Functional classifications in phytoplankton ecology: a comparative review of approaches and experiences

3openEmpirical models of phytoplankton groups and their recurrence in water bodies have traditionally made use of taxonomic classifications, implicitly or explicitly assuming that species classified together could share similar ecological properties. Nevertheless, the use of taxonomy in ecology has many drawbacks. From one side, many broader groups include species with very different ecological properties. From the other side, convergent evolution, the independent evolution of similar characters in different lineages, can explain why distantly phylogenetically related species can be linked together by close analogous ecological affinities. With the aim to obtain a better understanding of the functioning of the freshwater ecosystems, complementary approaches based on ecological criteria have been therefore proposed. The aim of this contribution is to critically review the rationale of the different classifications that have been proposed during the last three decades, highlighting the strengths and weaknesses of the different approaches. Besides the first classifications, which considered broad functional categories based on reproductive (r-K selection) and life strategies (C-S-R), successive formulations included the functional groups (FG), firstly established by C.S. Reynolds, the Morpho-Functional Groups (MFG- Salmaso & Padisák, 2007), and the Morphology-Based Functional Groups (MBFG - Kruk et al., 2010). In the original formulation of FG, species were put together if they showed similar dynamics and ecological requirements, implicitly assuming a similar response to a set of environmental and seasonal changing conditions. With successive refinements, morphological properties have been used to fit hitherto functionally unclassified taxa into existing FG. This classification has been widely used in many aquatic ecosystems, with applications in ecological status assessment. At the opposite, MBFG (totalling 7 groups) are exclusively based on morphological characters, irrespective of the temporal dynamics of the species. The MFG concept use a hybrid approach, integrating morphological, functional and, when ecologically relevant, taxonomic characters in the definition of groups. The comparative evaluation of the above classifications was attempted only very recently, and will be critically examined in this review. Finally, this work will provide an updating of the original MFG classification based on the application of the concept to real case phytoplankton studies.openSalmaso, N.; Naselli Flores, L.; Padisák, J.Salmaso, N.; Naselli Flores, L.; Padisák, J

Blowing in the wind: how many roads can a phytoplanktont walk down? A synthesis on phytoplankton biogeography and spatial processes

The selected theme of the 17th Workshop of the International Association for Phytoplankton Taxonomy and Ecology (IAP), ‘‘Biogeography and Spatial Patterns of Biodiversity of Freshwater Phytoplankton,’’ offered the opportunity to explore one neglected aspect of phytoplankton ecology: the distribution of species in the geographic space. This paper summarizes the outcomes of 20 selected contributions among those presented at the workshop. The articles report the results from studies carried out in five continents (only Oceania is not represented) and on a wide array of aquatic ecosystems (deep and shallow natural lakes, man-made lakes, temporary and permanent ponds, rivers). The topics analyzed by the contributors are related to Island Biogeography paradigms, dispersal vectors, survival strategies, environmental filters, dispersal distances, vertical and horizontal spatial variability of phytoplankton between and within water bodies, and of course, invasive algae. The overall analysis of the results presented clearly demonstrates that, as for many others organisms, there are ‘‘rules’’ governing freshwater phytoplankton spatial patterns and that these organisms also have a true biogeography, as nowadays is quite evident for several other groups in the same range of size. We can definitively conclude that the statement ‘‘Everything is everywhere’’ is obsolete, even though human activities tend to homogenize species distribution in the biosphere

Phytoplankton in extreme environments: importance and consequences of habitat permanency

