Inorganic and organic carbon biogeochemistry in the Gautami Godavari estuary (Andhra Pradesh, India) during pre-monsoon : the local impact of extensive mangrove forests

in Global Biogeochemical Cycles (2003), 17(4),

[1] The distribution and sources of organic and inorganic carbon were studied in the Gautami Godavari estuary (Andhra Pradesh, India) and in a mangrove ecosystem in its delta during pre-monsoon. In the ... [more ▼]

[1] The distribution and sources of organic and inorganic carbon were studied in the Gautami Godavari estuary (Andhra Pradesh, India) and in a mangrove ecosystem in its delta during pre-monsoon. In the oligohaline and mesohaline section (salinity 0–15) of the estuary, internal production of total alkalinity (TAlk) and dissolved inorganic carbon (DIC) was recorded, and the d13CDIC profile suggests that carbonate dissolution may be an important process determining the DIC dynamics in this section of the Godavari. The partial pressure of CO2 (pCO2) was fairly low along the entire salinity gradient, (293–500 ppm), but much higher and more variable (1375–6437 ppm) in the network of tidal mangrove creeks in the delta. Here, variations in the concentration and d13C of the DIC pool were shown to result largely from the mineralization of organic matter. The present study clearly identifies the mangrove creeks as an active site of mineralization and CO2 efflux to the atmosphere, but shows that these changes in the aquatic biogeochemistry are a localized feature, rapidly fading in the adjacent Kakinada Bay. Our data indicate that mineralization of dissolved organic carbon (DOC) of mangrove origin, and its subsequent efflux as CO2 to the atmosphere may represent an important fate for mangrove carbon. Although further quantification of this process in a variety of systems is required, we suggest that some of the current ideas on the role of mangroves in the carbon budget of the coastal zone may need to be reconsidered. [less ▲]

Carbonate dissolution in the turbid and eutrophic Loire estuary

in Marine Ecology. Progress Series (2003), 259

We measured particulate and dissolved organic carbon (POC and DOC), chlorophyll, oxygen, partial pressure of Co-2, pH, total alkalinity (TAlk) and particulate inorganic carbon (PIC) during a late summer ... [more ▼]

We measured particulate and dissolved organic carbon (POC and DOC), chlorophyll, oxygen, partial pressure of Co-2, pH, total alkalinity (TAlk) and particulate inorganic carbon (PIC) during a late summer cruise in the eutrophic Loire estuary. These parameters reveal an intense mineralisation of organic matter in the estuarine maximum turbidity zone (MTZ) that results in oxygen deficits (down to 20% of the saturation level) and high CO2 oversaturations (pCO(2) up to 2900 muatm). Several facts revealed the occurrence of carbonate dissolution in the Loire MTZ: large amounts of alkalinity were produced in the upper estuary, increasing its transfer to the ocean by 30%; the calculated saturation index showed a net undersaturation for aragonite and a slight undersaturation for calcite in the MTZ; and PIC decreased from 2.1% (% dry weight) in riverine suspension to 0.4% in the MTZ. A stoichiometric approach is used to assess the coupling between aerobic respiration and carbonate dissolution, where apparent oxygen utilisation, excess CO2, TAlk and dissolved inorganic carbon are compared quantitatively. About 20%, of the CO2 generated by respiration was involved in carbonate dissolution. The loss of PIC at the river-estuary transition quantitatively corresponds to the amount of authigenic calcite precipitated upstream in the highly eutrophic river. This suggests that CO2 exchange with the atmosphere along the eutrophic river-estuary continuum is buffered by carbonate precipitation in the autotrophic river and its dissolution in the heterotrophic estuary. [less ▲]

Aspects of inorganic carbon dynamics in the upwelling system off the Galician coast

in Journal of Marine Systems (2002), 32

In the present paper, we report data on the partial pressure of CO2 ( pCO2) in surface seawater off the Galician coast, obtained during four cruises carried out in summer (upwelling conditions). Over the ... [more ▼]

In the present paper, we report data on the partial pressure of CO2 ( pCO2) in surface seawater off the Galician coast, obtained during four cruises carried out in summer (upwelling conditions). Over the continental shelf, two processes that have opposite effects control pCO2 in surface waters: (a) the input from upwelling of deep cold water with high CO2 content that causes oversaturation of CO2 and (b) primary production that tends to decrease pCO2. In offshore waters, the distribution of pCO2 is mainly controlled by temperature change. In two distinct hydrographic coastal regions, the Rı´as Baixas area (RBA) and the Cape Finisterre area (CFA), the patterns of the distribution of pCO2 are complex but, in the Rı´as Baixas area, the averaged pCO2 values are systematically lower and temperature values higher. These differences between the two hydrographic regions are mainly related to the combination of outwelling from the Rı´as and the width of the continental shelf. In the Rı´as Baixas area, outwelling affects significantly the adjacent inner continental shelf but to a much lesser extent the outer continental shelf. In the Cape Finisterre area, the continental shelf is narrower and the ratio between the surface area of the shelf to the length of the shelf break is lower, inducing during an upwelling event, lower temperature and higher pCO2 values in surface waters than in the Rı´as Baixas area. [less ▲]

