Factores ambientales controladores del fitoplancton con énfasis en las cianobacterias potencialmente tóxicas en un lago somero utilizado como fuente de agua para potabilización: Laguna del Sauce, Maldonado, Uruguay

Abstract

Factores ambientales controladores del fitoplancton con énfasis en las cianobacterias potencialmente tóxicas en un lago somero utilizado como fuente de agua para potabilización: Laguna del Sauce, Maldonado, Uruguay Resumen Laguna del Sauce, principal fuente de agua para potabilización en Maldonado, Uruguay, ha registrado recurrentes eventos de floraciones de cianobacterias potencialmente tóxicas, que comprometen su uso como tal. Esto ha denotado la necesidad de un mayor conocimiento de los factores ambientales asociados a la composición fitoplanctónica y, en especial, a la ocurrencia de floraciones de cianobacterias. Mediante muestreos semanales estivales (2015-2016) de variables fisicoquímicas, nutrientes y fitoplancton, en seis sitios de Laguna del Sauce, se analizaron los factores ambientales asociados a la biomasa y composición fitoplanctónica, particularmente de cianobacterias. La alta variabilidad temporal y espacial observada en la composición fitoplanctónica presentó alternancia de floraciones de cianobacterias: Dolichospermum crassum, Cuspidothrix issatschenkoii, Microcystis aeruginosa, Microcystis panniformis y Sphaerocavum brasiliense. La turbiedad fue clave para regular la biomasa fitoplanctónica, mientras que la relación Nitrógeno total (NT):Ortofosfato (PO4) se asoció a la presencia diferencial de especies de cianobacterias. El análisis de las relaciones entre estos nutrientes puede contribuir a anticipar la ocurrencia de floraciones de diferentes especies de cianobacterias en este ecosistema, posibilitando la implementación de medidas de gestión orientadas a disminuir sus efectos adversos y, en particular, a asegurar el proceso de potabilización. Palabras clave: Floraciones nocivas, composición fitoplanctónica, biomonitoreo, aprovisionamiento de agua. AbstractSauce Lake, the main drinking water source in Maldonado, Uruguay, has been registering recurring events of potentially toxic cyanobacterial blooms that affect its service. This leads to the necessity of exploring the environmental drivers in the composition of phytoplankton, particularly in the presence of potentially toxic cyanobacteria. In this study we analyzed the environmental factors associated with phytoplankton composition and biomass, particularly of cyanobacteria. We sampled physicochemical variables, nutrients and phytoplankton during the summer 2015-2016 with a weekly frequency, in six sites of Sauce Lake. The results show a very high temporal and spatial variability in the phytoplankton composition, with cyanobacterial algal blooms of different taxa: Dolichospermum crassum, Cuspidothrix issatschenkoi, Microcystis aeruginosa, Microcystis panniformis y Sphaerocavum brasiliense. We observed that turbidity is a key factor controlling the total phytoplankton biomass, while the NT vs. PO4 concentrations determined the differential presence of potentially toxic cyanobacteria. The analysis of the relationship between these nutrients could contribute to anticipate different cyanobacterial harmful algal blooms in this ecosystem, enabling th...

Analysing the Impact of Climate Change on Hydrological Ecosystem Services in Laguna del Sauce (Uruguay) Using the SWAT Model and Remote Sensing Data

“…Cyanobacteria blooms have been recorded from 1960 to the present with increasing recurrence and persistence over time, which implies an important health threat due to their toxicity potential and the main use of this ecosystem as a tap water supply [30]. These cyanobacterial blooms caused disruptions in the water supply in 2015, despite institutional efforts on biomonitoring and purification [28]. These blooms also affect various productive and recreational activities in the area and compromise the availability of different ecosystem services [30].…”

“…Laguna del Sauce is the second-largest drinking water source in Uruguay, supplying 95% of the population in the Maldonado region, where a tourism influx during the summer doubles the local drinking water demand. Recently, this shallow lake has experienced an increased recurrence of cyanobacteria-events that have affected the purification process and restricted recreational use, generating great repercussions at the public opinion level [27,28]. Moreover, the Laguna del Sauce catchment is experiencing a land-use intensification trend, which along with climate change has the potential to aggravate the current problems associated with Laguna del Sauce as well as alter its hydrological performance.…”

Drivers of cyanobacteria dominance, composition and nitrogen fixing behavior in a shallow lake with alternative regimes in time and space, Laguna del Sauce (Maldonado, Uruguay)

“…Remarkably, in this ecosystem, during low turbidity periods, when cyanobacteria bloom, its composition is recurrently dominated by heterocystous N 2fixing species (Order Nostocales) and less frequently by non-heterocsytous N 2 -fixing cyanobacteria (e.g., Microcystis complex) (Gonza ´lez-Madina et al, 2017). This poses the question if the success of heterocystous N 2 -fixing cyanobacteria in this ecosystem relies on its ability to fix atmospheric nitrogen.…”

“…The drinking water crisis supply that occurred in 2015 promoted the implementation of new monitoring programs in order to understand the ecosystem dynamics and to develop an early warning system for the management of the drinking water supply (Crisci et al, 2017b;Gonza ´lez-Madina et al, 2017). In this study we analyzed, during two summer cycles (2015-2016 and 2016-2017), the phytoplankton dynamics on a weekly basis, both in the vegetated and in the open water regions of Laguna del Sauce.…”

Calidad de agua de los tributarios de la Laguna del Sauce, Maldonado, Uruguay, en base al Índice Diatomológico Pampeano (IDP)

“…Laguna del Sauce (Maldonado, Uruguay) es uno de los principales reservorios costeros que abastece de agua potable a más del 95% de la población fija y flotante del departamento de Maldonado. Este cuerpo de agua ha sido declarado como clase 1: aguas destinadas al abastecimiento de agua, según el Decreto 253/79 (Uruguay, 1979 El sistema Laguna del Sauce presenta un grado de eutrofización elevado, evidenciado por la recurrencia y persistencia de floraciones de cianobacterias (Rodríguez, et al, 2010;Mazzeo, et al, 2010;González-Madina, 2017). Para mitigar la eutrofización se generó un plan de acción y medidas de control de la degradación ambiental (MVOTMA, 2015).…”