Analysis of diversity of chromophytic phytoplankton in a mangrove ecosystem using rbcL gene sequencing

Abstract

Phytoplankton forms the basis of primary production in mangrove environments. The phylogeny and diversity based on the amplification and sequencing of rbcL, the large subunit encoding the key enzyme ribulose-1, 5-bisphosphate carboxylase/oxygenase was investigated for improved understanding of the community structure and temporal trends of chromophytic eukaryotic phytoplankton assemblages in Sundarbans, the world's largest continuous mangrove. Diatoms (Bacillariophyceae) were by far the most frequently detected group in clone libraries (485 out of 525 clones), consistent with their importance as a major bloom-forming group. Other major chromophytic algal groups including Cryptophyceae, Haptophyceae, Pelagophyceae, Eustigmatophyceae, and Raphidophyceae which are important component of the assemblages were detected for the first time from Sundarbans based on rbcL approach. Many of the sequences from Sundarbans rbcL clone libraries showed identity with key bloom forming diatom genera namely Thalassiosira, Skeletonema and Nitzschia. Similarly, several rbcL sequences which were diatom-like were also detected highlighting the need to explore diatom communities from the study area. Some of the rbcL sequences detected from Sundarbans were ubiquitous in distribution showing 100% identities with uncultured rbcL sequences targeted previously from the Gulf of Mexico and California upwelling system that are geographically separated from study area. Novel rbcL lineages were also detected highlighting the need to culture and sequence phytoplankton from the ecoregion. Principal component analysis revealed that nitrate is an important variable that is associated with observed variation in phytoplankton assemblages (operational taxonomic units). This study applied molecular tools to highlight the ecological significance of diatoms, in addition to other chromophytic algal groups in Sundarbans.

Exploring biogeographic patterns of bacterioplankton communities across global estuaries

“…Sagar Island is the biggest island of Indian Sundarbans and marks the westernmost part of this ecoregion. A predesignated station named as Stn3 (Mooriganga) (21° 40ʹ 40.6ʺ N, 88° 09ʹ 19.2ʺ E) which is part of the Sundarbans Biological Observatory Time Series (SBOTS) monitored since 2010 has been considered in this study (Bhattacharjee, Samanta, Danda, & Bhadury, ; Choudhury, Das, Philip, & Bhadury, ; Samanta & Bhadury, ). Huge freshwater from the Mooriganga estuary and diurnal tidal influx of coastal water from the Bay of Bengal gives rise to typical estuarine conditions in this station.…”

“…Four stations located across four estuaries in Sundarbans selected for this study are shown in Figure 1. Sagar Island is the biggest island of Indian Sundarbans and marks the westernmost part of this has been considered in this study (Bhattacharjee, Samanta, Danda, & Bhadury, 2013;Choudhury, Das, Philip, & Bhadury, 2015;Samanta & Bhadury, 2014). Huge freshwater from the Mooriganga estuary and diurnal tidal influx of coastal water from the Bay of Bengal gives rise to typical estuarine conditions in this station.…”

“…Biomass was concentrated by filtering through 0.22-µm nitrocellulose filter paper (Pall, USA) following a published protocol (Samanta & Bhadury, 2014). DNA was subsequently extracted using standard published protocol (Bostrӧm, Simu, Hagstrӧm, & Riemann, 2004).…”

Thalassiosira sundarbana sp. nov. (Bacillariophyta), an estuarine diatom from Sundarbans mangrove ecoregion based on morphology and molecular phylogeny

“…Bloom forming centric diatom genera such as Thalassiosira Cleve and Coscinodiscus Ehrenberg are detectable throughout the year in Sundarbans highlighting their importance in aquatic primary production (Biswas et al . ; Samanta & Bhadury ).…”

“…Nevertheless, very limited information exists to date from the context of Thalassiosira ecology in mangrove ecosystems. Based on a recent study using form ID large subunit of RuBisCO ( rbc L) phylogeny it has been shown that diatom assemblages are overwhelmingly dominated by Thalassiosira throughout the year in Sundarbans (Samanta & Bhadury ). Thus it is important to establish cultures of Thalassiosira from mangrove environments such as Indian Sundarbans for better understanding of their ecological significance in this ecosystem.…”