POSTER SESSION 2 TOPIC 8 Biogeochemical Hotspots

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POSTER SESSION 2 TOPIC 8 Biogeochemical Hotspots Powered By Docstoc
					            POSTER SESSION 2: TOPIC 8
    Biogeochemical Hotspots, Choke Points, Triggers,
          Switches and Non-linear Responses

PS2: 8.1
Three main sources of CH4 and H2S - Quantitative estimates of fluxes
in the ocean
Lein Alla
Shirshov institute of oceanology Russian Academy of sciences; 36. Nachimovsky,
117851, Moscow
Email: lein@geo.sio.rssi.ru

CH4 and H2S are going into the ocean from hydrothermal vents, the cold seeps and
anaerobic ments. Each type of these sources are characterized by the different isotopic
signature (d13C, d34S), various mineralization (sulfides or carbonates) and the divers
living chemosynthetic benthic communities. "The life on H2S " was determined on the
active hydrothermal fields MOR, "the life on CH4" WAS determined on the cold seeps
field. The active bacterial processes of CH4 formation and oxidation and SO4-reduction
and H2S-oxidation and another in the anaerobic sediments was observed.
Our biogeochemical results allow to suppose the practically all CH4 and H2S on the
hydrothermal fields MOR were utilized, on cold seeps fields and above anaerobic
sediments H2S and CH4 are partly oxidizing in water column, but the significant CH4-flux
and H2S -flux are going to the atmospphere. Another words, from three main different
sources of oceanic CH4 and H2S discussed only the seep CH4 -flux and the fluxes of H2S
and CH4 from anaerobic zone can reach the atmospheric reservoir and became involved
in the global methane and sulphur cycles. New experimental quantitative estimations of
CH4 and H2S fluxes in the ocean are discussed.
PS2: 8.2
The role of CO2 as driving force for the climate change from the last ice
period of Holocene to the recent interglacial conditions. An evidence
from the sediment depositions in a semienclosed marine system
(Pagassitikos Gulf/Hellas)
Anagnostou, Ch., Sioulas, A. & Karageorgis, A.
Researchers in the National Centre for Marine Research (NCMR)
Email: chanag@ncmr.gr

Sediment analyses of the depositions of Pagassitikos Gulf show aragonite formation in
the central part, with an age of 16.000 to 17.000 years. During this period, icecaps
dominated in the earth system, and the sea level was 100 to 120m lower than today. The
Pagassitikos Gulf was isolated from the open Aegean Sea and formed a lake.
For the aragonite formation, high concentrations of HCO3- and Ca++ in this lake
environment are required, and relative high atmospheric temperature are needed, in order
to lead to an intensive evaporation.
In this contribution we support the aspect that green house phenomena, due to CO2
concentration in the atmosphere, lead to the increase of the required concentrations for
the formation of aragonite, as well as to the increase of the temperature in the
atmosphere.
The green house effect was also the driving force for the climatic change from the last ice
period to the recent interglacial conditions.
This aspect is strongly supported in this work versus the general view that mainly
astronomic reasons are leading to the global climatic changes. This phenomenon is not
local, it is more widely extended. More data from other sites are needed to establish this
aspect. This presentation is a step toward this direction.
PS2: 8.3
How chemistry of the sea surface microlayer influences biogeochemical
processes at the atmosphere/ocean interface
A. Brinis, A. Momzikoff, L. Méjanelle, J. Fillaux, G. Gondry. P. Lebaron, G. Herndl and
A. Saliot
Laboratoire de Biogéochimie et Chimie Marines, Université Pierre et Marie Curie, UMR
CNRS 7094 ; Case 134 ; 4 Place Jussieu ; F-75252 Paris Cedex 05- France
Email: mejanel@ccr.jussieu.fr

