Phytoplankton and Zooplankton Associations in a Set of Alpine High Altitude Lakes: Geographic Distribution and Ecology

Abstract

Species composition and interactions, biomass dominance, geographic distribution and driving variables were investigated for two key elements of the pelagic food web of Alpine lakes, the phytoplankton and the zooplankton, based on a single sampling campaign during summer 2000. Altogether, 70 lakes were surveyed, 49 of which located in three different lake districts of the west and eastern Italian Alps and 21 in the central Austrian Alps (within the uppermost Danube catchment). In addition to the analysis of environmental variables affecting distribution and species structure of the two planktonic compartments, a brief review of the main research lines and hypotheses adopted in the past for the study of phytoplankton and zooplankton in high Alpine lakes is given. The lakes, investigated partly within the European project EMERGE (EVK1-CT-1999-00032) and partly within a regional project in the eastern Alps, comprise a wide range of morphological, chemical and trophic conditions. The phytoplankton communities were found to be diverse and mostly dominated by flagellates (chrysophytes, cryptophytes and dinoflagellates), and only to a lesser extent by non-motile green algae, desmids and centric diatoms. The zooplankton communities were mainly dominated by Alpine cladocerans and copepod species, while rotifers were abundant within one group of Italian lakes (sampled in early summer). The multivariate statistical analyses (CCA) showed that catchment features (i.e. percentage of vegetation cover and geochemical composition) and nitrate concentration are essential drivers for the phytoplankton, whereas for zooplankton also trophic status of the lakes and phytoplankton structure are important. The combined variance analysis of the lake clusters outlined by the multivariate analyses on phytoplankton and zooplankton data, respectively, allowed the identification of four principal lake types (three located on siliceous and one on carbonaceous bedrock), each one characterised by a certain combination of habitat features, which in their turn influence trophic state, and phytoplankton and zooplankton species composition and functionality.

Geographic distance and mountain ranges structure freshwater protist communities on a European scalе

“…Ecological factors, in particular abiotic factors such as nutrient concentrations, temperature and light and UV intensity are well known to affect protist community composition (e.g Sommaruga 2001, Sonntag et al 2010, Tolotti et al 2003, Tolotti et al 2006, Triadó-Margarit and Casamayor 2012. However, recent data provide increasing evidence that beyond the ecological factors also geographic distance and historical factors affect protist distribution at least on large scales (Filker et al 2016, Schiaffino et al 2016, Fernández et al 2017.…”

“…Besides climate, the pH and the concentration of ions and nutrients are particularly important structuring factors on the local scale (Azovsky et al 2016, Triadó-Margarit and Casamayor 2012, Wu et al 2009. A large-scale plankton analysis demonstrated temperature to be a major driver of community composition in the marine (de Vargas et al 2015) whereas nutrient concentrations and pH seem to be more important in freshwater communities (Tolotti et al 2003, Tolotti et al 2006, Triadó-Margarit and Casamayor 2012. Further, and particular along alpine gradients, elevation and environmental parameters co-varying with elevation such as UV-intensity also affect protist taxa and potentially shape communities (Sommaruga 2001, Sonntag et al 2010.…”

Distribution and ecological requirements of ostracods (Crustacea) at high altitudinal ranges in Northeastern Van (Turkey)

“…However, the upper altitudinal limits of ostracod distribution were not sampled in that study. More generally, reduced species diversity for aquatic species at high altitudes (e.g., insect herbivores, Lawton et al (1987); copepods, Jersabeck et al (2001); zoo and phytoplankton, Tolotti et al (2006); montane diatoms and desmids, Vyverman (1992); amphibians, Pounds et al (2006)) can be attributed to: (i) lack of suitable habitats, (ii) reduced resource diversity (e.g., lack of large aquatic bodies), (iii) increasing unpredictable conditions, (iv) climatic changes and (v) difficulty in active and/or passive dispersion (in this study). The ability of a species to occur in any aquatic bodies is limited by its active (i.e., swimming and walking) or passive dispersion (i.e., by means of birds, frogs and fish).…”

First record of planktonic crustaceans in Sardinian reservoirs

“…Sampling at a single time is not sufficient to cover the local biodiversity but, given the constraints, we sampled a number of sites representative of different characteristics, in a "space per time approach", successfully applied for other sites in Europe (e.g., for alpine lakes as part of the EMERGE Project; Tolotti et al 2006), which was complemented with additional information on the seasonal dynamics of the second largest reservoir. Seasonality is much more pronounced in Mediterranean reservoirs than in natural deep lakes of other regions, as a result of human activities and the climate.…”