-14 -12 -10 -8 -6 -4 -2 0 0 2 4 6 8 10 12 this study Jahnke et al. (1997) Jahnke and Jahnke (2000)
Berelson et al. (2007) decreasingCAL
of bottom waters Silverberg et al. (2000) FO2 (mmol O2 m-2 d-1) Ca C O3 di ss ol ut ion ( m m o l m -2 d -1)
Benthic remineralization in the northeast European continental
margin (northern Bay of Biscay)
Suykens K. 1, Schmidt S. 2, B. Delille1, L. Chou 2, C. De Bodt2, J. Harlay1,2, N. Fagel1, A.V. Borges 1, *
1ULg (BE), 2UBordeaux 1(FR) 3ULB (BE) * alberto.borges@ulg.ac.be
European Geosciences Union General Assembly, 2-7 May 2010
carbon (% OMLOI) indicate that benthic
organic carbon degradation rates were a direct function of the availability of organic matter. However, organic carbon degradation processes did not show a preference towards “fresher” phytoplanktonic OM as indicated by the lack of relationship between
water-sediment O2 fluxes and the Chlorophyll-a :
phaeopigments (Chl-a:Phaeo) ratios.
The correlation between water-sediment
fluxes of O2 and NO3- (FNO
3-) indicated a
close coupling of nitrification/denitrification and total benthic organic carbon degradation. The link between water-sediment fluxes of
total alkalinity (FTA*) and O2 indicated
metabolic driven dissolution of calcium
carbonates (CaCO3) in the sediments (~ 0.33 ±
0.47 mmol m-2 d-1) which represented ~ 1 % of
the pelagic calcification rates due to
coccolithophores measured during the
cruises. These CaCO3 dissolution rates were
below those reported in sediments of continental slopes and of the deep ocean, probably due to the high over-saturation with
respect to CaCO3 of the water column
overlying the continental shelf sediments of the northern Bay of Biscay.
The overall average during the 3 cruises of
benthic respiration was ~ -5.5 ± 1.5 mmol O2
m-2 d-1 which represents ~ 8 % of the pelagic
primary production measured during the
cruises (70 ± 44 mmolC m-2d-1). The overall
-11 -10 -9 -8 -7 -6 -5 -4 47 48 49 50 51 52 8+8bis 2006 2007 4+4bis 2008 1 2 5+5bis 6 9+9bis 10 11 12 Chapelle Bank Goban Spur 20 0 10 0 0 2000 4000 longitude (°E) la ti tude ( °N ) 0 2 4 6 8 -10.0 -7.5 -5.0 -2.5 0.0 r² = 0.64 %<63µm FO 2 ( m m o l O2 m -2 d -1) 0.00 0.25 0.50 0.75 1.00 -9 -8 -7 -6 -5 -4 -3 -2 r2 = 0.43 Chl-a (µg g-1) FO 2 (m m o l O2 m -2 d -1 ) 0 1 2 3 4 5 -10.0 -7.5 -5.0 -2.5 0.0 r2 = 0.28 ( ) %OMLOI FO 2 ( mmo l O2 m -2 d -1 ) 0.00 0.25 0.50 0.75 1.00 -9 -8 -7 -6 -5 -4 -3 -2 Chl-a:Phaeo FO 2 (m m o l O2 m -2 d -1 ) -1 0 1 2 -9 -8 -7 -6 -5 -4 -3 -2 r2 = 0.24 2006 2007 2008 FNO3 (mmol m-2 d-1) FO 2 (m m o l O2 m -2 d -1) -10 -8 -6 -4 -2 0 0.0 2.5 5.0 FO2 (mmol O2 m-2 d-1) F T A * ( mmo l m -2 d -1 )
Sediment characteristics and biogeochemical fluxes at the water-sediment interface at the northeast European continental margin (northern Bay of Biscay) were investigated in June 2006, May 2007 and 2008, at 18 stations on the shelf break (120 to 180 m), and at 2 stations on the continental slope (520 m and 680 m). Water-sediment
O2 fluxes (-2.4 to -8.4 mmol O2 m-2 d-1) were low compared to other
coastal environments, such as continental shelves and estuaries
(-11.0 to -210.0 mmol O2 m-2 d-1). The relationships between
water-sediment O2 fluxes and the grain size content < 63 µm and Chl-a
content of the top 1 cm of the sediments , as well as percent organic
average of benthic respiration represents ~ 4 % of the pelagic respiration in
the aphotic zone measured during the cruises (137 ± 60 mmolC m-2 d-1).
Rates of CaCO3 dissolution averaged for the three cruises (~ 0.33 ± 0.47
mmol m-2 d-1) represents ~ 1 % of the pelagic calcification rates due to
coccolithophores measured during the cruises (~34 ± 32 mmol m-2d-1). This
implies a decoupling of calcification by coccolithophores and the
dissolution in the sediments of CaCO3. Hence, PIC produced by
coccolithophores is either stored in the sediments or exported out of the system, but does not seem to be significantly dissolved in the sediments.
ΩCAL = 3.5 ΩCAL = 2.0 ΩCAL = 1.3
