Abstract
The risk of quagga mussel (Dreissena rostriformis bugensis Andrusov 1897) establishment into water-bodies of the western US has expanded the geographic concern regarding the ecological and economic impacts this species will have in aquatic ecosystems. Thresholds based on calcium concentrations, an element critical for mussel growth and physiology, have been used as a primary predictor of quagga mussel establishment success to aid management decisions. We evaluated the invasion potential of quagga mussels in low calcium waters using laboratory experiments to compare the survival, growth and reproductive potential of adult mussels held for 90 days at low (9 and 12 ppm), moderate (15 to 32 ppm) and high (72 ppm) calcium water concentrations. In conjunction with adult experiments, veliger stage survival, growth and settlement were evaluated under similar low, moderate, and high calcium water treatments. Adult mussels survived, grew and showed reproductive potential in low calcium water (12 ppm). Veligers were also able to survive, grow and settle in low calcium water. Higher levels of natural seston biomass appeared to improve adult mussel life history performance in low calcium water. Survival curve analysis predicted that 99% adult mortality could occur in <170 days at 9 ppm and 12 ppm, however water with >15 ppm could have adults surviving more than a year. The results from these bioassays provide further evidence that quagga mussels have higher risk of establishment in low calcium lakes if habitats exist that have slightly elevated calcium. These results should help emphasize the vulnerability of water-body in the 12 to 15 ppm calcium range that could potentially be at risk of establishing sustainable quagga mussel populations. Furthermore, these results provide insights into the uncertainty of using a single parameter in assigning establishment risk given the complexity of variables in specific water-bodies that influence life history performance of introduced species.
Highlights
The establishment and spread of dreissenid mussels exemplifies how disruptive invasive species can be via ecological impacts to foodwebs (Strayer, Hattala & Kahnle, 2004), nutrient cycling (Hecky et al, 2004) and biodiversity (Karatayev, Burlakova & Padilla, 1997)
Observational studies attribute the establishment of dreissenids in low calcium water-bodies to localized “hotspots” of calcium and, in many cases, appear to have extremely limited recruitment success (Lake George, Wimbush et al, 2009) or are sink populations that are dependent on larval production outside of the system (e.g., Illinois River, Schneider et al, 2003)
Lakes and reservoirs in the western United States that are near source mussel populations such as Lake Mead are more vulnerable to establishment than previously expected if calcium tolerance as the limiting factor is solely considered
Summary
The establishment and spread of dreissenid mussels exemplifies how disruptive invasive species can be via ecological impacts to foodwebs (Strayer, Hattala & Kahnle, 2004), nutrient cycling (Hecky et al, 2004) and biodiversity (Karatayev, Burlakova & Padilla, 1997). Information used to forecast dreissenid establishment in the western United States is based largely on knowledge developed during the dreissenid expansion in the Great Lakes Basin and Europe (Mackie & Claudi, 2013) It is uncertain how well the synthesis of these regional dreissenid studies that are largely based on zebra mussel ecology, applies to water-bodies of the western United States that are recently at risk of quagga mussels invasion. Observational studies attribute the establishment of dreissenids in low calcium water-bodies to localized “hotspots” of calcium (e.g., concrete boat ramps and piers, river inflows, groundwater) and, in many cases, appear to have extremely limited recruitment success (Lake George, Wimbush et al, 2009) or are sink populations that are dependent on larval production outside of the system (e.g., Illinois River, Schneider et al, 2003)
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