Spring to summer transition timing influences zooplankton phenology and temporal niche partitioning in the coastal zone of the White Sea

Abstract

Climatic changes are manifested through temporal shifts of seasonal events in environment, which may be critical for planktonic organisms. Temporal shift of seasonal warming curve in high latitudes affects phenology of aquatic organisms. Significant correlation between timing of phenological events in the life cycles of planktonic copepods and spring-summer temperature transition dates was revealed by canonical correlation analysis. We analyzed the long-term zooplankton and temperature time series (1961–2018) from the White Sea (66°19'50"N; 33°40'06"E, near the White Sea Biological Station of the Zoological Institute of the Russian Academy of Sciences). Two types of seasonal abundance dynamics of copepod juveniles and four types of the spring to summer transition were revealed. Each species demonstrated specific dynamics in response to each type of spring to summer transition. Species with similar ecological traits differed in their phenological response to the changes in the temperature dynamics. This phenomenon was explained, at least partly, by niche partitioning, when temporal niches of ecologically similar species were separated as a result of shifting the phenological events in time. The latter, in turn, was the result of organisms’ response to changes of spring to summer transition dynamics from year to year. We hypothesize that such separation may be one of the solutions of the “Paradox of the plankton”, favouring success of species-rich planktonic communities in high-latitude ecosystems, characterized by relative paucity of food resources and short productive season.