Luz María Mejía

Luz María Mejía
ETH Zurich | ETH Zürich · Department of Earth Sciences

PhD Biogeosciences

About

27
Publications
3,248
Reads
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188
Citations
Citations since 2016
11 Research Items
182 Citations
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201620172018201920202021202201020304050
201620172018201920202021202201020304050
201620172018201920202021202201020304050
Introduction
I am a Marine Biologist with expertise in biogeochemistry applied to past climate change and adaptations of marine eukaryotic algae to varying climate. The B system in diatoms and the Ca and Sr systems in coccolithophores provide information on their ability to adapt to changing seawater characteristics. C isotopes of organic matter inside diatom frustules appear to record past ocean CO2 dynamics. This information reveals potential future climate trends and adaptations of these organisms.
Additional affiliations
November 2010 - October 2015
University of Oviedo
Position
  • PhD Biogeosciences
Education
November 2010 - October 2015
University of Oviedo
Field of study
  • Biogeosciences
September 2009 - September 2010
University of Oviedo
Field of study
  • Marine Biodiversity and Conservation
August 2002 - March 2009
Universidad de Bogotá Jorge Tadeo Lozano
Field of study
  • Marine Biology

Publications

Publications (27)
Article
Full-text available
Coccolithophores play a key role in the marine carbon cycle and ecosystem. The carbonate shells produced by coccolithophore, named as coccolith, could be well preserved in the marine sediment for millions of years and become an excellent archive for paleoclimate studies. The micro-filtering and sinking–decanting methods have been successfully desig...
Preprint
Full-text available
Periodic ~400 kyr orbital scale variations in the ocean carbon cycle, manifest in indicators of deep sea dissolution and benthic 13C, have been observed throughout the Cenozoic but the driving mechanisms remain under debate. Changes in coccolithophore productivity may change the global rain ratio (Corganic: Cinorganic fluxes from ocean into sedimen...
Preprint
Full-text available
Coccolithophore play a key role in the marine carbon cycle and ecosystem. The 9 carbonate shells produced by coccolithophore, named as coccolith, could be well preserved in the marine sediment for million years and become an excellent archive for paleoclimate studies. The micro filtering and sinking-decanting method have been successfully designed...
Article
Full-text available
Coccolithophores are a group of phytoplankton widely distributed in the ocean, which secrete extracellular calcite plates termed coccoliths. Coccoliths have been increasingly employed as an archive for geochemical, ecological and paleoclimate studies in recent years. A robust application of coccolith-based geochemical proxies relies on understandin...
Article
Constraining the thermal evolution of the Arctic Ocean is hampered by notably sparse heat flow measurements and a complex tectonic history. Previous results from the Lomonosov Ridge in the vicinity of the North Pole, and the adjacent central Amundsen Basin reveal varied values, including those higher than expected considering plate cooling or simpl...
Article
Coccoliths comprise a major fraction of the global carbonate sink. Therefore, changes in coccolithophores’ Ca isotopic fractionation could affect seawater Ca isotopic composition, affecting interpretations of the global Ca cycle and related changes in seawater chemistry and climate. Despite this, a quantitative interpretation of coccolith Ca isotop...
Article
Extratropical sea surface temperature records from alkenones record a dramatic cooling of up to 17 °C over the last ∼14 Ma, but the relationship between this cooling and greenhouse gas forcing has been elusive due to sparse and contrasting reconstructions of atmospheric CO2 for the time period. Alkenone carbon isotopic fractionation during photosyn...
Poster
Preliminary results on Sr isotopic composition of cultures and fossil coccolithophores and potential mechanisms controlling Sr isotopes in coccolith calcite
Poster
New CO2 record from diatom d13C show CO2 decline since the late Miocene.
Conference Paper
Constraining the mechanisms driving coccolith δ44/40Ca and Sr/Ca variations from cultures, models and sediment record
Presentation
Full-text available
Culture studies have suggested temperature and kinetic effects as potential drivers for changes in coccolith Ca isotopic composition (δ44/40Ca) and Ca isotopic fractionation. However, the specific mechanisms affecting δ44/40Ca are still unclear. Moreover, additional interacting factors, such as carbon limitation under low CO2 could also play a role...
Presentation
Full-text available
The sedimentation of calcium carbonate (CaCO3) is the largest carbon (C) sink in the combined biosphere, atmosphere and ocean systems, and therefore influences the global C cycle. Coccolithophores are important contributors to CaCO3 sediment production, with contributions varying from 95% of the total marine CaCO3 in the Cenozoic to 50% in the mode...
