Evaluating high pH for control of dreissenid mussels

Abstract

Two field experiments were carried out using a custom built flow-through laboratory to test the effect of elevated pH on dreissenid musselsas a potential control method. Both experiments tested the ability of dreissenid pediveligers to settle under conditions of elevated pH and thelong-term survival of adult dreissenids under the same conditions. The two experimental sites had different water quality and differentspecies 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 precipitateformed under high pH conditions rather than the increase in background pH. No mortality of quagga mussel adults was observed in theexperimental pH levels at the lower Colorado River. At San Justo Reservoir, zebra mussel settlement decreased with increasing pH. Newsettlement was almost entirely absent at the highest pH tested (pH 9.6). The observed mortality of adult zebra mussels was low, but did tendto 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 ofseason treatment to eliminate adults. The high pH treatment would have to be tailored to the site water quality to prevent formation ofprecipitate during treatment and to minimize corrosive action on materials of construction

Evaluation of Passive Treatment Technologies for Septic Lagoon Capacity Expansion

“…Changes in wastewater constituents during the course of Trial 2 are illustrated in Figure 5-6. The results for DO and pH are shown in Figure 5-7 and were found to be consistent with those observed during Trial 1, where levels remained fairly constant and within the range optimal for zebra mussel viability, even at the time of zebra mussel death (Karatayev et al, 1998;Claudi et al, 2012). From Figure 5-6 it can be seen that the zebra mussels could reduce wastewater constituents from a 1:1 dilution of secondary wastewater.…”

“…and an optimum pH range of 7.3 to 9.3. (Karatayev et al, 1998;Claudi et al, 2012). As such, the DO concentrations and pH levels were considered to be within the optimal ranges required for zebra mussel viability in typical freshwater environments.…”

“…Zebra mussels have an optimum pH range of about 7.3 to 9.3 , with some studies noting an upper pH limit of zebra mussel tolerance of 9.3 to 9.6 (Bowman and Bailey, 1998). Another study investigating the lower pH limits of zebra mussels observed significant mortality of zebra mussels only at pH levels below 6.9, and only after having been exposed to this pH for a period of 10 weeks (Claudi et al, 2012). This suggests that zebra mussels should be able to survive at pH ranges of 7.0 to 9.6.…”

Temperature‐Related Responses of an Invasive Mussel and 2 Unionid Mussels to Elevated Carbon Dioxide

“…Carbon dioxide also inhibits byssal thread production (McMahon et al 1995;Payne et al 1998; and could prevent settlement of translocators and early life stages. Veliger settlement is reduced in water with pH <7.0 (Claudi et al 2012a(Claudi et al , 2012b, which we achieved with 20 atm PCO 2 at 20°C. Low-level, intermittent infusion of CO 2 could be an effective tool to prevent biofouling and new settlement of dreissenid mussels.…”

“…The resulting model predicted high mussel mortality (>80%) in a pH range of 6.5 to 8.0 when [Ca 2+ ] was <25 mg L −1 . Conductivity influenced the toxicity of potassium chloride (Moffitt et al 2016) and phosphoric acid (Claudi et al 2012b) to dreissenids and could likewise alter CO 2 toxicity. Claudi et al (2012b) reported approximately 40% mortality of adult quagga mussels after 10-wk exposure to pH 6.9 in lake water with conductivity of 300 to 360 µS cm −1 ; in a follow-up study, adult zebra mussel mortality was minimal after 8-wk exposure to a similar pH in water with 2-fold greater conductivity (613 µS cm −1 ).…”