, followed by heating to boil for one minute and by cooling to room temperature, then to adjust pH to 2.5 with 1.5 ml of 1 M chloroacetic acid solution, to dilute to 50 ml and measure the absorbance(A) at 434 nm against water with 1 cm cells. Copper concentration is determined from the decrease in absorbance by complexation as follows: Cu(ng/ml)=130×(A0-A), where A0 is the absorbance of reagent blank.
Increase in water temperature from an ambient of 15 degrees C to 20 and 25 degrees C increased the respiration rate in zebra mussels, Dreissena polymorpha, by 50 and 175%, respectively, and increased the toxicity of copper; a 48-hour lethal concentration to kill 50% of the organisms (LC50) of 775 mu g/L at 20 degrees C decreased to 238 mu g/L at 25 degrees C, and a 96-hour LC50 of 487 mu g/L at 20 degrees C reduced to 107 mu g/L at 25 degrees C. The oxygen consumption rate in the presence of 150 mu g/L copper decreased by 16% at 20 degrees C and by 50% at 25 degrees C. Thus, high temperatures may increase the toxicity of copper, and possibly other metals, to zebra mussels. Similar increases in heavy metal toxicity may also accompany global warming, which is expected to raise surface water temperature by 2 to 3 degrees C. Such temperature and heavy metal combinations may also be useful in designing field trials to control this nuisance species.
Chlorination is a widely used method to combat zebra mussel fouling in industrial cooling water systems. However, there is paucity of information on the sublethal effects of low-level chlorination on the zebra mussels. The physiological behaviour (shell valve movement, filtration rate, foot activity index and byssus thread production) and the byssus thread strength of different size groups (between 5 and 20 mm shell length) of zebra mussel, Dreissena polymorpha (Pallas), were studied at different chlorine concentrations (0.1-1.0 mg l−1) in the laboratory. The results indicated that D. polymorpha was able to sense chlorine at levels as low as 0.1 mg l−1 and this significantly reduced their physiological activities (9%-18%). D. polymorpha also showed a progressive reduction in physiological activities when chlorine concentrations were increased from 0 to 0.5 mg l−1. However, no significant differences in physiological activities were observed between 0.5 and 1.0 mg l−1 chlorine residuals (e.g. 89% and 93% reduction in foot activity index at 0.5 and 1.0 mg l−1, respectively). Shell opening frequencies of D. polymorpha in control experiments (0 mg l−1 residual chlorine) were about 18 times higher than those at 0.5 mg l−1 residual chlorine. Continuous dosing of at least 0.5 mg l−1 residual chlorine was found to be required before shell opening was critically impaired. Therefore, 0.5 mg l−1 residual chlorine appears to be the minimum chlorine level to be dosed continuously, for the successful control of D. polymorpha. The resistance of D. polymorpha to chlorine appeared to be lower than that for other mussel species in The Netherlands viz. Mytilus edulis L. and Mytilopsis leucophaeata (Conrad).
Freshwater mussels are exceptionally sensitive to many contaminants including metals, but the mechanisms of toxicity are not fully understood. Similarly, our understanding of the protective effects of dissolved organic matter (DOM) is also undergoing revision, since recent studies have found that DOM may also directly affect organism physiology, in addition to its well known capability in complexing and reducing bioavailability of metals. In the present study, these issues were investigated in juvenile (6-12 months old) freshwater mussels (Lampsilis siliquoidea) in moderately-hard reconstituted water (Ca(2+)=0.406mmol/L; Mg(2+)=0.537mmol/L; Na(+)=1.261mmol/L;K(+)=0.077mmol/L; hardness=80-100mg/L CaCO3; pH=8.02 and DOM=0.3mgC/L). Mussels were acutely exposed (24 and 96h) to Cu (0, 2 or 12μgCu/L) combined with three concentrations (0, 3 or 6mgC/L) of DOM of terrigenous origin (Luther Marsh). We analyzed unidirectional Na(+) influx, whole-body ion content (Na(+), K(+), Ca(2+) and Mg(2+)), enzyme (Na(+)/K(+)-ATPase, H(+)-ATPase and carbonic anhydrase) activities, copper bioaccumulation and oxidative stress-related parameters. Exposure to DOM alone caused a marked increase in the unidirectional Na(+) influx rate and a decrease in v-type H(+)-ATPase activity, suggesting that DOM alone can cause alterations in membrane transport functions and therefore, whole-body Na(+) metabolism. Unidirectional Na(+) influx rate and Na(+)K(+)-ATPase activity were inhibited when mussels were exposed to the higher Cu concentration tested (12μg Cu/L). The influx inhibition was ameliorated by the simultaneous presence of DOM. At this same Cu concentration, DOM also significantly protected mussels against whole-body Na(+) and K(+) losses associated with Cu exposure, as well as against Cu bioaccumulation. Oxidative stress parameters did not show clear trends across treatments. Overall, our results indicate that Cu is a potent ionoregulatory toxicant to freshwater mussels. They also demonstrate that natural DOM protects against both Cu bioaccumulation and ionoregulatory toxicity, and that at least part of this protection results from direct positive effects of DOM on Na(+) metabolism.
