Eva Calvo

• PhD in Chemistry
• Researcher at Institut de Ciències del Mar

Consistent evidence for a poorly ventilated deep Pacific Ocean that could have released its radiocarbon-depleted carbon stock to the atmosphere during the last deglaciation has long been sought. Such evidence remains lacking, in part due to a paucity of surface reservoir age reconstructions required for accurate deep-ocean ventilation age estimates...

Marine dissolved organic matter (DOM) is one of the largest reservoirs of reduced carbon on Earth. In the dark ocean (4200 m), most of this carbon is refractory DOM. This refractory DOM, largely produced during microbial mineralization of organic matter, includes humic-like substances generated in situ and detectable by fluorescence spectroscopy. H...

Understanding oceanic processes, both physical and biological, that control atmospheric CO(2) is vital for predicting their influence during the past and into the future. The Eastern Equatorial Pacific (EEP) is thought to have exerted a strong control over glacial/interglacial CO(2) variations through its link to circulation and nutrient-related ch...

The anthropogenic rise in atmospheric CO(2) is driving fundamental and unprecedented changes in the chemistry of the oceans. This has led to changes in the physiology of a wide variety of marine organisms and, consequently, the ecology of the ocean. This review explores recent advances in our understanding of ocean acidification with a particular e...

The oceans are becoming more acidic due to absorption of anthropogenic carbon dioxide from the atmosphere. The impact of ocean acidification on marine ecosystems is unclear, but it will likely depend on species adaptability and the rate of change of seawater pH relative to its natural variability. To constrain the natural variability in reef-water...

In this work, we present, for the first time, the seawater carbonate system measurements of two coastal time-series in the NW Mediterranean Sea, L’Estartit Oceanographic Station (EOS; 42.05°N 3.2542°E) and the Blanes Bay Microbial Observatory (BBMO; 41.665°N 2.805°E). At these two time-series, measurements of total alkalinity (TA), pH, and associat...

COVID-19 has led to global population lockdowns that have had indirect effects on terrestrial and marine fauna, yet little is known on their effects on marine planktonic communities. We analysed the effect of the spring 2020 lockdown in a marine coastal area in Blanes Bay, NW Mediterranean. We compared a set of 23 oceanographic, microbial and bioge...

The Mediterranean Sea is particularly sensitive to climate oscillations and represents a key location to study past climatic and oceanographic changes. One valuable source of paleoceanographic information is through molecular biomarkers in deep sea sediments. This approach has been applied in a number of studies in this basin, but only covering the...

Anthropogenic carbon emissions are causing changes in seawater carbonate chemistry including a decline in the pH of the oceans. While its aftermath for calcifying microbes has been widely studied, the effect of ocean acidification (OA) on marine viruses and their microbial hosts is controversial, and even more in combination with another anthropoge...

The footprint of human activities on the planet is so profound that many scientists are already suggesting that we have entered a new geological era, the Anthropocene. From among these activities, those that are accompanied by large emissions of carbon dioxide (CO2) affect our entire planet and, especially, the oceans. Besides becoming warmer, the...

Over the last deglaciation there were two transient intervals of pronounced atmospheric CO2 rise; Heinrich Stadial 1 (17.5-15 kyr) and the Younger Dryas (12.9-11.5 kyr). Leading hypotheses accounting for the increased accumulation of CO2 in the atmosphere at these times invoke deep ocean carbon being released from the Southern Ocean and an associat...

Modern biogeochemical conditions of the Eastern Equatorial Pacific (EEP) region are characterized by high macronutrient concentrations but low phytoplankton abundance due to both iron and silicic acid limitation. Since primary producers significantly impact the global carbon cycle, paleoproductivity in relation to climate change and nutrient availa...

Cold-Water Corals (CWCs), and most marine calcifiers, are especially threatened by ocean acidification (OA) and the decrease in the carbonate saturation state of seawater. The vulnerability of these organisms, however, also involves other global stressors like warming, deoxygenation or changes in sea surface productivity and, hence, food supply via...