At the boundary between the atmosphere and the ocean, the sea surface microlayer
(SML) plays a key role in governing transfer processes, such as evaporation, gas
exchange and emission of aerosols. All these processes are influenced by the nature and
enrichment of organic materials in the SML. The sea surface microlayer is also a site of
production and intense photochemical transformation of the organic carbon. A better
knowledge of SML chemical composition and of its variability within space and time
would benefit gas transfer models.
We present data on organic carbon, lipids and amino acids, in order 1) to characterize the
chemical composition of the SML in relation to underlying water and 2) to assess its
variability under various environmental conditions: coastal polluted (Barcelona) and
pristine waters (Banyuls sur mer). Whereas concentrations in Particulate Organic Carbon
(POC) are in a close range (0.20 - 0.34 mg/l) for both locations in September 2001,
concentrations of particulate fatty acids (major fraction of the lipids) are much higher in
Barcelona than in Banyuls. The average enrichment factor, defined as the ratio
concentration in the SML/concentration in the underlying water, is about two times for
fatty acids in Barcelona.
A tentative assessment of the daily variation of SML composition at the Banyuls station
evidences significant changes between morning and afternoon for POC (0.21- 0.34 mg/l),
Chlorophyll a (0.18 - 0.66 µg/l) and fatty acids (12.89 --; 29.86 µg/l). New perspectives
are discussed on the contribution of the SML to the carbon flux in the superficial ocean.
PS2: 8.4
Is the oxygen changing in the Mediterranean Sea?
M.S. El Boukhary1,2, D. Ruiz-Pino1, and J.P. Béthoux2
1
  Laboratoire de Biogéochimie et Chimie Marines, Paris, France
2
  Laboratoire d'Océanographie de Villefranche-sur-Mer, France
Email: boukhary@ccr.jussieu.fr

The Mediterranean Sea is subjected to strong environmental perturbations which led to
biogeochemical and circulation changes. Both modifications in nutrients abundance and
circulation patterns could lead to important changes in the oxygen content of
Mediterranean deep waters. In the present study, we estimate the long-term trends of the
oxygen content by using the historical data existing between 1960 and 2000 in the whole
Mediterranean sea. The shallow Gulf of Lions, the northern Adriatic and the Aegean bays
are characterised, for the period 1960-1988, by an intense oxygen decrease (0.2, 0.36 and
0.38 %/ year respectively). These decreases could result from increasing productivity
occurring linked to the P and N input increases since the last decades. The unique open
area where significant oxygen decrease is detectable is the Alboran Sea. This trend could
be linked to the high primary productivity in this sea compared to other open
Mediterranean areas (Antoine et al, 1995). The absence of an oxygen decrease in the
other open Mediterranean areas before 1988, could be due to a more important oxygen
contribution by deep water formation compared to remineralization processes. The
thermohaline circulation changes have affected considerably the oxygen trends in both
Western and Eastern basins after 1988. An oxygen decrease (0.7 %/ year) and an increase
(1.4 %/ year) are recorded in the Algero Provençal and Levantine very deep waters
respectively. These two changes are associated to the oxygen input coming from the
Aegean Sea newly formed deep water. This suggests an opposed trend to that prevailing
during sapropel formation.
PS2: 8.5
Material fluxes across mangrove and adjacent coastal areas in Rio de
Janeiro, Brazil
Claudia Hamacher1, Angela Wagener1, Mario Soares2, William Anderson3 and Silvana
Rodrigues4
1
  Depto. de Quimica, Pontificia Universidade Catolica do Rio de Janeiro, 22453-900 Rio
de Janeiro, Brazil.
2
  Depto. de Oceanografia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro,
Brazil.
3
  Earth Science Dept., Florida Intrenational University, Florida, USA
4
  Depto. de Quimica, Universidade Federal Fluminense, Niteroi, Brazil.
Email: angela@rdc.puc-rio.br

A mangrove area of 2,800 ha that lies between the ocean and the Bay of Sepetiba was
used as a model to test the effective influence of mangrove environments on the fertility
of coastal areas and on the fluxes of materials. The study was conducted seasonally
covering several tidal cycles and included measurements of dissolved and particulate
nutrient species, DOC, POC, pigments, dissolved oxigen, pH, temperature, salinity,
current velocities, nitrogen and carbon isotopes in the organic matter. The mangrove area
shows a positive hydrological balance with important contribution of underground water
flow.The inclusion of the underground contribution to the total water balance
evidenciated the remarkable exportation of materials from the mangrove to the coastal
areas. The isotopic signature of the exported organic material shows predominance of
mangrove origin. The mangrove behaves as a reactor reprocessing materials flowing from
Sepetiba Bay and exporting products of its own metabolism: nutrients and organic
substances in the particulate form. This has major implication upon the secondary
production of the coastal areas. In addition, the net flux of dissolved nitrogen species
(5.49. 106 mol/year)is very significant when compared with other mangrove areas in the
world as reported by the LOICZ programme. The net nitrogen balance points to an
efficient mechanism of new nitrogen production derived from bacterial fixation in the
mangrove. The importance of this mangrove area as a source of nutrients to the coastal
environment is compared with other major sources in the Southeast coast of Brazil.
PS2: 8.6
Biogeochemistry of Taiwan Strait Upwelling Ecosystem: Dynamics and
structure
Huasheng Hong, Bangqin Huang and Shaojing Li
Marine Environmental Laboratory of the Ministry of Education, College of
Oceanography and Environmental Science, Xiamen University, Xiamen 361005, China
Email: bqhuang@jingxian.xmu.edu.cn

