Oscar E Romero

MARUM, University of Bremen, PALEOCEANOGRAPHY, Faculty Member

Followers

103

Following

Co-authors

Public Views

My multiproxy research interest goals to the description of the dynamics of the silica cycle of the oceans, the contribution of diatoms and changes in paleoproductivity during the Neogene. Paleoproductivity studies often interpret formation of opal-rich sediment as evidence of high diatom productivity. That view is often difficult to reconcile in any simple way with data on present-day primary productivity, silica production, and opal accumulation. Combining biogenic opal with other "proxies", such as biomarkers, benthic and planktic foraminifers, and coccolithophorids, is the best way to achieve a coherent reconstruction of past surface ocean history. I intend to document the transformation of diatom assemblages within the ocean interior, and from biocoenosis to thanatocoenosis: variation of diatom in sediment traps at different water depths vs. sediments, in order to ascertain the preservation biases of the assemblages during settling and in the sediments.
Phone: 0049 421 218 65645
Address: MARUM-Pavillon
Room 0010
Bremen, Germany

less

Interests

Uploads

Papers by Oscar E Romero

Late Pleistocene-Holocene phytoplankton productivity in the Gulf of Alaska, IODP Site U1419

AGUFM, Dec 1, 2016

NEWS.SCIENCEMAG.ORG Climate 2015 11 Climate-Change-Can-T

www.nsf.gov news news summ.jsp cntn id=136975&org=NSF

Neritic/pelagic diatom ratio of mooring CB2_trap

Absolute abundance of benthic foraminifera in sediment core GeoB7926-2

(Table 1) AMS 14C dates and calibrated calendar dates of sediment core GeoB7926-2

Benthic foraminifera abundance data of sediment core GeoB7926-2

We present a high resolution, multiproxy study of the relationship between pelagic and benthic en... more We present a high resolution, multiproxy study of the relationship between pelagic and benthic environments of a coastal upwelling system in the subtropical NE Atlantic Ocean. Marine sediments corresponding to late MIS3 to the Holocene in the radiocarbon dated core GeoB7926, retrieved off Mauritania (21°N) were analysed to reconstruct productivity in surface waters and its linkage to deep waters during the last 35 ka BP. High latitude cold events and changes in atmospheric and oceanographic dynamics influenced upwelling intensity over this time period. Subsequently, this caused changes in primary productivity off this low-latitude coastal upwelling locality. The benthic foraminiferal fauna displays four main community shifts corresponding to fundamental climatic events, first of all during late MIS3 (35-28 ka BP), secondly from 28 to 19 ka BP (including Heinrich event 2 and the LGM), thirdly within Heinrich event 1, the Bølling Allerød and the Younger Dryas (18-11.5 ka BP) and finally during the Holocene (11.5-0 ka BP). In particular, strong pelagic-benthic coupling is apparent in MIS 3, as demonstrated by increased primary productivity, indicated by moderate DAR and the dominance of benthic foraminiferal species which prefer fresh phytodetritus. A decline in upwelling intensity and nutrient availability follows, which resulted in a proportionately larger amount of older, degraded matter, provoking a shift in the benthic foraminifera fauna composition. This rapid response of the benthic environment continues with a progressive increase in upwelling intensity due to sea level and oceanographic changes and according high surface production during the LGM. During Heinrich event 1 and the Younger Dryas, extreme levels of primary production actually hindered benthic environment through the development of low oxygen conditions. After this period, a final change in benthic foraminiferal community composition occurs which indicates a return to more oxygenated conditions during the Holocene.

Correction to “Detrital input, productivity fluctuations, and water mass circulation in the westernmost Mediterranean Sea since the Last Glacial Maximum”

Geochemistry Geophysics Geosystems, Mar 1, 2009

By presenting sea surface temperatures, planktonic oxygen isotope profiles, and bulk geochemical ... more

Download

The Pleistocene Labrador Sea, northwest North Atlantic (IODP Sites 1302/03, 1305 and ODP Site 646) with highlights on warm interglacials

AGUFM, Dec 1, 2007

Sites cored during expeditions 105 and 303 off southern Greenland (IODP 1305, ODP 646) and easter... more Sites cored during expeditions 105 and 303 off southern Greenland (IODP 1305, ODP 646) and eastern Canada (IODP 1302/1303) are ideally located for documenting the climatic and glacial history of adjacent lands in addition of providing information on thermohaline conditions in the northwest North Atlantic, notably with regard to convection in the Labrador Sea. Multiproxy studies (stable isotopes, pollen, dinocysts,

