Collaborative Proposal: Interactive Effects of UV Radiation and Vertical Mixing on Phytoplankton and Bacterial Productivity of Ross See Phaeocystis Blooms

0127022杰弗瑞紫外线辐射影响大多数水生生态系统近地表水域浮游生物过程的动态。特别是，南大洋在南半球春季期间受到影响，此时臭氧消耗会增强具有生物破坏性的紫外线辐射。虽然在估计紫外线辐射对南大洋细菌和浮游植物的定量影响方面取得了进展，但仍有一些重要问题有待解决。人们对南极洲群居的棕囊藻主导的系统的反应知之甚少。南极洲棕囊藻在罗斯海南部发育的多纳藻中主导着春季的水华。罗斯海也令人感兴趣，因为春季最南端的位置有开阔的水域，完全在臭氧层空洞内，而且有连续的日光，这意味着DNA修复的调节。一些研究表明，垂直混合可以显著改善南大洋和其他地方紫外线辐射的影响。然而，对表层湍流强度的测量有限，而且这些测量还没有与紫外线对浮游植物和浮游细菌的影响的平行研究相结合。为了解决这些问题，这项合作研究将侧重于罗斯海的垂直混合和紫外线辐射的影响。浮游植物和浮游细菌对紫外线辐射的光谱和时间响应将在实验室和太阳培养中进行表征。这将导致定义生物权重函数和响应模型，能够预测紫外线对光合作用、细菌结合和表层DNA损伤的影响的深度和时间分布。Diel采样将测量24小时周期内DNA损伤、细菌掺入、光合作用和荧光参数随深度变化的曲线。采样将包括随着Polyna的发展，具有不同风力驱动的混合和分层的站点。垂直混合测量程序针对典型的春季罗斯海情况进行了优化，在这种情况下，中等强度的湍流不足以在存在太阳加热和/或融化冰输入的地表淡水等稳定影响的情况下完全混合上层。细尺度垂直密度剖面将用自由落体CTD装置测量，这些剖面将被用来通过确定索普尺度直接估计大涡尺度。涡旋尺度和估计的湍流扩散系数将与地面层效应直接相关，并用于在地面混合层紫外线辐射响应模式中产生拉格朗日深度-时间轨迹。这项拟议的研究将是对罗斯海紫外线辐射影响的首次深入研究，并与之前在韦德尔-斯科舍省交汇处和帕尔默站地区的工作进行了宝贵的比较。它还将加强对罗斯海垂直混合过程、营养相互作用和生物地球化学循环的理解。

0127022JeffreyUltraviolet radiation influences the dynamics of plankton processes in the near-surface waters of most aquatic ecosystems. In particular, the Southern Ocean is affected in the austral spring period when biologically damaging ultraviolet radiation is enhanced by ozone depletion. While progress has been made in estimating the quantitative impact of ultraviolet radiation on bacteria and phytoplankton in the Southern Ocean, some important issues remain to be resolved. Little is known about responses in systems dominated by the colonial haptophyte Phaeocystis antarctica, which dominates spring blooms in a polyna that develops in the southern Ross Sea. The Ross Sea is also of interest because of the occurrence of open water at a far southerly location in the spring, well within the ozone hole, and continuous daylight, with implications for the regulation of DNA repair. A number of studies suggest that vertical mixing can significant modify the impact of ultraviolet radiation in the Southern Ocean and elsewhere. However, there are limited measurements of turbulence intensity in the surface layer and measurements have not been integrated with parallel studies of ultraviolet radiation effects on phytoplankton and bacterioplankton. To address these issues, this collaborative study will focus on vertical mixing and the impact of ultraviolet radiation in the Ross Sea. The spectral and temporal responses of phytoplankton and bacterioplankton to ultraviolet radiation will be characterized in both laboratory and solar incubations. These will lead to the definition of biological weighting functions and response models capable of predicting the depth and time distribution of ultraviolet radiation impacts on photosynthesis, bacterial incorporation and DNA damage in the surface layer. Diel sampling will measure depth-dependent profiles of DNA damage, bacterial incorporation, photosynthesis and fluorescence parameters over a 24 h cycle. Sampling will include stations with contrasting wind-driven mixing and stratification as the polyna develops. The program of vertical mixing measurements is optimized for the typical springtime Ross Sea situation in which turbulence of intermediate intensity is insufficient to mix the upper layer thoroughly in the presence of stabilizing influences like solar heating and/or surface freshwater input from melting ice. Fine-scale vertical density profiles will be measured with a free-fall CTD unit and the profiles will be used to directly estimate large-eddy scales by determining Thorpe scales. Eddy scales and estimated turbulent diffusivities will be directly related to surface layer effects, and used to generate lagrangian depth-time trajectories in models of ultraviolet radiation responses in the surface mixed layer. The proposed research will be the first in-depth study of ultraviolet radiation effects in the Ross Sea and provide a valuable comparison with previous work in the Weddell-Scotia Confluence and Palmer Station regions. It will also enhance the understanding of vertical mixing processes, trophic interactions and biogeochemical cycling in the Ross Sea.