There is hardly any sunshine exposed surface on this Earth, be it water or terrain, which would not support some biota. Still, many habitats offer harsh conditions requiring specialized physiological adaptations to survive. These environments are referred to as extremes; often inhabited by extremophilic organisms. In this review, characteristic species and assemblage properties of phytoplankton inhabiting extreme environments (especially lakes and pools where planktic life is potentially possible and independently of their origin) in terms of alkalinity, acidity, DOC, salinity, temperature, light and mixing regime will be outlined. Lakes characterized by more than a single extreme are common (e.g. saline + alkaline; acidic + high DOC + high metal content + low light). At the edge of extremes (e.g. pH of 1; salinity over ~ 100–150 g l−1) single species with appropriate physiological adaptation are selected and the phytoplankton is often dominated by a single species (monodominant) setting compositional diversity to zero. Under less extreme conditions permanent equilibria may persist; in many cases over several years in contrast to „average” lakes where equilibria are rare and ephemeral. Food webs depending on „extreme phytoplankton” are often atypical for example because the microbial loop is of prior importance or because birds are top predators

Study of akinetes in the sediments of large European lakes, and hatching experiments to infer long-term colonization dynamics by cyanobacteria

Distinct cyanobacteria belonging to Nostocales have the ability to form resting cells, which provide a mean to persist in harsh environmental conditions. Previous studies carried out in long-sediment cores, showed that akinetes could survive for long-time (up to over 60 years). Studying akinetes in lake sediments may provide a more comprehensive knowledge of past phytoplankton assemblages. The aim of this contribution is to study the colonization history of Nostocales by examining the vertical distribution of akinetes in the sediments of 4 European lakes included in the project EULAKES, namely lakes Garda (oligo-mesotrophic; Italy), Neusiedler (meso-eutrophic; Austria), Balaton (meso-eutrophic; Hungary), and Charzykowskie (eutrophic; Poland). Viability of akinetes was investigated by putting sediment taken from several sections of the core in ASM-1 culture medium at 18° for 16-21 days. The subsequent microscopic examination showed a very low diversity in Lake Garda, with the development of Dolichospermum lemmermannii in the first 10 cm (which correspond to the period since the 1980s). Lake Balaton showed a more diversified group of Nostocales, which included Aphanizomenon cf. gracile, followed by Aphanizomenon issatschenkoi, Aphanizomenon cf. capricorni, and Cylindrospermopsis raciborskii. A. cf. gracile was observed down to ca. 50 cm (>100 yr), whereas A. issatschenkoi and A. cf. capricorni were reported in the more recent sediments and more discontinuously. Anabaena viguieri was a typical representative in Lake Neusiedler down to 50 cm of core sediment (corresponding to the last ca. 60 years), along with Aphanizomenon gracile (in the first 10 cm, around 2000) and some unidentified Anabaena (between 20-60 cm, since early 1900s). In Lake Charzykowskie, the only Nostocales were Anabaena solitaria down to 60 cm of core sediment (late 1940s) along with an unidentified Anabaena sp. The observed differences provide an important platform to interpret the distribution of cyanobacteria in European lakes, which are characterized by different physiographic, climatic and trophic characteristic

Impairing the largest and most productive forest on our planet: how do human activities impact phytoplankton?

32012 SALM 4restrictedInternationalBothThis article summarizes the outcomes of the 16th Workshop of the International Association for Phytoplankton Taxonomy and Ecology. Four major issues dealing with the impact exerted by human activities on phytoplankton were addressed in the articles of this special volume: climate change and its impacts on phytoplankton, the role of land use in shaping composition and diversity of phytoplankton, the importance of autecological studies to fully understand how phytoplankton is impacted by stressors and the role of ecological classification to evaluate community changes due to the different impacts. Case studies from different types of aquatic environments (rivers, deep and shallow lakes, reservoirs, mountain lakes, and temporary ponds) and from diverse geographical locations (not only from the Mediterranean and temperate regions, but also from subtropical and tropical ones) have shown that a complex spectrum of human impacts, not exclusively linked to eutrophication, severely conditions structure and dynamics of phytoplankton assemblage both in the short and long terms. Moreover, the trade-offs between climate change and other human-induced stresses as eutrophication, agricultural and urban land use or water overexploitation contribute to make more severe the impact exerted by humans on phytoplankton and, in turn, on the functioning of aquatic ecosystems.restrictedSalmaso, N.; Naselli-Flores, L.; Padisak, J.Salmaso, N.; Naselli Flores, L.; Padisak, J