Taiwan Strait, southeast of China, is an important channel connecting the East China Sea
and the South China Sea. Due to its complex bottom topography, prevailing monsoon
forcing and conjunction of several current systems, the upwelling ecosystem has its
unique subtropical structure, and also, the hydrological, chemical and biological
processes are characterized by dramatic temporal and spatial variability. The structure
and the dynamic of the Taiwan Strait upwelling ecosystem will be briefly discussed
based on interdisciplinary studies combining field investigation with the AVHRR and
SeaWiFS images. There are several water masses in this region, the cold, low salinity
Coastal Water, the warm, high salinity South China Sea Warm water and the Kuroshio
Intruded Water. The water fronts showed seasonal and interannual variability. In summer,
when southwesterly wind prevails, there are wind-driven upwellings located along the
coastal of the Strait; and topographically induced upwellings near the Taiwan bank and
around Penghu Island, respectively. Upwelling is not only a hydrology phenomenon, but
also has a tremendous impact on the ecosystem. The timing and the location of pelagic
fishing grounds are coincident with the upwelling events. The biogeochemical cycling of
C, P in the strait depends largely on the physical forcing function (external input) and the
biological system structure (internal cycling). A negative correlation was found between
the level of P and local SST indices. In general, the region is characterized with low DIP
in the water; P may be considered the limiting element in regulating the primary
productivity there. It was estimated that the upwelling in summer time contributed 17%
of the P external input, and other study revealed the importance of nutrient fluxes from
the Taiwan Strait to the nutrient budget of the East China Sea. The primary producers in
the Strait were dominated by nano- and pico-phytoplankton with an average of 60-80 and
80% respectively, implying the subtropical ecosystem features of the region. According
to estimation from the ECOPATH model, the microbial food web could contribute up to
1/3 of the production which plays a significant function in the ecosystem. The physical
forcing of, and feedbacks to the ecosystems and biogeochemical processes were
pronounced in the Strait, the variations between ENSO and non-ENSO events were
observed.
PS2: 8.7
FORAMPROX -- an integrated ecological geochemical effort of proxy
amelioration
Frans J. Jorissen1, Elsa Cortijo2, Pierre Anschutz3, Jean-Claude Duplessy2, Christophe
Fontanier3, Marion Gehlen2, Emmanuelle Geslin1, Laurent Labeyrie2, Elisabeth Michel2,
Gert-Jan Reichart4, Sabine Schmidt2, Kazuyo Tachikawa5, Laurence Vidal5, Claire
Waelbroeck2
1
  Laboratoire d'Etude des Bio-Indicateurs Actuels et Fossiles, Université d'Angers,
UPRES EA 26-44, 2, Boulevard Lavoisier, 49005 Angers Cedex 01, France
2
  Laboratoire des Sciences du Climat et de l'Environnement, CNRS-CEA, Domaine du
CNRS, Allée de la Terrasse, 91198 Gif-sur-Yvette Cedex, France
3
  Département de Géologie et Océanographie, UMR CNRS 5805 EPOC, Université
Bordeaux 1, 33405 Talence, France
4
  Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, D-
27570 Bremerhaven, Germany
5
  CEREGE, Europole de l'Arbois BP 80, 13545 Aix en Provence, France
Email: frans.jorissen@univ-angers.fr

Longer, supra-historical time series of ecological processes and biogeochemical cycles
are crucial for our understanding of the sensitivity of the earth system to global change.
Such records can only be obtained in longer sedimentary records. For these sedimentary
records, a wide range of quantitative proxy methods exist which allow the quantitative
reconstruction of parameters such as (new versus recycled) Primary Production, bottom
water oxygen concentration, temperature and salinity. However, combined approaches,
using several proxies for the same parameter simultaneously, suggest that most of these
proxies are still rather imperfect. The French national program Foramprox (PROOF-
PNEDC) aims to arrive at more reliable proxy methods by integrating ecological studies
of the sea floor environment and geochemical studies on benthic foraminiferal
microfossils. We believe that geochemical proxy records (d13C, d18O, Mg/Ca, etc.) based
on the tests of microfossils can only be correctly interpreted if the functional role of the
organisms, and the episodicity of the ecosystem are fully understood. Therefore, we will
simultaneously study ecosystem functioning and the geochemistry of biologically
meditated carbonates in several ocean system hot spot areas (continental margins,
upwelling areas, deep water formation areas, oxygen minimum zones). In order to
deconvolve the impact of jointly operating ecological parameters, field results will be
accompanied by laboratory experiments, in which foraminiferal tests will be grown under
controlled conditions of temperature, salinity, oxygenation and organic flux.
PS2: 8.8
Giant Diatom Dumps as spatial and temporal biogeochemical hotspots
Alan E S Kemp
School of Ocean and Earth Science, University of Southampton, Southampton
Oceanography Centre, Southampton, SO14 3ZH
Email: aesk@soc.soton.ac.uk