Glacial–interglacial changes in atmospheric CO2 are generally attributed to changes in seawater carbon chemistry in response to large-scale shifts in the ocean’s biogeochemistry and general circulation. The Southern Ocean currently takes up more CO2 than any other and it is likely to have played a crucial role in regulating past atmospheric CO2. Ho...

A successful integrated ocean acidification (OA) observing network must include (1) scientists and technicians from a range of disciplines from physics to chemistry to biology to technology development; (2) government, private, and intergovernmental support; (3) regional cohorts working together on regionally specific issues; (4) publicly accessibl...

The oceans are warming, but it is unclear how marine productivity will be affected under future climate change. In this study we examined a wide range of paleoproductivity proxies along a latitudinal transect (36–58°S) in the SW Pacific during the early Holocene climatic optimum, to explore regional patterns of productivity in a slightly warmer‐tha...

Deep-sea corals (DSCs), similar to their tropical counterparts, potentially provide continuous, high-resolution records of surrounding seawater conditions for up to a century or more. Several CWC elemental and isotopic ratios have been suggested as useful proxies of past oceanic conditions, for example for temperature, nutrients and CO2 system para...

It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO2 during the las...

Marine biogeochemistry dynamics in coastal marine areas is strongly influenced by episodic events such as rain, intense winds, river discharges and anthropogenic activities. We evaluated in this study the importance of these forcing events on modulating seasonal changes in the marine biogeochemistry of the northwestern coast of the Mediterranean Se...

It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO2 during the las...

The early Holocene sea surface temperature (SST) gradient across the Subtropical Front (STF) to the east of New Zealand was ~2°C (measured between core sites MD97-2121 and MD97-2120): considerably less than the ~ 6°C modern gradient between the two core sites. We document the surface ocean temperatures east and south of New Zealand during the early...

Two mesocosms experiments were conducted in winter 2010 and summer 2011 to examine how increased pCO2 and/or nutrient concentrations potentially perturbate dissolved organic matter dynamics in natural microbial assemblages. The fluorescence signals of protein- and humic-like compounds were used as a proxy for labile and non-labile material, respect...

Detailed examination of the absorption spectra from dark ocean samples allowed us to identify and deconvolve two distinct chromophores centered at 302 nm (UV) and 415 nm (Visible) from the exponential decay curve characteristic of humic substances. The UV chromophore was ubiquitous in intermediate and deep waters and it has been proposed as the sec...

Nature Communications 6:5986 doi: 10.1038/ncomms6986 (2015); Published January292015; Updated June152016 The original version of this Article failed to fully credit the use of the Ocean Data View software in figures 1, 2 and 3, which appears below: Schlitzer, R., Ocean Data View, http://odv.awi.de, 2016.

Ocean acidification is increasing and affects many marine organisms. However, certain sponge species can withstand low-pH conditions. This may be related to their complex association with microbes. We hypothesized that species with greater microbial diversity may develop functional redundancy that could enable the holobiont to survive even if parti...

Ocean acidification (OA) and warming related to the anthropogenic increase in atmospheric CO2 have been shown to have detrimental effects on several marine organisms, especially those with calcium carbonate structures such as corals. In this study, we evaluate the response of two Mediterranean shallow-water azooxanthellate corals to the projected p...

Here we present a new set of high-resolution early Pleistocene records from the eastern equatorial Pacific (EEP). Sediment composition from Ocean Drilling Program Sites 1240 and 1238 is used to reconstruct past changes in the atmosphere-ocean system. Particularly remarkable is the presence of laminated diatom oozes (LDOs) during glacial periods bet...

We investigated the effects of an increase in dissolved CO2 on the microbial communities of the Mediterranean Sea during two mesocosm experiments in two contrasting seasons: winter, at the peak of the annual phytoplankton bloom, and summer, under lownutrient conditions. The experiments included treatments with acidification and nutrient addition, a...

