The Impact of Variations in the Climate on Seasonal Dynamics of Phytoplankton

Abstract

Phytoplankton, an assemblage of suspended, primarily autotrophic single cells and colonies, forms part of the base of the pelagic food chain in lakes. The responses of phytoplankton to anthropogenic pressures frequently provide the most visible indication of a long-term change in water quality. Several attributes related to the growth and composition of phytoplankton, such as their community structure, abundance as well as the frequency and the intensity of blooms, are included as indicators of water quality in the Water Framework Directive. The growth and seasonal succession of phytoplankton is regulated by a variety of external as well as internal factors (Reynolds et aI., 1993;Reynolds, 2006). Among the most important external factors ate light, temperature, and those associated with the supply of nutrients from point and diffuse sources in the catchment. The internal factors include the residence time of the lakes, the underwater light regime and the mixing characteristics of the water column. The schematic diagram (Fig. 14.1) shows some of the ways in which systematic changes in the climate can modulate these seasonal and inter-annual variations. The effects associated with the projected changes in the rainfall are likely to be most pronounced in small lakes with shOlt residence times (see George et aI., 2004 for some examples). In contrast, those connected with the projected changes in irradiance and wind mixing, are likely to be most important in deep, thermally stratified lakes.In this chapter, we use results acquired from a range of different European lakes to explore the potential effects of climate change on the seasonal development and the composition of phytoplankton. The time-series analysed are amongst the longest available in the region. Some of the lakes studied in CLIME have been sampled at weekly or fortnightly intervals for more than fifty years. These sites also cover a range of lake types from shallow to deep, small to large, and oligotrophic to eutrophic. P. Noges ([8)

Deep living Planktothrix rubescens modulated by environmental constraints and climate forcing

“…A positive NAO Febr index relates to years of relative high insolation, high air temperature and low precipitation in the catchment of Mondsee. A negative NAO Febr is associated with the opposite weather situation in the region (Dokulil et al, 2010;Nõges et al, 2010). We further show that an increase of hypolimnetic water temperatures by 0.1-0.2°C per decade was mediated by climate trends related to winter NAO signal (Dokulil et al, 2006).…”

Effect of extremely severe winters on under-ice phytoplankton development in a mesotrophic lake (Eastern Poland)

“…They generally belong to some motile algae, like dinophytes, cryptophytes, chrysophytes or flagellate chlorophytes (Nõges et al 2010). Despite convective mixing, small cell flagellate species are able to maintain their position in the water column, or move to places with better light conditions.…”

“…Despite convective mixing, small cell flagellate species are able to maintain their position in the water column, or move to places with better light conditions. Consequently, they can concentrate in large numbers in the upper water layer, often just beneath the ice cover (Kiili et al 2009, Nõges et al 2010.…”

The effect of ice phenology exerted on submerged macrophytes through physicochemical parameters and the phytoplankton abundance

“…The earlier ice-out on lakes determines changes in the physicochemical parameters, which are important to the abundant development of phytoplankton in spring (Weyhenmeyer et al, 2008;Laugaste et al, 2010;Nõges et al, 2010). However, our results show that the effect of mild winters on lakes can also be observed in following growing season (Tab.…”