Rarity, ecological memory, rate of floral change in phytoplankton—and the mystery of the Red Cock

Abstract

In this article, we attempt to estimate the contemporary phytoplankton species pool of a particular lake, by assessing the rate of floral change over a period of 15 years. Phytoplankton time series data from Lake Stechlin, an oligo-mesotrophic lake in the Baltic Lake District (Germany) were used. Of the 254 algal species recorded during the 15-year of studies with roughly biweekly sampling, 212 species were planktonic. In the individual plankton years, the recorded total number of species changed between 97 and 122, of which the number of dominants ([1% contribution to the annual average of total biomass) was only 10-19. The 15-year cumulative number of species exhibited an almost linear increase after an initial saturation phase. This increase was attributed to two reasons: increase of sample size and immigration of species new to the flora. Based on a probabilistic model developed in this study, we estimated the number of co-existing planktonic species of the lake as some 180, and the rate of floral change as 1-2 species per year. Of these coexisting species, only few maintain the matter-energy processing ecosystem functions in any particular plankton year. Selection of these dominants is probably driven by mesoclimatic cycles, coupled with human-induced forcing, like eutrophication. All others are hiding as an ecological memory, in the sense of the capacity or experiences of past states to influence present or future responses of the community. Data analyses suggest that selection of the 'memory species' that show temporary abundance increases over shorter (several years) periods are Electronic supplementary material The online version of this article (largely dependent upon the dominants. These results show that interspecific interactions and the particular autecological features of the dominants, together with their effects on the whole ecosystem, act as a major organizing force. Some phytoplankton species, like Planktothrix rubescens, are efficient ecosystem engineers with cascading effects of both a top-down and bottom-up nature. Historical scientific data on Planktothrix blooms in Lake Stechlin suggest cyclic patterns in long-term development of phytoplankton which, as the legend of the Red Cock suggests, dates back much further than scientific archives.

Haloleptolyngbya alcalis gen. et sp. nov., a new filamentous cyanobacterium from the soda lake Nakuru, Kenya

“…Hence, the taxa play an important role of influencing the present or future responses of the community. This phenomenon has been observed in different lakes in Europe (Padisák, 1992;Padisák et al, 2010). Dadheech et al (2009) detected DNA of several dormant taxa in the plankton and sediment of Kenyan lakes, such as Chroococcidiopsis which were not detectable by microscopy.…”

Occurrence and mass development of Mougeotia spp. (Zygnemataceae) in large, deep lakes

“…in 1998, reaching high biomass during spring in 2005 and 2006, then again in winter 2010/2011 (Zohary et al, 2012). Several observations indicate that Mougeotia is a permanent element of the phytoplankton flora in deep lakes even though blooms have not been observed (Padisák et al, 2010).…”

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

“…These organisms have a siliceous wall and present a high sedimentation rate, and they are dependent on the water mixing to maintain their high biomass (Reynolds et al, 1994;Stević et al, 2013). A high water-column mixing promotes materials resuspension and guarantees the position of phytoplankters in the euphotic zone (Padisák et al, 2010). Centric diatoms (e.g., FG B -Aulacoseira spp.)…”