Gypens Nathalie, Borges Alberto V, Speeckaert Gaelle, Lancelot Christiane
Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Brussels, Belgium.
Unité d'Océanographie Chimique, Université de Liège, Liège, Belgium.
PLoS One. 2014 Jan 17;9(1):e85862. doi: 10.1371/journal.pone.0085862. eCollection 2014.
We developed a module describing the dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) dynamics, including biological transformations by phytoplankton and bacteria, and physico-chemical processes (including DMS air-sea exchange). This module was integrated in the MIRO ecological model and applied in a 0D frame in the Southern North Sea (SNS). The DMS(P) module is built on parameterizations derived from available knowledge on DMS(P) sources, transformations and sinks, and provides an explicit representation of bacterial activity in contrast to most of existing models that only include phytoplankton process (and abiotic transformations). The model is tested in a highly productive coastal ecosystem (the Belgian coastal zone, BCZ) dominated by diatoms and the Haptophyceae Phaeocystis, respectively low and high DMSP producers. On an annual basis, the particulate DMSP (DMSPp) production simulated in 1989 is mainly related to Phaeocystis colonies (78%) rather than diatoms (13%) and nanoflagellates (9%). Accordingly, sensitivity analysis shows that the model responds more to changes in the sulfur:carbon (S:C) quota and lyase yield of Phaeocystis. DMS originates equally from phytoplankton and bacterial DMSP-lyase activity and only 3% of the DMS is emitted to the atmosphere. Model analysis demonstrates the sensitivity of DMS emission towards the atmosphere to the description and parameterization of biological processes emphasizing the need of adequately representing in models both phytoplankton and bacterial processes affecting DMS(P) dynamics. This is particularly important in eutrophied coastal environments such as the SNS dominated by high non-diatom blooms and where empirical models developed from data-sets biased towards open ocean conditions do not satisfactorily predict the timing and amplitude of the DMS seasonal cycle. In order to predict future feedbacks of DMS emissions on climate, it is needed to account for hotspots of DMS emissions from coastal environments that, if eutrophied, are dominated not only by diatoms.
我们开发了一个描述二甲基巯基丙酸内盐（DMSP）和二甲基硫醚（DMS）动态变化的模块，包括浮游植物和细菌的生物转化以及物理化学过程（包括DMS的海气交换）。该模块被整合到MIRO生态模型中，并应用于北海南部（SNS）的零维框架。DMS（P）模块基于从DMS（P）的来源、转化和汇的现有知识中得出的参数化方法构建，与大多数仅包含浮游植物过程（和非生物转化）的现有模型相比，它明确表示了细菌活动。该模型在分别以硅藻和定鞭藻棕囊藻为主的高产沿海生态系统（比利时沿海地区，BCZ）中进行了测试，硅藻是低DMSP生产者，棕囊藻是高DMSP生产者。在年度基础上，1989年模拟的颗粒态DMSP（DMSPp）产量主要与棕囊藻群落（78%）有关，而不是硅藻（13%）和纳米鞭毛虫（9%）。相应地，敏感性分析表明，该模型对棕囊藻的硫：碳（S:C）配额和裂解酶产量的变化反应更大。DMS同样来自浮游植物和细菌的DMSP - 裂解酶活性，只有3%的DMS排放到大气中。模型分析表明，DMS向大气的排放对生物过程的描述和参数化很敏感，强调了在模型中充分表示影响DMS（P）动态的浮游植物和细菌过程的必要性。这在富营养化的沿海环境中尤为重要，如以大量非硅藻水华为主的北海南部，而从偏向开阔海洋条件的数据集中开发的经验模型不能令人满意地预测DMS季节循环的时间和幅度。为了预测DMS排放对气候的未来反馈，需要考虑沿海环境中DMS排放的热点地区，这些地区如果富营养化，不仅以硅藻为主。
