Invasive Elodea nuttallii and other abundant native macrophytes in Lake Müggelsee (Germany)
Mass development of the non-native species E. nuttallii is a challenge in many water bodies in Germany. In Lake Müggelsee, this species, together with other native submerged macrophytes, has dramatically increased in abundance in 2017 and 2018, potentially as a result of decreased nutrient loading and mutual facilitation with the invasive quagga mussel leading to decreasing periphyton shading and increased water clarity.
The lake is used intensively for drinking water production by bank filtration, navigation, and recreation, and is subject to climate change, anthropogenic pollution and hydromorphological alterations. Macrophytes are not yet managed and the risks of mowing Elodea and other submerged macrophytes have so far not been quantified, but could potentially be serious because a switch to a turbid state could affect drinking water production, especially if cyanobacteria would develop blooms. The stakeholder involved in this case study is the Senatsverwaltung Berlin (regional environmental authority).
Lake Müggelsee: Floating green algae (Enteromorpha) on top of abundant submerged macrophytes in 2017 (top left and right), dense stands of the invasive species Elodea nuttallii (bottom left, pictures: S. Hilt) in 2017 and mixed stands of abundant native species Najas major, Ceratophyllum demersum and invasive E. nuttallii in 2018 (bottom right, picture: Klaus van de Weyer)