Disinfection by-products (DBPs) have been regulated in finished drinking water for more than 25 years. This article, adapted from the Clarke Prize Lecture delivered by the author, analyzes several aspects related to the science and policy of DBP regulation and control and highlights deficiencies that are undermining public health protection. These deficiencies include limitations in the epidemiological studies that were conducted on the adverse health effects of DBPs and led to their regulation as well as shortcomings in the regulatory approach that the US Environmental Protection Agency has adhered to over the past quarter-century. In addition, water suppliers have been relatively shortsighted in their methods of controlling DBP formation and must look to long-term management and treatment methods. Drawing on his 31 years of research on the subject, the author has developed concrete suggestions for improving DBP health effects studies, regulatory approaches, and control strategies.
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.
Hypochlorite, permanganate, and peroxide with iron were compared for their effectiveness against adult zebra mussels (Dreissena polymorpha). The effects of hypochlorite and permanganate at applied concentrations of 0.5-2.5 mg/L were contrasted in continuous and intermittent 28-day static renewal tests. In addition, 0.5-10 mg free Cl₂/L, 0.5-2.5 mg KMnO₄/L, and 1-5 mg H₂O₂/L (with iron at 25 percent of the H₂O₂) were applied continuously for 28 or 56 days in flow-through systems. Permanganate was usually less effective than hypochlorite, and both were much more effective than the peroxide-iron combination. The data also indicated that intermittent treatments were ineffective (mussels avoided the chemical by closing up during treatments), that chlorine and permanganate were less toxic at lower temperatures, and that less chlorine was needed for a given kill when lower concentrations were applied. Se comprobó la efectividad del hipocloruro, permanganate, y peróxido con hierro en el control de las almejas cebra adultas (Dreissena polymorpha). Los efectos del hipocloruro y el permanganate a concentraciones de aplicación de 0.5 y 2.5 mg/L fueron comparadas en pruebas estáticas renovadoras en forma continua e intermitente por 28 días. Además, 0.5-10 mg de Cl₂ libre/L, 0.5-2.5 mg KMnO₄/L, y 1-5 mg H₂O₂/L (con hierro al 25 por ciento del H2O2) fueron aplicados en forma continua de 28 a 56 días en sistemas directos. El permanganate fue generalmente menos efectivo que el hipocloruro, y ambos fueron mucho más efectivos que la combinación de peróxido con hierro. Los datos indicaron que los tratamientos intermitentes fueron inefectivos (las almejas evitaron el producto químico cerrándose durante los tratamientos), que el cloro y el permanganate eran menos tóxicos a bajas temperaturas, y que se necesitaba menos cloro en un tratamiento dado cuando se usaban menos concentraciones.
Intuitively, cumulative and synergistic effects of combined biocides seem a promising avenue to explore in managing the biofouling zebra mussel. However, such an approach has not been comprehensively examined. In this study, the potential of a binary mixture of poly(diallyldimethyl ammonium chloride) and potassium chloride for zebra mussel control was investigated. The toxicity of the mixed biocides to both adults and veligers was evaluated in laboratory static bioassays. The combined toxicity of the chemicals was observed to depend on the life stage of the mussels. For adults, it was shown to vary with the magnitude of the response under consideration. When producing low lethal effects (below around 25% mortality), the chemicals acted synergistically on the mature organisms and tended to be additive, whilst at high mortality levels, they operated more than additively. In contrast, regardless of the response level under consideration, the toxins appeared to exert additive or less than additive effects on the veligers depending on the potassium chloride dosage. These results have direct practical implications for zebra mussel control. They suggest that the mixture under analysis is very promising for use in mitigation programmes targeted at adults, but its potential for use in proactive treatments to control veligers is not as definitive. The paper also includes a discussion on the contribution the ecotoxicological background on mixture toxicity may have to the development of combined chemical treatments for pest mitigation. Therefore, it may have further application in the setting of experimental protocols for designing control methods.
