Phytoplankton functional and morpho-functional approach in large floodplain rivers

Abstract

Influence of hydrological characteristics and nutrient concentrations on phytoplankton was investigated in four large rivers (Mura, Drava, Danube and Sava) in the Pannonian ecoregion in Croatia to understand how phytoplankton of rivers can be explained by the ''different functional group approach''. To gain a clearer understanding of the factors that affect river phytoplankton, the present study examined phytoplankton biomass and composition in relationship with physical and chemical parameters assessed in detail by preparing self-organising maps using functional groups and morpho-functional groups. Total nitrogen along with water residence time showed to be the best predictor to determine phytoplankton biomass and chlorophyll a.Phytoplankton diversity increased with higher water discharge, but it had the consequence of diluting algae and decreasing biomass. Bacillariophyceae and Chlorophyceae species dominated the phytoplankton assemblages in all rivers. Diatoms predominated in rivers with shorter residence time. Dominant diatom codons of functional groups were C, D and TB while morpho-functional groups were represented by only diatom group VI. As residence time increased, the proportion of chlorococcalean green algae, represented by functional group codon T and morpho-functional group IV grew in summer. Since potamoplankton is dominated by diatoms, functional groups with its fine partition of diatom codons proved to be excellent descriptor of the potamoplankton. Application of morpho-functional groups originally developed from the lake data, showed to be limiting because of the predominating presence of only one diatom group.

Phytoplankton functional groups indicators of environmental conditions in floodplain rivers and lakes of the Paraná Basin

“…In this sense, the absence of FGs as indicators in the rivers was probably due to the high water flow that promotes dispersal stochasticity and prevents to determine the relationship between the environmental conditions and the phytoplankton distribution . Moreover, the hydrodynamics of the rivers difficult the phytoplankton establishment because of the wash-out that increases the biovolume losses (Abonyi et al, 2012;Stanković et al, 2012;Devercelli & O'Farrell, 2013;Fraisse et al, 2013). This study demonstrated that the use of phytoplankton FGs is an alternative to obtain ecological and environments responses in the floodplain since the FGs were efficient indicators of hydrological periods and the environmental conditions in lakes and rivers.…”

“…Whereas the low FG L O biovolume registered in periods with high water-column mixing (dry periods) could be explained by the sensitivity of these organisms to deep (e.g. reservoirs) and prolonged mixing Padisák et al, 2009;Borics et al, 2012). We do not disregard the possibility that the high contribution of FG L O in the rivers could be related to the influence of the upstream reservoirs in the Paraná and Paranapanema Rivers, as the dispersion of organisms from the reservoir can influence the structure in downstream (Bovo-Scomparin et al, 2013).…”

“…The diversity patterns of the aquatic communities response to the temporal variation of the environmental conditions of floodplains (Neiff, 1990). For instance, phytoplankton presents higher diversity in dry periods than in flooding (Devercelli, 2006(Devercelli, , 2010Nabout et al, 2006;Lasne et al, 2007;Loverde-Oliveira et al, 2007;Stanković et al, 2012;Bovo-Scomparin et al, 2013).…”

“…Lakes have a high productivity-diversity ratio and an important role in the maintaining the biodiversity and system integrity (Korhonen et al, 2011;Stomp et al, 2011;Borics et al, 2012). On the other hand, highly dynamic rivers select species that are adapted to high flow and turbidity (Devercelli & O'Farrell, 2013;Fraisse et al, 2013).…”

Functional diversity of phytoplankton highlights long‐term gradual regime shift in the middle section of the Danube River due to global warming, human impacts and oligotrophication

“…We use two complementary functional approaches: the functional group (FG) concept sensu Reynolds (Reynolds, Huszar, Kruk, Naselli-Flores, & Melo, 2002) and the functional trait (FT) approach (Litchman & Klausmeier, 2008;Weithoff, 2003). Functional approaches have enabled better understanding of complex riverine processes repeatedly, such as river continuum and zonation (Abonyi, Leitão, Lanc ßon, & Padis ak, 2012;Abonyi et al, 2014), floodplain dynamics (Devercelli, 2006; Stankovi c, Vlahovi c, Gligora, V arb ır o, & Borics, 2012;Stevi c, Mihaljevi c, & Spoljari c, 2013) and various aspects of biomass/diversity relationships .…”