Branched GDGTs as Proxies in Surface Sediments From the South-Eastern Brazilian Continental Margin

Ceccopieri, Milena; Carreira, Renato S.; Wagener, Angela L.R.; Hefter, Jens; Mollenhauer, Gesine

doi:10.3389/feart.2019.00291

Cited by 10 publications

(6 citation statements)

References 84 publications

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“…10b). This matches the findings from other shelf areas, where in situ brGDGT production is most pronounced at 50-300 m water depth (e.g., Sinninghe Ceccopieri et al, 2019). Despite the sedimentary in situ contribution to the total pool of brGDGTs in this zone, the total brGDGT concentration is substantially lower than the crenarchaeol concentration which results in a low BIT index.…”

Section: Soil-microbial Omsupporting

confidence: 87%

The dispersal of fluvially discharged and marine, shelf-produced particulate organic matter in the northern Gulf of Mexico

Yedema¹,

Sangiorgi²,

Sluijs³

et al. 2023

Biogeosciences

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Abstract. Rivers play a key role in the global carbon cycle by transporting terrestrial organic matter (TerrOM) from land to the ocean. Upon burial in marine sediments, this TerrOM may be a significant long-term carbon sink, depending on its composition and properties. However, much remains unknown about the dispersal of different types of TerrOM in the marine realm upon fluvial discharge since the commonly used bulk organic matter (OM) parameters do not reach the required level of source- and process-specific information. Here, we analyzed bulk OM properties, lipid biomarkers (long-chain n-alkanes, sterols, long-chain diols, alkenones, branched and isoprenoid glycerol dialkyl glycerol tetraethers (brGDGTs and isoGDGTs)), pollen, and dinoflagellate cysts in marine surface sediments along two transects offshore the Mississippi–Atchafalaya River (MAR) system, as well as one along the 20 m isobath in the direction of the river plume. We use these biomarkers and palynological proxies to identify the dispersal patterns of soil–microbial organic matter (SMOM), fluvial, higher plant, and marine-produced OM in the coastal sediments of the northern Gulf of Mexico (GoM). The Branched and Isoprenoid Tetraether (BIT) index and the relative abundance of C32 1,15-diols indicative for freshwater production show high contributions of SMOM and fluvial OM near the Mississippi River (MR) mouth (BIT = 0.6, FC321,15 > 50 %), which rapidly decrease further away from the river mouth (BIT < 0.1, FC321,15 < 20 %). In contrast, concentrations of long-chain n-alkanes and pollen grains do not show this stark decrease along the path of transport, and especially n-alkanes are also found in sediments in deeper waters. Proxy indicators show that marine productivity is highest close to shore and reveal that marine producers (diatoms, dinoflagellates, coccolithophores) have different spatial distributions, indicating their preferred niches. Close to the coast, where food supply is high and waters are turbid, cysts of heterotrophic dinoflagellates dominate the assemblages. The dominance of heterotrophic taxa in shelf waters in combination with the rapid decrease in the relative contribution of TerrOM towards the deeper ocean suggest that TerrOM input may trigger a priming effect that results in its rapid decomposition upon discharge. In the open ocean far away from the river plume, autotrophic dinoflagellates dominate the assemblages, indicating more oligotrophic conditions. Our combined lipid biomarker and palynology approach reveals that different types of TerrOM have distinct dispersal patterns, suggesting that the initial composition of this particulate OM influences the burial efficiency of TerrOM on the continental margin.

show abstract

Section: Soil-microbial Omsupporting

confidence: 87%

The dispersal of fluvially discharged and marine, shelf-produced particulate organic matter in the northern Gulf of Mexico

Yedema¹,

Sangiorgi²,

Sluijs³

et al. 2023

Biogeosciences

View full text Add to dashboard Cite

show abstract

“…This matches the findings from other shelf areas, where in situ brGDGT production is most pronounced at 50-300 m water depth (e.g. SinningheDamsté, 2016;Ceccopieri et al, 2019).…”

supporting

confidence: 90%

The dispersal of fluvially discharged and marine, shelf-produced particulate organic matter in the northern Gulf of Mexico

