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- Acclimation of Red Sea macroalgae to solar radiation: photosynthesis and thallus absorptancePublication . Figueroa, Felix L.; Martinez, Brezo; Israel, Alvaro; Neori, Amir; Malta, Erik-jan; Ang, Put, Jr.; Inken, Sven; Marquardt, Ronny; Rachamim, Tamar; Arazi, Uri; Frenk, Sammy; Korbee, NathalieThallus absorptance, daily courses of maximal quantum yields of chlorophyll fluorescence of photosystem II (F-v/F-m) and electron transport rates (ETR) were determined in 3 macroalgae (Hypnea spinella, Rhodophyta; Sargassum vulgare, Phaeophyta; and Ulva lactuca, Chlorophyta) collected from a low nutrient supply (LNS) ecosystem (Red Sea, Gulf of Aqaba, Eilat, Israel). In addition, U. lactuca grown previously in high nutrient supply (HNS) fishpond effluents was used to evaluate the effect of nutrient enrichment on photosynthesis. Short-term (2 d) and mid-term (5 d) effects of both photosynthetically active radiation (PAR) and full solar irradiance (PAB: PAR+UVA+UVB) at 3 solar irradiance treatments (no neutral filters, no NF; 2 neutral filter layers, 2NF; and 4 neutral filter layers, 4NF simulating levels of irradiance at 5, 10 and 20 m depth respectively) were evaluated in algae incubated with running seawater. Significant effects of time (variation throughout the day) and irradiance (number of neutral filters) on both F-v/F-m and ETR were observed. Photoinhibition occurred at noon under the no NF (up to 40% decrease) and 2NF (up to 30% decrease) treatments; however, full recovery in all treatments was reached in the afternoon (dynamic photoinhibition) except in H. spinella. The highest maximum ETR was observed in the no NF treatment despite its strongest photoinhibitory effect. The decrease in F-v/F-m at noon was similar to or higher under the PAB than under the PAR treatment alone, depending on the species. Photoinhibition was lower and the maximum ETR was higher in HNS than in LNS U. lactuca, indicating positive effects of nutrient supply on both photosynthesis and photoprotection. The maximum ETRs exhibited by different algae may be related to their zonation in the field and the resulting energy supply.
- Effects of nutrient supply on photosynthesis and pigmentation in Ulva lactuca (Chlorophyta): responses to short-term stressPublication . Figueroa, Felix L.; Israel, Alvaro; Neori, Amir; Martinez, Brezo; Malta, Erik-jan; Ang, Put, Jr.; Inken, Sven; Marquardt, Ronny; Korbee, NathalieThe effects of nutrient supply on photosynthesis (estimated as chlorophyll fluorescence), chlorophyll content, biomass yield and proximate chemical composition of tank cultivated Ulva lactuca L. (Chlorophyta) were evaluated. To assess the effect of nutrient supply on resistance capacity against short-term stress, algae grown in high nutrient supply (FINS) fishpond effluents and in low nutrient supply (LNS) oligotrophic seawater were transferred to small vessels with increased irradiance of PAR and UV radiation (PAR+UVA and PAR+UVA+UVB using cut-off filters) and increased temperature as compared to culture tanks. Electron transport rate and chlorophyll content were higher in HNS than in LNS algae. Effective quantum yield and chlorophyll content decreased after short-term exposure to high PAR irradiance. Full recovery of photosynthesis in the shade was observed under a moderately higher temperature (Delta+6 degrees C). UVB exposure reduced the negative effect of UVA on photosynthesis and pigment accumulation under temperature stress (Delta+10 degrees C), particularly in FINS algae. Growth under HNS appeared to accelerate acclimation of Ulva lactuca to short-term environmental changes, such as higher temperatures (as in heat waves) and higher UV radiation. Furthermore, nitrogen enrichment reduced the common inhibitory effects of short-term stress such as increased irradiance, UV radiation and temperature on photosynthesis.