Climatically-controlled siliceous productivity in the eastern Gulf of Guinea during the last 40 000 yr

Crosta, Xavier; Romero, Oscar E; Ther, Olivier; Schneider, Ralph R

doi:10.5194/cp-8-415-2012

Cited by 18 publications

(35 citation statements)

References 72 publications

(119 reference statements)

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“…The marine diatom community is dominated by coastal planktonic and brackish species. Coastal planktonic diatoms thrive in neritic, oligo‐to‐mesotrophic waters with high to moderate dissolved silica levels, becoming more abundant during intervals of weak turbulence and responding mainly to moderate upwelling (Romero and Armand, ; Crosta et al , ). Main components of the brackish group mostly live attached to a substratum as epipelic, epiphytic or epizoic diatoms.…”

Section: Resultsmentioning

confidence: 99%

How a river submerges into the sea: a geological record of changing a fluvial to a marine paleoenvironment during early Holocene sea level rise

Hepp

Romero

Mörz

et al. 2019

J Quaternary Science

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Coastal seas, and in particular estuarine systems, were significantly affected by Quaternary sea level changes. Furthermore, the dynamics of shelf and coastal evolution have had a strong impact on coastal landscapes inhabited by humans. The postglacial evolution of the vast North Sea shelf with its huge drainage systems, e.g. the Elbe Paleovalley and its tributary system, is an excellent research target to understand how coastal shelf environments change in response to sea level rise. In this study, we investigate infill sediments of the Paleo‐Ems valley – a drowned extension of the modern Ems River and part of the Elbe Paleovalley drainage system. Radiocarbon‐dated transgression sequences provide several new observations regarding the mode and rate of the river system submerging due to the Holocene transgression. Thus, the Paleo‐Ems valley submerged within a short time span of~200 years since the river was not able to adjust its gradient to the rapid rising sea level. The fate of the Paleo‐Ems is exemplary for the rapid change of a former fluvial landscape into a coastal landscape and finally into a submarine seascape. © 2019 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd.

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Section: Resultsmentioning

confidence: 99%

How a river submerges into the sea: a geological record of changing a fluvial to a marine paleoenvironment during early Holocene sea level rise

Hepp

Romero

Mörz

et al. 2019

J Quaternary Science

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“…Cyst assemblages were determined by light microscopy (Zeiss Axiovert, 400× magnification). The taxonomy of calcareous dinoflagellate cysts follows Vink et al (2002) and Elbrächter et al (2008), while that of organic-walled dinoflagellate cysts is according to Zonneveld and Pospelova (2015).…”

Section: Calcareous and Organic-walled Dinoflagellate Cystsmentioning

confidence: 99%

Flux variability of phyto- and zooplankton communities in the Mauritanian coastal upwelling between 2003 and 2008

