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

摘要

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, N2-fixation, phagotrophic potential, growth form/complexity (unicell, filamentous, colony- or coenobiumforming) and motility. Our results have revealed that there is a significant inverse relationshipudbetween the functional group diversity used in our study and trophic state (total phytoplanktonudbiomass) as opposed to species diversity, where no correlation was observed. In addition, groupudevenness showed an even stronger negative correlation with trophic state, while species evennessudyielded only a weak relationship. The observed variability in functional group diversity suggestsudthat such an approach could provide an efficient means of revealing structural changes inudphytoplankton communities, establishing new hypotheses and highlighting fundamental points inudecosystem functioning.