A comparison of phytoplankton size-fractions in Mondsee, an alpine lake in Austria: distribution, pigment composition and primary production rates

Abstract

Production rates, abundance, chlorophyll a (Chl a) concentrations and pigment composition were measured for three size classes (<2 mm, 2-11 mm and >11 mm) of phytoplankton from May to December 2000 in deep, mesotrophic, alpine lake Mondsee in Austria. The study focuses on differences among phytoplankton size fractions characterised by their surface area to volume ratio ([mm 2 l À1 : mm 3 l À1 ]), pigment distribution patterns and photosynthetic rates. Particular attention was paid to autotrophic picophytoplankton (APP, fraction <2 mm) since this size fraction differed significantly from the two larger size fractions. Among the three fractions, APP showed the highest surface area to volume ratios and a high persistence in the pattern of lipophilic pigments between temporarily and spatially successive samples (about 80% similarity of pigment composition between samples over seasons and depths). The epilimnetic abundance of APP varied seasonally with an annual maximum of 180 · 10 3 cells ml À1 in June (at 4-9 m). The minimum (October at 12 m) was more than an order of magnitude lower (4.9 · 10 3 ml À1 ). APP peaked during autumn and contributed between 24% and 42% to the total areaintegrated Chl a (10-23 mg m À2 ) and between 16% and 58% to total area-integrated production (5-64 mg m À2 h À1 ) throughout seasons.

Do current European lake monitoring programmes reliably estimate phytoplankton community changes?

“…Lake Mondsee is an example of an originally ice-covered temperate lake undergoing a transition from a dimictic to a monomictic mixing pattern in the course of the ongoing lake warming (Ficker et al, 2017). Lake Mondsee is one of the best studied lakes in Austria with long-term phytoplankton datasets from the last 40 years (Findenegg, 1969;Dokulil & Skolaut, 1986;Dokulil & Jagsch, 1992;Greisberger et al, 2008;Dokulil & Teubner, 2012). Even longer records ([ 50 years) are available for some abiotic parameters such as Secchi depth .…”

The role and composition of winter picoeukaryotic assemblages in shallow Central European great lakes

“…Similarly higher 540 P B max values were obtained for APP than for the larger-sized phytoplankton fraction in a 541 temperate coastal ecosystem (Morán, 2007) and in Lake Mondsee (Greisberger et al, 2008). 542…”

“…Mondsee, APP contribution to total primary production was highest (as much as 58%) in the 126 autumn-winter period (Greisberger et al, 2008). However, it should be noted that in the case 127 of Lake Kinneret, the minimum temperature in winter does not drop below 10 °C (Malinsky-128 Rushansky et al, 1997), as opposed to the abovementioned lakes, which usually possess ice 129 cover.…”

Balance between primary and bacterial production in North Patagonian shallow lakes

“…For instance, the small-sized phytoplankton fraction (picophytoplankton: 0.2-2 lm) do best in resource-poor habitats in comparison with the larger size fraction (phytoplankton [2 lm) (Callieri 2008) for the same reason as bacteria (high surface to volume ratio). Therefore, picophytoplankton often dominates the summer production in oligotrophic clearwater lakes (Stockner 1991;Callieri et al 2007) and in autumn in the mesotrophic, Alpine lake Mondsee in Austria (Greisberger et al 2008). In addition, picophytoplankton seems to be pre-adapted to low levels of photosynthetically active radiation (PAR; Callieri et al 1996;Gervais et al 1997).…”