Modern oceanographic observations offer only a snapshot of ocean biogeochemical
processes. Insights from deep sea cores suggest that we may still be missing the
significance of some of the key processes or events which drive oceanic biogeochemical
cycling. The Ocean Drilling Program has recovered extensive laminated diatomaceous
sediments from open-ocean settings not previously associated with such deposits (Eastern
Equatorial Pacific, Mediterranean, Southern Ocean) and together with records from
marginal basins these have shed a new light on the different styles of diatom production
and demonstrate that giant and mat-forming diatoms may actually dominate the export
flux and are thus key drivers of oceanic biogeochemistry. The recognition that much of
this diatom production is at depth also has important implications for the effectiveness of
satellite-derived algorithms of oceanic primary and export production. Synergy between
the modern JGOFS experiments in the equatorial Pacific and Southern Ocean and ODP
Legs in these key oceanic areas have also highlighted the importance of the interaction
between giant diatoms and oceanic frontal zones that focus exceptional export
production. Some of the key oceanic frontal regions, such as the polar front may
represent biogeochemical hotspots which require more study. More oceanographic
experiments, especially targeting deep chlorophyll maxima, are required to inform us of
the ecology of the giant and mat-forming diatoms that appear equally at home in the
ocean deserts and some of its most productive areas and their ineraction with oceanic
frontal zones.
PS2: 8.9
Interannual variability and future change of air-sea CO2 fluxes in the
Southern Ocean

N. Metzl1, C. Brunet1, A. Jabaud-Jan1, C. Pierre2, A Poisson1 and B. Schauer1
1
  LBCM/IPSL, Université Pierre et Marie Curie, Case 134, 4, Place Jussieu. 75252 Paris
Cedex 05. France
2
  LODYC/IPSL, Université Pierre et Marie Curie, Case 100.4, Place Jussieu. 75252 Paris
Cedex 05. France
Email: metzl@ccr.jussieu.fr

The temporal variations of the carbon dioxide system and air-sea CO2 fluxes are analysed
in the South-Western Indian Ocean (20°S-60°S), based on data collected in 1998-2002
during seven cruises conducted onboard the R.V. Marion-Dufresne (IPEV/TAAF) in the
frame of the OISO observational program (IPSL/INSU). Compared to seasonal signals,
significant interannual variations of ocean fCO2 have been observed in all regions, from
the subtropics to high latitudes in the Southern Ocean. During austral summer, the
variations of ocean CO2 sources and sinks are associated to regional sea surface
temperature anomalies but not always directly controled by warming and cooling. For
example, in the open ocean zone of the Southern Ocean, the oceanic CO2 sink is stronger
during warm events, because higher primary production dominates the temperature effect
on ocean f CO2. On the opposite, during cold events, the summer oceanic CO2 sink is
reduced. During this productive season, the Southern Ocean could also become a CO2
source as large as the source observed during winter when mixed-layer is deep and
primary production is low. The analysis of the interannual variability of the carbon
dioxide system, including external and internal forcings that operate during both warm
and cold events (e.g. changes in light, stratification, primary production, ecosystems…),
could help in evaluating futur oceanic f CO2 distributions and air-sea CO2 fluxes
simulated by global coupled carbon models in climate change scenario.
PS2: 8.10
Oxygen Minimum Layer (OML) modeling: Organic Matter (OM)
recycling or preservation? A possible CO2 and N2O coupling?
Paulmier, A. and D. Ruiz-Pino
Laboratoire de Biogéochimie et Chimie Marines (LBCM)
Email: paulmier@ccr.jussieu.fr

