Phytoplankton as an indicator of the ecosystem state of the Kondopoga Bay of Lake Onego under cage trout farming

Abstract

Phytoplankton studies in the coastal and pelagic part of the Kondopoga Bay of Lake Onego nearby the cage trout farms (2019, 2021) revealed high quantitative indicators of its development, characterizing the bay as meso-eutrophic. In terms of number, diatoms (up to 79%) were dominant communities, while cyanobacteria and green algae – subdominant (up to 40%). Indicator species of the β-mesosaprobic zone prevailed; polysaprobionts were also present. Potentially toxic species Microcystis aeruginosa (Kütz.) Kütz., Aphanizomenon flos-aquae L. Ralfs., Coelosphaerium kuetzingianum Näg., Oscillatoria limnetica Lemm. were noted. Analysis of long-term dynamics of phytoplankton showed the increasing development of all groups of phytoplankton (including dominant species) in the pelagic part of the bay. This indicates eutrophication of the previously mesotrophic bay due to nutrients supplied with wastes from trout farms.

Keywords

• indicator species
• algae
• eutrophication
• saprobity
• cage trout farming