| Title | Transparent exopolymer particles (TEP), phytoplankton and picocyanobacteria along a littoral-to-pelagic depth-gradient in a large subalpine lake |
| Abstract | Transparent exopolymer particles (TEP) play an important role in the organic carbon cycle of many aquatic systems but the production and distribution of TEP have been studied mainly in the marine envirotunent, neglecting the large oligotrophic lakes. We selected Lake Maggiore, one of the most important freshwater reserve in Northern Italy, to study the horizontal and vertical distribution of TEP and of its possible drivers. Samplings along a transect in the Borromeo basin were performed in May, July and September 2019. Total organic carbon (TOC), TEP, chlorophyll-alpha (Chl) of different algal groups, picocyanobacteria, bacteria and eukaryotes counting, were measured at six stations and five depths. Our study showed that TEP exhibited a clear vertical heterogeneity from surface to the bottom related to the autotrophic microorganisms that are the main source of TEP and are prevalent in the euphotic zone of the lake. On the other hand, TEP was fairly evenly distributed along the horizontal transect from littoral to pelagic zone, although patches were present in spring, when TEP concentrations were low. in contrast to TEP, TOC and to a lesser extent Chl and bacteria showed horizontal heterogeneity, in some months. In Lake Maggiore TEP indeed was an important fraction of total organic carbon (TOC), making up to 54% of TOC (in carbon units: 910 mu g C L-1) and it was significantly correlated with Chl. The highest TEP concentration (1.44 mg GX eq L-1) was measured in September 2019, in coincidence with an episode of superficial foam appearance. Considering the biomass as Chl concentrations, the algal group mostly related to TEP was that of brown algae, particularly diatoms; but considering the numbers, the picocyanobacteria and bacteria were more significantly correlated to TEP. The presence of pennate diatoms in May and July, with their TEP-related chlorophyll, did not produce TEP in as high concentration as that observed in September in the presence of centric diatoms and of very high numbers of picocyanobacteria and bacteria. |
| Source | Journal of limnology (Testo stamp.) 80 (3) |
| Keywords | TEP horizontal distributionfoamspicocyanobacteria and phytoplankton distributionLake Maggiorelittoral-pelagic transects |
| Journal | Journal of limnology (Testo stamp.) |
| Editor | Istituto per lo Studio degli Ecosistemi., Verbania Pallanza, Italia |
| Year | 2021 |
| Type | Articolo in rivista |
| DOI | 10.4081/jlimnol.2021.2021 |
| Authors | Callieri, Cristiana; Salvador Hernandez-Aviles, J.; Eckert, Ester M.; Rogora, Michela; Tartari, Gabriele; Sforzi, Tommaso; Sabatino, Raffaella; Bertoni, Roberto |
| Text | 464327 2021 10.4081/jlimnol.2021.2021 ISI Web of Science WOS 000752953000003 TEP horizontal distribution foams picocyanobacteria and phytoplankton distribution Lake Maggiore littoral pelagic transects Transparent exopolymer particles TEP , phytoplankton and picocyanobacteria along a littoral to pelagic depth gradient in a large subalpine lake Callieri, Cristiana; Salvador Hernandez Aviles, J.; Eckert, Ester M.; Rogora, Michela; Tartari, Gabriele; Sforzi, Tommaso; Sabatino, Raffaella; Bertoni, Roberto CNR; Univ Nacl Autonoma Mexico Transparent exopolymer particles TEP play an important role in the organic carbon cycle of many aquatic systems but the production and distribution of TEP have been studied mainly in the marine envirotunent, neglecting the large oligotrophic lakes. We selected Lake Maggiore, one of the most important freshwater reserve in Northern Italy, to study the horizontal and vertical distribution of TEP and of its possible drivers. Samplings along a transect in the Borromeo basin were performed in May, July and September 2019. Total organic carbon TOC , TEP, chlorophyll alpha Chl of different algal groups, picocyanobacteria, bacteria and eukaryotes counting, were measured at six stations and five depths. Our study showed that TEP exhibited a clear vertical heterogeneity from surface to the bottom related to the autotrophic microorganisms that are the main source of TEP and are prevalent in the euphotic zone of the lake. On the other hand, TEP was fairly evenly distributed along the horizontal transect from littoral to pelagic zone, although patches were present in spring, when TEP concentrations were low. in contrast to TEP, TOC and to a lesser extent Chl and bacteria showed horizontal heterogeneity, in some months. In Lake Maggiore TEP indeed was an important fraction of total organic carbon TOC , making up to 54% of TOC in carbon units 910 mu g C L 1 and it was significantly correlated with Chl. The highest TEP concentration 1.44 mg GX eq L 1 was measured in September 2019, in coincidence with an episode of superficial foam appearance. Considering the biomass as Chl concentrations, the algal group mostly related to TEP was that of brown algae, particularly diatoms; but considering the numbers, the picocyanobacteria and bacteria were more significantly correlated to TEP. The presence of pennate diatoms in May and July, with their TEP related chlorophyll, did not produce TEP in as high concentration as that observed in September in the presence of centric diatoms and of very high numbers of picocyanobacteria and bacteria. 80 Published version https //doi.org/10.4081/jlimnol.2021.2021 Transparent exopolymer particles TEP , phytoplankton and picocyanobacteria along a littoral to pelagic depth gradient in a large subalpine lake Versione finale lim_2021_80 3 _2021_opt.pdf Articolo in rivista Istituto per lo Studio degli Ecosistemi. 1129 5767 Journal of limnology Testo stamp. Journal of limnology Testo stamp. J. limnol. Testo stamp. Journal of limnology. Testo stamp. roberto.bertoni BERTONI ROBERTO SFORZI TOMMASO cristiana.callieri CALLIERI CRISTIANA SABATINO RAFFAELLA michela.rogora ROGORA MICHELA estermaria.eckert ECKERT ESTER MARIA gabriele.tartari TARTARI GABRIELE |
