The Beauty is a beast: Does leachate from the invasive terrestrial plant Impatiens glandulifera affect aquatic food webs?

Abstract

Invasive alien species are a major threat to ecosystems. Invasive terrestrial plants can produce allelochemicals which suppress native terrestrial biodiversity. However, it is not known if leached allelochemicals from invasive plants growing in riparian zones, such as Impatiens glandulifera , also affect freshwater ecosystems. We used mesocosms and laboratory experiments to test the impact of I. glandulifera on a simplified freshwater food web. Our mesocosm experiments show that leachate from I. glandulifera significantly reduced population growth rate of the water flea Daphnia magna and the green alga Acutodesmus obliquus , both keystone species of lakes and ponds. Laboratory experiments using the main allelochemical released by I. glandulifera , 2‐methoxy‐1,4‐naphthoquinone, revealed negative fitness effects in D. magna and A. obliquus . Our findings show that allelochemicals from I. glandulifera not only reduce biodiversity in terrestrial habitats but also pose a threat to freshwater ecosystems, highlighting the necessity to incorporate cross‐ecosystem effects in the risk assessment of invasive species.

Allelochemical run-off from the invasive terrestrial plant Impatiens glandulifera decreases defensibility in Daphnia

“…1 A, B). This result is in accordance with our former findings and indicates direct toxic effects of the compound 42 . It was shown that naphthoquinones like 2-MNQ can increase the amount of reactive oxygen species (ROS) in cells, which can harm DNA and other cell compartments 53 .…”

“…1 B). Similar to the reduction in body length we cannot differentiate whether 2-MNQ directly interfered with the induction of this defensive trait or whether tail-spine length was reduced due to an overall impact on the fitness of the organism 42 . However, in either way this may increase the risk of a successful attack.…”

“…The source for Impatiens glandulifera is a leave isolate, which we purchased from Merck KGaA: https://www.sigmaaldrich.com/DE/de/product/aldrich/189162 , as purified 2-methoxy-1,4-naphthoquione (2-MNQ) (Merck KGaA, CAS-number: 2348-82-5, Darmstadt, Germany; 98% purity isolated from I. glandulifera leaves). Due to its low solubility in water, the 2-MNQ powder was dissolved in 100 µl DMSO (Dimethylsulfoxide 99.7% purity; Bernd Kraft GmbH, Duisburg, Germany) per litre medium 42 .…”

“…We compared the effect of 2-MNQ on the expression of inducible defences in both Daphnia species (2-MNQ & kairomones) to animals that were solely exposed to kairomones of predators and to control animals not exposed to any of these compounds 42 . We performed acute toxicity studies in Diller et al 42 . We determined an EC50 of 2.84 mg/l (95%—Confidence interval: 2.809 and 2.869 mg/l).…”

“…It was shown that a similar compound, juglone (5-hydroxy-1,4-naphthoquinone), an allelochemical produced by the black walnut tree, Juglans nigra , can increase the mortality in D. magna , when the animals are treated with finely ground walnut hulls or the purified substance 37 , 41 . Recently, for 2-MNQ below 12 mg/l it has been shown to alter fitness of D. magna as well by increasing the mortality (EC 50 = 2.84 mg/l), reducing body size (EC 50 = 0.649 mg/l) and number offspring (EC 50 = 1.60 mg/l) 42 . However, if allelochemicals released by terrestrial invasive plants do interfere with the expression of chemically induced inducible defensive traits in different Daphnia species, keystone species in lakes and ponds, is not studied yet.…”