Article
Modern primary productivity on the Agulhas Bank, off South Africa, has been proposed to be linked to the mid-latitude westerlies. A paleoproductivity record from this area may therefore resolve temporal changes in the westerlies′ dynamics. Accordingly, we produced a coccolith Sr/Ca-based paleoproductivity record from core MD96-2080 (Agulhas Bank sl...
Poster
Full-text available
Diatom cell geometry and size limit CO2 availability by diffusion, which has been shown to be an important factor, together with growth rate, in controlling δ13C and Ep. Large centric diatoms (CD) may be more sensitive to CO2 limitation and use a higher proportion of HCO3- for photosynthesis at low [CO2]. Consequently, bulk diatom δ13C may differ f...
Article
Full-text available
Despite the importance of diatoms in regulating climate and the existence of large opal-containing sediments in key air-ocean exchange areas, most geochemical proxy records are based on carbonates. Among them, Boron (B) content and isotopic composition have been widely used to reconstruct pH from foraminifera and coral fossils. We assessed the poss...
Poster
Full-text available
Cell geometry and size, control availability of CO2 by diffusion, which in turn, has been shown to be a determinant factor, together with growth rate, in the control of δ13C and Ep1,2. Large-centric cells may be more sensitive to CO2 depletion and use a higher proportion of HCO3- for photosynthesis at low [CO2]. Consequently, bulk diatom δ13C may d...
Poster
Full-text available
Despite the importance of diatoms in regulating climate, most geochemical records are based on carbonates. Among them, B content and δ11B has been widely used to reconstruct pH from foraminifera and coral fossils. We present preliminary results of δ11B on diatom opal and compare them to δ11B on inorganically precipitated opal. We measured B content...
Presentation
Cell geometry and size limit diffussive CO2 availability, which control δ13C and Ep. Large centric cells may be more sensitive to CO2 limitation and use more HCO3- . Consequently, bulk diatom δ13C may differ from that of diatoms with different geometries and sizes, whose Ep may depend on form/size adaptations to variable [CO2]. Frustules from sedim...
Poster
We describe the isotopic measurement of δ13C in very small samples of diatom opal (nanomolar quantities of C) both from fossil sediments and cultures. We use a nano-EA system composed of a combustion elemental analyzer (EA3000 series, Eurovector), with standard 18 mm diameter quartz oxidation-reduction reactors and an ash removal device that aids i...
Poster
Full-text available
Diatoms of distinct cell sizes have different surface area to volume ratios resulting in differing diffusive supply of CO2 and different needs for active carbon acquisition mechanisms. Large cells may be more sensitive to CO2 depletion and additionally use a higher amount of HCO3- as C source to increase C uptake efficiency at low CO2 concentration...
Presentation
Full-text available
Diatoms are important climate modulators because of their key role in CO2 uptake, especially in nutrient-rich areas and glacial periods, providing relevant geological records of past climate, productivity and oceanography. Since boron (B) speciation in seawater is controlled by pH, the study of B content in diatom opal could be used to reconstruct...
Conference Paper
Full-text available
Carbon isotopic fractionation in fossil algal biomarkers is typically interpreted to reflect atmospheric CO 2 changes assuming simple diffusive uptake of CO 2 by cells, however modern algae employ a diverse array of additional strategies to concentrate DIC inside the cell (CCMs). We previously hypothesized that the size-correlated range of vital ef...
Article
Because boron speciation in seawater is controlled by pH there has been wide interest in using the concentration and isotopic composition of B in marine biominerals to reconstruct past changes in ocean pH. Biomineralization may modulate B incorporation either through cellular pH regulation or uptake processes. We investigate the effect of biominer...
Article
Full-text available
Diatoms are particularly important in climate modulation, since they account for a large part of the worldwide productivity and ocean CO2 uptake, especially in nutrient-rich areas. Their study provides a long geological record of past productivity, oceanographic conditions and climate. In this work we model and measure B/Si ratios in cultured and f...
Poster
Full-text available
Diatoms are particularly important in climate modulation, since they account for a large part of the worldwide productivity and ocean CO2 uptake, especially in nutrient-rich areas. Their study provides a long geological record of past productivity, oceanographic conditions and climate. In this work we model and measure B/Si ratios in cultured and f...
Poster
Paleoproductivity in the SO during the penultimate glacial cycle: evidence from coccolith Sr/Ca ratios

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