Yedema

Sangiorgi

Sluijs

et al. 2022

Preprint

View full text Add to dashboard Cite

Abstract. Rivers play a key role in the global carbon cycle by transporting terrestrial organic matter (TerrOM) from land to the ocean. Upon burial in marine sediments, this TerrOM may be a significant long-term carbon sink, depending on its composition and properties. However, much remains unknown about the dispersal of different types of TerrOM in the marine realm upon fluvial discharge as the commonly used bulk OM parameters do not reach the required level of source- and process-specific information. Here, we analysed bulk OM properties, lipid biomarkers (long-chain n-alkanes, sterols, long-chain diols, alkenones, branched and isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs)), pollen, and dinoflagellate cysts in marine surface sediments along two transects offshore the Mississippi and Atchafalaya Rivers (MAR), as well as one along the 20 m isobath in the direction of the river plume. We use these biomarkers and palynological proxies to identify the dispersal patterns of soil-, fluvial, higher plant, and marine produced OM in the coastal sediments of the northern Gulf of Mexico (GoM). The Branched and Isoprenoid Tetraether (BIT) index and the relative abundance of C32 1,15-diols indicative for freshwater production show high contributions of soil and fluvial OC near the Mississippi River mouth (BIT = 0.6, FC32 1,15 >50 %), which rapidly decrease further away from the river mouth (BIT <0.1, FC32 1,15 <20 %). In contrast, concentrations of long-chain n-alkanes and pollen grains do not show this stark decrease along the path of transport, and especially n-alkanes are also found in sediments in deeper waters. Proxy indicators show that marine productivity is highest close to shore, and reveal that marine producers (diatoms, dinoflagellates, coccolithophorids) have different spatial distributions, indicating their preferential niches. Close to the coast, where food supply is high and waters are turbid, cysts of heterotrophic dinoflagellates dominate the assemblages. The dominance of heterotrophic taxa in shelf waters in combination with the rapid decrease in the relative contribution of TerrOM towards the deeper ocean, suggests that TerrOM input may trigger a priming effect that results in its rapid decomposition upon discharge. In the open ocean far away from the river plume, autotrophic/phototrophic dinoflagellates dominate the assemblages, indicating more oligotrophic conditions. Our multi-disciplinary approach reveals that different types of TerrOM have distinct dispersal patterns, suggesting that the initial composition of this particulate OM influences the burial efficiency of TerrOM on the continental shelf and open ocean.

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“…This suggests that marine derived brGDGTs preserved in sediments are significantly produced in situ by benthic microorganisms, since the pH of porewater in marine sediments vary significantly due to complex redox conditions related to the physical and chemical characteristics of bottom water, the nature of solid components of sediments and the dissolution of carbonates(Jourabchi et al, 2005).We chose three cases to further elaborate the source of brGDGTs in marine sediments. In the Brazilian margin(Ceccopieri et al, 2019), Berau delta (Sinninghe Damsté, 2016) and Svalbard fjord(Peterse et al, 2009) sediments, the ΣIIIa/ΣIIa values show increasing trends seawards, indicating enhanced contribution of marine derived brGDGTs (Fig.4). Meanwhile, the MBT' index, exhibiting a contrary tendency as the ΣIIIa/ΣIIa index, gradually decreases (lower temperature) seawards.…”

mentioning

confidence: 99%

Global scale production of brGDGTs by benthic marine bacteria: Implication for developing ocean bottom environmental proxies

Xiao

Jiang

et al. 2022

Global and Planetary Change

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Branched GDGTs as Proxies in Surface Sediments From the South-Eastern Brazilian Continental Margin

Cited by 10 publications

References 84 publications

The dispersal of fluvially discharged and marine, shelf-produced particulate organic matter in the northern Gulf of Mexico

The dispersal of fluvially discharged and marine, shelf-produced particulate organic matter in the northern Gulf of Mexico

The dispersal of fluvially discharged and marine, shelf-produced particulate organic matter in the northern Gulf of Mexico

Global scale production of brGDGTs by benthic marine bacteria: Implication for developing ocean bottom environmental proxies

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