La Matière Organique en Mer Méditerranée

Richard Sempéré (MIO)

In relation with: MERMEX group: X. Durrieu de Madron, C. Guieu, I. Pairaud, P. Testor, C. Rabouille, O. Radakovitch, F. Carlotti, F. Van Wambeke, P. Conan, C. Estournel, F. D’Ortenzio, K. Desboeufs, M.

Mallet, E. Pullido-Villena, JO Irisson, C. Santinelli…

•  Largest semi-enclosed basin of the Earth •  Surface area: 2.5 x 106 km2 •  Coastline: 46 x 103 km

•  0.7% surface; 0.25% of volume •  Surrounded by three continents

Mean features of Med Sea

•  Formed 150 millions years ago •  During the Messinian salinity crisis (5.6 millions yrs ago) becomes

dessicated •  5.33 millions yrs ago, Atlantic waters rapidly refilled the basin

0 25 50 75 100 m

UV-A Penetration Depth (Sept 2001)

UV-A Penetration Depth (March 2001)

Med Sea main features!•  Averaged depth : 1500 m (deepest point:

5267 m Ionian sea)

•  Two undersea volcano •  Two deep hypersaline anoxic basins

Eastern Med. Sea

•  Deep water temperature > 12°C

•  Evaporation exceeds Precipitation+Runoff, that is compensated by an inflow of Atlantic water of 0.5-1 106m3/s at Gibraltar

•  High annual average total solar radiation flux = 168 Wm2 due to weak cloud cover

•  Phytoplanktons dominate the visible light attenuation in Pacific, whereas in the Med. Sea, additional substances compete with algae for visible photons (CDOM, dusts?)

DESERT DUST

FOREST FIRES

POLLUTION

(Sea

WiF

S im

age,

© N

ASA

& O

rbim

age)

Med. marine air is mostly “continental” ! A natural laboratory, close from us, to study

(i) the ageing of continental air masses during long-range transport, (ii) the impact of aerosol on the regional climate, (iii) the impact of atmos. deposition on low-Chl, low-nutrient surface waters

BIOGENIC EMISSIONS

http://charmex.lsce.ipsl.fr

DESERT DUST The Mediterranean from space on a given summer day

Courtesy F. Dulac

Occurrence'of'extreme'atmospheric'events'in'the'Med'Sea'

Biomass!burning!

ex.$in$Greece$in$August$2007:$several$weeks$of$emissions$and$inputs$to$the$surface$waters$

Saharan!Dust!event!

ex. event in western Med.: dust input to the surface waters may reach 50 tons of dust km-2 within 2 days

2!examples!

These events may decrease marine primary production (PP) by decreasing available radiation or increase PP by injecting nutrients like phosphorus Saharan events : How those high inputs of new phosphorus will impact New Production, in particular from diazotrophs ? Other extreme events : River flood, Storms, Heat waves

July.$16>2003$

EMDW

WMDW

AW (0-100 m) S~36.0

AdDW

AW (0-100 m) S~38.0-38.6

NAdDW

CDW TDW

LIW (200-500 m) S~39.0-39.1

LIW (200-500 m) S~38.4

AW (0-100 m) S~37.0

Mistral Bora

General!oceanic!circula9on!features!

!

Courtesy, C. Santinelli (2014)

Physical and biogeochemical features

•  Nutrient stœchiometry is not constant over the bassin (East–West gradient and surface-deep waters gradients

•  Strong dynamic (general circulation + dense water formation + mixing) in specific area ! determine the distribution of nutrients at large scale

Bosc et al., 2004

•  Strong trophic gradients; very poor waters in the Eastern Bassin; strong seasonal variability

N/P!=!25!

N/P!=!20!

