Short-term effects of increased CO2, nitrate and temperature on photosynthetic activity in Ulva rigida (Chlorophyta) estimated by different pulse amplitude modulated fluorometers and oxygen evolution

Abstract

Short-term effects of pCO2 (700 – 380 ppm; HC-LC) and nitrate content (50-5 βM; HN-LC) on photosynthesis, estimated by different pulse amplitude modulated (PAMs) fluorometers and by oxygen evolution, were investigated in Ulva rigida (Chlorophyta) under solar radiation (ex-situ) and in the laboratory under artificial light (in-situ). After 6-days of incubation at ambient temperature (AT), algae were subjected to a 4 oC-temperature increase (AT+4oC) for 3 d. Both in-situ and ex-situ, maximal electron transport rate (ETRmax) and in situ gross photosynthesis (GP) measured by O2 evolution presented the highest values under HCHN, and the lowest under HCLN, across all measuring systems. Maximal quantum yield (Fv/Fm), and ETRmax of PSII (ETR(II)max) and of PSI (ETR(I)max), decreased under HCLN under AT+4°C. Ex situ ETR was higher than in situ ETR. At noon, Fv/Fm decreased (indicating photoinhibition), whereas ETR(II)max and maximal non-photochemical quenching (NPQmax) increased. ETR(II)max decreased under AT+4oC in contrast to Fv/Fm, photosynthetic efficiency (αETR) and saturated irradiance (EK). Thus, U. rigida exhibited a decrease in photosynthetic production under acidification, LN levels and AT+4oC. These results emphasize the importance of studying the interactive effects between environmental parameters using in-situ vs. ex-situ conditions when aiming to evaluate the impact of global change on marine macroalgae.

Short-term nutrient removal efficiency by Ulva pseudorotundata (Chlorophyta): potential use for Integrated Multi-Trophic Aquaculture (IMTA)

“…F v /F m usually decreases in periods of higher photosynthetically active radiation (PAR), signalizing photoinhibition and increased energy dissipation (Figueroa et al 2020). In this study, however, this variation did not exhibit a marked depression during the afternoon (between 180 and 420 min of experiment)…”

“…Photoinhibition mechanisms, recognized as a reversible interruption of the photosynthetic electron transport chain to protect seaweed against overexposure to solar radiation (Maxwell and Johnson 2000), are usually observed in photosynthetic studies, when F v /F m is monitored along the day (Figueroa et al 2020).…”

Seasonal Photoacclimation and Vulnerability Patterns in the Brown Macroalga Lessonia spicata (Ochrophyta)

“…Y(NPQ) was higher under nutrient-enriched periods compared to low conditions. The high values of Y(NPQ) are indicative of a high photoprotective capacity, whereas high values of Y(NO) reflect the inability of a plant to protect itself against damage by excess illumination [44]. Indeed, similar trends were shown by [44] in the green alga Ulva rigida.…”

“…The high values of Y(NPQ) are indicative of a high photoprotective capacity, whereas high values of Y(NO) reflect the inability of a plant to protect itself against damage by excess illumination [44]. Indeed, similar trends were shown by [44] in the green alga Ulva rigida. The authors evidenced that the differences in energy losses, and the photosynthetic conditions are more favorable under high nutrients conditions, than low carbon and nitrate.…”

Reducing self-shading effects in Botryococcus braunii cultures: effect of Mg2+ deficiency on optical and biochemical properties, photosynthesis and lipidomic profile

“…Thus, at high-medium level of MgSO 4, the quenching mechanism mainly through Y (NPQ) indicates a . Stress conditions such as increased UVB radiation or low carbon availability produced an increase in the NPQ max in green alga Ulva rigida (Figueroa et al 2014(Figueroa et al , 2021. Since NPQ max is the ratio Y (NPQ) : Y (NO) , it is shown that stress conditions favored the photoregulated yield loss increasing the photoprotection capacity.…”