Solar forcing, climate dynamics and human activities in Mediterranean Mountains during the last millennium: the Lake Estanya record (Southern Pyrenees, NE Spain)

Download

A two-decades (1988–2009) record of diatom fluxes in the Mauritanian coastal upwelling: Impact of low-frequency forcing and a two-step shift in the species composition

Eastern Boundary Upwelling Ecosystems (EBUEs) are among the most productive marine regions in the... more Eastern Boundary Upwelling Ecosystems (EBUEs) are among the most productive marine regions in the world's oceans. Understanding the degree of interannual to decadal variability in the Mauritania upwelling system is key for the prediction of future changes of primary productivity and carbon 18 sequestration in the Canary Current EBUE as well as in similar environments. A multiannual sediment trap experiment was conducted at the mooring site CBmeso (='Cape Blanc mesotrophic', ca. 20°N, ca. 20°40'W) in the high-productive Mauritanian coastal waters. Here, we present results on fluxes and 21 the species-specific composition of the diatom assemblage for the time interval between March 1988 and May 2009. The temporal dynamics of diatom populations allows to propose three main diatom productivity/flux intervals: (i)

Download

A 2-decade (1988–2009) record of diatom fluxes in the Mauritanian coastal upwelling: impact of low-frequency forcing and a two-step shift in the species composition

Biogeosciences, 2021

Download

Sampling intervals, fluxes, percentages of total flux, organic carbon and lithogen for sediment trap CB9

We combined the analysis of sediment trap data and satellite-derived sea surface chlorophyll to q... more We combined the analysis of sediment trap data and satellite-derived sea surface chlorophyll to quantify the amount of organic carbon export to the deep sea in the upwelling induced high production area off northwest Africa. In contrast to the generally global or basin-wide adoption of export models, we used a regionally fitted empirical model. Furthermore, the application of our model was restricted to a dynamically defined region of high chlorophyll concentration in order to restrict the model application to an environment of more homogeneous export processes. We developed a correlation-based approximation to estimate the surface source area for a sediment trap deployed from 11 June 1998 to 7 November 1999 at 21.25°N latitude and 20.64°W longitude off Cape Blanc. We also developed a regression model of chlorophyll and export of organic carbon to the 1000 m depth level. Carbon export was calculated for an area of high chlorophyll concentration (>1 mg/m**3) adjacent to the coast on a daily basis. The resulting zone of high chlorophyll concentration was 20,000-800,000 km**2 large and yielded a yearly export of 1.123 to 2.620 Tg organic carbon. The average organic carbon export within the area of high chlorophyll concentration was 20.6 mg/m**2d comparable to 13.3 mg/m**2d as found in the sediment trap results if normalized to the 1000 m level. We found strong interannual variability in export. The period autumn 1998 to summer 1999 was exceeding the mean of the other three comparable periods by a factor of 2.25. We believe that this approach of using more regionally fitted models can be successfully transferred even to different oceanographic regions by selecting appropriate definition criteria like chlorophyll concentration for the definition of an area to which it is applicable.

Seasonal flux patterns of mooring CB4_trap

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

Biogeosciences, 2020

Continuous multiyear records of sediment-trapgained microorganism fluxes are scarce. Such studies... more Continuous multiyear records of sediment-trapgained 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 Published by Copernicus Publications on behalf of the European Geosciences Union. 188 O. E. Romero et al.: Plankton variability off Mauritania 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.

Download

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

Biogeosciences Discussions, 2019

Continuous multiyear records of sediment trap-gained microorganism fluxes are scarce. Such studie... more 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 dinoflagellates, foraminifera and pteropods in the Eastern Boundary Upwelling Ecosystem (EBUE) of the Canary Current. A multiannual, continuous sediment trap experiment was conducted at the mooring site CB eu (Cape Blanc eutrophic, ~20°N, 18°W; trap depth = ca. 1,300 m) off Cape Blanc, 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 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 dinoflagellates cysts, and planktonic foraminifera occur simultaneously. Peaks of calcareous

Download

Changes in the Dust‐Influenced Biological Carbon Pump in the Canary Current System: Implications From a Coastal and an Offshore Sediment Trap Record Off Cape Blanc, Mauritania

