Kuhnhenn Verena, Krägel Jürgen, Horstmann Ulrich, Miller Reinhard
Leibniz-Institut für Meereswissenschaften, Düsternbrooker Weg 20, Kiel 24105, Germany.
Colloids Surf B Biointerfaces. 2006 Jan 15;47(1):29-35. doi: 10.1016/j.colsurfb.2005.11.021. Epub 2006 Jan 4.
The study of interfacial properties in the marine environment is important for the understanding of air-sea gas exchange processes, especially with respect to the behaviour of entrained air bubbles. Seawater contains surfactant material, much of which is thought to origin from the exudation of dissolved organic material (DOM) by phytoplankton. This study aims at investigating the influence of different phytoplankton species on the surface shear viscosity of an air-water interface. Measurements of surface shear viscosity were carried out with the ISR1 interfacial shear rheometer. Surface shear viscosities of stock cultures of Phaeocystis sp., Thalassiosira rotula, Thalassiosira punctigera and Nitzschia closterium as well as of F/2 nutrient medium and seawater were measured. The surface shear viscosity of N. closterium was investigated during different stages of its growth as well as for an unfiltered stock culture sample and its filtrate. Results reveal that the influence of phytoplankton on the surface shear viscosity is species specific. An increase in surface shear viscosity occurred for the N. closterium stock culture only. The remaining cultures showed similar behaviour to F/2 nutrient medium. The increase of surface shear viscosity during the growth of N. closterium occurred mainly during the exponential growth phase. The increases in surface shear viscosity depend on the presence of phytoplankton cells in the sample. The formation of compact mechanical structures at the air-water interface originating from the aggregation of DOM released by N. closterium as a cause for the observed increases in surface shear viscosity is discussed.
研究海洋环境中的界面特性对于理解海气气体交换过程非常重要，特别是对于夹带气泡的行为而言。海水中含有表面活性剂物质，其中大部分被认为源自浮游植物释放的溶解有机物质（DOM）。本研究旨在调查不同浮游植物种类对气 - 水界面表面剪切粘度的影响。使用ISR1界面剪切流变仪进行表面剪切粘度的测量。测量了棕囊藻属、圆筛藻、星脐圆筛藻和新月菱形藻的原种培养物以及F/2营养培养基和海水的表面剪切粘度。研究了新月菱形藻在其生长的不同阶段以及未过滤的原种培养样品及其滤液的表面剪切粘度。结果表明，浮游植物对表面剪切粘度的影响具有物种特异性。仅新月菱形藻原种培养物的表面剪切粘度有所增加。其余培养物表现出与F/2营养培养基相似的行为。新月菱形藻生长过程中表面剪切粘度的增加主要发生在指数生长期。表面剪切粘度的增加取决于样品中浮游植物细胞的存在。讨论了由新月菱形藻释放的DOM聚集在气 - 水界面形成紧密机械结构，这是观察到的表面剪切粘度增加的原因。
