BIOSOPE CRUISE Laboratoire d’Océanographie et de Biogéochimie Campus de Luminy Marseille cedex 09 Patrick RAIMBAULT Nicole GARCIA Gerd SLAWYK Main objectives To study the biogeochemical properties of different trophic regimes in the south east Pacific To describe distribution of biogenic elements and productivity levels with special attention of new production

N2 Nitrate Nitrite Ammonium Phosphate Silicate Phytoplankton Microbial loop New production REGENERATION (NH 4, NO 3 ) Particulate organic matter: COP, NOP, POP,  15 N EXCRETION DO 15 N/DO 13 C Dissolved organic matter COD, NOD, POD Trophic chain Nitrate Nitrite Ammonium Phosphate Silicate Detritical material COP, NOP, POP Dissolved organic matter COD, NOD, POD Euphotic zone Deep ocean CO 2 sédimentation Primary production HYDRODYNAMIQUE CO 2 Regenerated production EXPORT PRODUCTION Conceptual scheme of carbon and nitrogen cycles in the euphotic zone indicating the different nutrient pools (in blue) and biological processes (in red) measured during the BIOSOPE cruise. BIOSOPE New production and export carbon Diazotrophy N2N2

N2 Nitrate Phosphate Silicate Phytoplankton Microbial loop New production Particulate organic matter: COP, NOP, POP,  15 N EXCRETION DO 15 N/DO 13 C Dissolved organic matter COD, NOD, POD Trophic chain UPWELLING Detritical material COP, NOP, POP Dissolved organic matter COD, NOD, POD Euphotic zone Deep ocean CO 2 sédimentation Primary production HYDRODYNAMIQUE CO 2 EXPORT PRODUCTION Conceptual scheme of carbon and nitrogen cycles in the euphotic zone indicating the different nutrient pools (in blue) and biological processes (in red) measured during the BIOSOPE cruise. UPWELLING New production and export carbon Nanoplankton

N2 Nitrite Ammonium Phosphate Silicate Phytoplankton Microbial loop REGENERATION (NH 4, NO 3 ) Particulate organic matter: COP, NOP, POP,  15 N EXCRETION DO 15 N/DO 13 C Dissolved organic matter COD, NOD, POD Trophic chain Nitrate Nitrite Ammonium Phosphate Silicate Detritical material COP, NOP, POP Dissolved organic matter COD, NOD, POD Euphotic zone Deep ocean CO 2 sédimentation Primary production HYDRODYNAMIQUE CO 2 Regenerated production EXPORT PRODUCTION Conceptual scheme of carbon and nitrogen cycles in the euphotic zone indicating the different nutrient pools (in blue) and biological processes (in red) measured during the BIOSOPE cruise. OLIGOTROPHY New production and export carbon Diazotrophy

BIOSOPE Parameters 1.Biogenic elements (C/N/P); POM on 0.2µm 2.Chlorophyll a 3.Daily primary production ( 13 C) and new production ( 15 N) 4.Nitrogen fixation ( 15 N) 5.Ammonium regeneration and nitrification ( 15 N) 6.DO 15 N and DO 13 C release rates 7.Variation of natural abundance of 15 N (  15 N) In red, recent parameters included in our field works (see below)

POOL OF NUTRIENTS Nanomolar levels (Raimbault al.1990) Nanomolar levels (Holmes et al., 1999) Conventional procedures ?? ) Results from PECHE cruises DYFAMED site

POOL OF PARTICULATE ORGANIC MATTER Extraction in Methanol (Raimbault et al., 1988) C/N/P on the same sample (Raimbault et al., 1999a)

POOL OF DISSOLVED ORGANIC MATTER C/N/P on the same sample (Raimbault et al., 1999b) CARBON NITROGEN PHOSPHORUS

BIOLOGICAL FLUXES OF CARBON AND NITROGEN 13 C/ 15 N 2 dual labelling C-N excretion on the same filtrate (Raimbault et al., 1999c) (Raimbault et al., in progress) 15 N 2 fixation Montoya et al., 1996

Estimation of nitrogen fixation by the 15 N procedure ( Montoya et al., 1996) Good reproductibility at low rates Nitrogen fixation is detected in the <10 µm fraction Results from Diapalis cruises Importance in nitrogen and carbon budgets in oligotrophic systems?? A NEW new production ????

Primary production (x3) New production Regenerated production Diffusion 1 Diffusion 2 Diffusion 3 NH 4 regeneration Nitrification DON excretion 300 ml + HgCl l samples 13 C/ 15 NO 3 13 C/ 15 NH 4 Incubation (12h/24h) Filtration GF/F Mass spectrometry Slawyk et Raimbault., 1995 Raimbault et al., 1999 Raimbault et al., 2000 Slawyk et al., 2000 Dual Labelling procedure ( 13 C/ 15 N) proposed for the Biosope cruise 13 C/ 15 N 2 DOC excretion (in progress) 300 ml + HgCl 2

Variation of natural abundance of 15 N =  15 N In deep water :  15 N = % It is a non intrusive mean of estimating the degree of N recycling in the photic zone Recent N depletion :  15 N = % N 2 fixation :  15 N = 0 % Persistent oligotrophy :  15 N < 0 % Requirements: precision of 0.3‰ PON = 5 µmoles = 70 µg

FIRST TESTS

Additional experiments ??? C/N/P in sediment traps Free floatting net for Trichodesmium Limitation of new production

On board requirements 1-2 scientists: P. Raimbault + student ??? Surface of laboratory: 6 m 2. Incubators on the sun deck ( 2 m 2 ) with circulation of surface water. Sampling before sunset for productivity experiments

NOP and POP measured on GF/F and 0.2µm PTFE membranes in oligotrophic waters

Estimation of primary production by by the 13 C procedure Comparaison of primary production rates obtained with 13 C and 14 C isotopic procedures MINOS POMME