et al. 2020

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Abstract. Continuous multiyear records of sediment-trap-gained microorganism fluxes are scarce. Such studies are important to identify and to understand the main forcings behind seasonal and multiannual evolution of microorganism flux dynamics. Here, we assess the long-term flux variations and population dynamics of diatoms, coccolithophores, calcareous and organic dinoflagellate cysts, foraminifera and pteropods in the eastern boundary upwelling ecosystem of the Canary Current. A multiannual, continuous sediment trap experiment was conducted at the mooring site CBeu (Cap Blanc eutrophic; ∼20∘ N, 18∘ W; trap depth is ca. 1300 m) off Mauritania (northwest Africa), between June 2003 and March 2008. Throughout the study, the reasonably consistent good match of fluxes of microorganisms and bulk mass reflects the seasonal occurrence of the main upwelling season and relaxation and the contribution of microorganisms to mass flux off Mauritania. A clear successional pattern of microorganisms, i.e., primary producers followed by secondary producers, is not observed. High fluxes of diatoms, coccolithophores, organic dinoflagellate cysts, and planktonic foraminifera occur simultaneously. Peaks of calcareous dinoflagellate cysts and pteropods mostly occurred during intervals of upwelling relaxation. A striking feature of the temporal variability of population occurrences is the persistent pattern of seasonal groups contributions. Species of planktonic foraminifera, diatoms, and organic dinoflagellate cysts typical of coastal upwelling, as well as cooler-water planktonic foraminifera and the coccolithophore Gephyrocapsa oceanica, are abundant at times of intense upwelling (late winter through early summer). Planktonic foraminifera and calcareous dinoflagellate cysts are dominant in warm pelagic surface waters, and all pteropod taxa are more abundant in fall and winter when the water column stratifies. Similarly, coccolithophores of the upper and lower photic zones, together with Emiliania huxleyi, and organic dinoflagellate cysts dominate the assemblage during phases of upwelling relaxation and deeper layer mixing. A significant shift in the “regular” seasonal pattern of taxa relative contribution is observed between 2004 and 2006. Benthic diatoms strongly increased after fall 2005 and dominated the diatom assemblage during the main upwelling season. Additional evidence for a change in population dynamics is the short dominance of the coccolithophore Umbilicosphaera annulus, the occurrence of the pteropod Limacina bulimoides and the strong increase in the flux of calcareous dinoflagellate cysts, abundant in warm tropical oligotrophic waters south of the study area after fall 2005. Altogether, this suggests that pulses of southern waters were transported to the sampling site via the northward Mauritania Current. Our multiannual trap experiment provides a unique opportunity to characterize temporal patterns of variability that can be extrapolated to other eastern boundary upwelling ecosystems (EBUEs), which are experiencing or might experience similar future changes in their plankton community.

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“…The surface sediment at 22 • W just east of M1 also reveals the highest diol index (0.22), likely due to its closer vicinity to the Guinea Dome center. Several studies have reported P. alata diatoms offshore of northwest Africa (Lange et al, 1998;Treppke et al, 1996;Crosta et al, 2012;Romero et al, 1999), pointing to P. alata as a plausible source organism. The sedimentary annual diol indices compare well with the sediment trap indices (Fig.…”

Section: Lcd Sources and Seasonalitymentioning

confidence: 99%

Long-chain diols in settling particles in tropical oceans: insights into sources, seasonality and proxies

Bar

Ullgren

Thunnell³

et al. 2019

Biogeosciences

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Abstract. In this study we analyzed sediment trap time series from five tropical sites to assess seasonal variations in concentrations and fluxes of long-chain diols (LCDs) and associated proxies with emphasis on the long-chain diol index (LDI) temperature proxy. For the tropical Atlantic, we observe that generally less than 2 % of LCDs settling from the water column are preserved in the sediment. The Atlantic and Mozambique Channel traps reveal minimal seasonal variations in the LDI, similar to the two other lipid-based temperature proxies TEX86 and U37K′. In addition, annual mean LDI-derived temperatures are in good agreement with the annual mean satellite-derived sea surface temperatures (SSTs). In contrast, the LDI in the Cariaco Basin shows larger seasonal variation, as do the TEX86 and U37K′. Here, the LDI underestimates SST during the warmest months, which is possibly due to summer stratification and the habitat depth of the diol producers deepening to around 20–30 m. Surface sediment LDI temperatures in the Atlantic and Mozambique Channel compare well with the average LDI-derived temperatures from the overlying sediment traps, as well as with decadal annual mean SST. Lastly, we observed large seasonal variations in the diol index, as an indicator of upwelling conditions, at three sites: in the eastern Atlantic, potentially linked to Guinea Dome upwelling; in the Cariaco Basin, likely caused by seasonal upwelling; and in the Mozambique Channel, where diol index variations may be driven by upwelling from favorable winds and/or eddy migration.

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Climatically-controlled siliceous productivity in the eastern Gulf of Guinea during the last 40 000 yr

Cited by 18 publications

References 72 publications

How a river submerges into the sea: a geological record of changing a fluvial to a marine paleoenvironment during early Holocene sea level rise

How a river submerges into the sea: a geological record of changing a fluvial to a marine paleoenvironment during early Holocene sea level rise

Flux variability of phyto- and zooplankton communities in the Mauritanian coastal upwelling between 2003 and 2008

Long-chain diols in settling particles in tropical oceans: insights into sources, seasonality and proxies

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