Convergence and divergence in organization of phytoplankton communities under various regimes of physical and biological control

Abstract

The hypothesis that physical constraints may be as important, if not more important, than\ud biological ones in shaping the structure of phytoplankton assemblage was tested by analyzing longterm (11–29 years) phytoplankton series in eight lakes and nine sites located along a latitudinal gradient in the Northern hemisphere. Phytoplankton biomass was used and similarity of assemblages in same months of the annual data sets was then calculated by subtracting the Bray–Curtis dissimilarity index from 1. The extent of biological and physical forcing was partly based on ‘‘expert evaluation’’: the importance of four physical (light availability, temperature, conductivity, and sediment stirring up) and five biological variables (basic nutrients [SRP-, DIN-, SRSi-availability] as estimators\ud of competition straight, importance of grazing, and importance of parasitism) was evaluated month by month by arbitrarily scaling from 1 to 5 the intensity of each variable and then summing them in the appropriate subgroup. Since the number of\ud physical variables is less than that of the biological ones, the latter was rescaled to reach the same maximum attainable value of physical variables. The results showed an extremely high variability, making evident that each lake, although showing the same\ud metabolic processes, behaves as an individual with regard to its phytoplankton structure. More generally, it was possible to highlight a largely more important role of physical constraints in shaping both biomass and composition of phytoplankton. This is especially true in winter. In addition, the results were compared to the outcomes of the PEG model, since a plasticity\ud in the structure of phytoplankton much greater than that reported in this widely acknowledged model has been recorded in the data set used. This high variability found in this study in relation to physical constraints might also explain the different patterns of phytoplankton growth observed from Northern temperate to Mediterranean lakes as well as those occurring in shallow and deep lakes

Diversity patterns of trait-based phytoplankton functional groups in two basins of a large, shallow lake (Lake Balaton, Hungary) with different trophic state

“…Our conclusion is in agreement with those of Padisák et al (2010), who stressed the importance of physical forcing (including low temperature as a major factor) in shaping phytoplankton biomass and composition in winter. During these periods functional group diversity was low in both basins, although diversity in the western part showed somewhat higher variability.…”

Spatial heterogeneity and seasonal succession of phytoplankton functional groups along the vertical gradient in a mesotrophic reservoir

“…Thus, efficiency in nutrient uptake is a major force shaping phytoplankton morphology in oligotrophic and mesotrophic environments . In Mediterranean reservoirs, generally, the CpSpR successional pattern was observed among phytoplankton assemblage (Padisa´k et al, 2010;Rigosi and Rueda, 2012). In the higher part of the trophic spectrum, this succession pattern was obvious, where z mix /z eu < 3.5 (Naselli-Flores, 2014).…”

Phytoplankton Diversity of Jiaolai Estuary in Laizhou Bay and Relationship with Oceanic Environmental Factors

“…International policies and regulations such as EU Water Framework Directive and Marine Strategy Framework Directive put forward that characteristics of phytoplankton structure are important indexes of water quality assessment and water ecology conditions [2,3]. Jiaolai River is an important runoff to the sea in Laizhou Bay and a wide area of chemical industrial parks lies on the east coasts of its estuary.…”