Evaluation of gross primary production, community respiration, and net community production in various benthic communities (Posidonia oceanica seagrass meadow, Posidonia oceanica litter, epilithic macro-algae) in the Bay of Revellata (Corsica) using optodes

Poster (2013, May 07)

Biogeochemistry and carbon mass balance of a coccolithophore bloom in the northern Bay of Biscay (June 2006)

Poster (2013, May)

Primary production (PP), calcification (CAL), bacterial production (BP) and dark community respiration (DCR) were measured along with a set of various biogeochemical variables, in early June 2006, at ... [more ▼]

Primary production (PP), calcification (CAL), bacterial production (BP) and dark community respiration (DCR) were measured along with a set of various biogeochemical variables, in early June 2006, at several stations at the shelf break of the northern Bay of Biscay. The cruise was carried out after the main spring diatom bloom that, based on the analysis of a time-series of remotely sensed chlorophyll-a (Chl-a), peaked in mid-April. Remotely sensed sea surface temperature (SST) indicated the occurrence of enhanced vertical mixing (due to internal tides) at the continental slope, while adjacent waters on the continental shelf were stratified, as confirmed by vertical profiles of temperature acquired during the cruise. The surface layer of the stratified water masses (on the continental shelf) was depleted of inorganic nutrients. Dissolved silicate (DSi) levels probably did not allow significant diatom development. We hypothesize that mixing at the continental slope allowed the injection of inorganic nutrients that triggered the blooming of mixed phytoplanktonic communities dominated by coccolithophores (Emiliania huxleyi) that were favoured with regards to diatoms due to the low DSi levels. Based on this conceptual frame, we used an indicator of vertical stratification to classify the different sampled stations, and to reconstruct the possible evolution of the bloom from the onset at the continental slope (triggered by vertical mixing) through its development as the water mass was advected on-shelf and stratified. We also established a carbon mass balance at each station by integrating in the photic layer PP, CAL and DCR. This allowed computation at each station of the contribution of PP, CAL and DCR to CO2 fluxes in the photic layer, and how they changed from one station to another along the sequence of bloom development (as traced by the stratification indicator). This also showed a shift from net autotrophy to net heterotrophy as the water mass aged (stratified), and suggested the importance of extracellular production of carbon to sustain the bacterial demand in the photic and aphotic layers. [less ▲]

Two year study of CO2, CH4 and N2O dynamics and fluxes in four rivers in Belgium (Meuse, Ourthe, Geer and Blanc Gravier)

Poster (2013, April 07)

Teleconnections between ecosystem productivity and climate indices in a tropical great lake

Poster (2013, April 07)

Variability of North Sea pH and CO2 pumping in response to North Atlantic Oscillation forcing

Poster (2013, April 07)

The influence of biogeochemical processes on the pH dynamics in the seasonally hypoxic saline Lake Grevelingen

Poster (2013, April 07)

CO2, CH4 and N2O dynamics and fluxes in the brackish Lake Grevelingen (The Netherlands)

Poster (2013)

Lake Grevelingen in the South West Netherlands is a former estuary locked off from the sea by two dikes and a brackish lake since 1971 (salinities from 29 to 33 during our sampling). It is connected with ... [more ▼]

