Morpho-physiological traits of toxic cyanobacterial blooms in a Pampean (Argentina) shallow lake

COCCIOLO, FIORELLA TATIANA; YEMA, LILEN; SÁNCHEZ, MARÍA LAURA; GONZÁLEZ, CAROLINA; O'FARRELL, INÉS

Gwangju

Congreso; SIL 2021; 2022

International Society of Limnology (SIL)

Cyanobacterial blooms impair the shallow lakes in the Pampean region which is greatly affected by anthropic activities. In this study we present the ecological characterization of the assemblage of bloom forming cyanobacteria from laguna Salada de Monasterio (SM), Buenos Aires. The relationships between abundance, biomass and morphology of the species with the environmental conditions are assessed in SM along two warm periods. SM was seriously impaired by blooms dominated by Raphidiopsis mediterranea, which in the first stage was accompanied by Planktothrix agardhii, Anabaenopsis cf. circularis, A. cunningtonii and Cuspidothrix issatschenkoi, whereas in the second period by C. issatschenkoi. Total abundance and biovolume were positively correlated; less intense blooms were registered in the second period with a higher water level. Alert Level 2 for drinking water and the guide level 2 for recreational waters (World Health Organization, WHO), in terms of cell abundance, were exceeded at both warm periods. The morphological differences observed among species were associated with responses to the light availability in the water column dependent on the water level of SM. R. mediterranea presented a direct association between filament length and width that favoured its development, even in scenarios with high turbidity and light limitation, where the other species were not found. Dissolved organic nitrogen (NOD) would be the major nitrogen source due to its high concentration (average: 3.76 mg/L); no relationship was found between the proportion of heterocytes per vegetative cell of fixing Nostocales and the concentration of NOD, and the relationship with DIN is not clear. A low frequency of akinetes was found for Anabaenopsis and C. issatschenkoi, indicating a favorable scenario for their development. LR and -YR microcystins were registered in the first period with concentrations exceeding 1µg/L (WHO guidance level), with P. agardhii and Anabaenopsis being the potential toxin producers; saxitoxin was not detected.