Sargassum stenophyllum (Fucales, Ochrophyta) responses to temperature short-term exposure: photosynthesis and chemical composition

Abstract

Sargassum species form extensive benthic beds in tropical and subtropical low intertidal and subtidal zones, acting as important drivers for marine community structure. Temperature, as one of the most important abiotic factor, affects seaweed performance and triggers changes in metabolic responses; therefore, laboratory experiments involving temperature ranges are tools for understanding seaweed engineering. The aim of this study was to assess the physiological vulnerability and sensitivity of Sargassum stenophyllum C. Martius exposed to five different temperatures by analyzing photosynthetic performance and chemical composition related to carbon and nitrogen metabolism. There were no significant differences in energy quenching between treatments, except at 35 °C, which showed decreased photochemical quenching and increased non-regulated non-photochemical quenching. Chlorophyll a and chlorophyll c at 15 °C and 35 °C exhibited lower amounts at the end of experiment. Protein content showed progressive diminution in the treatments. Total soluble carbohydrates content showed higher concentration as temperature increased. After 7 days, total amino acid content showed increase from 15 °C to 30 °C. No generalization between the amino acid patterns, although glutamine and glutamate content at 15 °C and 35 °C were reduced; and the highest values of isoleucine and leucine were detected at 35 °C. We postulated that accumulation of certain chemical compounds in S. stenophyllum results from a reallocation of carbon and nitrogen, osmoregulation responses and protection against oxidative stress. Results suggest this species' tolerance ranges between 15 °C and 30 °C and sensitivity at 35 °C.

Thermal vulnerability of the Levantine endemic and endangered habitat-forming macroalga, Gongolaria rayssiae: implications for reef carbon

“…The respiration rates we measured exponentially increased with the temperature as it was shown in other seaweed species (Piñeiro-Corbeira et al, 2018;Dıáz-acosta et al, 2021) and it could indicate a possible shift towards heterotrophic metabolism (Brown et al, 2004;Bennett et al, 2022b). Studies conducted on other representatives of the order Fucales showed marked signs of tissue necrosis at higher temperatures (Flukes et al, 2015;Graiff et al, 2015;Urrea-Victoria et al, 2020). Similarly, the high respiration rate we recorded at 35°C (Figure 4C) is likely to be the result of microbial community activity associated to the decaying seaweed, as indicated by G. rayssiae's discoloration, tissue necrosis and deterioration at these higher temperatures (Supplementary Figure S8).…”

Concise review of genus Lessonia Bory

“…Lessonia flavicans, L. nigrescens, and L. trabeculata extracts provide a mixture of fucans and alginic acid that may be applied in agriculture as a pesticide against harmful fungi in wheat and tobacco (Percival et al 1983;Chandía et al 2004Chandía et al , 2005Matsuhiro and Zambrano 2004). Fucoidan and alginic acid compositions are altered depending on the environmental conditions to which the seaweeds are exposed (water motion, light and temperature) (Martins et al 2011;Valiente and Mogollón 2013;Harb et al 2018;Urrea-Victoria et al 2020). For example, Lessonia from exposed sites produces a high content of polysaccharides compared to sheltered sites, in addition to different gel quality throughout the year (Chandía et al 2004(Chandía et al , 2005Valiente and Mogollón 2013;Leal et al 2018;Zou et al 2019).…”