Direct and indirect pCO2 measurements in a wide range of pCO2 and salinity values

in Aquatic Geochemistry (2001), 7

Recent improvements in both Infra-red spectroscopy and equilibrator techniques have allowed to determine, for the first time, pCO2 using simultaneously and continuously both the direct and indirect ... [more ▼]

Recent improvements in both Infra-red spectroscopy and equilibrator techniques have allowed to determine, for the first time, pCO2 using simultaneously and continuously both the direct and indirect methods in an estuary where pCO2 values range from 500 to 8500 µatm and salinity from 0 to 30. Our results show that both methods are in excellent agreement in the whole estuary (r2 = 0.999, n = 1075, p < 0.0001). Thus, the NBS (US National Bureau of Standards) scale, although inadequate for seawater samples, is appropriate for estuarine waters and can be applied with confidence to calculate pCO2. [less ▲]

Short-term variations of the partial pressure of CO2 in surface waters of the Galician upwelling system

in Progress in Oceanography (2001), 50(2-4), 283-302

The partial pressure of CO2 (pCO2) and dissolved oxygen saturation level (%O2) were monitored continuously during a cruise in August 1998, which sampled surface waters off the Galician coast. Data are ... [more ▼]

The partial pressure of CO2 (pCO2) and dissolved oxygen saturation level (%O2) were monitored continuously during a cruise in August 1998, which sampled surface waters off the Galician coast. Data are presented from two Lagrangian experiments carried out in an upwelling on the continental shelf and in the core of an offshore filament. The data show that daily variations in surface pCO2 and oxygen (%O2) were controlled by the diurnal cycle of primary production/respiration, temperature variations and air–sea exchange. Data obtained during various cross-shelf and cross-filament transects are also discussed and give an insight into the processes controlling large scale variations of pCO2 and %O2 in the Galician upwelling system. These data suggest that upwelling filaments are an important feature of the inorganic carbon cycle of upwelling systems. However more field data in the various eastern boundary current systems worldwide are needed. [less ▲]

Daily and seasonal variations of the partial pressure of CO2 in surface seawater along the Belgian and southern Dutch coastal areas

in Journal of Marine Systems (1999), 19

The variations of the partial pressure of CO2 pCO2.and related parameters were determined in surface seawater along the Belgian coast, from January 1995 to June 1996, at both daily and seasonal time ... [more ▼]

The variations of the partial pressure of CO2 pCO2.and related parameters were determined in surface seawater along the Belgian coast, from January 1995 to June 1996, at both daily and seasonal time scales. The distribution of pCO2 in this area is regulated by river input from the Scheldt, biological activity and hydrodynamics. The contribution of each of these processes varies as a function of the considered time scale: i. the daily variation of pCO2 depends on the tide although modulated by the biological diel cycle; ii. the seasonal variation of pCO2 depends on the input from the Scheldt and the seasonal variations of phytoplanktonic biomass. During winter, the plume of the river Scheldt is oversaturated in pCO2 with respect to the atmosphere. During spring and summer, phytoplankton blooms occur both in the lower Scheldt estuary and in the river plume and may lead to undersaturation of pCO2 in the easternmost area of the river plume. However, the degradation of phytoplankton induces oversaturation of pCO2, in the westernmost area of the plume. Furthermore, the inter-annual variation of pCO2 depends partly on the fluctuations of the discharge of the Scheldt. Our preliminary results strongly suggest that, on an annual basis, the Scheldt plume behaves as a net source of CO2 to the atmosphere [less ▲]

Distribution of inorganic carbon and related parameters in surface waters of the English Channel during spring 1994

in Journal of Marine Systems (1996), 7

Particle fluxes over a Mediterranean seagrass bed: a one-year sediment trap experiment

in Marine Ecology. Progress Series (1995), 126

Métaux lourds et isotopes stables du carbone dans la matière particulaire: distribution sur le plateau continental nord-ouest européen

in Bulletin de la Société Royale des Sciences de Liège (1994), 63

La matière en suspension de la couche de surface du plateau continental nord-ouest européen. II. Teneur en métaux lourds et transfert dans la chaîne trophique

in Bulletin de la Société Royale des Sciences de Liège (1992), 61

Samples of suspended matter (MS) from the North Sea have been analysed for its heavy metal content. Unexpected high levels of copper have been recorded. The Scheldt Estuary reveals to be an important ... [more ▼]

Samples of suspended matter (MS) from the North Sea have been analysed for its heavy metal content. Unexpected high levels of copper have been recorded. The Scheldt Estuary reveals to be an important source of zinc, lead and cadmium for the sea. The transfer of metals from the MS to mussels is low. [less ▲]