科研之友
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摘要
The seasonal variation of seston stable isotopes signature of carbon (delta C-13) in Lake Maggiore during 2008 was related to seasonal variation of the lake phytoplankton community, investigated in terms of phytoplankton taxonomic groups, morpho-functional groups (MBFG), cell size classes and cell shape classes. Three open water stations were selected to reflect truly pelagic, influenced by littoral and riverine carbon sources: phytoplankton samples were collected from two water depths, 0-20 m and 25-50 m. Among stations differences in delta C-13 signatures of seston were statistically non significant, confirming that allochthonous input may become important only after exceptional rainfall events. Nonparametric multiplicative regression (NPMR) was utilized to identify among the phytoplankton parameters (taxonomic groups, MBFG, cell shapes, cell sizes) which were the best predictors of the PC variation. Bacillariophyceae and two morpho-functional groups, Group 6 (non-flagellated organisms with siliceous exoskeletons) and Group 3 (large filamentous algae with aerotopes) were statistically significant. Non-metric multidimensional scaling (NMS) ordination was used to investigate differences in phytoplankton samples and their relationship with delta C-13 variation. When morphological and functional phytoplankton traits were superimposed, the NMS ordination showed that cylinder cells (for cell shape classes), class 500-2000 mu m(3) (for cell size classes) and Group 6 (for MBFG) were the most related to delta C-13 variation. Our study confirms that the variation in the pelagic VC seston most probably reflects changes in phytoplankton carbon isotopic signature, consequent to changes in availability of carbon sources depending on the season and due to different isotopic fractionation of phytoplankton taxonomic groups. Statistical investigations have allowed us to investigate the potential role of phytoplankton morphological and functional traits in the seasonal variation of delta C-13 and to suggest their importance in the interpretation of natural stable isotopes studies in lake ecosystems.
- 出版日期2012
