Biogeochemical drivers of the dynamic of Vibrio species in two estuaries of the Argentinian Patagonia

OKUNO, K.; STREITENBERGER, M. E.; KOPPRIO, G.; BIANCALANA, F.; YAMASAKI, S.; BALDINI, M; KOCH, B. P.; GRAEVE, M.; MARTÍNEZ, A.; LARA, R. J.

Bremen

Conferencia; ECSA 56 Coastal systems in transition: From a 'natural' to an 'anthropogenically-modified' state; 2016

LEIBNIZ CENTER FOR TROPICAL MARINE ECOLOGY, ELSEVIER, ECSA

The interactions between hydrological factors, nutrients, and cultivable bacteria were studied from late spring to early autumn in the Río Negro (RN) and Río Colorado (RC) estuaries. RN was impacted by a sewage discharge, while RC was affected by several irrigation works producing hydrological changes such as an increased salinity. Vibrio species linked to water-borne diseases were detected with a highly sensitive and specific multiplex Polymerase Chain Reaction (PCR) assay: V. cholera and V parahaemolyticus were found respectively in the 65 % and the 28% of the cases (n= 189), respectively. The positive cases of V. cholera were generally related but not exclusively to lower salinities (<1), whereas V. parahaemolyticus to higher salinities (>1). Vibrio vulnificus was only detected at one station of RN in a seston fraction. Cultivable Vibrio counts (CVC) were principally correlated with salinity in RN (r= 0.73, p<0.001) and RC (r= 0.72, p<0.001). No significant relations were found among CVC and particulate organic matter nor chlorophyll a in both estuaries. In RC, CVC were correlated with nitrate (r= 0.87, p<0.001), phosphate ( r= 0.41, p=0.012) and dissolved organic carbon (r= 0.69, p<0.001). Conversely, no significant correlation were found between CVC and inorganic nor organic nutrients in RN. The correlation of ammonium with heterotrophic bacteria (r= 0.88, p<0.001) and fecal coliforms(r= 0.78, p<0.001) evidenced the strong effect of the sewage discharge in RN. Salinity was the main factor driving the dynamic of CVC. Despite the non-correlative evidence of RN, nutrients have directly or indirectly an effect in the abundance, biofilm formation, motility, virulence and changes in the stationary phase of Vibrio species. An increased salinization and trophic state in both estuaries due to anthropogenic and climate-driven changes are expected to increase the impact of Vibrio species on human and ecosystem health.