Effects of CO2 perturbation on phosphorus pool sizes and uptake in a mesocosm experiment during a low productive summer season in the northern Baltic Sea
Effects of CO2 perturbation on phosphorus pool sizes and uptake in a mesocosm experiment during a low productive summer season in the northern Baltic Sea
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DOI：
10.5194/bg-13-3035-2016
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发表时间：
2015-10
期刊：
影响因子：
4.9
通讯作者：
M. Nausch;L. Bach;J. Czerny;Josephine Goldstein;H. Grossart;Dana Hellemann;T. Hornick;E. Achterberg;K. Schulz;U. Riebesell
中科院分区：
文献类型：
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作者：
M. Nausch;L. Bach;J. Czerny;Josephine Goldstein;H. Grossart;Dana Hellemann;T. Hornick;E. Achterberg;K. Schulz;U. Riebesell
摘要。尽管在许多水生系统中，磷通常控制着浮游植物的发育，但关于自然水域中二氧化碳水平增加对磷循环影响的研究尚缺乏。我们研究的目的是分析二氧化碳浓度升高对磷池大小和吸收的影响。2012年夏季，在Storfjarden（波罗的海芬兰湾西部）进行了co2操纵中尺度实验，并在峡湾周围水域进行了磷动态研究。各群落及峡湾表层水体溶解有机磷（DOP）浓度分别为0.26±0.03和0.23±0.04µmol L−1，是总磷池（TP）的主要组成部分，而磷酸盐（PO4）是最低组成部分，群落和峡湾的平均浓度分别为0.15±0.02和0.17±0.07µmol L−1。PO4向DOP的转化是PO4转化的主要途径。约82%的PO4转化为DOP，而只有18%的PO4转化为颗粒磷（PP）。在中观系统中测量到的PO4摄取速率在0.6至3.9 nmol L−1 h−1之间。其中约86%是在浮游植物生物量增加期间通过粒径分数1000µatm实现的。此外，我们在未处理的中游生物中发现了显著的关系（例如，PP和Chl a之间的关系），这在高fCO2条件下没有观察到。因此，可以假设PP形成与浮游植物生长之间的关系随CO2升高而变化。从结果可以推断，当促进PO4向POP的转化时，CO2对P库的明显影响与浮游植物的生长相耦合。另一方面，PO4向DOP的转化似乎没有受到影响。此外，有迹象表明，二氧化碳升高可能改变了P的细胞调节机制，改变了细胞成分之间的关系。
Abstract. Studies investigating the effect of increasing CO2 levels on the phosphorus cycle in natural waters are lacking although phosphorus often controls phytoplankton development in many aquatic systems. The aim of our study was to analyse effects of elevated CO2 levels on phosphorus pool sizes and uptake. The phosphorus dynamic was followed in a CO2-manipulation mesocosm experiment in the Storfjarden (western Gulf of Finland, Baltic Sea) in summer 2012 and was also studied in the surrounding fjord water. In all mesocosms as well as in surface waters of Storfjarden, dissolved organic phosphorus (DOP) concentrations of 0.26 ± 0.03 and 0.23 ± 0.04 µmol L−1, respectively, formed the main fraction of the total P-pool (TP), whereas phosphate (PO4) constituted the lowest fraction with mean concentration of 0.15 ± 0.02 in the mesocosms and 0.17 ± 0.07 µmol L−1 in the fjord. Transformation of PO4 into DOP appeared to be the main pathway of PO4 turnover. About 82 % of PO4 was converted into DOP whereby only 18 % of PO4 was transformed into particulate phosphorus (PP). PO4 uptake rates measured in the mesocosms ranged between 0.6 and 3.9 nmol L−1 h−1. About 86 % of them was realized by the size fraction 1000 µatm during periods when phytoplankton biomass increased. In addition, we found significant relationships (e.g., between PP and Chl a) in the untreated mesocosms which were not observed under high fCO2 conditions. Consequently, it can be hypothesized that the relationship between PP formation and phytoplankton growth changed with CO2 elevation. It can be deduced from the results, that visible effects of CO2 on P pools are coupled to phytoplankton growth when the transformation of PO4 into POP was stimulated. The transformation of PO4 into DOP on the other hand does not seem to be affected. Additionally, there were some indications that cellular mechanisms of P regulation might be modified under CO2 elevation changing the relationship between cellular constituents.