Short-term effects of CO2, nutrients and temperature on three marine macroalgae under solar radiation

Abstract

Three macroalgal species belonging to Chlorophyta (Ulva rigida), Rhodophyta (Ellisolandia elongata) and Phaeophyceae (Heterokontophyta; Cystoseira tamariscifolia), naturally growing at the same shore level and representing 3 morpho-functional groups, were exposed to short-term changes in temperature under different carbon and nitrogen regimes. Experiments were conducted in outdoor tanks at 4 combinations of carbon and nitrogen levels under reduced solar radiation. In vivo chl a fluorescence parameters and pigment contents were monitored to assess diurnal physiological responses and potential for recovery. Strong fluctuations in chl a fluorescence parameters, but not in chl a content, were observed in response to diurnal variation in solar radiation and light climate within the tanks; sensitivity varied between algal species and, in some cases, depended on the carbon and nitrogen regime. Nitrogen uptake was similarly high in U. rigida and E. elongata and lowest in C. tamariscifolia. In U. rigida and E. elongata, chl a concentrations decreased after high-carbon treatments. Effective photosystem II quantum efficiency was reduced in all species at noon, and lowest in C. tamariscifolia. The results highlight the complexity of physiological short-term acclimations which were most likely linked to biochemical changes at the cellular level. Long-term experiments are required in future for more comprehensive investigation of the observed interactive effects of the different environmental parameters

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

“…In addition, the light climate in the tanks depended on the positioning of the species. U. rigida, with its freely moving thalli in the tank's water flow, presented more variable canopy episodes than C. tamariscifolia (fixed position) or than E. elongata, which was located at the bottom (see Stengel et al 2014). Thus, in addition to the biooptical characteristic of the thalli, the canopy effect in the tanks must be taken into account to explain light ab sorption.…”

“…during the + 4°C treatment. Detailed hourly temperature fluctuations can be found in Stengel et al (2014). Orthophosphate at 2 µM was included in both LN and HN treatments.…”

“…The experimental design is described in detail by Stengel et al (2014). Briefly, the 3 species were cultivated in a mesocosm system, with either high or low C and N conditions: high CO 2 (HC): 700 ppm vs. low CO 2 (LC): 380 ppm; high nitrate level (HN): 50 µM vs. low nitrate level (LN): 5 µM.…”

Rhodoliths in Brazil: Current knowledge and potential impacts of climate change

“…CARPENTER, 2012;MARTIN et al, 2013;NOISETTE et al, 2013;COMEAU et al, 2014) and light conditions (GAO;ZHENG, 2010;COMEAU et al, 2014), or local factors, such as nutrient concentration (RUSSELL et al, 2009;STENGEL et al, 2014). Besides a variety of studies investigating the OA response in coralline algae, only a few studies have been performed on the effect of the increase in seawater temperature and possible synergistic effects of ocean warming and acidification (see Figure 6B).…”

Introduction

“…The experimental conditions simulated climate change scenarios ex pected at the end of this century. The effects of nutrients, pH, temperature and irradiance on the diurnal and daily responses of in vivo chlorophyll a fluorescence in the 3 algae are presented in Stengel et al (2014). WG4 conducted field studies in the Natural Park of Cape of Gata ( Fig.…”