Invasive Crayfish Threaten the Development of Submerged Macrophytes in Lake Restoration

Abstract

Submerged macrophytes enhance water transparency and aquatic biodiversity in shallow water ecosystems. Therefore, the return of submerged macrophytes is the target of many lake restoration projects. However, at present, north-western European aquatic ecosystems are increasingly invaded by omnivorous exotic crayfish. We hypothesize that invasive crayfish pose a novel constraint on the regeneration of submerged macrophytes in restored lakes and may jeopardize restoration efforts. We experimentally investigated whether the invasive crayfish (Procambarus clarkii Girard) affects submerged macrophyte development in a Dutch peat lake where these crayfish are expanding rapidly. Seemingly favourable abiotic conditions for macrophyte growth existed in two 0.5 ha lake enclosures, which provided shelter and reduced turbidity, and in one lake enclosure iron was added to reduce internal nutrient loading, but macrophytes did not emerge. We transplanted three submerged macrophyte species in a full factorial exclosure experiment, where we separated the effect of crayfish from large vertebrates using different mesh sizes combined with a caging treatment stocked with crayfish only. The three transplanted macrophytes grew rapidly when protected from grazing in both lake enclosures, demonstrating that abiotic conditions for growth were suitable. Crayfish strongly reduced biomass and survival of all three macrophyte species while waterfowl and fish had no additive effects. Gut contents showed that crayfish were mostly carnivorous, but also consumed macrophytes. We show that P. clarkii strongly inhibit macrophyte development once favourable abiotic conditions for macrophyte growth are restored. Therefore, expansion of invasive crayfish poses a novel threat to the restoration of shallow water bodies in north-western Europe. Prevention of introduction and spread of crayfish is urgent, as management of invasive crayfish populations is very difficult.

Influence of inlet water on the biotic and abiotic variables in a fish pond

“…In fact, they absorb excessive loads of water nutrients and function as biological filters (Van der Wal et al, 2013). According to Travaini-Lima et al (2015), macrophytes in constructed wetland system contributes towards removal of heavy metals from waste water in farm ponds of subtropical regions, mainly free floating species.…”

First Scientific Records of the Invasive Red Swamp Crayfish, Procambarus clarkii (Girard, 1852) (Crustacea: Cambaridae) in Malta, a Threat to Fragile Freshwater Habitats

“…Moreover, it cannot be excluded that these crayfish might be carriers of exotic microorganisms, such as Aphanomyces astaci (Dieguez-Uribeondo et al, 1995;Aquiloni et al, 2011), spreading it to other crustaceans (Svoboda et al, 2014). In other freshwater systems throughout Europe this species has been found to drastically reduce the biomass and survival of establishing macrophytes (van der Wal et al, 2013) and macroinvertebrates (Garcia et al, 2015). While other recent research in Italy has found that some microfungal flora species living in its gut are potential phytopathogenic, making P. clarkii a potential vector of plant diseases (Garzoli et al, 2014), further increasing the risk to local biodiversity especially in an ecologically important Tree Protected Area, such as at Fiddien Valley (Government Notice 473, 2011).…”

Towards a mechanistic understanding of individual‐level functional responses: Invasive crayfish as model organisms

“…Feeding rates (this study) and boldness (Linzmaier et al, 2018) differed for male and female spiny-cheek crayfish. Usio and Townsend (2002) found that male Paranephrops zealandicus had higher feeding rates than females when feeding on leaf litter. Food conversion is usually the same for both sexes (Rodgers, Saoud, & Rouse, 2006).…”

“…cheek crayfish (using a pair of 10-sided dice), as consumption is generally assumed to be independent of sex (Usio & Townsend, 2002).…”