Zebra mussels (Dreissena polymorpha) invaded the Great Lakes in 1986 and are considered to be a nuisance species, because of their rapid population growth and their strong byssal attachment to a variety of man-made and natural surfaces. Research on possible antifouling materials or coatings has revealed few nontoxic substrates that even retard attachment of mussels. The influence of several substrate characteristics in combination (material, texture, orientation, and sunlight) on zebra mussel settlement was examined. Settlement of post-veliger mussels on experimental plates indicated that the mussels attached in higher numbers on upper versus lower horizontal surfaces, textured versus smooth surfaces, shaded versus sunlit surfaces, PVC versus Plexiglas, and plastic (PVC and Plexiglas) versus glass. Zebra mussels did not show strong preferences among several additional substrate materials (wood, Fiberglas, concrete, limestone, aluminum, and raw steel) but they strongly avoided galvanized steel. These results confirm field observations of locations in which mussels are most likely to be found. Information about zebra mussel substrate preferences may enhance the design of monitoring programs and the integrated management of mussels in vulnerable areas.
Zebra mussels (Dreissena polymorpha) invaded the Great Lakes in 1986 and are considered to be a nuisance species, because of their rapid population growth and their strong byssal attachment to a variety of man-made and natural surfaces. Research on possible antifouling materials or coatings has revealed few nontoxic substrates that even retard attachment of mussels. The influence of several substrate characteristics in combination (material, texture, orientation, and sunlight) on zebra mussel settlement was examined. Settlement of post-veliger mussels on experimental plates indicated that the mussels attached in higher numbers on upper versus lower horizontal surfaces, textured versus smooth surfaces, shaded versus sunlit surfaces, PVC versus Plexiglas, and plastic (PVC and Plexiglas) versus glass. Zebra mussels did not show strong preferences among several additional substrate materials (wood, Fiberglas, concrete, limestone, aluminum, and raw steel) but they strongly avoided galvanized steel. These results confirm field observations of locations in which mussels are most likely to be found. Information about zebra mussel substrate preferences may enhance the design of monitoring programs and the integrated management of mussels in vulnerable areas.
This paper reports that since introduction into the lower Great Lakes, the density of zebra mussels at Monroe Power Plant in western Lake Erie has increased dramatically. In fall 1988 densities in the intake canal were less than 50 per sq. meter but increased to over 700,000 per sq meter by fall 1989. Intake structures and associated equipment are covered by a layer of mussels 5-8 cm thick. High densities have fouled trash bars, main steam condensors, heat exchangers and low pressure service water systems. Blockage of main stream condensors is 10-20 percent with most of blockage caused by druses (clusters) that slough from intake structures. To minimize operational problems, hydroblasting has been used to remove mussels from the most vulnerable components.
While chemical control of zebra mussels (Dreissena polymorpha) has proven effective in closed systems, the high dosages required for adult eradication restricts the use of chemical-based strategies in field management plans. One option is to identify the most chemical-sensitive life stage and tailor management techniques to control that life stage. This would optimize target efficacy while minimizing chemical release into the environment, risk to non-target species, and cost of chemical required. In this study, the relative sensitivity of D. polymorpha life stages was investigated from free gametes to 72-h old trochophores and adults, using cupric sulfate (CuSO4) and the algaecide, Cutrine®-Ultra. In both forms of copper exposure, early life stages were orders of magnitude more sensitive than adults. For example, the highest 24-h LC50 value for the early life stages to Cutrine®-Ultra was 13 μg Cu/L, while the adult 48-h LC50 value was 1,214 μg Cu/L. Moreover, adults were highly resistant to short-term (24 h) exposures of Cutrine®-Ultra, even at much higher concentrations (4,630 μg Cu/L), while 24-h old D. polymorpha larvae showed 99% mortality after only 52 minutes of exposure to 331 μg Cu/L as Cutrine®-Ultra, a concentration well within the permitted label application. There were only marginal differences in sensitivity to CuSO4 and Cutrine®-Ultra for larvae tested after fertilization; it is possible that Cutrine®-Ultra is more toxic than CuSO4 at fertilization. Chemical management strategies targeting early larval stages of D. polymorpha are likely more cost-efficient and less prone to non-target environmental impact than strategies aimed at adults.
