Potamopyrgus antipodarum has a moderate environmental impact in the Great Lakes.
Potential:
This species has a high reproductive capacity and a wide tolerance of abiotic conditions, increasing the potential for populations to grow and be widely-distributed (Alonso and Castro-Diez 2008). It is likely to find all shallower waters (<50 m depth) as suitable habitat (USEPA 2008). Potamopyrgus antipodarum has yet to colonize streams in the Great Lakes basin, but these are the habitats in which the snail is expected to exert significant impacts (Levri et al. 2007). Due to its ability to colonize empty spaces and habitats in early successional phases, P. antipodarum may also have greater invasion success in disturbed areas; however, its impacts are not limited to these types of systems (Alonso and Castro-Diez 2008).
Abundant populations of introduced P. antipodarum may outcompete other grazers for food resources and inhibit colonization by other macroinvertebrates and native snails (Kerans et al. 2005). Thus far, research efforts focused on interactions between P. antipodarum and native invertebrates have yielded mixed results, from commensalism to competition (Brenneis et al. 2010). In one Australian stream, increasing densities of P. antipodarum were positively correlated with density and species richness of native invertebrates, possibly due to coprophagy (ingestion of the snail's feces) (Schreiber et al. 2002). However, in Europe, P. antipodarum has caused declines in species richness and abundance of native snails in constructed ponds (Strzelec 2005).
A colonization experiment in Yellowstone National Park found a negative relationship between the abundance of P. antipodarum colonizers and native macroinvertebrate colonizers on stone tiles placed in several rivers, suggesting that P. antipodarum may interfere with the colonization activity of native species (Kerans et al. 2005). However, across sites, Kerans et al. (2005) did not find significant negative correlations between the densities of P. antipodarum and native macroinvertebrate densities, and overall impacts in this area remain largely unknown.
Brenneis et al. (2010) used field surveys, stable isotope analysis, and a laboratory experiment to analyze the extent of competition between P. antipodarum and native benthic invertebrates in the Columbia River Estuary. The authors found that while P. antipodarum was among one of the most abundant invertebrates, its abundance was also positively correlated with other native invertebrates (Brenneis et al. 2010). Stable isotope analysis indicated that the diet of P. antipodarum overlaps with the diets of coexisting invertebrates; however, the authors also found that P. antipodarum foraging was decreased in the presence of native Gnorimosphaeroma insulare, while foraging of G. insulare was unaffected by interspecific competition. Intraspecific competition had a stronger effect than interspecific competition for both species (Brenneis et al. 2010).
Cross et al. (2010) did not detect any impact on native species biomass following the invasion of P. antiodarum in Glen Canyon of the Colorado River. In contrast, field surveys below the Flaming Gorge Dam, documented an overall decrease in total invertebrate abundance following P. antipodarum invasion (Vinson et al. 2007). Interestingly, some invertebrate groups that were not affected by P. antipodarum overall were reduced in the presence of P. antipodarum in certain habitats (e.g., amphipods in eddies and mayflies in runs/riffles) (Vinson et al. 2007). In an enclosure competition experiment in Branbury Springs, ID, Richards (2004) found that resource-related competitive interactions likely have adverse effects on growth rates of a threatened native snail, Taylorconcha serpenticola, at P. antipodarum densities above 4,000 m-2. Riley et al. (2008) also found that P. antipodarum was a superior competitor to a native snail Pyrgulopsis robusta in Yellowstone National Park, documenting a negative correlation between their growth rates. Interestingly, analysis indicated that both species consumed similar amounts of algal resources, discrediting resource acquisition ability as a mechanism for interspecific competition. The authors suggest that adverse impacts on P. robusta could stem from lower maintenance costs or more efficient resource conversion within P. antipodarum (Riley et al. 2008).
Potamopyrgus antipodarum may have an impact on higher trophic levels of the food web. While P. antipodarum has been documented as a food source for Chinook salmon (Oncorhynchus tshawytscha; Bersine et al. 2008), brown trout (Salmo trutta; Vinson et al. 2007), and rainbow trout (Oncorhynchus mykiss), its lack of digestibility could be detrimental to its predators (Vinson and Baker 2008). Vinson and Baker (2008) found that 53.8% of New Zealand mudsnails passed through the digestive system of rainbow trout alive, with only 8.5% of snails estimated to have been fully digested. Furthermore, rainbow trout that were fed on a diet of P. antipodarum lost 0.14–0.48% of their initial weight per day. Unsuitability of P. anitopodarum as a food source and its potential competitive effects within lower trophic levels may affect food availability and alter food web processes in invaded systems (Kerans et al. 2005).
Potamopyrgus antipodarum is capable of serving as a host for a number of trematode parasites, although the extent of occurrence and consequences in its nonindigenous range is largely unknown (see Morley 2008).
A study by Arango et al. (2009) found that P. antipodarum altered periphyton community composition over a short time period by selective feeding. The study also suggested that by selectively grazing on non-nitrogen-fixing components of the algal assembly, P. antipodarum was able to increase nitrogen fixation in a high-productivity stream. In geothermal streams of the western U.S., P. antipodarum can reach densities of 300,000 snails/m2 and has been shown to alter nutrient (nitrogen and carbon) flows, consume a large portion of daily gross primary production (GPP), and account for most of the invertebrate production (Hall et al. 2003, Hall et al. 2006). For instance, Hall et al. (2006) found that P. antipodarum production accounted for 65–92% of invertebrate production within three geothermal streams. In one of these streams, the authors documented a biomass production rate of 194 gm-2 yr-1—among the greatest reported for any stream benthic invertebrates, and much higher than the observed production rate of natives (4.4-5.1 gm-2 yr-1) (Hall et al. 2006). Potamopyrgus antipodarum also appeared to play a large role in nitrogen cycling through extensive ammonium excretion (Hall et al. 2006). Although the authors suggest that P. antipodarum impact has been high in this area, comparably severe consequences are not yet widely reported, and may be partially attributed to this system’s particular hydrology, temperature, and productivity (Hall et al. 2006).
Current research on the socio-economic impact of Potamopyrgus antipodarum in the Great Lakes is inadequate to support proper assessment.
Potential:
Densities have reached 500,000 individuals per square meter in a Snake River tributary of Idaho (Richards et al. 2001); a species this prolific has potential to be a biofouler at facilities drawing from infested waters. Historically, P. antipodarum has both blocked and been distributed through water pipes in Australia (Ponder 1988).
If P. antipodarum has adverse impacts on food web interactions in invaded ecosystems (see above), it is possible that certain recreationally or commercially valuable species such as rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) could be negatively impacted at high snail densities (NZMWG 2007).
There is little or no evidence to support that Potamopyrgus antipodarum has significant beneficial effects in the Great Lakes.
Potential:
Partially due to their relatively high tolerance of environmental stressors, P. antipodarum is often used as a research organism to test novel experimental/analytical techniques (e.g., Myrick 2009, Schmitt et al. 2010a) or to test the physiological effects of toxic chemicals an aquatic fauna—particularly effects on the endocrine system (e.g., Alonso and Camargo 2009, Gust et al. 2009, Schmitt et al. 2010b)