Lake Grevelingen in the South West Netherlands is a former estuary locked off from the sea by two dikes and a brackish lake since 1971 (salinities from 29 to 33 during our sampling). It is connected with the North Sea by sluices, has a surface area of 108 km2, a mean depth of 5.3 m, a maximum depth of 48 m, and about 60% of the area the depth is less than 5 m. In summer, anoxia occurs in bottom waters. From January 2012 to December 2012 a biogeochemical survey was conducted at monthly interval at a fixed station (35 m depth) at Den Osse. Here, we focus on the analysis of partial pressure of CO2, and concentrations of CH4 and N2O obtained throughout the water column. pCO2 followed a typical seasonal cycle for temperate coastal environments shifting from CO2 over-saturation in winter to spring CO2 under-saturation due to the spring phytoplankton bloom, and shifting back to over-saturation in fall. Unlike the adjacent Southern Bight of the North Sea and the adjacent Oosterschelde, CO2 under-saturation prevailed in summer in Lake Grevelingen. CH4 values were minimal in winter ( 20 nM) and as stratification developed during spring and summer a distinct maximum of CH4 (up to 730 nM) developed at the pycnocline (5 to 10 m). N2O showed little seasonal variations and only a very faint increase with depth, except in August when bottom waters became anoxic. At this time, N2O shown a maximum ( 22 nM) at the oxycline (probably related to enhanced N2O production by nitrification at low O2 concentrations), and decreased in the anoxic layer ( 3 nM) (probably related to denitrification). [less ▲]

A uniform, quality controlled Surface Ocean CO2 Atlas (SOCAT)

in Earth System Science Data (2013), 5(1), 125-143

A well-documented, publicly available, global data set of surface ocean carbon dioxide (CO2) parameters has been called for by international groups for nearly two decades. The Surface Ocean CO2 Atlas ... [more ▼]

A well-documented, publicly available, global data set of surface ocean carbon dioxide (CO2) parameters has been called for by international groups for nearly two decades. The Surface Ocean CO2 Atlas (SOCAT) project was initiated by the international marine carbon science community in 2007 with the aim of providing a comprehensive, publicly available, regularly updated, global data set of marine surface CO2, which had been subject to quality control (QC). Many additional CO2 data, not yet made public via the Carbon Dioxide Information Analysis Center (CDIAC), were retrieved from data originators, public websites and other data centres. All data were put in a uniform format following a strict protocol. Quality control was carried out according to clearly defined criteria. Regional specialists performed the quality control, using state-of-the-art web-based tools, specially developed for accomplishing this global team effort. SOCAT version 1.5 was made public in September 2011 and holds 6.3 million quality controlled surface CO2 data points from the global oceans and coastal seas, spanning four decades (1968–2007). Three types of data products are available: individual cruise files, a merged complete data set and gridded products. With the rapid expansion of marine CO2 data collection and the importance of quantifying net global oceanic CO2 uptake and its changes, sustained data synthesis and data access are priorities. [less ▲]

The BONUS-GoodHope IPY project: dynamics and biogeochemistry interactions in the Southern Ocean south off Africa

Book published by EGU (2013)

Les eaux continentales comme sources de gaz à effet de serre vers l’atmosphère : étude pilote dans 4 cours d’eau en Wallonie

Scientific conference (2012, October 25)

Les eaux continentales (fleuves et lacs) sont d’importantes composantes des cycles globaux du carbone et de l’azote. Elles transportent du carbone et de l’azote organique et inorganique des écosystèmes ... [more ▼]

Les eaux continentales (fleuves et lacs) sont d’importantes composantes des cycles globaux du carbone et de l’azote. Elles transportent du carbone et de l’azote organique et inorganique des écosystèmes terrestres vers les océans. Cependant, ce transport n’est pas passif et les eaux continentales produisent, dégradent, stockent et échangent du carbone et de l’azote avec l’atmosphère. Ainsi, les eaux continentales émettent du dioxyde de carbone (CO2), du méthane (CH4) et du protoxyde d’azote (N2O) vers l’atmosphère. Le CO2, CH4 et N2O sont les principaux gaz à effet de serre (GES) anthropiques, et le N2O est en plus le plus important agent anthropique de destruction de la couche d’ozone. L’Unité d’Océanographie Chimique a mené une étude pilote dans quatre cours d’eau à proximité de la ville Liège (Meuse, Ourthe, Geer et Ruisseau du Blanc Gravier) qui ont été étudiés afin de décrire la dynamique du CO2, CH4 et N2O et d’en estimer les flux émis des eaux de surface vers l’atmosphère. Les conditions ainsi que les résultats de l’étude seront présentés lors de cet exposé. [less ▲]