Directed diversity manipulations within natural phytoplankton communities

Abstract

AbstractThere is general concern about the rapid decline in biodiversity. The consequences of biodiversity declines are expected to impact ecosystem functioning. Primary production is one of the ecosystem—functions where existing data already support such expectations. However, for a mechanistic understanding of these processes more experimental investigations are needed. In terrestrial primary producer communities a directed removal of species is one important tool in the experimental portfolio to study the consequences of a decline in biodiversity. However, this is notoriously difficult in suspended aquatic primary producer communities consisting of mostly unicellular phytoplankton. As phytoplankton are responsible for about 50% of global primary production, detailed knowledge of whether and how diversity declines will impact the functioning of natural phytoplankton communities is of crucial importance. Here, we tested two different methods, dilution and disturbance—to manipulate diversity of natural freshwater plankton communities along an experimental gradient in a directed way. Dilution will alter community composition by affecting mainly rare species whereas disturbance will affect mainly stress sensitive species. Both methods resulted in distinct and replicable species richness gradients. Such gradients enable the mechanistic study of general responses to biodiversity loss in natural phytoplankton communities with shared evolutionary history in an ecological meaningful way.