Dreissenid Environmental, Economic, and Cultural Effects
The economic costs associated with dreissenids are significant. The economic impact of zebra and quagga mussels to the hydropower systems on the Columbia and Snake Rivers is of particular concern. If introduced into the CRB, dreissenid mussels could affect all submerged components and conduits of this system, including fish passage facilities, navigation locks, raw water distribution systems for turbine cooling, fire suppression and irrigation, trash racks, diffuser gratings, and drains.
The following studies are examples of documented and estimated costs of a dreissenid introduction:
The infestation of zebra mussels in the Great Lakes has cost the power industry $3.1 billion between 1993–1999, including a total economic impact of more than $5 billion (WRP 2009). The power generation industry in the Great Lakes expends $1.2 million annually per power plant to monitor and control zebra mussels, and $1.7 million annually to research better zebra mussel control methods. Water treatment plants pay $480,000–$540,000 annually to control zebra mussels, and municipal water treatment facilities pay $353,000 annually to control zebra mussels (Colautti et al. 2006).
In the Lower Colorado River, the Hoover Dam has incurred, or planned, costs totalling $10,231,208 for construction, supplies, services, and operations and maintenance to address dreissenid mussel infestations since invasive mussels were first discovered in 2007 (Bureau of Reclamation 2016).
Annual welfare losses (i.e., costs or loss of benefits) of a dreissenid invasion in the CRB is estimated at $64 million, although that estimate did not include losses related to fish and wildlife resources (Warziniack et al. 2011).
The direct economic impacts (impacts to dams, removal from boat launches, direct impacts to fishing) of invasive mussels to the State of Washington is estimated to be $43,112,000. Total economic activity at risk is 500 lost jobs and $27.8 million in labor income (Community Attributes, Inc. 2017).
Idaho estimated an infestation of zebra mussels would cost the state $94,474,000 to hydropower facilities, other dams, drinking water systems, golf courses, boat facilities and maintenance, hatcheries and aquaculture industries, loss of angler days, and irrigation (Idaho Aquatic Nuisance Species Task Force 2009).
A recent economic study commissioned by the Montana Invasive Species Council (Nelson 2019) estimated that if dreissenid mussels were to colonize all water bodies in Montana, the potential economic damages would total between $72.4 to $121.9 million in mitigation costs, $23.9 to $112.1 million in lost revenue, and $288.5 to $497.4 million in property value losses. Excluding property value losses, the top three stakeholder industries facing the largest potential economic impacts from dreissenid mussel invasion were tourism, hydropower, and irrigation, accounting for 60 to 75 percent of the total potential damages statewide (Nelson 2019).
The environmental impacts of zebra and quagga mussels to lakes and rivers is profound. Both species compete effectively with many native species and may completely replace native mussels, causing dramatic alterations of the native food chain (Hogan et al. 2007). The introduction of zebra and quagga mussels into the CRB, which drains 258,500 square miles in seven western states and Canada, has the potential to threaten native species, particularly salmon and trout and essential fish habitat (Pacific Fishery Management Council 2014), as well as cultural, industrial, agricultural, recreational, navigation, and subsistence use of waters.
Once established, dreissenid mussels can dramatically alter the ecology of a water body and associated fish and wildlife populations. As filter feeders, they selectively remove phytoplankton and other particles from the water column, shifting production from the pelagic to the benthic portion (Sousa et al. 2009). In Lake Michigan, dreissenid invasions have caused significant phytoplankton community structure shifts, including dominance in cyanobacteria (deStasio et al. 2014). In Lake Simcoe, Ontario, Canada, there were significant and sustained declines in phytoplankton biovolumes and chlorophyll a during the 12 years following invasion by dreissenids (Baranowska et al. 2013).
Dreissenids have accelerated the decline of freshwater bivalves, nearly extirpating native unionids 25 years after invasive mussels were introduced to the Great Lakes region (Burlakova et al. 2014). By attaching themselves to the surfaces of other bivalves, dreissenid mussels can starve freshwater mussels and drive indigenous populations to local extinction (Montgomery and Wells 2010). Dreissenid mussels can also affect dissolved oxygen through respiration, and dissolved calcium carbonate concentrations through shell building (Strayer 2009). The filtering capabilities of dreissenids increase water transparency, decrease chlorophyll concentrations, and increase the amount of pseudofeces (Claxton et al. 1998). Increases in pseudofeces reduce oxygen levels, which makes water pH more acidic and toxic (Snyder et al. 1997). Increased water clarity increases light penetration and causes growth in aquatic plants (Zhu et al. 2006). Dreissenids also bioaccumulate pollutants, which can be passed up the food chain, increasing wildlife exposure to organic pollutants (Snyder et al. 1997). Polychlorinated biphenyl (PCB) concentrations in mussel tissue are correlated to sediment PCB levels, indicating mussels may provide an entry point for PCBs into nearshore benthic food webs (Macksasitorn et al. 2015).
Maintaining biocultural diversity and cultural resilience depends on continued access to culturally salient native biota (Pfeiffer and Ortiz 2007). Community members face challenges retaining, or reviving, their ancestral traditions when invasive species diminish cultural access (Pfeiffer and Voeks 2008). When invasive species displace culturally important native species, cultural storyscapes (i.e., the place-based intergenerational narrative maintained by a native society, which incorporates both tangible and intangible traditions) are affected by altering the character of sacred, or ritual sites, and displacing, or diminishing the growth of ethnobiologically important native species in ancestral gathering sites (Pfeiffer and Voeks 2008).
Invasive species also have indirect effects on culture, such as affecting human health and well-being through the use of toxic chemicals to mitigate biological invasions (Mackenzie 2003).
Culturally important native aquatic species have been displaced or reduced through the introduction of non-native species for recreational fishing, negatively impacting indigenous groups reliant on wild harvest of these species (Pfeiffer and Voeks 2008). Escaped farmed Atlantic salmon (Salmo salar) threaten wild salmonids in the Pacific Northwest, where native salmon are of significant cultural and spiritual importance to tribes (Pfeiffer and Voeks 2008). Invasive European green crab (Carcinus maenas) are displacing native marine and freshwater mussels, impacting tribes that harvest these native species for ornamental and ceremonial ware (Pfeiffer and Voeks 2008).
The most significant effects of invasive species have been introduced diseases that have produced catastrophic reductions in population and associated social breakdown in the Americas (Mitchell 2003) to cultural disorientation in Australia (Carey and Roberts 2002).
Invasive species create changes in narratives and lexicons, causing native peoples to designate invasive species based on their place, or culture, of origin (Pfeiffer and Voeks 2008). Some invasive species that displace culturally important native species either serve to facilitate, or impoverish, culture (Pfeiffer and Voeks 2008).
Cultural attachment to, and acceptance of, invasive species can perpetuate invasive species spread and introduction (Pfeiffer and Voeks 2008).