LIGHT ABSORPTION AND MAXIMUM QUANTUM YIELD OF PHOTOSYNTHESIS DURING AUTUMN PHYTOPLANKTON BLOOM IN THE WESTERN BLACK SEA

• Date: 2023
• Main Authors: Чурілова, Т. Я., Фіненко, З. З., Тугрул, С.
• Format: Article
• Language: English
• Published: Marine Ecological Journal 2023
• Subjects: хлорофіл а; фітопланктон; поглинання світла; максимальний квантовий вихід; біогенні елементи
• Online Access: https://mej.od.ua/index.php/mej/article/view/447
• Journal Title: Marine Ecological Journal

In the frame of GEF/UNDP Black Sea Ecosystem Recovery Project the effect of nutrient availability on phytoplankton light absorption and maximum quantum yield of carbon fixation (фmax) has been investigated. It has been found out that chlorophyll a concentration (Chl a) varied from 0.3 to 10 mg m-3 increasing from deep-water region to shelf waters. At the shallow stations, where upper mixed layer spread deeper the bottom of euphotic zone, the homogenous pigment distribution was observed. In the deep-water region the Chl a profiles showed the presence of a deep Chl a maximum (DCM) below a seasonal density cline. The functional characteristics of phytoplankton showed depthdependent variation. The phytoplankton from DCM was characterized 20 % lower values of spectral averaged Chl a – specific light absorption aph  (0.016±0.0025 m2 (mgChl)-1) and more than in two times higher values of фmax (0.070±0.012 molC (mol quanta)-1) compared with the surface phytoplankton aph  (0.021±0.0035 m2 (mgChl)-1) andфmax (0.030±0.0078 molC (mol quanta)-1). From offshore to shallow stations the increasing of surface Chl a concentration was accompanied with slight decrease of aph  (on ~20 %) and significant increase of фmax up to its theoretical limit - 0.1 molC (mol quanta)-1, which were caused by an increase in nutrient supply across the shelf.