Les objectifs scientifiques SeaWiFS satellite surface chlorophyll concentration observations (10 years) showed that Med. Sea is characterized by different trophic regimes

Coastal: high biomass in winter and a more reduced biomass in spring.

bloom in late winter-early spring months

�Intermittently blooming� zones with erratic regimes alterning intense biomass accumulation and oligotrophic conditions

Oligotrophic regions: higher and quite constant biomasses in fall-winter and lower and uniform values in late spring-summer

D’Ortenzio and Ribera d’Alcalà (2009)

NWestern

Winter mixing Unit and sinking POC: gC m-2yr-1

(Carlson et al., 2001; Avril et al., 2002; Moutin and Raimbault, 2002; Boldrin et al., 2002; Turchetto et al., 2012; Santinelli, 2014)

DOC/POC input due to winter mixing and dense water formation

1000 m

surface

Mesopelagic waters: Mineralization rate: 1.8-13.2 µMCyr-1

Tyrrhenian Sea Adriatic Sea

DOC: 10.9

Winter mixing

DOC: 3.2 DOC: 15.4

Sink. POC: 16.9 POC: 3.6-4.8 POC: 2.4

Dense water formation

WMDW: 0.14-1.2 Sv DOC: 9.5 x 1012 gC yr-1

NAdDW: 0.07 Sv DOC: 1.0 x 1012 gC yr-1

LIW: 1.0-1.5 Sv DOC: 10 x 1012gC yr-1

Levantine Int. water

East West

Unit: 1012gC yr-1

(Copin Montegut, 1993; Polat and Tugrul, 1996; Sempere et al., 2000; 2002, 2003; Dafner et al., 2001; Panagiotopoulos et al., 2013; Pulido Villena et al., 2008; De Vicente et al., 2012; Santinelli, 2014)

DOC : River Runoff, Atmospheric input, Straits

DOC stock in Med Sea ≈ 1980 x 1012 gC Primary production ≈ 276 x 1012gC yr-1

Atmospheric DOC: 5-9 Rivers DOC = 0.64-0.71

Prosope cruise-Autumn

Santinelli, Sempéré et al. (2013)

DOC and BP-Autumn W-E transect

DOC

BP

DOC and bacterial production (BP)-Autumn W-E transect

REGIONALISATION: Bio- and eco-regionalization of the Mediterranean Sea from data analysis in international databases

+ data collected by MERMEX

Spatial distribution of the Mediterranean marine ecosystems of the MS. Each ecoregion detected here represents a characteristic species association from primary producers to top predators forced by similar environmental conditions

Reygondeau et al. (2014)

Med Sea = 0.7% of global Ocean volume, but a major reservoir of diversity (18%) that might be affected by introduction of many thermophilic species and global change

=> disturbance of ecological status, changes in the trophic chain and consequently on the resources

Links with Biodivmex!

December 5th 2012 Med. Sea Biodiversity

groundwaters megacities

Rivers, groudwaters

Hydrodynamics and ecological processes

Land-Sea interactions and extreme events

air-sea interactions

Main driving forces in

Mediterranean Sea

Natural forcing in Med Sea

•  Global Warming-Acidification •  Pollutant effects

Projections for Med Sea

•  Impact on oceanic circulation, on biogeochemical cycles on community structures

Tourism: 158 millions in 1996 (1/4 of world� tourism!!) => 300 millions in 2025

Ci9zens:!

$450$millions$in$2000$$$>>$550$millions$$in$2025$

==> Pollution : metals, oil (1 million tons/year - i.e. 20% of the global oil pollution in the world� oceans), drugs, hormones, several organic compounds and plastics. ==> Impact on exploited Resources ?

$$

High!concentra9on!of!people!in!coastal!area!

The'modern'anthropogenic'pressure'in'the'Mediterranean'basin'

PCB DD

T

Bio-Accumulat ion

PAH

BPA

PCB

DDT

Procaryote PAE

Plankton

High Trop. levels

Zooplank.

fish

Excretion, cycling

Bio-Accumulat ion

Assimilation

•  Pollutants impact on C cycle. Ex. POPs associated to microplastics (MP). LABEX OT-Med, JPI Ocean (submitted)

Impact on biogeochemical cycles ?

Spatial distributions – and loads Costeau 7 April 2011

St1$St2$St3$

St5$

St6$ St7$St4$St8$St9$

St10$Zooplancton!

200>1000$μm$1000$–$2000$μm$

60>200μm$Phytoplancton!

