Photosynthesis and lipid composition of the Antarctic endemic rhodophyte Palmaria decipiens: effects of changing light and temperature levels

Abstract

In coastal waters, Antarctic rhodophytes are exposed to harsh environmental conditions throughout the year, like low water temperatures ranging from ¡1.8°C to 2°C and high light during the summer season. Photosynthetic performance under these conditions may be aVected by slowed down enzymatic reactions and the increased generation of reactive oxygen species. The consequence might be a chronic photoinhibition of photosynthetic primary reactions related to increased fragmentation of the D1 reaction centre protein in photosystem II. It is hypothesized that changes in lipid composition of biomembranes may represent an adaptive trait to maintain D1 turnover in response to temperature variation. The interactive eVects of high light and low temperature were studied on an endemic Antarctic red alga, Palmaria decipiens, sampled from two shore levels, intertidal and subtidal, and exposed to mesocosm experiments using two levels of natural solar radiation and two diVerent temperature regimes (2-5°C and 5-10°C). During the experimental period of 23 days, maximum quantum yield of photosynthesis decreased in all treatments, with the intertidal specimens exposed at 5-10°C being most aVected. On the pigment level, a decreasing ratio of phycobiliproteins to chlorophyll a was found in all treatments. A pronounced decrease in D1 protein concentration occurred in subtidal specimens exposed at 2-5°C. Marked changes in lipid composition, i.e. the ratio of saturated to unsaturated fatty acids, indicated an eVective response of specimens to temperature change. Results provide new insights into mechanisms of stress adaptation in this key species of shallow Antarctic benthic communities.

Multifaceted characterization of a Lemanea fluviatilis population (Batrachospermales, Rhodophyta) from a glacial stream in the south-eastern Alps

“…To our knowledge, there have been no studies regarding the lipid content of this taxon and how this may relate to thermal niche. However, the effects of temperature on fatty acids composition patterns have been addressed by some studies on micro-(e.g., FuSChino et al 2011;Flaim et al 2012;Leblond et al 2015) and macroalgae (e.g., BeCKer et al 2010).…”

Fatty acid compositions associated with high-light tolerance in the intertidal rhodophytes Mastocarpus stellatus and Chondrus crispus

“…Additionally, respective acclimations in antenna pigments (e.g. phycobilins), which result in further adjustments of light harvesting to various light climates, were also frequently observed [16,55]. Why those pigments did not show clear species-or habitat-specific differences in our study remains to be resolved.…”

“…Furthermore, the algae have to adjust their thylakoid membrane fluidity to the prevailing environmental conditions in order to maintain the integrity of these membranes, and thus, a proper operation of the photosynthetic machinery in a highly variable environment. Photosystem II is embedded in the thylakoid membrane, so that the rate of the D1 reaction center protein repair cycle, especially the re-integration of de-novo synthesized proteins via lateral diffusion through the membrane, depends strongly on membrane fluidity [16] and references therein]. Besides this, optimal membrane fluidities under variable environmental conditions are needed in order to stabilize membrane-associated proteins and to maintain electron transport chains and transmembrane proton gradients [17].…”

“…[19][20][21][22]. Becker et al [16] reported, for example, that the Antarctic red alga Palmaria decipiens acclimated to different temperature regimes by adjusting the degree of fatty acid saturation. In addition, variations in light conditions were also shown to affect the membrane fatty acid composition of macroalgae, but they did not reveal consistent responses [e.g.…”

Stress tolerance of Antarctic macroalgae in the early life stages

“…A similar tendency, although less marked, was observed in I. cordata and P. endiviifolia. It is known that various processes related to photoprotection, e.g., D1 protein turnover, enzyme repair mechanisms, and dissipative quenching, operate more efficiently at higher temperatures [29,30]. Thus, the lower inhibition of photosynthesis observed at 12°C compared to 2 and 7°C could be regarded as an efficient acclimation of photosynthesis in these macroalgae.…”