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

Abstract

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 lg 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 taxon.Handling editor:

Modelling the plankton groups of the deep, peri-alpine Lake Bourget

“…These ndings therefore suggest that the disappearance of P. rubescens from Lake Bourget was actually due to competitive exclusion, facilitated by the phenomena called the priority e ect (Hodge et al, 1996), in which, the species with higher initial concentrations outcompete their competitors with lower initial concentrations by making the abiotic environment inhabitable by the others. The priority e ect has been previously reported from eld measurements (Tapolczai et al, 2014) and mesocosm experiments (Sommer and Lewandowska, 2011). Vertical distributions obtained under di erent scenarios (not shown) suggest that the priority e ect is manifested as a bistability of both phytoplankton composition and vertical distribution of phytoplankton biomass (as in Ryabov et al, 2010).…”

Blowing in the wind: how many roads can a phytoplanktont walk down? A synthesis on phytoplankton biogeography and spatial processes

“…Increasing evidence substantiates that in some cases it is rather the trophic change itself and not its direction that may lead to blooms of some species. For instance, blooms of Mougeotia have repeatedly been reported from a number of deep lakes when external phosphorous load reduction reached a certain threshold (Tapolczai et al, 2015).…”

Application of remote sensing for the optimization of in-situ sampling for monitoring of phytoplankton abundance in a large lake

“…After the implementation of phosphorus reduction plans in the early 1970's, the phosphorus concentration in Lake Geneva has decreased by almost 80% (BFS, 2013; www.cipel.org), going along with an improvement of the water quality and a slight reduction of the algal biomass towards the 1990's (Rimet, 2013). Thereafter, despite the ongoing decrease of phosphorus in Lake Geneva, phytoplankton biomass started to increase again (Anneville et al, 2002), reaching new record peaks in (Rimet, 2013Tapolczai et al, 2015).…”