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

Abstract

The application of functional approaches in understanding phytoplankton community-level responses to changes in the environment has become increasingly widespread in recent years.Eutrophication is known to cause profound modifications in ecosystem processes, however, the underlying relationships between environmental drivers and phytoplankton diversity and functioning are complex and largely unknown. Therefore, in the present study we investigated and compared the temporal diversity patterns of phytoplankton functional groups in the mesotrophic eastern and eutrophic western basin of the shallow Lake Balaton situated in Hungary. Diversity data were derived from taxonomic composition and biomass data corresponding to the years 2005-2006 and 2008-2009. With the use of cluster analysis phytoplankton species were classified into eight distinct groups representing different combinations of functionally relevant traits including greatest axial linear dimension, surface to volume ratio, photosynthetic pigment composition, N 2 -fixation, phagotrophic potential, growth form/complexity (unicell, filamentous, colony-or coenobium-2 forming) and motility. Our results have revealed that there is a significant inverse relationship between the functional group diversity used in our study and trophic state (total phytoplankton biomass) as opposed to species diversity, where no correlation was observed. In addition, group evenness showed an even stronger negative correlation with trophic state, while species evenness yielded only a weak relationship. The observed variability in functional group diversity suggests that such an approach could provide an efficient means of revealing structural changes in phytoplankton communities, establishing new hypotheses and highlighting fundamental points in ecosystem functioning.

Biodiversity ecosystem functioning research in freshwater phytoplankton: A comprehensive review of trait-based studies

“…Negative relationships were present in 11.5% of cases, which means a decreasing ecosystem functioning as trait diversity increased. As an explanation for this pattern, authors suggest that under some condi- tions one single productive taxa with particular traits might dominate, leading to low functional diversity coupled to high biomass (Pälffy et al, 2013;Santos et al, 2014). Unfortunately, none of the studies reviewed here explicitly tested the suggested mechanisms and remained purely conjectural.…”

“…The six studies can be separated into two categories: field and laboratory studies. The former includes four studies in which both trait-based diversity and ecosystem functioning data were obtained from natural conditions (Vogt et al, 2010;Pälffy et al, 2013;Santos et al, 2014;Fontana et al, 2017). In the other two studies, diversity was directly manipulated under highly controlled conditions in the laboratory (Shurin et al, 2014;Steudel et al, 2016).…”

“…The other two field studies did not report the number of species analyzed. Field data were collected in a variety of freshwater systems around the world: Vogt et al (2010) included data from 65 lakes in Canada, Pälffy et al (2013) from one single lake in Hungary, Santos et al (2014) included 19 reservoirs from Brazil, whereas Fontana et al (2017) reported data from 28 lakes in total, 2 from Switzerland and 26 from the Danube delta in Romania.…”

“…Type of study Main conclusion Vogt et al, 2010 Field Trait-based diversity was positively associated with total community biovolume Pälffy et al, 2013 Field Significant negative correlations between total biomass, functional group diversity and functional group evenness Santos et al, 2014 Field A positive relation between productivity and diversity, except for functional evenness for which the relation was negative Fontana et al, 2017 Field Trait evenness exhibited a robust negative relationship with biomass Biodiversity ecosystem functioning research in freshwater phytoplankton: A comprehensive review of trait-based studies 181…”

“…The third biomass related variable, used in two field studies was total community biomass (Vogt et al, 2010;Fontana et al, 2017). The two nonbiomass related ecosystem functions included in the other field studies are chlorophyll a concentration (Pälffy et al, 2013;Santos et al, 2014) and a proxy for resource use efficiency calculated as the ratio between total biomass and available total phosphorous (Fontana et al, 2017).…”