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Importance of intertidal sediment processes and porewater exchange on the water column biogeochemistry in a pristine mangrove creek (Ras Dege, Tanzania)
- Source :
- Biogeosciences Discussions, Biogeosciences Discussions, European Geosciences Union, 2007, 4 (1), pp.317-348, Biogeosciences, Biogeosciences, European Geosciences Union, 2007, 4 (3), pp.311-322, Biogeosciences, Vol 4, Iss 3, Pp 311-322 (2007), Biogeosciences, 4(3), 311-322. European Geosciences Union, ResearcherID, Bouillon, S, Middelburg, J J, Dehairs, F, Borges, A V, Abril, G, Flindt, M, Ulomi, S & Kristensen, E 2007, ' Importance of intertidal sediment processes and porewater exchange on the water column biogeochemistry in a pristine mangrove creek (Ras Dege, Tanzania) ', Biogeosciences, vol. 4, pp. 311-322 ., University of Southern Denmark
- Publication Year :
- 2018
-
Abstract
- International audience; We conducted diurnal sampling in a tidal creek (Ras Dege, Tanzania) to document the variations in a suite of creek water column characteristics and to determine the relative influence of tidal and biological driving forces. Since the creek has no upstream freshwater inputs, highest salinity was observed at low tide, due to evaporation effects and porewater seepage. Total suspended matter (TSM) and particulate organic carbon (POC) showed distinct maxima at periods of highest water flow, indicating that erosion of surface sediments and/or resuspension of bottom sediments were an important source of particulate material. Dissolved organic carbon (DOC), in contrast, followed the tidal variations and was highest at low tide. Stable isotope data of POC and DOC exhibit large variations in both pools, and followed tidal variations. Although the variation of d13CDOC (-23.8 to -13.8‰) was higher than that of d13CPOC (-26.2 to -20.5‰) due to the different end-member pool sizes, the d13C signatures of both pools differed only slightly at low tide, but up to 9‰ at high tide. Thus, at low tide both DOC and POC originated from mangrove production. At high tide, on the other hand, the DOC pool had signatures consistent with a high contribution of seagrass-derived material, whereas the POC pool was dominated by marine phytoplankton. Daily variations in CH4, and partial pressure of CO2 (pCO2) were similarly governed by tidal influence and were up to 7- and 10-fold higher at low tide, which stresses the importance of exchange of porewater and diffusive fluxes to the water column. Furthermore, this illustrates that constraining an ecosystem-level budget of these greenhouse gases in tidal systems requires a careful appraisal of tidal variations. When assuming that the high dissolved inorganic carbon (DIC) levels in the upper parts of the creek (i.e. at low tide) are due to inputs from mineralization, d13C data on DIC indicate that the source of the mineralized organic matter has a signature of -22.4‰, which shows that imported POC and DOC from the marine environment contributes strongly to overall mineralization within the mangrove system. Our data show a striking example of how biogeochemical processes in the intertidal zone appear to be prominent drivers of element concentrations and isotope signatures in the water column, and how pathways of dissolved and particulate matter exchange are fundamentally different. The estimated export of DIC through porewater exchange appears considerably larger than for DOC, suggesting that if this mechanism is indeed a major driver of solute exchange, benthic mineralization and subsequent export as DIC could represent a very significant and previously unaccounted fate of mangrove-derived C. Budgeting efforts should therefore pay attention to understanding the mechanisms and quantification of different pathways of exchange within and between both zones.
- Subjects :
- 0106 biological sciences
Biogeochemical cycle
010504 meteorology & atmospheric sciences
Water flow
french-guiana
tidal creek
ISW, Tanzania
lcsh:Life
Intertidal zone
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences
01 natural sciences
estuary
[PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]
Water column
avicennia-marina
lcsh:QH540-549.5
Dissolved organic carbon
Organic matter
14. Life underwater
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
organic-matter
Mangrove swamps
Pore water
Ecology, Evolution, Behavior and Systematics
aquatic ecosystems
0105 earth and related environmental sciences
Earth-Surface Processes
Total organic carbon
chemistry.chemical_classification
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere
[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]
sand flat
Intertidal environment
methane oxidation
010604 marine biology & hydrobiology
lcsh:QE1-996.5
Biogeochemistry
dissolved inorganic carbon
6. Clean water
lcsh:Geology
lcsh:QH501-531
Oceanography
chemistry
13. Climate action
southeastern us
Environmental science
lcsh:Ecology
Subjects
Details
- Language :
- English
- ISSN :
- 17264189, 18106277, 18106285, and 17264170
- Database :
- OpenAIRE
- Journal :
- Biogeosciences Discussions, Biogeosciences Discussions, European Geosciences Union, 2007, 4 (1), pp.317-348, Biogeosciences, Biogeosciences, European Geosciences Union, 2007, 4 (3), pp.311-322, Biogeosciences, Vol 4, Iss 3, Pp 311-322 (2007), Biogeosciences, 4(3), 311-322. European Geosciences Union, ResearcherID, Bouillon, S, Middelburg, J J, Dehairs, F, Borges, A V, Abril, G, Flindt, M, Ulomi, S & Kristensen, E 2007, ' Importance of intertidal sediment processes and porewater exchange on the water column biogeochemistry in a pristine mangrove creek (Ras Dege, Tanzania) ', Biogeosciences, vol. 4, pp. 311-322 ., University of Southern Denmark
- Accession number :
- edsair.doi.dedup.....1c204e2d38f718c1735d7ed2b12c24d7