In situ, satellite and reanalysis data from numerical models were used to study the characteristic features of Chl variability in the Baltic Sea. The analysis is focused on the years 2003–2020 when regular observations of ocean color with the MODIS AQUA are available. In the Baltic Sea, there is a pronounced annual cycle in physical conditions in the water column, driven by seasonal cycles in atmospheric forcing. The seasonal cycle of Chl concentration does not conform to the picture known from classical models, with low phytoplankton concentration when nutrients are low. In contrast, in the Baltic Sea, the concentration of Chl is high even during the summer months when nutrients are depleted. This can be explained by a continuous supply of nutrients by runoff from land, as well as by a significant contribution to primary production by phytoplankton able to survive in environment poor in dissolved nutrients. There is also a considerable interannual variability in Chl. There are many possible cause/effect interactions involved, but the data series are still too short to make clear which of them are the most important. The most striking event was a spring bloom in 2008.

中文翻译：

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波罗的海公海表层水中叶绿素a浓度的变化

在现场，卫星和数值模型的再分析数据被用来研究波罗的海叶绿素变化的特征。分析重点是 2003 年至 2020 年，当时可以使用 MODIS AQUA 定期观测海洋颜色。在波罗的海，受大气强迫季节性循环的驱动，水体物理条件存在明显的年度循环。叶绿素浓度的季节周期与经典模型中已知的情况不相符，当营养物质较低时，浮游植物浓度较低。相比之下，在波罗的海，即使在养分耗尽的夏季，叶绿素的浓度也很高。这可以通过陆地径流持续供应养分，以及能够在溶解养分匮乏的环境中生存的浮游植物对初级生产的重大贡献来解释。 Chl 也存在相当大的年际变化。涉及许多可能的因果相互作用，但数据系列仍然太短，无法明确其中哪一个是最重要的。最引人注目的事件是2008年的春季花开。