Subfossil Cladocera in relation to contemporary environmental variables in 54 Pan‐European lakes

Abstract

Summary 1. Changes in cladoceran subfossils in the surface sediments of 54 shallow lakes were studied along a European latitude gradient (36–68°N). Multivariate methods, such as regression trees and ordination, were applied to explore the relationships between cladoceran taxa distribution and contemporary environmental variables, with special focus on the impact of climate. 2. Multivariate regression tree analysis showed distinct differences in cladoceran community structure and lake characteristics along the latitude gradient, identifying three groups: (i) northern lakes characterised by low annual mean temperature, conductivity, nutrient concentrations and fish abundance, (ii) southern, macrophyte rich, warm water lakes with high conductivity and high fish abundance and (iii) Mid‐European lakes at intermediate latitudes with intermediate conductivities, trophic state and temperatures. 3. Large‐sized, pelagic species dominated a group of seven northern lakes with low conductivity, where acid‐tolerant species were also occasionally abundant. Small‐sized, benthic‐associated species dominated a group of five warm water lakes with high conductivity. Cladoceran communities generally showed low species‐specific preferences for habitat and environmental conditions in the Mid‐European group of lakes. Taxon richness was low in the southern‐most, high‐conductivity lakes as well as in the two northern‐most sub‐arctic lakes. 4. The proportion of cladoceran resting eggs relative to body shields was high in the northern lakes, and linearly (negatively) related to both temperature and Chl a, indicating that both cold climate (short growing season) and low food availability induce high ephippia production. 5. Latitude and, implicitly, temperature were strongly correlated with conductivity and nutrient concentrations, highlighting the difficulties of disentangling a direct climate signal from indirect effects of climate, such as changes in fish community structure and human‐related impacts, when a latitude gradient is used as a climate proxy. Future studies should focus on the interrelationships between latitude and gradients in nutrient concentration and conductivity.

Younger Dryas Cladocera assemblages from two valley mires in central Poland and their potential significance for climate reconstructions

“…It is not surprising that such taxa persisted in the YD, because these species are known to occur over a wide range of conditions, and they are tolerant of environmental stress (Duigan & Birks, 2000); they are also common in northern and in European mountain lakes (Kamenik et al, 2007;Bjerring et al, 2009). These species were often found to be pioneer taxa, i.e., early immigrants following the retreat of the ice (Szeroczyńska, 1998a).…”

“…The development of these lakes is reflected by the accumulation of mineral/organic sediments (at the Korzeń site) or by the accumulation of mineral deposits (at the Kolonia Bechcice site). Therefore, most of the species from the YD found in these oxbow-lake deposits are littoral, macrophyte/sedimentassociated taxa, which were common in European lakes (Bjerring et al, 2009). Chydorid species as Pleuroxus spp., Graptoleberis testudinaria, and Camptocercus rectirostris live in warm water, but they are also primarily associated with vegetation.…”

“…Other environmental factors, such as the pattern of the habitat (structures such as plantgrowth forms) and substrate types are likely to have played significant roles at these sites: chydorids live in littoral regions and depend largely on the habitats provided by aquatic vegetation (Duigan & Birks, 2000;Bjerring et al, 2009). The development of these lakes is reflected by the accumulation of mineral/organic sediments (at the Korzeń site) or by the accumulation of mineral deposits (at the Kolonia Bechcice site).…”

“…It seems possible that the above-mentioned warmer or milder environmental conditions during this interval gave rise to the observed changes in the valley mires. However, environmental changes can hamper Cladocera-based climate reconstructions (Korhola, 1999;Duigan & Birks, 2000;Bjerring et al, 2009). Additionally, some of these species belong to typical southern fauna of Fennoscandia, according to their latitudinal affinities (Harmsworth, 1968), but the ecology of some species is not yet clear (e.g.…”

Disentangling natural and anthropogenic drivers of changes in a shallow lake using palaeolimnology and historical archives

“…The most abundant body part was chosen for each species to represent the number of individuals and the percentages were calculated from the sum of individuals. The habitat preferences for cladocerans were based on Bjerring et al (2009).…”