Ecophysiological growth characteristics and modeling of the onset of the spring bloom in the Baltic Sea

The onset of spring bloom in temperate areas is a transition period where the low productive, winter phytoplankton community is transformed into a high productive spring community. Downwelling irradiance, mixing depth and the ability of the phytoplankton community to utilize the light, are key parameters determining the timing of the onset of the spring bloom. Knowing these parameters would thus provide tools for modeling the spring bloom and enhance our knowledge of ecophysiological processes during this period.Our main objective with this study was to provide data for the growth characteristics of some key species forming the spring bloom in the Gulf of Finland, and to apply those results in a simple dynamic model for the onset of the spring bloom, in order to test if the timing of the spring bloom predicted by the models corresponds to field observations. We investigated the photosynthetic characteristics of three diatoms and two dinoflagellates (Chaetoceros wighamii, Melosira arctica, Thalassiosira baltica, Scrippsiella hangoei and Woloszynskia halophila), at low temperatures (4–5 °C). All of these species are common during spring bloom in the Baltic Sea.Cultures of these species were acclimated to different irradiance regimes prior to measurements of photosynthesis, respiration, pigment concentration and light absorption. We did not find a positive relationship between respiration and growth rate, and we hypothesize that this relationship, which is well established at higher temperatures, is negligible or absent at low temperatures (< 10 °C). Photosynthetic maximum (P_m), and maximum light utilization coefficient (α) was lowest and respiration (R) highest in the dinoflagellates.We made a model of the onset of the spring bloom in the western part of Gulf of Finland, using the obtained data together with monitoring data of mixing depth and water transparency from this area. Model results were compared to field observations of chlorophyll-a (Chl-a) concentration. There was a good agreement between the model predictions and the observed onset of the spring bloom for the diatoms. S. hangoei, however, was not able to reach positive production in the model, and W. halophila had the similar growth characteristics as S. hangoei. Consequently, these species must have other competition strategies enabling them to exist and grow during spring bloom.     

基于PLPS调研方法的步行和自行车交通规划设计评估

开展系统性的步行、自行车交通调研和实证分析,对于弥补城市相关基础数据不足、梳理现状问题、指导规划设计、评估实施效果等有重要意义,有助于改善城市步行和自行车出行环境、引导市民绿色出行.首先介绍了PLPS调研的目的及具体方法,包括公共生活和公共空间两部分调研.以重庆市渝中半岛步行交通示范项目实践为例,探讨PLPS方法在项目...     

世界级城市街道重建策略研究——以上海市黄浦区为例

长期以来受以车为主导的规划建设理念影响,中国许多城市新建、改建道路存在尺度失衡、品质降低、活力不足等问题。首先介绍纽约、伦敦、哥本哈根、莫斯科、墨尔本等世界级城市街道重建实践经验。以上海市黄浦区为例,采用公共生活—公共空间(PLPS)调研方法,对34处地点进行行人流量调查,并针对5个公共空间进行停留活动统计。由此分析黄浦区现状街道网络的主要问题与诉求,进而提出街道重建的规划设计策略及措施推进时序。以南京东路为示范项目,探讨其现存问题并提出具体改造方案。