Under-ice environmental conditions, planktonic communities and ichthyofauna in dystrophic lakes

Abstract

High content of humic substances and low pH values are factors limiting the species richness and abundance of some organisms in dystrophic lakes. Unfavourable winter conditions (i.e. low water temperature, poor light conditions, ice/snow cover) may additionally restrict their development. The aim of this study was to compare ice-on (winter) and ice-off (summer) abiotic (organic carbon, total phosphorus and nitrogen) and biotic (chlorophyll a, phytoplankton, ciliates, rotifers, crustaceans, fish) parameters in five dystrophic lakes of the Wigry National Park (north-east Poland). We tested the hypothesis that the abundance and diversity of planktonic organisms in dystrophic lakes could be lower in winter than in summer. Our results showed that the winter period, with ice and snow cover, was characterised by clearly higher oxygen concentrations, pH values and conductivity, but lower total phosphorus concentrations, species richness of phytoplankton, ciliates, rotifers and crustaceans, and phytoplankton to zooplankton biomass ratios in comparison to the summer. All of the studied groups of organisms, except rotifers, reached relatively high abundances and biomasses in both seasons and, in some lakes, they were higher in winter than in summer. Our results suggest that fish composition and abundance did not play an important role in structuring plankton communities. The small dystrophic lakes, although located close to one another, differed in terms of abiotic parameters and had specific species compositions of phyto-and zooplankton. Warmer winters, which are the result of climate change, may favour the intensive development of planktonic communities under the ice in dystrophic lakes of temperate climatic zones.

Humic lakes with inefficient and efficient transfer of matter in planktonic food webs

“…The maximum depth of the lakes ranged from 3.5 to 8 m (Table 1 ). The biomass and the number of fish species were very low in the studied lakes 25 , 48 . Dystrophic conditions were evaluated by the hydrochemical dystrophy index (HDI), which uses data on surface water pH, electric conductivity, and DIC/DOC ratio 4 .…”

“…On the other hand, the high biomass of phytoplankton contrasts with the low biomass of zooplankton in dystrophic lakes, which results in low efficiency of the transfer of matter and energy in planktonic food webs 20 – 22 . Furthermore, dystrophic lakes are unproductive from a fishery point of view, with low fish densities or an absence of fish 23 – 25 . Thus, a large amount of food and low fish pressure in temperate humic lakes usually do not lead to the mass development of large-bodied zooplankton, and the limiting factors for zooplankton growth are unclear.…”

“…Zooplankton communities in temperate dystrophic lakes are generally characterized by low species richness of crustaceans and rotifers and are often dominated by one or two species ( Asplanchna priodonta , Ceriodaphnia quadrangula , and Eudiaptomus gracilis ) 25 , 28 , 29 . Moreover, very similar zooplankton communities exist in different dystrophic lakes 30 .…”

Planktonic communities in a small post-peat reservoir (Ustka Forest District, Poland)

“…Species of genera Ascomorpha and Polyarthra prefer acidic environments (Rybak 1994). Other studies performed in dystrophic water bodies reported occurrence of the same genera, for example, Polyarthra, Lecane, Colurella and Trichocerca (Demetraki-Paleolog and Kolejko 2011);Polyarthra, Trichocerca and Keratella cochlearis (Kuczyńska-Kippen 2008); Asplanchna, Colurella, Lecane, Polyarthra and K. cochlearis (Demetraki-Paleolog et al 2018); Polyarthra, Trichocerca, K. cochlearis and Asplanchna (Karpowicz and Ejsmont-Karabin 2018); Ascomorpha, Trichocerca, K. cochlearis and Asplanchna (Kalinowska et al 2021); and Ascomorpha, Asplanchna, Colurella and Polyarthra (Quiroga et al 2013). These studies also reported other genera that were not noted in the reservoir studied.…”

“…According to a literature review, the abundance and composition of plankton in post-peat reservoirs remain understudied (Mieczan 2007;Demetraki-Paleolog and Kolejko 2011). Similar studies in dystrophic lakes are more advanced and are concentrated on the impact of environmental parameters on phytoplankton or zooplankton distribution (Karpowicz and Ejsmont-Karabin 2018;Lebret et al 2018;Kalinowska et al 2021). Kalinowska et al (2021) emphasised that majority of studies in dystrophic lakes are carried out during the growing season and the winter planktonic communities are less thoroughly studied.…”