Physiological acclimation to gradients of solar irradiance within mats of the filamentous green macroalga Chaetomorpha linum from southern Spain

Abstract

Chaetomorpha linum (Müller) Kützing is a dominant mat-forming green macroalgal species within eutrophic systems. Its structure, comprising thick mats of interwoven filaments, requires acclimation to either high or low irradiance along a steep gradient of light arising from selfshading. Occurring in high-light environments, such as that along the southern coast of Spain, C. linum mats represent an excellent model system for studying spatial differences in photoacclimation and also the interactive effects of photosynthetically active and ultraviolet radiation on photoinhibition. This study was conducted in eutrophic brine-pond systems along the Bay of Cádiz (southern Spain). For periods of up to 1 wk, C. linum mats were exposed to natural solar radiation under different cut-off filters to study the effects of different wavelength ranges on photosynthetic activity, pigment and protein composition, and the occurrence of oxidative stress and changes in enzymatic activity of superoxide dismutase (SOD). The results revealed a particularly high tolerance of C. linum photosynthesis to high light and UV exposure. Addition of the UV-B range (280 to 315 nm) to photosynthetically active radiation, resulted in inhibition of non-photochemical quenching, a delay in recovery from photoinhibition, and an increase in both lipid peroxidation and SOD activity. In contrast, pigment and protein data revealed acclimation to the high irradiances of photosynthetically active radiation, but no additional effect of UV radiation. The data suggest that even in a highradiation environment such as southern Spain, UV-B radiation plays a minor role in photoacclimation of C. linum, but is effective in increasing both the generation and scavenging of oxidative stress. The UV-induced increase in SOD activity represents an important physiological acclimation mechanism of C. linum, enabling it to thrive under high UV radiation and high-light conditions. KEY WORDS: Chaetomorpha linum · Photosynthesis · Superoxide dismutase · Ultraviolet radiationResale or republication not permitted without written consent of the publisher

Short-term effects of increasing CO2, nitrate and temperature on three Mediterranean macroalgae: biochemical composition

“…organized in mats. Bischof et al (2006b) also showed the photo acclimation within mats of the filamentous green macroalga Chaetomorpha lin um, presenting much less photoinhibition than the first layers of thalli with high light exposure. Falkenberg et al (2013) reported that turf algae responded to enrichment of CO 2 and nutrients, whereas canopy-forming species responded only to nutrient enrichment; they concluded that the identification of how these conditions modify resource availability may help predict to what extent such major ecosystem components and the communities they support may adapt to future conditions.…”

Physiological, biochemical, and ultrastructural responses of the green macroalga Urospora penicilliformis from Arctic Spitsbergen to UV radiation

“…A microscale variation in pigment concentrations (Beach and Smith 1996a) and photosynthetic performance (Beach and Smith 1996b) between tissues from the canopy and understory microsites is reported among tropical intertidal turf-forming red macroalgae. The protective function of self-shading is also reported in Ulva and Chaetomorpha forming multilayers of floating mats during algal blooms (Bischof et al 2002b(Bischof et al , 2006. Acclimation to high PAR and UVR levels, especially in tropical regions, is essential for stress resistance and persistence of intertidal algae (Beach and Smith 1996a, b;Hanelt and Roleda 2009).…”

“…This response was not observed in filamentous gametophyte (this study) and in propagules (zoospores and gametes; Roleda et al 2009) of Urospora. Other defense mechanism against UVR-induced oxidative stress includes increase in superoxide dismutase activities reported in several green algae belonging to the genera Chaetomorpha, Cladophora, and Ulva (e.g., Choo et al 2004;Bischof et al 2006). Other targets which may reduce photosynthetic efficiency under UVR and high PAR include the ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), and structural chloroplast lipids (glycolipids and phosphatidylglycerol; Bischof et al 2002a;Khotimchenko and Yakovleva 2004).…”

Morpho-functional patterns and zonation of South Chilean seaweeds: the importance of photosynthetic and bio-optical traits

“…mats) can serve the function of enhancing tolerance to environmental stress, e.g. excessive photodamage in shallow waters (Johansson & Snoeijs 2002, Raven & Kübler 2002, Middelboe & Binzer 2004, Bischof et al 2006a). Thus, it was recognized that gradients in light availability and the concomitant light requirements for photosynthesis of seaweeds and seagrasses have important morpho-functional implications which can also be studied in the context of zonation (e.g.…”