Air-dispersed phytoplankton in a Mediterranean River-Reservoir System (Aliakmon-Polyphytos, Greece)

The air-dispersed phytoplankton diversity and colonization potential, in a Mediterranean River-Reservoir System (Aliakmon-Polyphytos, Northern Greece), were studied. Phytoplankton samples were collected weekly, from five sampling sites in the river-reservoir system (for 11 weeks) and from jars replaced weekly for 10 successive weeks placed at one colonization site (CS) (for 10 weeks). The algal diversity in the river-reservoir system was high. The air-dispersed algae in the CS jars included taxa of the local species pool (reservoir phytoplankton), including taxa of the airborne algae common in most biogeographic regions. Both small- and large-sized phytoplankton in the vegetative form of unicells, small coenobia, large colonies and filaments were observed in the CS jars. Nanoplanktic algae and among them the known allergenic chlorophyte Chlorella were the most frequent and abundant air-dispersed algae. The large-sized chlorophytes Mougeotia sp. and Ulothrix sp. were also frequently air-dispersed in the CS jars. Chlorophytes exhibited the highest colonization potential, followed by diatoms and cyanobacteria. Evidence is provided that over short distances, the wind is an important agent for the dispersal of phytoplankton with different colonization potentials, including the bloom-forming toxic cyanobacterium Microcystis aeruginosa.