Global Biogeochemical Cycles, 2019

Long‐term data characterizing the oceans' biological carbon pump are essential for understand... more Long‐term data characterizing the oceans' biological carbon pump are essential for understanding impacts of climate variability on marine ecosystems. The “Bakun upwelling intensification hypothesis” suggests intensified coastal upwelling due to a greater land‐sea temperature gradient influenced by global warming. We present long time series of bathypelagic (approximately 1,200–3,600 m) particle fluxes from a coastal (CBeu: 2003–2016) and an offshore (CBmeso: 1988–2016) sediment trap setting located in the Canary Current upwelling. Organic carbon (Corg) and biogenic opal (BSi, diatoms) fluxes were twofold to threefold higher at the coastal upwelling site compared to the offshore site, respectively, and showed higher seasonality with flux maxima in spring. A relationship between winter and spring BSi fluxes to the North Atlantic Oscillation index was best expressed at the offshore site CBmeso. Lithogenic (dust) fluxes regularly peaked in winter when frequent low‐altitude dust stor...

Download

High-latitude forcing of diatom productivity in the southern Agulhas Plateau during the past 350 kyr

Paleoceanography, 2015

The hydrography of the Indian-Atlantic Ocean gateway has been connected to high-latitude climate ... more The hydrography of the Indian-Atlantic Ocean gateway has been connected to high-latitude climate dynamics by oceanic and atmospheric teleconnections on orbital and suborbital timescales. A wealth of sedimentary records aiming at reconstructing the late Pleistocene paleoceanography around the southern African continent has been devoted to understanding these linkages. Most of the records are, however, clustered close to the southern South African tip, with comparatively less attention devoted to areas under the direct influence of frontal zones of the Southern Ocean/South Atlantic. Here we present data of the composition and concentration of the diatom assemblage together with bulk biogenic content and the alkenone-based sea surface temperature (SST) variations for the past 350 kyr in the marine sediment core MD02-2588 (approximately 41°S, 26°E) recovered from the southern Agulhas Plateau. Variations in biosiliceous productivity show a varying degree of coupling with Southern Hemisphere paleoclimate records following a glacial-interglacial cyclicity. Ecologically well-constrained groups of diatoms record the glacial-interglacial changes in water masses dynamics, nutrient availability, and stratification of the upper ocean. The good match between the glacial maxima of total diatoms concentration, Chaetoceros spores abundance, and opal content with the maximum seasonal cover of Antarctic ice and the atmospheric dust records points to a dominant Southern Hemisphere forcing of diatom production. Suborbital variability of SST suggests rapid latitudinal migrations of the Subtropical Front and associated water masses over the southern Agulhas Plateau, following millennial contractions and expansions of the subtropical gyres. Warmings of the upper ocean over site MD02-2588 during terminations IV to I occurred earlier than that in the Antarctic Vostok, which is indicative of a Northern Hemisphere lead. Our multiparameter reconstruction highlights how high-latitude atmospheric and hydrographic processes modulated orbital highs and lows in primary production and SST as triggered by northward transport of Si, eolian dust input, and latitudinal migrations of frontal zones. ROMERO ET AL.

Download

The interplay between the surface and bottom water environment within the Benguela Upwelling System over the last 70 ka

Paleoceanography, 2016

The Benguela Upwelling System (BUS), located between 30 and 20°S, is one of the fundamental high‐... more The Benguela Upwelling System (BUS), located between 30 and 20°S, is one of the fundamental high‐productivity systems of the world ocean. The BUS has previously been studied in terms of primary productivity and ecology over glacial‐interglacial timescales; however, the response and coupling with the benthic environment have received little attention. Here, for the first time, we present a high‐resolution reconstruction of the BUS highlighting the link between surface and benthic productivity and their response to climatic and oceanographic changes over the last 70 ka. The study is based on benthic foraminiferal faunal analysis together with analyses of diatom assemblages, grain size of the terrigenous fraction, and stable O and C isotopic and bulk biogenic components of core GeoB3606‐1. We reveal significant shifts in benthic foraminiferal assemblage composition. Tight coupling existed between the surface and bottom water environment especially throughout marine isotope stages 4 and...

Download

Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

Biogeosciences, 2016

Coastal upwelling systems account for approximately half of global ocean primary production and c... more Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia-Canary, Benguela, Peru-Humboldt, California, and Somalia-Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

Download

Oscar E Romero

Uploads

Papers by Oscar E Romero

Log In