| Title | Recent cyanobacteria abundance in a large sub-tropical reservoir inferred from analysis of sediment cores |
| Abstract | Salto Grande is a large South American reservoir on the border between Uruguay and Argentina that was impounded in 1979 and experiences recurrent, massive cyanobacteria blooms. A water-monitoring program was initiated 20 years after the dam was built, hence the causes and onset of cyanobacteria blooms remain poorly known. We collected two sediment cores from the old river channel in the reservoir (z = 17 m) and used physical, chemical and biological variables in the sediments, along with existing limnological data, to explore the history of cyanobacteria in the sub-tropical water body. Cyanobacteria fossil pigments were present at low concentrations during the first 24 years after impoundment, but more than doubled thereafter. Phytoplankton abundance tracked shifts in cyanobacteria pigment concentration, indicating an overall increase in all primary producers. Several sediment variables indicate a decline in water quality after 2003, such as increases in the number of photosynthetic sulfur bacteria and a reduction in sediment magnetic susceptibility. Akinetes (dormant cyanobacteria cells, Order Nostocales) in recent reservoir deposits were abundant and five species germinated under laboratory conditions, underscoring the ability of akinetes to initiate cyanobacteria blooms. The germinated assemblage reflected closely the composition of cyanobacteria blooms in the reservoir. Recorded increases in air temperature and decreases in wind speed, together with other variables (e.g. nutrients), can promote the large, recurrent cyanobacteria blooms. Invasion of the bivalve Limnoperna fortunei apparently promoted cyanobacteria blooms by preferential feeding on other phytoplankton taxa, and perhaps by altering nutrient concentrations and ratios. This work highlights the potential for using multiple variables in sediment cores from large reservoirs to better understand the responses of biota to multiple environmental stressors. |
| Source | Journal of paleolimnology 63 (3), pp. 195–209 |
| Keywords | AkinetesCyanobacteriaPaleolimnologyPigmentsReservoir |
| Journal | Journal of paleolimnology |
| Editor | Kluwer Academic, Boston, Paesi Bassi |
| Year | 2020 |
| Type | Articolo in rivista |
| DOI | 10.1007/s10933-020-00110-8 |
| Authors | Gangi, Daniela; Plastani, María Sofía; Laprida, Cecilia; Lami, Andrea; Dubois, Nathalie; Bordet, Facundo; Gogorza, Claudia; Frau, Diego; de Tezanos Pinto, Paula |
| Text | 454294 2020 10.1007/s10933 020 00110 8 Scopus 2 s2.0 85078916833 Akinetes Cyanobacteria Paleolimnology Pigments Reservoir Recent cyanobacteria abundance in a large sub tropical reservoir inferred from analysis of sediment cores Gangi, Daniela; Plastani, Maria Sofia; Laprida, Cecilia; Lami, Andrea; Dubois, Nathalie; Bordet, Facundo; Gogorza, Claudia; Frau, Diego; de Tezanos Pinto, Paula Centro de Investigaciones en Fisica e Ingenieria del Centro de la Provincia de Buenos Aires; Istituto di Ricerca sulle Acque, Italy; ETH Zurich; Instituto Nacional de Limnologia; Consejo Nacional de Investigaciones Cientificas y Tecnicas; Eawag Swiss Federal Institute of Aquatic Science and Technology; Universidad de Buenos Aires; Comision Tecnica Mixta de Salto Grande CTM Salto Grande is a large South American reservoir on the border between Uruguay and Argentina that was impounded in 1979 and experiences recurrent, massive cyanobacteria blooms. A water monitoring program was initiated 20 years after the dam was built, hence the causes and onset of cyanobacteria blooms remain poorly known. We collected two sediment cores from the old river channel in the reservoir z = 17 m and used physical, chemical and biological variables in the sediments, along with existing limnological data, to explore the history of cyanobacteria in the sub tropical water body. Cyanobacteria fossil pigments were present at low concentrations during the first 24 years after impoundment, but more than doubled thereafter. Phytoplankton abundance tracked shifts in cyanobacteria pigment concentration, indicating an overall increase in all primary producers. Several sediment variables indicate a decline in water quality after 2003, such as increases in the number of photosynthetic sulfur bacteria and a reduction in sediment magnetic susceptibility. Akinetes dormant cyanobacteria cells, Order Nostocales in recent reservoir deposits were abundant and five species germinated under laboratory conditions, underscoring the ability of akinetes to initiate cyanobacteria blooms. The germinated assemblage reflected closely the composition of cyanobacteria blooms in the reservoir. Recorded increases in air temperature and decreases in wind speed, together with other variables e.g. nutrients , can promote the large, recurrent cyanobacteria blooms. Invasion of the bivalve Limnoperna fortunei apparently promoted cyanobacteria blooms by preferential feeding on other phytoplankton taxa, and perhaps by altering nutrient concentrations and ratios. This work highlights the potential for using multiple variables in sediment cores from large reservoirs to better understand the responses of biota to multiple environmental stressors. 63 Published version http //www.scopus.com/record/display.url eid=2 s2.0 85078916833 origin=inward Gangi et al. 2020 Recent cyanobacteria abundance in a large sub trop.pdf articolo pdf Gangi et al. 2020 Recent cyanobacteria abundance in a large sub trop.pdf Articolo in rivista Kluwer Academic 0921 2728 Journal of paleolimnology Journal of paleolimnology J. paleolimnol. andrea.lami LAMI ANDREA |
