Environmental impact on diversity and distribution of tintinnid (Ciliata: Protozoa) along Hooghly Estuary, India: A multivariate approach

The spatiotemporal distribution, diversity and biomass of the choreotrich ciliate tintinnid, the ubiquitous planktonic protist, were analysed from nine sampling sites (n = 252) of diverse environmental stresses along the Hooghly Estuary, eastern part of India during March 2012 to August 2014. Among 32 identified tintinnid species, the agglomerated genera Tintinnopsis (20 sp), dominated the community (similar to 62%) followed by Tintinnidium (2 sp), Leprotintinnus (2 sp), Codonellopsis, Stenosemella, Helicostomella, Favella, Eutintinnus, Metacylis, Dadayiellaand Wangiella (each comprising single species). A wide range of seasonal variations in tintinnid abundance was recorded maximum (2067 +/- 893 ind. l(-1)) for Tintinnopsis beroidea and minimum (11 +/- 4 ind. l(-1)) for Metacylis sp. during the investigation period. The biomass and daily production rate of tintinnid ranged from 0.004-2.764 mu g C l(-1) and 0.04-3.54 mu g C l(-1) day(-1) respectively. An overall dominance and diversity of the small-sized tintinnid (lorica length < 76 mu m) belonging to the genera Tintinnopsis sp., Tintinnidium sp., Codonellopsis sp., Wangiella sp., Eutintinnus sp., Metacylis sp. and Helicostomella sp. was pronounced, accounting similar to 66% of the total tintinnid abundance. K-dominance curves were plotted against log rank k, showed species dominance over the investigated sites. The multidimensional scaling (MDS) Canonical Analysis of Principal coordinates (CAP) highlighting a significantly different spatial distribution of tintinnid. Principal Component Analysis (PCA) map showed clustering of core species with chl a and nitrate and could be considered as the crucial factors controlling the distribution and seasonal patterns of tintinnid. Biota-environment (BIOENV) analyses also reveal that these two parameters were the significant causative factors, suggesting that tintinnid may be used as a bioindicator for discriminating water quality in this estuarine system. The study provided detailed information of microzooplankton which enhances our understanding regarding its crucial role in marine ecosystem and complex biotic interactions for maintaining the ecological and economic stability. (C) 2017 Elsevier B.V. All rights reserved.