0

5#000

10#000

15#000

ST1 ST2 ST3 ST9 ST4 ST7 ST5

CB#153

0

100

200

300

400

500

ST1 ST2 ST3 ST9 ST4 ST7 ST5

BDE.47BDE.47

0

5#000

10#000

15#000

ST1 ST2 ST3 ST9 ST4 ST7 ST5

p,p'#DDE

Marseille$

East West

ng.kg>1$dw.$

Rhône$

PBDEs Urban&inputs&&

OCPs Riverine fluxes &

PCBs East - West&

" Spatial and temporal (poster Tiano et al.) variation in plankton contamination

" Contaminants in all plankton size classes

" Rapid uptake of contaminants by plankton

" Trophic transfer in plankton not always seen

MERMEX 2015 Workshop

Tiano!et!al.!2014;!Tronczyński!et!al.!unpublished!

# Thermohaline$ circulaKon$ is$ driven$ by$difference$ of$ density$ between$ AtlanKc$ Ocean$and$Med.$Sea.$$

# Different$areas$of$dense$water$ formaKon$that$play$a$role$on$the$general$circulaKon,$transfer$of$carbon$ to$ deeper$ layers$ and$ availability$ of$nutrients$for$marine$organisms$and$ressources.$$

There!is!a!!"Conveyor!Belt"!system!similar!to!those!of!global!Ocean!

Global!warming:!Changes!of!Med!Sea!hydrodynamic!

!

Dense!water!forma9on!

ATMOSPHERIC,INPUTS,,

PYROGENIC

ATMOSPHERIC,INPUTS,,SAHARAN

WINDS

RIVERS

STRAITS

Anthropogenic forcing in Med. Sea

Strong!anthropogenic!pressure!

with!geographical!and!seasonal!

imbalances!

Surface!waters!:$+$1.1°C$$$$in$27$years$$

Deep!waters!:$+$0.05°C$$in$10$years$

A!changing!environment!:!

!onYgoing!increase!of!temperature!

Annual$mean$temperatures$in$the$Mediterranean$area$are$likely$to$increase$more$than$the$global$mean$(IPCC,$2007)$

1995$ 2005$Deep$water$at$DYFAMED$(Marty$&$Chiaverini,$2002)$

A!unique!coupled!system!(ocean/

atmosphere/con9nent)!

Possible change that may affect winter convection in open Mediterranean Sea ! By using IPCC-A2-scenario (Surface T (+3.1°C ) and S (+ 0.48 psu)) Somot et al. (2006) indicated

Somot$et$al.Clim.$Dyn.$(2006)$

Possibility$ of$ decrease$ of$ surface$ density$ and$winter$ deep>water$ formaKon$ at$ the$end$ of$ the$ 21st$ century,$ the! Mediterranean! thermohaline! circula9on! (MTHC)!

weakening! can!be!evaluated!as! −40%! for! the! intermediate!waters!and!−80%! for!

the!deep!circula9on!with!respect!to!presentYclimate!condi9ons!

Change!in!organic!ma_er!export!in!the!mesopelagic!waters!of!the!Med!Sea?!

Decrease!of!nutrient!uplia!,!Oxygen!transfer!and!Ressources!?!

Warming!!Changes!in!water!masses!circula9on!

Sensors (T, S, NO3, Chla et CDOM, O2, BB, PAR)

Dense water formation (DEWEX results, WP1 MERMEX)

1km ~2-5km

Data Centers

Land Station

Scientific/ operational community,

users

Profiling floats

Gliders

Most data available in real time (T, S, Chla, O2) at Coriolis/Sedoo

Dewex experiment: Gliders, Profiling floats, Drifters, Cruises, Moorings (WP1 MERMEX, DEWEX)…

01/07/2012 -> 07/10/2013 30 Glider deployments ~ 13,000 profiles (0-1000m) 6 CTD cruises ~ 400 profiles (0-bottom) 27 Argo ~ 1,500 profiles (0-1000m or 0-2000m) 10 Marisondes and surface drifters

Pot. Temp Salinity Pot. Dens. Oxygen Fluo Chla Turbidity north south Northern Current

