Steady state phytoplankton in a deep pre-alpine lake: species and pigments of epilimnetic versus metalimnetic assemblages

Abstract

The vertical distribution pattern of algal species, chlorophylls and specific carotenoids present in the dimictic prealpine Ammersee (Bavaria, Germany) are given for the year 2001. A detailed taxonomic list of the phytoplankton species is recorded, along with light micrographs and detailed descriptions of the flagellates. A deep chorophyll maximum, mainly built by Planktothrix rubescens, was common in this deep mesotrophic lake. The three most dominant species among 83 identified taxa alternated seasonally and reached significant biovolumes in both the epiand the metalimnion (Planktothrix rubescens > Ceratium hirundinella > unicellular centric diatoms > Asterionella formosa > Fragilaria spp. > Anabaena lemmermannii > Phacotus lenticularis and less frequent dominant was Rhodomonas minuta). We define a steady state phytoplankton assemblage in Ammersee as a stable community in terms of species composition and standing crop. The stability of species composition was measured by Bray-Curtis similarity between monthly samples and indicate the change of individual biovolumes of species from month to month. The stability of standing crop was evaluated by the net change of total biovolume for the same time intervals. Focussing on steady state phytoplankton assemblages we compared three spatially heterogeneous environments for vertical niche separation within the top 12 m: the euphotic epilimnion (2 and 5 m), the euphotic metalimnion (7 m) and the metalimnion below the euphotic zone with dim-light less than 1% (10 and 12 m). The definition of a steady state assemblage on both ends hold true only for metalimnetic layers at dim-light levels below 1% in Ammersee. At this metalimnetic layer more than 80% similarity in phytoplankton composition between successive monthly samples was reached, associated with almost zero net changes of total biovolume only. The greater the contribution of the three most dominant taxa to biovolume, the higher were the Bray-Curtis similarities at metalimnetic depths below the euphotic zone. Zooplankton biomass had very little effect on species assemblages in the metalimnion, while parameters related to stratification (Schmidt stability) as well as those of trophy (TP, Chl) correlated with species changes. The similarity values between successive monthly samples from all the euphotic layers never reached more than 60% and were usually significantly lower, even if biovolume net changes were around zero. Both the high fluctuations of the ratio of photosynthetic versus photo-protective carotenoids (PSC:PPC) and the statistical significance of correlations between the change of species and environmental-biotic parameters separate the euphotic layer of the top 7 m as a homogenous community from deeper strata. At all sampling depths within this euphotic zone the increase of sunshine duration was associated with an increase of the carotenoid ratio PSC:PPC, but no relationship was found for the deeper layers. The change of species in the euphotic layer was not significantly related to thermal stability, TP o...

Does pigment composition reflect phytoplankton community structure in differing temperature and light conditions in a deep alpine lake? An approach using HPLC and delayed fluorescence techniques1

“…This finding agrees with other reports of phytoplankton composition in deep layers in lakes (Lindholm 1992, Gervais 1998, Knapp et al. 2003, Teubner et al. 2003).…”

“…Violaxanthin occurs in some freshwater chrysophytes, but it reached only low concentrations due to low cell abundances in Mondsee. Investigation of individual marker pigments also made it possible to quantify specific taxonomic groups—for example, the close relationship between P. rubescens and oscillaxanthin in Mondsee, similar to findings reported from the deep chl maximum in prealpine Ammersee (Bavaria, Germany; Teubner et al. 2003).…”

“…The normalized DF excitation spectra highlighted the variation within photosynthetically active pigments relative to photosynthetically active chl a with seasons and depths in Mondsee. In addition, we studied the β‐carotene:chl a ratio to see if this ratio might serve as a rough estimator of the balance between photoprotection and light‐harvesting behavior in plankton communities analyzed by HPLC (Teubner et al. 2001, 2003, Yacobi 2003).…”

Temperature modulated effects of nutrients on phytoplankton changes in a mountain lake

“…Teubner et al, 2003;Reynolds, 2006), led to a moderate variability in both biomass and seasonal distribution of flagellates MFGs. Teubner et al, 2003;Reynolds, 2006), led to a moderate variability in both biomass and seasonal distribution of flagellates MFGs.…”

Cyanobacterial bloom termination: the disappearance of Planktothrix rubescens from Lake Bourget (France) after restoration

“…Jacquet et al, 2005. Teubner et al (2003) and Dokulil & Teubner (2005) reported that P. rubescens could develop considerable biomass at TP around 10 lg P L À1 , so it is surprising that P. rubescens did not develop at similar concentrations in Lake Bourget. Such episodic occurrences of P. rubescens were also observed in Lake Nantua and Mondsee (Feuillade, 1994;Dokulil & Teubner, 2012).…”