| Title | Phytoplankton functional traits and seston stable isotopes signature: a functional-based approach in a deep, subalpine lake, Lake Maggiore (N. Italy) |
| Abstract | The seasonal variation of seston stable isotopes signature of carbon (?13C) 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 ?13C 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 ?13C 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 ?13C variation. When morphological and functional phytoplankton traits were superimposed, the NMS ordination showed that cylinder cells (for cell shape classes), class 500-2000 ?m3 (for cell size classes) and Group 6 (for MBFG) were the most related to ?13C variation. Our study confirms that the variation in the pelagic ?13C 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 ?13C and to suggest their importance in the interpretation of natural stable isotopes studies in lake ecosystems. |
| Source | Journal of limnology (Online) 71 (1), pp. 84–94 |
| Journal | Journal of limnology (Online) |
| Editor | Istituto per lo Studio degli Ecosistemi, Pavia, Italia |
| Year | 2012 |
| Type | Articolo in rivista |
| DOI | 10.4081/jlimnol.2012.e8 |
| Authors | Caroni, Rossana ;Free, Gary ;Visconti, Anna;Manca, Marina |
| Text | 219849 2012 10.4081/jlimnol.2012.e8 Phytoplankton functional traits and seston stable isotopes signature a functional based approach in a deep, subalpine lake, Lake Maggiore N. Italy Caroni, Rossana ;Free, Gary ;Visconti, Anna;Manca, Marina JCR, European Commission, Ispra VA ;JCR, European Commission, Ispra VA ;CNR ISE, Pallanza Verbania ;CNR ISE, Pallanza Verbania The seasonal variation of seston stable isotopes signature of carbon 13C 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 13C 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 13C 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 13C variation. When morphological and functional phytoplankton traits were superimposed, the NMS ordination showed that cylinder cells for cell shape classes , class 500 2000 m3 for cell size classes and Group 6 for MBFG were the most related to 13C variation. Our study confirms that the variation in the pelagic 13C 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 13C and to suggest their importance in the interpretation of natural stable isotopes studies in lake ecosystems. 71 Phytoplankton functional traits and seston stable isotopes signature 2012_A0_005.pdf Articolo in rivista Istituto per lo Studio degli Ecosistemi 1723 8633 Journal of limnology Online Journal of limnology Online J. limnol. Online Journal of limnology. Online VISCONTI ANNA marinamarcella.manca MANCA MARINA MARCELLA TA.P04.016.004 Ecologia teorica e applicata degli ecosistemi acquatici |
