Taxonomic size structure consistency of the English Channel phytoplankton

Abstract

Here we report the worldwide first results on long-term variability of marine phytoplankton taxonomic size structure based on traditional taxonomic size spectra (TTSS). The Plymouth Marine Laboratory monitoring database for station L4 was used to build annual TTSS patterns (1992–2005) and estimate their similarity with the help of hierarchical cluster analysis. Almost identical TTSS patterns were observed each year. While the height of the main peaks was slightly variable, their horizontal positions were unchanged. Whereas the above patterns resembled the phytoplankton TTSS established for the subtropical Lake Kinneret, the L4 spectrum size range was much broader and the distance between the main peaks approximately two times greater. The similarity level (Pearson r = 0.872–0.992) in TTSS pairs for station L4 was comparable to the estimates established at several lakes, while being much higher than in the inter-ecosystem (L4 and Kinneret) pairs ( r = 0.317–0.578). Thus, the phenomenon of long-term consistency of phytoplankton taxonomic size structure, found previously at freshwater ecosystems, for the first time is confirmed for marine phytoplankton, which speaks in favor of much higher generality of this important structural property of aquatic communities. The TTSS multi-annual consistency can be helpful for long-term monitoring, environment protection and forecasting. The evident and permanent difference in the peak positions between ecosystems opens a way for additional analyses which can be helpful for the development of theoretical models. A set of plausible mechanisms, capable to produce and support the empirically obtained distribution patterns, is discussed.