Long-term dynamics of photosynthetic pigments in plankton of a large plains reservoir

N M Mineeva

doi:10.15421/012102

Abstract

Long-term observations are necessary to analyze and predict changes occurring in biological communities under global and regional climatic changes. The data on seasonal and long-term dynamics of chlorophyll in plankton of the Rybinsk Reservoir (Upper Volga, Russia) obtained in May – October 2009–2019 at six standard stations using the fluorescence method are presented. In the years with contrasting hydroclimatic conditions and water regime, the chlorophyll content varied from 1–3 to >100 μg/L. The significant variability of mean seasonal values (7.9 ± 0.5 μg/L in 2009 to 27.6 ± 1.7 μg/L in 2013 with variation coefficients of 52–134%) indicates the low resistance of the community. The total chlorophyll content is associated with the development of three main phytoplankton divisions i.e., diatoms, cyanoprokaryots, and green algae. The trophic status of the reservoir was characterized as mesotrophic in 2009 and 2017, eutrophic in 2011–2014, and moderately eutrophic in other years. In the long-term seasonal cycle of phytoplankton, there are five periods with stable temperature conditions and transparency, but variable chlorophyll content. A moderate positive relationship was found between the seasonal dynamics of chlorophyll and water temperature, but a moderate negative relationship with transparency. The priority factors regulating the long-term dynamics of chlorophyll include the NAO indices, Wolf numbers, temperature, and underwater light conditions, as well as the inflow volume and water level. Water regime limits the development of phytoplankton.

Highlights

It is well known that global climatic changes that have a significant impact on the structure and dynamics of biological communities of aquatic ecosystems (Adrian et al, 2009; Bertani et al, 2016; Özkan et al, 2016) continue to take place the beginning of the XXI century (Vtoroy, 2014)
In the years with contrasting hydroclimatic conditions and water content (2009–2019), the chlorophyll concentrations in the plankton of the Rybinsk Reservoir varied within a broad range with significant variability of the mean seasonal values, which indicates the low stability of the community
The effect of environmental factors on the development of phytoplankton varied in different years

Summary

Introduction

It is well known that global climatic changes that have a significant impact on the structure and dynamics of biological communities of aquatic ecosystems (Adrian et al, 2009; Bertani et al, 2016; Özkan et al, 2016) continue to take place the beginning of the XXI century (Vtoroy, 2014). Photosynthetic pigments, which are the universal ecological and physiological characteristics of the development and photosynthetic activity of algae, as well as the ecological state of water bodies, are widely used in the study of the autotrophic community in aquatic ecosystems. Longterm data have made it possible to study the seasonal and interannual dynamics of pigments, its relationship with regional and global environmental factors (Pautova & Rosenberg, 1999; Kopylov, 2001; Sygareva et al, 2016; Lazareva, 2018). Differentiated determination of chlorophyll in cyanoprokaryotes, diatoms and green algae made it possible to obtain new data on the seasonal and interannual dynamics of large taxonomic groups of phytoplankton, their contribution to the total chlorophyll content and their relationship with environmental factors in the years with different hydroclimatic conditions.

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Conclusion