Current research on the environmental impact of Nasturtium officinale in the Great Lakes is inadequate to support proper assessment.
Realized:
Nasturtium officinale can hybridize with N. microphyllum Boenn. ex Rchb, another invasive found in the Great Lakes, to produce the hybrid N. X sterile (Airy Shaw) Oefelein (Bleeker et al. 1999). However, this hybrid only produces viable seeds when the female parent is N. mircophyllum (Howard and Lyon 1952). The sterile hybrid can still propagate and expand vegetatively (Reznicek et al. 2011). Observations in Germany found that N. x sterile is more rigorous and is quicker at establishing itself from cuttings than either parent species (Bleeker et al. 1999). Nasturtium X sterile individuals have been found in Wisconsin (Robert W. Freckman Herbarium 2012). Newman et al. (1992) found that watercress produces a chemical defense that deters generalist feeders such as the amphipod Gammarus pseudolimnaeus, the caddisflies Hesperophylax designates and Limnephilus spp., and the physid snail Physella spp. (Newman et al. 1992).
Potential:
Nasturtium officinale can host the Spongospora subterranea (crook root fungus) and yellow spot virus (Walsh and Phelps 1991). Cabbage black-ringspot versus and the cucumber mosaic virus has been found on cultivated populations of Nasturtium officinale (Howard and Lyon 1952).
Watercress is able to take up large amounts of nitrate from water bodies it lives in. The nitrogen is released when the plants die and decompose; however, if the plants are removed (as is the goal with most invasive species) this could alter the amount of nitrogen available (Howard-Williams et al. 1982).
Watercress can grow into large mats in slow parts of streams, typically in the bends and curves of the steam’s path. If populations get big enough, they could contribute significantly to the meanders of the stream (Kullberg 1974). However, Benson et al. (2004) found that this species causes minimal impact on natural communities in the Northwest region of the United States (Benson et al. 2004).
There is little or no evidence to support that Nasturtium officinale has significant socio-economic impacts in the Great Lakes.
Potential:
Nasturtium officinale can host the crook root fungus, yellow spot virus, cabbage black-ringspot virus, and the cucumber mosaic virus (Howard and Lyon 1952, Walsh and Phelps 1991). If watercress is growing near cultivated lands, these viruses could infect and damage crops.
Watercress can also host Fasciola hepatica, common liver fluke (CDC 2013). People can become infected by eating raw watercress contaminated with fluke larvae (CDC 2013).
Nasturtium officinale has a moderate beneficial effect in the Great Lakes.
Realized:
Nasturtium officinale can be eaten raw, has high concentrations of vitamins and minerals, and has a peppery flavor (Benson et al. 2004, Robert W. Freckman Herbarium 2012, State of Washington 2013). This species is harvested recreationally and grown commercially in the United States (CANSWP 2006, State of Washington 2013). People can become infected by eating raw watercress contaminated with fluke larvae (CDC 2013).
Watercress has been used an herbal remedy for a variety of ailments: common cold; sore throat; earache; improve heart, kidney, and respiration health; the juice has been used to heal skin sores and acne (Robert W. Freckman Herbarium 2012).
Potential:
Nasturtium officinale has potent anti-oxidative properties and may have applications in the prevention of free radical-related diseases (Bahramikia and Yazdanparast 2010). Gill et al. (2007) found that consumption of watercress may lead to decreased damage to DNA and increased carotenoid concentrations; ultimately reducing the risk of cancer.
In test sites monitored by Redding et al. (1997), N. officinale was able to significantly reduce the concentrations of ammonia-N, nitrate-N and phosphorus in the wastewater. Effective treatment was dependent on harvesting the plant biomass (Redding et al. 1997). Nasturtium officinale is able to withstand the stress and accumulate moderate amounts of arsenic, nickel, and lead (Duman and Ozturk 2010, Keser and Saygideger 2010, Ozturk et al. 2010). A year after the closure of a paper mill on a stream in Michigan, this species was one of a few found growing downstream of the polluted site (Kullberg 1974). This ability to take up nutrients and contaminants make N. officinale a possible candidate for use in phytoremediation or wastewater treatment operations.
In Washington, watercress was reportedly eaten by ducks, muskrats and deer (Robert W. Freckman Herbarium 2012).