Flood induced changes in the diversity of yeasts from the mangroves of Valanthakadu, Kerala, India

Abstract

This is the first report on the influence of the devastating August 2018 floods of Kerala on yeast communities associated with the mangrove ecosystem of Valanthakadu, 'Kochi’s oxygen parlour’. Samples were collected for the study from six stations in Valanthakadu during three different periods with regard to floods i.e. April – May 2018: Pre flood (PRF), September – October 2018: Just after floods (JAF), and March 2019: Post floods (POF) and plated onto Malt-yeast-glucose-peptone agar for isolation and enumeration. Morphologically distinct colonies were picked, clustered on biochemical basis, representative strains identified on molecular basis or using API 20 C AUX strip. On enumeration, the average colony counts of yeasts in the sediments were found to be greater than in water samples. Out of 89 morphologically distinct yeast strains isolated, the majority were non-pigmented (73 %) and belonged to the phyla Ascomycetes (58 %). Six different yeast genera: Candida spp., Cryptococcus spp., Hortaea sp., Rhodotorula spp., Rhodosporidiobolus sp., and Trichosporon sp. were recorded in this study. C. tropicalis was noted to be not only the predominant species but also resilient to the effect of floods. Flood was found to influence the diversity of yeasts, with the introduction of certain genera ( Hortaea wernekii (first report)) and the loss of certain others ( C. gatti ). Analysis of diversity indices evidently revealed the influence of floods, with an increase in yeast diversity just after floods (1.62) when compared to other periods of sampling. A change in the hydrolytic profile of isolates was also noticed in relation to floods. This study clearly indicated that floods do affect the diversity of yeast communities and their function in the ecosystems, at least temporarily. Nevertheless, the long-term impacts remain unknown and deserve further studies.