Marine Resources Development Institute of Jiangsu, Huaihai Institute of Technology, Lianyungang 222005, China.
Marine Resources Development Institute of Jiangsu, Huaihai Institute of Technology, Lianyungang 222005, China.
Harmful Algae. 2016 Nov;59:51-58. doi: 10.1016/j.hal.2016.09.004. Epub 2016 Oct 1.
The large-scale green tides, consisting mainly of Ulva prolifera, have invaded the coastal zones of western Yellow Sea each year since 2008, resulting in tremendous impacts on the local environment and economy. A large number of studies have been conducted to investigate the physiological traits of U. prolifera to explain its dominance in the green tides. However, little has been reported regarding the response of U. prolifera to changing environmental factors via morphological variation. In our experiments, we found remarkable morphological acclimation of U. prolifera to various temperature (20 and 25°C) and salinity (10, 20, and 30) conditions. U. prolifera had more, but shorter branches when they were cultured at lower temperature and salinity conditions. To investigate the significance of these morphological variations in its acclimation to changes of environmental factors, physiological and biochemical traits of U. prolifera grown under different conditions were measured. Higher temperature increased the relative growth rate while salinity did not affect it. On the other hand, higher temperature did not enhance the net photosynthetic rate whilst lower salinity did. The increased net photosynthetic rate at lower salinity conditions could be attributed to more photosynthetic pigments-chlorophyll a, chlorophyll b, and carotenoids-in thalli due to there being more branches at lower salinity conditions. Increased numbers of branches and thus an increased intensity of thalli may be helpful to protect thalli from increased osmotic pressure caused by lower salinity, but it led to more shading. In order to capture enough light when being shaded, thalli of U. prolifera synthesized more photosynthetic pigments at lower salinity levels. In addition, higher temperature increased nitrate reductase activity and soluble protein content but variations in salinity did not impose any effect on them. Our results demonstrate conclusively that U. prolifera can acclimatize in the laboratory to the changes of environmental factors (salinity and temperature) by morphology-driven physiological and biochemical variation. We suggest that the morphological plasticity of U. prolifera may be an important factor for it to outcompete other algal species in a changing ocean.
自 2008 年以来，大规模的绿潮（主要由石莼属绿藻组成）每年都会侵袭黄海西部沿海地区，对当地的环境和经济造成了巨大的影响。大量研究已经开展，旨在探究石莼属绿藻的生理特性，以解释其在绿潮中的优势地位。然而，关于石莼属绿藻通过形态变化对环境因子变化的响应，却鲜有报道。在我们的实验中，发现石莼属绿藻在不同温度（20 和 25°C）和盐度（10、20 和 30）条件下具有显著的形态适应。在较低温度和盐度条件下培养时，石莼属绿藻具有更多但更短的分枝。为了探究这些形态变化在其适应环境因子变化中的意义，我们测量了在不同条件下生长的石莼属绿藻的生理生化特性。较高的温度增加了相对生长率，而盐度则没有影响。另一方面，较高的温度并没有提高净光合速率，而较低的盐度则提高了净光合速率。在较低盐度条件下，净光合速率的增加可能归因于由于分枝较多，藻体中光合色素——叶绿素 a、叶绿素 b 和类胡萝卜素的含量增加。分枝数量的增加和藻体强度的增加可能有助于保护藻体免受低盐度引起的渗透压增加的影响，但这也导致了更多的遮荫。为了在遮荫时捕获足够的光，石莼属绿藻在低盐度下合成了更多的光合色素。此外，较高的温度增加了硝酸还原酶活性和可溶性蛋白含量，但盐度变化对它们没有任何影响。我们的研究结果表明，石莼属绿藻可以通过形态驱动的生理生化变化，在实验室中适应环境因子（盐度和温度）的变化。我们认为，石莼属绿藻的形态可塑性可能是其在变化的海洋中与其他藻类物种竞争的一个重要因素。
