Wang Ying, Qu Tongfei, Zhao Xinyu, Tang Xianghai, Xiao Hui, Tang Xuexi
Department of Marine Ecology, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003 China.
Springerplus. 2016 Jun 17;5(1):775. doi: 10.1186/s40064-016-2488-7. eCollection 2016.
Green tides have occurred in the Yellow Sea, China, every year from 2007 to 2015. The free-floating Ulva prolifera (Müller) J. Agardh was the causative macroalgal species. The co-occurring, attached U. intestinalis was also observed. Photosynthetic capacities were determined using chlorophyll fluorescence in situ and after 7 days lab acclimation, and a significant differences were noted. Pigment composition showed no obvious differences, but concentrations varied significantly, especially chlorophyll b in U. prolifera two times increase was observed after acclimation. The optimal photochemical efficiency of PS II (Fv/Fm) was significantly higher in U. prolifera. Photosynthetic rate (α), maximum relative electron transport rate (rETRmax), and minimum saturating irradiance (Ek), obtained from rapid light response curves (RLCs), showed almost the same photosynthetic physiological status as Fv/Fm. Quenching coefficients and low temperature (77 K) chlorophyll fluorescence emission spectra of thylakoid membranes analysis showed U. prolifera has a better recovery activity and plasticity of PSII than U. intestinalis. Furthermore, energy dissipation via non-photochemical quenching (NPQ) and state transitions showed efficacious photoprotection solution especially in U. prolifera suffered from the severe stresses. Results in the present study suggested that U. prolifera's higher photosynthetic capacity would contribute to its free-floating proliferation, and efficacious photoprotection in addition to favorable oceanographic conditions and high nutrient levels support its growth and aggregation.
2007年至2015年期间，中国黄海每年都会出现绿潮。漂浮的浒苔（Ulva prolifera (Müller) J. Agardh）是引发绿潮的大型藻类物种。同时还观察到了附着生长的肠浒苔（U. intestinalis）。通过原位叶绿素荧光以及7天的实验室驯化后测定光合能力，发现存在显著差异。色素组成没有明显差异，但浓度变化显著，尤其是浒苔中的叶绿素b在驯化后增加了两倍。浒苔中PS II的最佳光化学效率（Fv/Fm）显著更高。从快速光响应曲线（RLC）获得的光合速率（α）、最大相对电子传递速率（rETRmax）和最小饱和辐照度（Ek），与Fv/Fm显示出几乎相同的光合生理状态。对类囊体膜的猝灭系数和低温（77 K）叶绿素荧光发射光谱分析表明，浒苔比肠浒苔具有更好的PSII恢复活性和可塑性。此外，通过非光化学猝灭（NPQ）和状态转换进行的能量耗散显示出有效的光保护作用，尤其是在遭受严重胁迫的浒苔中。本研究结果表明，浒苔较高的光合能力有助于其漂浮增殖，除了有利的海洋学条件和高营养水平外，有效的光保护也支持其生长和聚集。
