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

0127022杰弗里紫外线辐射影响浮游生物的动态过程在近地表沃茨的大多数水生生态系统。特别是，南大洋在南极春季受到影响，此时臭氧消耗增强了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数量影响方面取得了进展，但仍有一些重要问题有待解决。鲜为人知的是，在系统中占主导地位的殖民地附着植物Phaeocystis anaerotica，占主导地位的春天开花的水螅，在罗斯海南部的发展。罗斯海也是一个有趣的地方，因为春季在遥远的南方出现了开放的水域，正好在臭氧洞内，并且持续的日光，这对DNA修复的调节有影响。一些研究表明，垂直混合可大大改变紫外线辐射对南大洋和其他地方的影响。然而，有有限的测量湍流强度在表层和测量尚未整合的平行研究紫外线辐射对浮游植物和浮游细菌的影响。 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日光培养中进行表征。 这将导致生物加权函数和反应模型的定义，能够预测紫外线辐射对光合作用的影响的深度和时间分布，细菌的掺入和DNA的破坏在表层。昼夜采样将在24小时周期内测量DNA损伤、细菌掺入、光合作用和荧光参数的深度依赖性概况。 取样将包括在海盆发展过程中具有对比鲜明的风驱动混合和分层的站点。 垂直混合测量的程序进行了优化，典型的春季罗斯海的情况下，中间强度的湍流是不够的混合上层彻底稳定的影响，如太阳能加热和/或表面淡水输入从融冰的存在。将用自由落体CTD装置测量细尺度垂直密度剖面，并通过确定索普尺度，将剖面用于直接估计大涡尺度。涡旋尺度和估计的湍流扩散率将直接与表面层效应有关，并用于在表面混合层紫外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-斯科舍汇流和帕尔默站地区以前的工作进行了有价值的比较。它还将增进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了解。

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.