2015/05/01 by Shogo Kokubu, Gregory N. Nishihara, Yuki Watanabe +3 · 1 citation
Earth and Planetary Sciences · #Atmospheric chemistry and aerosols #Marine and coastal ecosystems #Marine and coastal plant biology
paper · doi:10.2216/15-007.1
crossref issued 2015/05/01 · crossref published 2015/05/01 · crossref published-print 2015/05/01 · openalex publication_date 2015/05/01 · crossref created 2015/06/24 · crossref published-online 2019/03/21 · crossref deposited 2019/03/21 · openalex created_date 2025/10/10 · crossref indexed 2026/07/27 · openalex updated_date 2026/07/29
:The effect of irradiance and temperature on the photosynthesis of a Japanese native brown alga, Sargassum fusiforme, was determined by using dissolved oxygen sensors and pulse amplitude–modulated fluorometry. In situ measurements of the effective quantum yield (ΦPSII) decreased as irradiance increased at 12:00 PM and recovered in the late afternoon, indicating that a proportionately greater number of reaction centres were closed. Likewise, laboratory measurement after 6 hours of exposure to low and high (300 and 1000 μmol photons m−2 s−1, respectively) irradiances showed a relatively greater decrease in ΦPSII at high irradiance, and both treatments recovered overnight. A model of the net photosynthesis–irradiance relationship determined at 20°C revealed that the net photosynthetic rate quickly increased at irradiances below the estimated saturation irradiance of 391 μmol photons m−2 s−1 [95% Bayesian credible interval (BCI) of 299–515 μmol photons m−2 s−1]. Gross photosynthesis and dark respiration rates determined over a range of temperatures (8–36°C) revealed that the maximal gross photosynthetic rate was 24.1 (BCI: 21.5–26.8) μg O2 gww−1 min−1 at 22.9°C (BCI: 19.8–25.8), and the dark respiration rate increased nonlinearly from a low of 0.5 μg O2 gww−1 min−1 at 8°C to a high of 8.9 μg O2 gww−1 min−1 at 36°C. The highest value of the quantum yield (Fv/Fm = ΦPSII at 0 μmol photons m−2 s−1) was estimated to occur at 22.9°C (BCI: 21.8–23.9) and was 0.72 (BCI: 0.70–0.73). The specimens examined appeared to be well adapted to the natural temperature range of the study site. Although the irradiances on the fronds were strong enough to induce a drop in quantum yield, our evidence clearly suggests that full recovery occurs overnight.