Lakes of the White Sea coast have altered owing to postglacial land uplift, changing from marine lagoon to freshwater conditions. The Lake Krivoe (deep, transparent, and stratified) at the Cape Kartesh (northern Karelia) formed via isolation from the sea and is made up of two basins filled with organic-rich sediments. As for the trophic status, the pelagic zone of the lake has remained oligotrophic since the 1960s. Diatoms and phytopigments were studied in a sediment core from a deep part of the lake. A high concentration of valves of benthic and periphytonic diatom species was observed in the core, indicating a significant contribution of these producers to the lake productivity. The lake bottom sediments were classified as highly productive (hypertrophic) based on their phytopigment concentration. Thus, benthic producers can play a key role in the ecosystems of arctic lakes, and the idea is important to consider when monitoring.
Berezina et al. (2026) studied this question.