Plankton food web and its seasonal dynamics in a large monsoonal estuary (Cochin backwaters, India)-significance of mesohaline region

Abstract

The paper presents the ecology and dynamics of plankton food web in the Cochin backwaters (CBW), the largest monsoonal estuary along the west coast of India. The data source is a time series measurement carried out in the CBW during the Spring Intermonsoon (March-May) and the Southwest Monsoon (June-September). The plankton food web consisting of autotrophic/heterotrophic picoplankton, autotrophic/heterotrophic nanoplankton, microzooplankton, and mesozooplankton was quantified in relation to the seasonal hydrographical settings in the CBW. The study showed that significant changes in the abundance and dynamics of plankton food web components were governed mostly by the spatial and seasonal changes in hydrography rather than short-term changes induced by tide. During the Spring Intermonsoon, all plankton consumers in the CBW was higher than the Southwest Monsoon, and the trophic interaction was more effective in upstream where there was a close coupling between all prey components and their consumers. During the Southwest Monsoon, on the other hand, the trophic interaction was more effective downstream where the abundance of all plankton consumers was significantly higher than the upstream. Based on statistical analyses NMDS/SIMPROF and RDA, we demarcated the spatial difference/mismatch in the prey and consumer distribution in the CBW and showed that a more efficient plankton food web exists in the mesohaline regions during both seasons. This suggests that a noticeable spatial shift occurs seasonally in the active plankton food web zone in the CBW; it is upstream during the Spring Intermonsoon and downstream during the Southwest Monsoon.

Viral-Induced Mortality of Prokaryotes in a Tropical Monsoonal Estuary

“…0.24 ± 0.96–0.48 ± 0.5 mg C m −3 ). The abundance of microzooplankton grazers was noticeably high in the mesohaline regions during PRM (mean = 3.11 × 10 4 l −1 at S4, against mean = 1.11 × 10 4 l −1 at S3; part of this study, published by Sooria et al, 2015). High grazing pressure has been shown to enhance viral lysis and production (Weinbauer et al, 2007; Pradeep Ram and Sime-Ngando, 2008).…”

“…Hence, the major hydrological variable is salinity. The salinity gradient drives the existence of diverse species which can propagate under oligohaline, mesohaline, or marine conditions (Sreedevi, 2007; Sooria et al, 2015). As viruses are dependent on the metabolic status of their hosts, factors such as salinity that affect host activity can critically influence viral proliferation.…”

“…High grazing pressure has been shown to enhance viral lysis and production (Weinbauer et al, 2007; Pradeep Ram and Sime-Ngando, 2008). The high abundance of grazers, especially during PRM in mesohaline regions of the estuary, suggests that grazers can serve as important causative agents of bacterial mortality, thus affecting the viral production, directly and/or indirectly (Sooria et al, 2015). In fact, during PRM, all the planktonic components, especially the grazers were much more abundant that in MON.…”

The Various Applications of a Novel Configuration Anaerobic Fluidized Bed Reactor for Wastewater Treatment

“…Representative OTUs were selected on the basis of having an over 2% abundance rate in each sludge sample. Correspondence analysis was performed to determine the appropriate type of model for direct gradient analysis, redundancy analysis (RDA) was performed with CANOCO software (Šmilauer 󠄀 and 󠄀Lepš, 󠄀2014;Sooria et al, 2015). During the start-up period, 250 mL of seed sludge from an anaerobic filter reactor (located at the Faculty of Engineering, Chulalongkorn University) with a total solids content of 8,443 ± 588 mg/L was mixed with 1,000 mL of granular rubber and were added to the reactor.…”