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Fluxes of phytopigments and labile organic matter to the deep ocean in the NE Atlantic Ocean

Fluxes of phytopigments and labile organic matter to the deep ocean in the NE Atlantic Ocean
Fluxes of phytopigments and labile organic matter to the deep ocean in the NE Atlantic Ocean
Downward fluxes of labile organic matter (phytopigments, proteins and carbohydrates) were measured between September 1996 and August 1998 at three depths 1000 m, 3000 m and 4700 m (c. 100 mab) over the Porcupine Abyssal Plain (PAP, NE Atlantic), to provide detailed information on the biochemical characteristics of organic inputs to the deep sea. Temporal changes in the carbohydrate and protein fluxes were compared to carbohydrate and protein contents of the surficial sediment on the seabed beneath the traps at 4850 m depth. Fluxes of carbohydrate, protein and phytopigments (chlorophylls-a and -b, and phaeophytins-a and -b) displayed strong seasonal variations, but limited interannual variability between the two years of measurement. Fluxes of labile organic matter were characterised by strong pulses which occurred in spring and early summer, suggesting that the deep PAP area experiences relatively predictable patterns of vertical fluxes. No major quantitative differences in organic matter fluxes were observed between traps at different depths, but highest carbohydrate fluxes (time-weighted mean 2.4 mg m?2 d?1) were observed at 4700 m, whereas highest protein fluxes were observed at 1000 m (time-weighted mean 2.1 mg m?2 d?1). Carbohydrate, protein and phytopigment fluxes were correlated significantly, suggesting that settling material was associated with primary organic matter (i.e., phytodetritus) inputs from the photic layer. The contributions of chlorophyll-a and -b, and of phaeophytin-a and -b did not change significantly with increasing depth. Nor did the ratio of total phaeopigments to total chlorophylls did change greatly with depth (0.3–0.4 at both 3000 m and 4700 m depth) suggesting that degradation rates in the sinking particles were low. Protein and carbohydrate concentrations in the sediments at 4850 m depth (collected during 6 cruises between 1996 and 1998) and vertical fluxes at 3000 m depth followed inverse temporal patterns; peak concentrations of protein in the sediment corresponded to low vertical fluxes of particulate proteins. These data suggest that there is a decoupling between pelagic input and benthic accumulation. However, bacterial secondary production and sedimentary RNA concentrations displayed temporal patterns similar to those of the vertical fluxes, suggesting that increases in the metabolism of the smallest-sized biota was associated with maxima in the organic matter supply. Our results also suggest that benthic utilisation could exceed the organic matter being supplied by the vertical fluxes.
NORTHEAST ATLANTIC OCEAN, PHYTOPIGMENTS, PROTEINS, CARBOHYDRATES
0079-6611
89-104
Fabiano, M.
e6f825e4-3bd8-4cae-a857-7886b1f66b8b
Pusceddu, A.
4be1bead-67d6-472d-a559-2d5256bd50d1
Dell'anno, A.
0ba126d0-628a-4385-ab26-c386d2d5e93d
Armeni, M.
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Vanucci, S.
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Lampitt, R.S.
dfc3785c-fc7d-41fa-89ee-d0c6e27503ad
Wolff, G.A.
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Danovaro, R.
eb18bf32-d311-4a1b-a93b-73cf78a55cec
Fabiano, M.
e6f825e4-3bd8-4cae-a857-7886b1f66b8b
Pusceddu, A.
4be1bead-67d6-472d-a559-2d5256bd50d1
Dell'anno, A.
0ba126d0-628a-4385-ab26-c386d2d5e93d
Armeni, M.
bfc5ab36-e6f0-45d2-864b-5ec35a6d30c1
Vanucci, S.
ef3756ab-7a1b-41dd-82bb-ff05c261408d
Lampitt, R.S.
dfc3785c-fc7d-41fa-89ee-d0c6e27503ad
Wolff, G.A.
3a42c086-8356-449b-9d40-9b16758733c2
Danovaro, R.
eb18bf32-d311-4a1b-a93b-73cf78a55cec

Fabiano, M., Pusceddu, A., Dell'anno, A., Armeni, M., Vanucci, S., Lampitt, R.S., Wolff, G.A. and Danovaro, R. (2001) Fluxes of phytopigments and labile organic matter to the deep ocean in the NE Atlantic Ocean. Progress in Oceanography, 50 (1/4), 89-104. (doi:10.1016/S0079-6611(01)00049-0).

Record type: Article

Abstract

Downward fluxes of labile organic matter (phytopigments, proteins and carbohydrates) were measured between September 1996 and August 1998 at three depths 1000 m, 3000 m and 4700 m (c. 100 mab) over the Porcupine Abyssal Plain (PAP, NE Atlantic), to provide detailed information on the biochemical characteristics of organic inputs to the deep sea. Temporal changes in the carbohydrate and protein fluxes were compared to carbohydrate and protein contents of the surficial sediment on the seabed beneath the traps at 4850 m depth. Fluxes of carbohydrate, protein and phytopigments (chlorophylls-a and -b, and phaeophytins-a and -b) displayed strong seasonal variations, but limited interannual variability between the two years of measurement. Fluxes of labile organic matter were characterised by strong pulses which occurred in spring and early summer, suggesting that the deep PAP area experiences relatively predictable patterns of vertical fluxes. No major quantitative differences in organic matter fluxes were observed between traps at different depths, but highest carbohydrate fluxes (time-weighted mean 2.4 mg m?2 d?1) were observed at 4700 m, whereas highest protein fluxes were observed at 1000 m (time-weighted mean 2.1 mg m?2 d?1). Carbohydrate, protein and phytopigment fluxes were correlated significantly, suggesting that settling material was associated with primary organic matter (i.e., phytodetritus) inputs from the photic layer. The contributions of chlorophyll-a and -b, and of phaeophytin-a and -b did not change significantly with increasing depth. Nor did the ratio of total phaeopigments to total chlorophylls did change greatly with depth (0.3–0.4 at both 3000 m and 4700 m depth) suggesting that degradation rates in the sinking particles were low. Protein and carbohydrate concentrations in the sediments at 4850 m depth (collected during 6 cruises between 1996 and 1998) and vertical fluxes at 3000 m depth followed inverse temporal patterns; peak concentrations of protein in the sediment corresponded to low vertical fluxes of particulate proteins. These data suggest that there is a decoupling between pelagic input and benthic accumulation. However, bacterial secondary production and sedimentary RNA concentrations displayed temporal patterns similar to those of the vertical fluxes, suggesting that increases in the metabolism of the smallest-sized biota was associated with maxima in the organic matter supply. Our results also suggest that benthic utilisation could exceed the organic matter being supplied by the vertical fluxes.

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Published date: 2001
Keywords: NORTHEAST ATLANTIC OCEAN, PHYTOPIGMENTS, PROTEINS, CARBOHYDRATES

Identifiers

Local EPrints ID: 7908
URI: http://eprints.soton.ac.uk/id/eprint/7908
ISSN: 0079-6611
PURE UUID: 6fdc5c1a-9ff6-481f-93e7-c4af017867ae

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Date deposited: 10 Aug 2004
Last modified: 15 Mar 2024 04:49

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Contributors

Author: M. Fabiano
Author: A. Pusceddu
Author: A. Dell'anno
Author: M. Armeni
Author: S. Vanucci
Author: R.S. Lampitt
Author: G.A. Wolff
Author: R. Danovaro

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