Economic and Environmental Damages

 

Many of the potential impacts of dreissenids are unclear due to the limited time scale of North American colonization (Benson et al. 2017), however because they are polymorphic and rapidly adapt to extreme environmental conditions, dreissenids have potential significant long-term impacts to North American waters (Mills et al. 1996). Establishment of dreissenid mussels in the Columbia River Basin (CRB) would be expensive, requiring extensive maintenance to the nuclear power plant and hydroelectric dams, fish ladders, fish bypass facilities, navigation locks, and irrigation pumping. In an economic impact report prepared for Bonneville Power Administration, the one-time cost to install mussel treatment systems was estimated at more than $23 million dollars and annual costs were estimated at $1.5 million (Independent Economic Analysis Board 2010). Because of the high value of fishery and aquatic resources in the CRB, and because no controls exist for mussels in open natural systems, the ecological costs of a CRB invasion could be much larger than other costs (Independent Economic Analysis Board 2013).

 

Flow restriction—Dreissenid mussels can cause substantial economic damage by infesting municipal, industrial, and agricultural water systems and attaching themselves to the substrates of pipes, dams, and diversion pathways. This restricts the flow of water through the systems, impacting component service life, system performance, and maintenance activities. The annual cost to power plants and municipal drinking water systems in North America has been estimated between $267 million and $1 billion dollars (Pimental 2005; Connelly et al. 2007).

 

Drinking water intakes—Mussels foul intake piping and water processing infrastructure, increasing maintenance costs and degrading water flavor due to mussel waste and decomposition in water lines (National Invasive Species Advisory Committee 2016). O’Neill (1997) estimated an annual cost of $4.2 million to address projected mussel infestations in 100 Idaho water treatment facilities ($42,000 per facility). Zebra mussel densities were as high as 700,000/square meter at one power plant in Michigan, and the diameters of pipes have been reduced by two-thirds at water treatment facilities (Benson et al. 2017). 

 

Irrigation—–The total economic impact on irrigation facilities is influenced by the number of points of diversion; each point of diversion or point of use could potentially be affected by dreissenids (National Invasive Species Advisory Council 2016). Mussels can foul water conveyances that are seasonally dry, and fouling and shell production from mussel establishment is cumulative (National Invasive Species Advisory Council 2016). Although mussel establishment in pipes and pumps is well documented, research on mussel-related flow reduction in irrigation systems is minimal.

 

Ecological function—Once established, dreissenid mussels can dramatically alter the ecology of a water body and associated fish and wildlife populations. As filter feeders, they 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 concentrations during the 12 years following invasion by dreissenids (Baranowska et al. 2013).

 

Native mussels are significantly threatened by the presence of invasive mussels. 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. Increased water clarity increases light penetration and causes growth in aquatic plants. 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).

 

Boating facilities—Marinas, docks, and boat launches experience increased costs from dock and boat launch fouling and infrastructure deterioration (O’Neill 1997).

 

Fish hatcheries and aquaculture—Hatchery and aquaculture facilities are vulnerable to dreissenid fouling, including pipes, pumps, and raceway structures (O’Neill 1997). Invasive mussels have the potential to disrupt operations at fish hatcheries (Stephenson and Koger 2011). Seasonal stocking of fish from a contaminated facility poses a risk to any water receiving these fish (Stephenson and Koger 2011).

 

Boater costs—Boaters experience increased costs estimated at $265 per boat (Vilaplana and Hushak 1994) for anti-fouling paints and per-boat maintenance costs and permit fees. Recreational and navigational vessels can be affected by increased drag associated with attached mussels, and small mussels can enter engine cooling systems, causing overheating and damage (Benson et al. 2017).

 

Recreational fishing—To date, research on the impacts of mussels to recreational fishing is limited, however, Vilaplana and Hushak (1994) documented a four percent decrease in boater recreation because of mussel introduction. Fishing gear can be fouled if left in the water for long periods (Benson et al. 2017).