Occurrence and distribution of plankton-associated and free-living toxigenic Vibrio cholerae in a tropical estuary of a cholera endemic zone

• Published in: Wetlands ecology and management Vol. 20; no. 3; pp. 271 - 285
• Main Authors: Neogi, Sucharit Basu, Islam, M. Sirajul, Nair, G. Balakrish, Yamasaki, Shinji, Lara, Rubén J
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer-Verlag 01.06.2012; Springer Netherlands; Springer Nature B.V
• Subjects: Abundance; Algae; Aquatic ecosystems; aquatic habitat; Aquatic habitats; Aquatic plants; Bacillariophyceae; Bacillariophyta; bacteria; Bacterial diseases; Biogeography; Biomedical and Life Sciences; Brackish; Cell culture; Chemical properties; Chitin; Cholera; Colonies; Colony-forming cells; Conservation Biology/Ecology; Copepoda; Cyanobacteria; Diatoms; disease outbreaks; Dominant species; Environmental Law/Policy/Ecojustice; Epidemics; Epidemiology; Estuaries; freshwater; Freshwater & Marine Ecology; Freshwater environments; Habitat; Hydrology/Water Resources; Life Sciences; Marine; Marine & Freshwater Sciences; Marine aquaculture; Organic matter; Original Paper; Particulate matter; particulates; Pathogenic bacteria; Pathogens; Physicochemical properties; Phytoplankton; Plankton; Plankton surveys; Rotifera; Salinity; Salinity effects; serotypes; Spreading; Stormwater runoff; Suspended particulate matter; Vibrio cholerae; Water Quality/Water Pollution; Waterborne diseases; Wetlands; Zooplankton; Bangladesh; ISW, Bangladesh; Phytoplankton; Chitin; Zooplankton; Salinity
• ISSN: 0923-4861; 1572-9834
• DOI: 10.1007/s11273-012-9247-5

Cholera epidemics are thought to be influenced by changes in populations of estuarine Vibrio cholerae. We investigated the abundance and distribution of this bacterium, as “free-living” (<20 μm fraction) and associated with microphytoplankton (>20 μm) or zooplankton (>60 μm), in the Karnaphuli estuary of Bangladesh during pre- and post-monsoon seasons. Cultivable Vibrio populations were ~102–104 colony forming units (CFU) ml−1 in the high saline zone (19–23 practical salinity unit, PSU) and declined in freshwater (<101 CFU ml−1). Culture independent detection of toxigenic V. cholerae O1 and O139 serogroups revealed a higher abundance of “free-living” (104–105 cells l−1) than those attached to plankton (101–103 cells l−1). However, “free-living” O1 and O139 cells were sometimes absent in the medium saline and freshwater areas (0.0–11 practical salinity unit [PSU]). In contrast, plankton samples always harbored these serogroups despite changes in salinity and other physico-chemical properties. Microphytoplankton and zooplankton were dominated by diatoms and blue-green algae, and copepods and rotifers, respectively. Toxigenic V. cholerae abundance did not correlate with plankton abundance or species but had a positive correlation with chitin in the <20 μm fraction, where suspended particulate matter (SPM), V. cholerae and chitin concentrations were highest. C:N ratios indicated that organic matter in SPM originated predominantly from plankton. The differential occurrence of “free-living” and attached V. cholerae suggests a pivotal function of plankton in V. cholerae spreading into freshwater areas. The probable association of this pathogen with organisms and particles in the nanoplankton (<20 μm) fraction requires validation of the concept of the “free living” state of V. cholerae in aquatic habitats.