North Balearic Front

Mixed patch

Gliders: •  Reveal a wide range of variability (small!basin scales) •  Are present at sea even during strong weather conditions •  Allow to study the physical-biogeochemical coupling

A vertical section from a glider:

eddies Plumes ~1km

Multidisciplinary data: (WP1 MERMEX, DEWEX)

Chlorophyll Gliders transects

(WP1 MERMEX, DEWEX)

Sunmex (MERMEX WP4), Marseille Bay UV and PAR radiations effects on marine ecosystems

In relation with mixed layer

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0

0.1

7/11/719/12/7

5/2/814/2/8

26/3/829/4/8

5/5/823/6/8

10/7/8

Atmosphere

2 m depth water column

23/9/814/10/8

25/11/87/12/8

UV

R-B

/UV

R-A

*10

•  These UVR values are the first ever reported on an annual basis in Mediterranean Sea.

•  Examination of the ratios of UVR-B/UVR-A shows that UVR-B increased 7 to 8 fold more than its UVR-A during the summer.

UVR-B/UVR-A x 10

Radiative fluxes

H(0-,λ)

H(5,λ)

H(10,λ)

H(m,λ)

0 1 2 3 4 5 6

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

H(0-,λ)

H(5,λ)

H(10,λ)

H(m,λ)

0.0 0.2 0.4 0.6 0.8 1.0 1.2

0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014

Dose at 380 nm (kJ m-2)

Dose at 305 nm (kJ m-2)

June 08

December 08

aCDOM(350) = 0.123 m-1

Kd(305) = 0.48 Kd(380) = 0.17

Zm = 6 m

aCDOM(350) = 0.112 m-1

Kd(305) = 0.28 Kd(380) = 0.14

Zm = 50 m

The wavelength 305 nm is used as biologically effective wavelength for the induction of DNA damages (CPDs), while 380 nm is used as biologically effective wavelength for the induction of photorepairs (PERs).

UV-B (305 nm) and UV-A (380 nm) doses (H(Zm,λ) in kJ m-2)

received beneath surface [H(0-,λ)], 5 and 10 m [H(5,λ) H(10,λ)] and mean doses received within the mixed layer [H(m,λ)]

0

10

20

30

40

50

60

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Q

Zm

Q =

H(m

,305

)/H(m

,380

)(%

)

Date

Z m(m

)

Ratio (Q) of the mean doses received within the mixed layer at 305 (UV-B) and 380 nm (UV-A) along with mixed layer depth (Zm in m) at solar noon at the SOLEMIO station: SUNMEX

Q in % = H(m,305)]/H(m,380) x 100]. mixed layer depth (Zm in m).

Sarmiento$et$al.$1998,$Bopp$et$al.$2001,$Doney$et$al.$2006$

Mechanisms:$increased$ocean$straKficaKon$!$reduced$nutrient$supply$/$light$limitaKon$

MulKple$Stressors:$changes$in$NPP$

Increase of photochemical oxidation reactions

singlet$oxygen$transfer$to$associated$bacteria$

adached$bacteria$

1O2!

growth$limitaKon$

death$and/or$repulsive$effect$

minor$bacterial$degradaKon$of$phytoplankton$components$

LimitaKon$of$bacterial$growth$

Minor$biodegradaKon$of$phytoplankton$components$$

Solar$radiaKon$induce$Transfer$of$singlet$oxygen$from$dead$phytoplanktonic$cells$to$adached$bacteria$$

$senescent$phytoplankton$cells$hν

Rontani et al. (2013); Petit (PhD) et al. (2013, 2014)

Metabolic and structural changes of the bacterial community in response to the phototransformations of dissolved and particulate organic matter in the Mediterranean Sea

PHOTOMED

Radiative fluxes

Thank you

MERMEX group: X. Durrieu de Madron, C. Guieu, I. Pairaud, P. Testor, C. Rabouille, O. Radakovitch, F. Carlotti, F. Van Wambeke, P.

Conan, C. Estournel, F. D’Ortenzio, K. Desboeufs, M. Mallet, E. Pullido-Villena, JO Irisson, C. Santinelli…