The OML, a primitive ocean persistence, shows currently an extension, due to the
Primary Production (PP) increase. Why does the OML still exist? Will the ocean become
one day completely anoxic? Simultaneously OML, CO2atm and N2Oatm increase occur on
the G-IG, but no on the smaller scale. Would OML in formation or established have
different behavior?
A theoretical modeling is performed to include the OML role in the OM transfer to deep
layer and in the CO2/N2O fluxes. We assume the OML possesses an higher (oxycline)
and a lower (anoxic) remineralisation power. OM degradation (oxic/anoxic, oxic rate),
input (bloom production) and turnover (size/shape, stratification determining the sinking
rate) are modeled. The OML modeling was carried out in 2 steps: 1) highlight the 2
OML's behaviors in term of recycling (active phase) and preservation (passive phase) and
characterize the shift between these 2 phases; this is based on the comparison between the
quantity of OM (surface input) remineralized with and without OML. 2) Determine
during the active phase the OM impact on the OML thickening, from a OM/O2 budget.
These steps suggest: 1) The OML behavior depends on the OML thickness, whose
threshold is determined by the oxycline. So, the OML would fertilize (thin/active OML,
OML-regenerated production) or limit (thick/passive OML) the PP. 2) The thickness
grows up with the PP until a saturation. Thus, in case of a OML thickening and extension
similar mechanisms, an homeostatic global ocean would prevent from its own asphyxia.
The CO2 (remineralisation) and N2O (production) high release would correspond only to
OML in formation.
PS2: 8.11
Variability of particulate seawater properties related to bottom mixed
layer-associated internal waves in shallow water on a time scale of hours
Robert Turnewitsch1, Gerhard Graf2
1
  Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, UK
2
  University of Rostock, Institute of Aquatic Ecology - Marine Biology, Albert-Einstein-
Str. 3, D-18059 Rostock, Germany
Email: rxt@soc.soton.ac.uk

To obtain information on relations between internal wave-controlled hydrographic
variability in bottom mixed layers (BMLs) and particle-associated BML parameters,
depth distributions of density, relative turbidity, relative chlorophyll a (Chl a) and relative
phycoerythrin fluorescence (Phyco), total particulate matter (TPM), particulate carbon
(PC) and particulate nitrogen (PN) were obtained at a shallow-water site in the course of
a temporally highly resolved 1-day time series. Density distribution showed evidence for
a bottom mixed layer (BML) and undulations of BML thickness probably caused by
near-inertial internal waves. Wave-induced hydrographic variability was reflected in the
spatio-temporal distribution of particle-associated data: (1) Turbidity, Chl a and Phyco
distributions followed wave-like hydrographic variability; (2) relative pigment
fluorescence in the BML and in the layer above the BML was inversely coupled; (3)
dense transient clouds of PC- and PN-depleted TPM, having their highest TPM loads in
the BML, occurred on leading wave faces. Leading wave faces and wave backs are
suggested to be locations of preferred vertical exchange between the surface sediment,
BML and the layer above BML). Different processes control relative turbidity in the
BML (decoupled from Chl a) and in the layer above the BML (coupled to Chl a). Most of
the time spatial variability of the Chl a/Phyco ratio was higher within the BML than in
the layer above the BML. It is concluded that the BML itself and in co-action with
passing internal waves, effectively controls the communication between the interior water
column and the sediment.
PS2: 8.12
Are Asymmetric Flow Fields Around Kilometer-Scale Topographic
Seafloor Elevations Reflected in the Sediment?
Robert Turnewitsch1, Niko Lahajnar2, John Thomson1, Ian Croudace1
1
  Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, UK.
2
  University of Hamburg, Institute of Biogeochemistry and Marine Chemistry,
Grabenstrasse 27, D-20357 Hamburg, Germany
Email: rxt@soc.soton.ac.uk

Abyssal hills, knolls and seamounts are ubiquitous and abundant features of the oceanic
seafloor. Physical oceanographic studies have indicated that there are asymmetric flow
fields enfolding such seafloor elevations: On the northern hemisphere the lateral
asymmetry in the flow exhibits an accelerated flow to the left of the elevation, looking
downstream, and decelerated flow to the right. We expect this asymmetry to be reflected
in the intensity and quality of sediment deposition. To address the proposed effect on
intensity of sediment deposition we assessed the spatial distribution of sedimentary
excess 210Pb (210Pbxs) inventories using samples taken from the four major slopes and
the summit of an abyssal knoll in the NE Atlantic, and from a reference site on the
abyssal plain. Sediment inventories of 210Pbxs were compared to the expected 210Pb
input from the water column. On the summit and on the western slope 210Pbxs
inventories are smaller than expected. There is also some evidence for 210Pbxs
inventories on the northern and eastern slopes to be somewhat higher than expected. This
spatial 210Pbxs pattern coincides with the predicted pattern of flow intensity (high on the
summit and in the west, lower in the northeast) around the topographic elevation. Other
parameters suggest an additional effect of the hydrodynamic asymmetry on the
composition of the sedimentary deposit. Given the ubiquity of kilometer-scale
topographic seafloor elevations, possible consequences of the described asymmetries for
general pattern formation in the deep ocean are discussed.