Abstract
Tintinnid community structure was investigated by plankton net (20 mu m) sampling in the water column (0-200 m) at 33 stations during the spring inter-monsoon (10 March to 9 April 2012) in the eastern equatorial Indian Ocean. A total of 126 species belonging to 32 genera were recorded. Tintinnid abundance and biomass in the range of 193-2983 ind. m(-3) and 0.99-14.75 mu g C m(-3) were positively related to integrated chlorophyll a (chl a) concentration. Taxonomic and morphological diversity were not significantly related to integrated chl a concentration and size diversity, estimated by size-fractionated chl a concentration in the water column of 0-200 m, but were negatively correlated to the depth of the deep chlorophyll maximum. Species abundance distributions at most stations (31 of 33) and in the 3 zones-the northern zone of the equator, the southern zone of the equator (SEQ) and the equator (EQ)-followed a typical lognormal distribution. The geometric distribution gave the best fit for the distribution of lorica oral diameter size-classes in the NEQ and SEQ. Our results suggest that the community structure of tintinnids is governed by the underlying water column environment rather than by the neutral theory of random colonization from a large species pool.
Highlights
Tintinnids are characterized by the possession of a lorica, which is thought to protect the cell from predators, facilitate escape by rapid sinking and assist filter feeding (Agatha et al 2013)
Lorica morphology forms the basis of tintinnid identification, and provides information on the ecology of the organism
The maximum size of natural prey ingested and preferred prey size are closely related to lorica oral diameter (LOD) (Dolan 2010)
Summary
Tintinnids are characterized by the possession of a lorica, which is thought to protect the cell from predators, facilitate escape by rapid sinking and assist filter feeding (Agatha et al 2013). Lorica morphology forms the basis of tintinnid identification, and provides information on the ecology of the organism. Tintinnid ciliates are a common component of planktonic microzooplankton and occur in all of the world’s oceans (Pierce & Turner 1992, 1993). Only a small proportion of total microzooplankton, tintinnids are much more abundant than other groups (e.g. foraminifera and radiolarians). Tintinnids are secondary consumers at the base of the food web, grazing mainly on nanoplankton, as well as on picoplankton (Dolan et al 2006a). As copepods are seldom able to prey directly on the dominating primary producers in oligotrophic tropical systems (Calbet & Landry 1999), the microbial food web performs a crucial role in the transfer of energy up the food chain
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