Rain-Franco Angel, Muñoz Claudia, Fernandez Camila
Graduate Program in Oceanography, Department of Oceanography, University of Concepción, Concepción, Chile.
Department of Oceanography, COPAS SURAUSTRAL program and Interdisciplinary center for Aquaculture Research (INCAR), University of Concepción, Concepción, Chile.
PLoS One. 2014 Jun 26;9(6):e100224. doi: 10.1371/journal.pone.0100224. eCollection 2014.
We investigated the production of ammonium by the photodegradation of dissolved organic matter (DOM) in the coastal upwelling system off central Chile (36°S). The mean penetration of solar radiation (Z1%) between April 2011 and February 2012 was 9.4 m, 4.4 m and 3.2 m for Photosynthetically Active Radiation (PAR; 400-700 nm), UV-A (320-400 nm) and UV-B (280-320 nm), respectively. Ammonium photoproduction experiments were carried out using exudates of DOM obtained from cultured diatom species (Chaetoceros muelleri and Thalassiosira minuscule) as well as natural marine DOM. Diatom exudates showed net photoproduction of ammonium under exposure to UVR with a mean rate of 0.56±0.4 µmol L(-1) h(-1) and a maximum rate of 1.49 µmol L(-1) h(-1). Results from natural marine DOM showed net photoproduction of ammonium under exposure to PAR+UVR ranging between 0.06 and 0.2 µmol L(-1) h(-1). We estimated the potential contribution of photochemical ammonium production for phytoplankton ammonium demand. Photoammonification of diatom exudates could support between 117 and 453% of spring-summer NH4(+) assimilation, while rates obtained from natural samples could contribute to 50-178% of spring-summer phytoplankton NH4(+) requirements. These results have implications for local N budgets, as photochemical ammonium production can occur year-round in the first meters of the euphotic zone that are impacted by full sunlight.
我们研究了智利中部沿海上升流系统（南纬36°）中溶解有机物（DOM）光降解产生铵的情况。2011年4月至2012年2月期间，光合有效辐射（PAR；400 - 700纳米）、UV - A（320 - 400纳米）和UV - B（280 - 320纳米）的太阳辐射平均穿透深度（Z1%）分别为9.4米、4.4米和3.2米。使用从培养的硅藻物种（穆氏角毛藻和微小海链藻）获得的DOM渗出物以及天然海洋DOM进行了铵光生产实验。硅藻渗出物在紫外线辐射下显示出铵的净光生产，平均速率为0.56±0.4微摩尔·升⁻¹·小时⁻¹，最大速率为1.49微摩尔·升⁻¹·小时⁻¹。天然海洋DOM的结果显示，在PAR + UVR照射下铵的净光生产范围为0.06至0.2微摩尔·升⁻¹·小时⁻¹。我们估计了光化学铵生产对浮游植物铵需求的潜在贡献。硅藻渗出物的光氨化作用可以满足春夏季NH₄⁺同化需求的117%至453%，而从天然样品获得的速率可以满足春夏季浮游植物NH₄⁺需求的50%至178%。这些结果对当地的氮预算有影响，因为在受全日照影响的真光层最初几米内，光化学铵生产全年都可能发生。
