Influence of river discharge on zooplankton diet in the Godavari estuary (Bay of Bengal, Indian Ocean)

In estuaries, detrital (i.e., non-living) organic matter (OM) contributes significantly to the particulate organic matter (POM) pool and we hypothesize that it may be a major source of estuarine zooplankton diet. To test this hypothesis, the isotopic composition of carbon (d13C) and nitrogen (d15N) of phytoplankton, zooplankton, and POM was assessed in the Godavari estuary (Bay of Bengal, Indian Ocean) during wet (November) and dry periods (January). As a result of higher riverine discharge, POM concentrations and values of the C/Chl-a ratio during the wet period were higher than those measured during the dry one. Relatively lower δ13CPOM values were observed during wet than dry period and contrasting to that was found for δ15NPOM. Detritus from fresh water algae and C3 plants contributed significantly to the POM pool during the wet and dry period, respectively. Based on isotopic mixing model, detrital OM and phytoplankton mostly characterized the POM pools during the wet and dry periods, respectively. Accordingly, our results suggest also that the zooplankton diet was mostly supported by detrital OM during the wet period and by both phytoplankton and detrital OM during the dry one. The zooplankton trophic level (TL, 2.7) during the wet period was relatively higher than that (1.9) during the dry one, suggesting a relative higher preference for detritus than phytoplankton during the wet period. The results of this study allowed us confirming that detrital OM can significantly support zooplankton production in the Godavari estuary

Tidally-modulated high frequency internal waves in Gautami-Godavari estuary, East coast of India

1695-1707<span style="font-size:9.0pt;line-height: 150%;font-family:" times="" new="" roman";mso-fareast-font-family:calibri;mso-bidi-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="" lang="EN-US">Time series temperature and salinity (at 1 hour interval) and currents data (10 min interval) at surface (3 m) and bottom (14 m), collected in the   Gautami-Godavari estuary during 25-27 September 2008 were utilized to document the characteristics of Internal waves (IWs) and to infer their generation mechanism.  Based on the stability criteria, two High Frequency (HF) significant modes in the Internal Wave (IW) field at frequencies 96.67 cph (10 m depth) and 71.15 cph (14 m depth) have been identified. At these modes, IW parameters viz., wave length (L), wave number (κ), potential energy (PE), baroclinic potential energy (BPE) and phase speed (ci)  and displacement function (η(z,t)) have been computed (with salinity and currents data) objectively by adopting well known harmonic technique through Principal Component Analysis (PCA). Results revealed that (1) first mode: IW was found to move with a phase speed of 0.13 m s-1 and wave length of 0.0056 km (wave number=178.64 cycles km-1) having energies of 0.0006 J m-2 (potential) and 0.0027 J m-2 (baroclinic) whereas (2) second mode:  0.09 m s-1, 0.0076 km, 131.48 cycles km-1, 0.0055 J m-2, 0.020 J m-2 and 0.094 m s-1 for L, κ, PE, BPE and ci respectively. η(z,t) was found to be positive (elevation-type IWs) and negative values (oscillation-type) during IW propagation of two modes respectively wherein  mode 2 is more energetic (8 times) than mode 1. Tidally-modulated force may be the possible mechanism to generate HF IWs under ebb period.</span

Seasonal, weathering and water use controls of silicon cycling along the river flow in two contrasting basins of South India

International audienc

A global sea surface carbon observing system: inorganic and organic carbon dynamics in coastal oceans

Coastal environments are an important component of the global carbon cycle, and probably more vulnerable than the open ocean to anthropogenic forcings. Due to strong spatial heterogeneity and temporal variability, carbon flows in coastal environments are poorly constrained. Hence, an integrated, international, and interdisciplinary program of ship-based hydrography, Voluntary Observing Ship (VOS) lines, time-series moorings, floats, gliders, and autonomous surface vessels with sensors for pCO2 and ancillary variables are recommended to better understand present day carbon cycle dynamics, quantify air-sea CO2 fluxes, and determine future long-term trends of CO2 in response to global change forcings (changes in river inputs, in the hydrological cycle, in circulation, sea-ice retreat, expanding oxygen minimum zones, ocean acidification, ?) in the coastal oceans. Integration at the international level is also required for data archiving, management, and synthesis that will require multi-scale approaches including the development of biogeochemical models and use of remotely sensed parameters. The total cost of these observational efforts is estimated at about 50 million US dollars per year