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

[127022]杰弗里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。特别是南大洋在南方春季期间受到影响，因为臭氧耗竭加强了对生物有害的紫外线辐射。虽然在估计紫外线辐射对南大洋细菌和浮游植物的数量影响方面取得了进展，但仍有一些重要问题有待解决。人们对由殖民地褐藻主导的系统的反应知之甚少，该系统在罗斯海南部形成的多聚藻中主导着春季的繁殖期。人们对罗斯海感兴趣的另一个原因是，春天在遥远的南方出现了开阔的水域，正好在臭氧空洞内，而且日照持续，这对DNA修复的调节有影响。许多研究表明，垂直混合可以显著改变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，而且测量还没有与紫外线辐射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，这项合作研究将重点关注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日光孵育中进行表征。这将导致定义生物加权函数和响应模型，能够预测紫外线辐射对光合作用、细菌掺入和表层DNA损伤的深度和时间分布。在24小时的周期内，Diel取样将测量DNA损伤、细菌结合、光合作用和荧光参数的深度依赖谱。采样将包括站与对比风驱动混合和分层多聚体的发展。垂直混合测量方案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太阳加热和/或融化冰的地表淡水输入等稳定影响的存在下彻底混合上层。采用自由落体CTD装置测量细尺度垂直密度剖面，并通过确定索普尺度直接估算大涡尺度。涡旋尺度和估计的湍流扩散率将与表层效应直接相关，并用于在表层混合层紫外线辐射响应模型中生成拉格朗日深度-时间轨迹。拟议的研究将是对罗斯海紫外线辐射效应的第一次深入研究，并与威德尔-斯科舍汇合处和帕尔默站地区以前的工作进行有价值的比较。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.