Chlorination is the most common antifouling procedure, but the search for alternatives is ongoing. Although concentrations that kill adults will also be effective against larvae, it is advisable to evaluate the toxicity of any candidate toxicant against the combatable life stage. For mussels, the earliest life stages are the most vulnerable ones and thus may require the lowest doses biocides. Since the period of larval presence is restricted to a couple of months, a pointed dosage of biocides during this period will be as effective as a continuous dosage throughout the year. This study reports on the lethal acute toxicity of sodium hypochlorite and peracetic acid to 4 h old embryos of Mytilopsis leucophaeata and Dreissena polymorpha. Chlorination was found effective against M. leucophaeata from a concentration of 0.6 mg/l onwards, even at short exposure times. Commercial peracetic acid showed to be a very good alternative in both species although the most appropriate level still has to be determined.
Mussel control in cooling water systems is generally achieved by means of chlorination. Chlorine is applied continuously or intermittently, depending on cost and discharge criteria. In this paper, we examined whether mussels will be able to survive intermittent chlorination because of their ability to close their valves during periods of chlorination. Experiments were carried out using three common species of mussels: a freshwater mussel, Dreissena polymorpha, a brackish water mussel, Mytilopsis leucophaeata and a marine mussel, Mytilus edulis. The mussels were subjected to continuous or intermittent (4 h chlorination followed by 4 h no chlorination) chlorination at concentrations varying from 1 to 3 mg l(-1) and their responses (lethal and sublethal) were compared to those of control mussels. In addition, shell valve activity of mussels was monitored using a Mussel-monitor. Data clearly indicate that mussels shut their valves as soon as chlorine is detected in the environment and open only after chlorine dosing is stopped. However, under continuous chlorination mussels are constrained to keep the shell valves shut continuously. The mussels subjected to continuous chlorination at 1 mg l(-1) showed 100% mortality after 588 h (D. polymorpha), 966 h (Mytilus edulis) and 1104 h (Mytilopsis leucophaeata), while those subjected to intermittent chlorination at 1 mg l(-1) showed very little or no mortality during the same periods. Filtration rate, foot activity index and shell valve movement of D. polymorpha, Mytilopsis leucophaeata and Mytilus edulis decreased more than 90% at 1 mg l(-1) chlorine residual when compared to control. However, mussels subjected to intermittent chlorination showed a similar reduction (about 90%) in filtration rate, foot activity index and shell valve movement during chlorination and 3% during breaks in chlorination. The data indicate that intermittent chlorination between 1 and 3 mg l(-1) applied at 4 h on and 4 h off cycle is unlikely to control biofouling if mussels are the dominant fouling organisms.
This study concerns a chronic copper release in an aquatic ecosystem: Mirgenbach reservoir; which is characterized by high salinity, conductivity and hardness, a eutrophic state and a high temperature. To study the bioavailability of copper in the biotic compartments, the sampling covered the entire food chain (phyto- and zooplankton, macroalgae, aquatic plants, crustaceans, mollusks, and fish). Of the organisms present, the filter feeder Dreissena polymorpha, the detritivorous Bithynia tentaculata and Orconectes limosus were most contaminated by copper. The level of copper found in fish was the lowest. Body copper concentrations recorded in the present study show large variability between species even in some that are closely related. In most cases, however, the metal handling strategy, feeding habits, morphology and ecology can, at least partially, explain the metal content recorded. Pollution factors have been used to assess the state of contamination of the food chain. This study showed finally that the copper in the lake is bioavailable and bioaccumulated by organisms up to high levels and some effects of long-term toxicity of copper on benthic community and planktonic biomass were pointed out.
The overall objective of this study was to investigate the impact of blending membrane-treated water treatment plant (WTP) residuals with plant-filtered water on finished water quality in terms of biostability and disinfectant by-product (DBP) formation. Filter backwash water (FBWW) was treated with a pilot-scale ultrafiltration (UF) membrane to produce permeate that was blended with plant-finished water. The batch studies involved storing samples for a specified time with a disinfectant residual to simulate residence time in the distribution system. Both chlorinated and non-chlorinated FBWW streams were evaluated, and the experimental design incorporated free chlorine, monochloramine, and chlorine dioxide in parallel to a model system that did not receive a disinfectant dose. The results of the study found that blending 10% UF-treated FBWW with plant-filtered water did not have an impact on water biostability as monitored with heterotrophic plate counts (HPCs) or DBP concentrations as monitored by TTHM and HAA5 concentrations. However, the presence of preformed THM and HAA species found in chlorinated FBWW streams may result in higher levels of initial DBP concentrations in blended water matrices, and could have a significant impact on finished water quality in terms of meeting specific DBP guidelines or regulations.
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