Work

Response of a Benthic Sargassum Population to Increased Temperatures: Decline in Non-Photochemical Quenching of Chlorophyll a Fluorescence (NPQ) Precedes That of Maximum Quantum Yield of PSII

Year: 2025

Type: article

Abstract: Sargassum is an important primary producer of rocky bottom communities in coastal ecosystems. Like other parts of the planet, benthic populations of S. natans from Ilha Grande Bay, southeastern Brazil, have been suffering from different forms of natural and anthropogenic disturbances, in particular increasing seawater temperatures. In this study, we focused on understanding the effects of temperature on the photosynthetic performance of S. natans using PAM fluorometry. Measurements in the field revealed the dynamics of effective and maximum quantum yields (ΔF/F’m and Fv/Fm, respectively), as well as the dynamics of photoprotection mechanisms. The stress induced by incubation at 32-35°C, caused a decrease in Fv/Fm by 33% on the first day and approximately 20% on subsequent days. Additionally, direct estimates of the net photosynthesis of S. natans by measurements of dissolved oxygen concentration showed that an increase in temperature inhibited photosynthesis. In the laboratory, using specimens of S. natans and Padina gymnospora, we verified the effect of temperature on the fate of the energy absorbed by the PSII antenna using complementary quantum yields. Exclusively in Sargassum, temperatures in the range of 32 to 35ºC promoted a decline of non-photochemical quenching of chlorophyll fluorescence before the decline of Fv/Fm, indicating that PSII is destroyed in the absence of the NPQ photoprotection.

Source: Plants

DOI: 10.3390/plants14050759

Authors: Ricardo M. Chaloub, Rodrigo Mariath V. da Costa, João da Silva, Cristina A.G. Nassar, Fernanda Reinert, Maria Teresa M. Széchy