Occurrence and mass development of Mougeotia Spp. (Zygnemataceae) in large, deep lakes

Over the last decades, mass developments by the filamentous conjugating green alga Mougeotia have been followed in three large peri-alpine lakes(Lake Geneva, Lake Garda, Lake Maggiore) and in the sub-tropical Lake Kinneret. The aim of this study is to highlight annual and interannual patterns of Mougeotia biomass in the studied lakes and select key environmental parameters that may favour and maintain its mass development. Our results confirm former studies that planktic Mougeotia favours meso-oligotrophic conditions and becomes dominant when annual mean total phosphorus concentrations in the epilimnion fall below 20 ?gl-1. This triggering factor has effect with interactions of other environmental circumstances such as the water column stability. Physiological and morphological features of the taxon make it a successful competitor under stratified conditions. Results also showed that in three out of the four studied lakes, the annual peak was higher when the annual population development started earlier. Focusing on Lake Geneva, depth and strength of the thermocline, as well as wind speed in the beginning of summer that can cause nutrient replenishment and mix the epilimnion are key factors in the blooming of the taxon

How length of light exposure shapes the development of riverine algal biomass in temperate rivers?

The impact of cumulative daily solar radiation (CDSR) on the biomass of river phytoplankton (Chl-a) in the growing season was studied using a large dataset of rivers in the Carpathian Basin. The amount of solar radiation was cumulated over the range of 1–60 days. The CDSR–Chl-a relationship could be described by linear regression and appeared to be significant for almost all watercourses with the exception of rivers with short water residence time. To determine the most relevant time period of CDSR impacting phytoplankton biomass, the slopes of regressions were plotted against the accumulating number of days of light exposure (1–60). Two characteristic shapes were obtained: unimodal for rhithral rivers with hard substrate and steady increase for lowland potamal rivers with fine substrate. In both cases, there is an increasing tendency in the slope values with water residence time (WRT). It was demonstrated that CDSR has a pronounced impact on river phytoplankton biomass even in cases when WRT was shorter than the cumulated solar radiation period. These results indicate that development of phytoplankton within the river channel is a complex process in which meroplankton dynamics may have significant impacts. Our results have two implications: First, CDSR cannot be neglected in predictive modelling of riverine phytoplankton biomass. Second, climate models forecast increased drought with subsequently increased CDSR in several regions globally, which may trigger a rise in phytoplankton biomass in light-limited rivers with high nutrient concentrations

Data for: The potential of exact sequence variants (ESVs) to interpret and assess the impact of agricultural pressures on stream diatom assemblages revealed by DNA metabarcoding

These data contains the supplementary material for the manuscript entitled "The potential of exact sequence variants (ESVs) to interpret and assess the impact of agricultural pressures on stream diatom assemblages revealed by DNA metabarcoding"THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Factors triggering the occurence and excessive development of Mougeotia spp. in large lakes

During the last decades the filamentous green alga, Mougeotia spp. has been giving important contributions to the phytoplankton of some large peri-alpine lakes (Lake Geneva, Lake Garda, Lake Maggiore) and also in subtropical Lake Kinneret. Excessive Mougeotia blooms have been observed in these lakes but with different frequencies and intensities. While Lake Maggiore and Lake Kinneret were affected only a few years, Lake Geneva and Lake Garda displayed regular blooms. Besides the ecological consequences, these blooms cause practical problems in professional fishing. Mougeotia spp. has many features making it a good competitor; low sinking velocity, resistance to grazing, effective phosphorus uptake. In this study we focus on bottom-up environmental factors related to human activities, lake restoration processes or to global climate change that may trigger changes favouring development of Mougeotia sp

Occurrence and mass development of Mougeotia spp. (Zygnemataceae) in large, deep lakes

Over the last decades, mass developments by the filamentous conjugating green alga Mougeotia have been followed in three large peri-alpine lakes (Lake Geneva, Lake Garda, Lake Maggiore) and in the sub-tropical Lake Kinneret. The aim of this study is to highlight annual and interannual patterns of Mougeotia biomass in the studied lakes and select key environmental parameters that may favour and maintain its mass development. Our results confirm former studies that planktic Mougeotia favours meso-oligotrophic conditions and becomes dominant when annual mean total phosphorus concentrations in the epilimnion fall below 20 µg l−1. This triggering factor has effect with interactions of other environmental circumstances such as the water column stability. Physiological and morphological features of the taxon make it a successful competitor under stratified conditions. Results also showed that in three out of the four studied lakes, the annual peak was higher when the annual population development started earlier. Focusing on Lake Geneva, depth and strength of the thermocline, as well as wind speed in the beginning of summer that can cause nutrient replenishment and mix the epilimnion are key factors in the blooming of the taxo