There to stay: invasive filamentous green alga Mougeotia in Lake Kinneret, Israel

Mougeotia (Zygnematales, Charophyta) first appeared in the plankton of Lake Kinneret in 1998. While initially rare, from 2004 onwards it was present in the plankton continuously, forming massive blooms in spring (2005, 2006, 2012) or in winter (2010), occasionally appearing in different morphological and life cycle forms. Mougeotia maintained its population under a wide range of water temperatures, nutrient concentrations, solar radiation, pH levels and stratification patterns, making it a highly versatile alga. In multiple regression, year and month as the only predictors explained 36% of the pattern of Mougeotia biomass. However, Mougeotia biomass could not be explained by any of the environmental parameters considered. Modeling the temporal dynamics of Mougeotia biomass using an autoregressive integrated moving average (ARIMA(1,0,0)) explained 56% of variability indicating that intraspecific factors (e.g., competition for nutrients or self-shading) may determine the dynamics of Mougeotia biomass. To explain the lack of relationships with the environmental parameters, we hypothesize that (1) Mougeotia possesses exceptional physiological plasticity and/or (2) Lake Kinneret may host two or more genetically distinct cryptic species of Mougeotia with different environmental niches. Both explanations may hinder any inference on Mougeotia– environment relationships and require confirmation by experimental work.