EPPO Global Database

EPPO Reporting Service no. 11 - 2020 Num. article: 2020/259

Azolla filiculoides negatively affects invaded environments

Azolla filiculoides (Azolloideae: EPPO Observation List of Invasive Alien Plants) is an invasive aquatic fern species native to North America and widespread in the EPPO region. It can have negative effects on the aquatic system when it forms dense mats over the surface of waterbodies preventing sunlight from penetrating the water. The effect of A. filiculoides mats on Mediterranean temporary waters was assessed using outdoor mesocosms with sediments from an invaded marsh and amphibian larvae from surrounding wetlands. A. filiculoides formed a dense mat over the water surface in the experimental tanks, which decreased pH and oxygen concentration, and increased nutrients, nitrogen and phosphorus compounds in the water compared to mesocosms without A. filiculoides. Macrophyte abundance and richness were reduced under the A. filiculoides mat. Invaded mesocosms also had higher phytoplankton abundance and different zooplankton composition, which was mainly characterized by higher abundance of juvenile copepods. For amphibian development, tadpoles required a longer developmental period and the western spadefoot toad, Pelobates cultripes, had significantly lower survival in the presence of A. filiculoides (4.8% compared to 60% survival in Azolla free mesocosms). The results show that A. filiculoides can have wide negative impacts and should be controlled in invaded habitats.


Pinero-Rodriguez M, Fernandez-Zamudio R, Arribas R, Gomez-Mestre I, Diaz-Paniagua C (2020) The invasive aquatic fern Azolla filiculoides negatively impacts water quality, aquatic vegetation and amphibian larvae in Mediterranean environments. Biological Invasions, doi.org/10.1007/s10530-020-02402-6.