Photosynthetic apparatus variability of the rigid hornwort (Ceratophyllum demersum L.) from the Saksagan River influenced by the mine activity

Abstract

Aquatic ecosystems are the final absorbers of various pollutants, so require complex monitoring to control their condition. Macrophytes and other aquatic plants serve as reliable indicators of the hydro ecosystems ecological state, as they provide an integral assessment of the aquatic environment in time and space. Changes in chlorophyll a and chlorophyll b content and ratio in the rigid hornwort (Ceratophyllum demersum L.) leaves depending on the water hydro chemical parameters of Saksagan River in the zones of influence of "Ternivska" and "Oktyabrska" mines (Kryvyi Rih city) were studied. The purpose of the work was to find out the features of C. demersum photosynthetic apparatus reorganization as plants adaptive reaction to the technogenic transformation of river ecosystem. The water mineralization changes in the range of 1.2–2.9 g/L and fluctuations in the nitrates and nitrites content in the Saksagan River different sections were established. Both an increase and a decrease in the content of chlorophyll both forms in C. demersum leaves were detected, but more significant changes were related to chlorophyll b content. The photosynthetic pigments total content in plant leaves was the highest in the most mineralized areas (points of return water discharge and 500 m below of "Ternivska" mine), and it was the lowest due to sharp water mineralization increasing (500 m below the return water discharge of "Oktyabrska" mine). Significant variability in the photosynthetic pigments content and ratio indicates flexible regulation of their synthesis in C. demersum leaves to maintain the efficiency of the photosynthetic apparatus under conditions of water pollution. The revealed regularities indicate the active protection of the photosynthetic process in the C. demersum leaves, which is an important prerequisite for the plant’s survival in adverse conditions and the preservation of the structure and productivity of the water ecosystem of the Saksagan River.