An ex situ and in vitro approach to delineate pennate diatom species with bioindicator potentials in a well mixed tropical estuarine ecosystem

Abhishek Mukherjee,Tarun Kumar De,Sabyasachi Chakraborty,Subhajit Das

doi:10.21472/bjbs.030607

Abstract

An experiment was performed on selected pennate diatom species collected from the well mixed waters of the Hooghly Estuary with the aim of distinguishing the ones with qualities to be employed as monitors of their ecosystem. The Hooghly Estuary is enriched with domestic, sewage and agricultural effluents and coastal upwelling along with tide-mediated advective circulation from the mangrove forests ensure concomitant nutrient pool replenishment in this ecoregion. There have been several attempts to establish certain centric diatom species as bioindicators in various parts of the world owing to their better responsiveness to sudden shifts in stoichiometry but hardly any with pennate diatoms. Pennate diatoms are typical benthic mat formers in the intertidal regions, on submerged surfaces and thus bear greater feasibility to be employed as accurate pointers to long term deviations in their respective ecosystems, in spite of the greater sensitivity of the centric diatoms. The study was carried out in laboratory controlled environment to minimize the interference from other extrinsic factors compromising the outcome and also due to the fact that such studies to be performed in natural conditions require a decent financial support and time to conclusively arrive upon the objectives. From the present endeavour it was inferred that Nitzschia sigmoidea, Pleurosigma angulatum and Ulnaria oxyrhyncus (formerly Synedra ulna var. oxyrhyncus) stood a good chance of being recruited as bioindicators to eutrophic well mixed estuaries, similar to the one they had been sampled from.

Highlights

IntroductionDiatoms vary greatly in their shapes and sizes and as a result have a varied surface area to volume ratio, enabling them to exploit and utilize available growth sustaining resources better than their co-habitators
One of the most dominant life forms in the aquatic realm of the earth is the phytoplankton and diatoms are the most populous phytoplankton communities belonging to the Family Bacillariophyceae
The study is more significant as it is the first attempt to understand the roles pennate diatoms in the Sagar Island and surrounding regions as biomonitor of anthropogenic perturbations and if established, can certainly be added to the few findings from earlier research by Mukherjee et al (2015a, b) in order to render the information holistic and helpful to any policy maker and future researchers

Summary

Introduction

Diatoms vary greatly in their shapes and sizes and as a result have a varied surface area to volume ratio, enabling them to exploit and utilize available growth sustaining resources better than their co-habitators. Due to their ephemeral life span, phytoplankton can respond quickly to subtle changes in their ambient environment and such responses in phytoplankton may serve as beacons of ISSN 2358-2731/BJBS-2016-0029/3/6/7/299. Timmermans (2001) studied the growth rates of large and small Southern Ocean diatoms in relation to the availability of micronutrients (Fe+3) in natural seawater. Studies such as these are available aplenty but exactly the species wise phytoplankton (diatom) indicators of the nutrient status have not been studied in details in the Hooghly Estuarine Region of the Bay of Bengal

Objectives

Methods

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Discussion

Conclusion