Increased nutrient loading and rapid changes in phytoplankton expected with climate change in stratified South European lakes: sensitivity of lakes with different trophic state and catchment properties

Abstract

We hypothesised that increasing winter affluence and summer temperatures, anticipated in southern Europe with climate change, will deteriorate the ecological status of lakes, especially in those with shorter retention time. We tested these hypotheses analysing weekly phytoplankton and chemistry data collected over 2 years of contrasting weather from two adjacent stratified lakes in North Italy, differing from each other by trophic state and water retention time. Dissolved oxygen concentrations were higher in colder hypolimnia of both lakes in the second year following the cold winter, despite the second summer was warmer and the lakes more strongly stratified. Higher loading during the rainy winter and spring increased nutrient (N, P, Si) concentrations, and a phytoplankton based trophic state index, whilst the N/P ratio decreased in both lakes. The weakened Si limitation in the second year enabled an increase of diatom biovolumes in spring in both lakes. Chlorophyll a concentration increased in the oligo-mesotrophic lake, but dropped markedly in the eutrophic lake where the series of commonly occurring cyanobacteria blooms was interrupted. The projected increase of winter precipitation in southern Europe is likely to increase the nutrient loadings to lakes and contribute to their eutrophication. The impact is proportional to the runoff/in-lake concentration ratio of nutrients rather than to the retention time, and is more pronounced in lakes with lower trophy.

Phylogenetic conservation of freshwater lake habitat preference varies between abundant bacterioplankton phyla

“…PA bacterial communities may also be more sensitive to global change stressors (land use change, species invasions, changes in geochemical cycles (Chapin III et al ., ). First, the changes in run‐off patterns due to urban and agricultural land development and climate change could alter the nature and amount of suspended solids delivered to freshwater lakes (Adrian et al ., ; Nõges et al ., ; Michalak et al ., ). Second, an invasive dreissenid mussel that has major impacts on aquatic systems in North America and Eastern Europe (Dame and Olenin, ; Ruesink et al ., ; Higgins and Vander Zanden, ) was recently shown to preferentially remove PA bacteria from freshwater systems through size‐selective filter feeding (Cotner et al ., ; V.J.…”

Differences in phytoplankton dynamics and community structure between a wet year and dry year in the Zhoucun Reservoir

“…Field surveys have been conducted on the influence of shortterm rainfall on algal blooms and the phytoplankton community. For example, Nõges et al (2011) showed that precipitation increased nutrient levels and algal biomass in Lake Varese and Paidere et al (2007) reported that floods increased phytoplankton diversity and decreased phytoplankton biomass in two floodplain lakes. In addition, the effects of nutrients on phytoplankton communities have been compared among different water bodies in the same area: Gikuma-Njuru et al (2013) revealed that the Nyanza Gulf of Lake Victoria was P-deficient and dominated by non-nitrogen-fixing cyanobacteria, whereas Lake Victoria as a whole was N-deficient and occupied by diazotrophic cyanobacteria and diatoms.…”

Preliminary molecular identification of cylindrospermopsin-producing Cyanobacteria in two Polish lakes (Central Europe)

“…Climate change increases water temperatures and nutrient concentration and hence the intensity of eutrophication. In consequence, global warming causes massive cyanobacteria bloom in many water bodies (Delpla et al, 2009;Nõges et al, 2011). Ultimately, cyanobacterial blooms and their toxins pose a serious threat to public health through water supply systems, recreation or agriculture, and to the natural environment.…”