Protistan diversity does peak in the horohalinicum of the Baltic Sea: Reply to Ptacnik et al. (2011)

Abstract

In reply to the Comment by Ptacnik et al. (2011; Mar Ecol Prog Ser 432:291-292), a sub- stantiation is given for the use of the simplest method to conduct a meta-analysis of published plank- ton data sets and annotated checklists aimed at refining the 'Artenminimum' (species-minimum) con- cept (Remane 1934; Zool Anz 7(Suppl):34-74). The applicability of this concept, which originally derived from macrozoobenthos data, was tested by Telesh et al. (2011; Mar Ecol Prog Ser 421:1-11) for plankton species using much larger data sets, and these results backed up the novel 'protistan species-maximum concept' for the horohalinicum of the Baltic Sea. Re-fitting our algorithm to the available data sets after the critical comments of Ptacnik et al. (2011) did not alter the shape of the plankton diversity trends, and the original conclusions that (1) the brackish-water Baltic Sea is not poor in plankton species, (2) Remane's curve is invalid for plankton, and (3) protistan species richness peaks in the horohalinicum at salinities of 5 to 8 remained robust. The suggestion by Ptacnik et al. (2011) to use a more detailed statistical analysis for describing the patterns of overall plankton diver- sity is recognized as a perspective for future research of changes in plankton communities within the Baltic Sea salinity gradient, although it cannot be implemented until spatially representative zoo- plankton data sets become available.