Human-induced ocean acidification impacts marine life. Marine bacteria are major drivers of biogeochemical nutrient cycles and energy fluxes1; hence, understanding their performance under projected climate change scenarios is crucial for assessing ecosystem functioning. Whereas genetic and physiological responses of phytoplankton to ocean acidifica...

Bacterioplankton communities are made up of a small set of abundant taxa and a large number of low-abundant organisms (i.e., 'rare biosphere'). Despite the critical role played by bacteria in marine ecosystems, it remains unknown how this large diversity of organisms are affected by human-induced perturbations, or what controls the responsiveness o...

EEP (ODP 1240) provides a unique opportunity to reconstruct coupled changes in the atmosphere-ocean systems through the analysis of lithic and biogenic components, from 1.6 to 2.2 Ma. The methodology combines δ18O in benthic foraminifera, Uvigerina spp. abundance, Sibio, TOC, lithic fraction and Fe-XRF composition. Throughout the studied period, ca...

Ocean acidification is directly related to increasing atmospheric CO2 levels due to human activities and the active role of the global ocean in absorbing part of this anthropogenic CO2. Here we present an assessment of the pH changes that have occurred along 24.5°N in the Subtropical North Atlantic through comparison of pH observations conducted in...

Due to the increase, in last years, of carbon dioxide (CO2) level in the atmosphere we start monitoring with the expandable seafloor observatory OBSEA a variety of parameters related with ocean acidification. Our research team has installed an underwater pH sensor in the OBSEA observatory in order to compare the sea pH data with the CO2 data collec...

Cold-water coral (CWC) reefs constitute one of the most complex deep-sea habitats harboring a vast diversity of associated species. Like other tropical or temperate framework builders, these systems are facing an uncertain future due to several threats, such as global warming and ocean acidification. In the case of Mediterranean CWC communities, th...

Research interest on jellyfish has grown exponentially over the last years and studies focusing on the biology and ecology of the jellyfish polyp stage are being recognized as crucial in understanding jellyfish proliferations. Due to the difficulty of conducting in situ work with jellyfish polyps, laboratory experiments are the most used approach....

Research interest on jellyfish has grown exponentially over the last years and studies focusing on the biology and ecology of the jellyfish polyp stage are being recognized as crucial in understanding jellyfish proliferations. Due to the difficulty of conducting in situ work with jellyfish polyps, laboratory experiments are the most used approach....

Deep-water ecosystems are characterized by relatively low carbonate concentration values and, due to ocean acidification (OA), these habitats might be among the first to be exposed to undersaturated conditions in the forthcoming years. However, until now, very few studies have been conducted to test how cold-water coral (CWC) species react to such...

Cold-water coral (CWC) reefs constitute one of the most complex deep-sea habitats harboring a vast diversity of associated species. Like other tropical or temperate framework builders, these systems are facing an uncertain future due to several threats, such as global warming and ocean acidification. In the case of Mediterranean CWC communities, th...

Deep-water ecosystems are characterized by relatively low carbonate concentration values and, due to ocean acidification (OA), these habitats might be among the first to be exposed to undersaturated conditions in the forthcoming years. However, until now, very few studies have been conducted to test how cold-water coral (CWC) species react to such...

We analyzed the temporal variability of dissolved organic matter (DOM) in a NW Mediterranean coastal site (l'Estartit). We monitored simultaneously: chemical (inorganic and organic nutrients), physical (temperature and salinity) and biological (chlorophyll a and prokaryotic abundance) variables over 3 years. Seawater samples were taken monthly at f...

The mean predicted decrease of 0.3 to 0.4 pH units in the global surface ocean by the end of the century has prompted urgent research to assess the potential effects of ocean acidification on the marine environment, with strong emphasis on calcifying organisms. Among them, the Mediterranean red coral (Corallium rubrum) is expected to be particularl...

In recent years, some of the ramifications of the ocean acidification problematic derived from the anthropogenic rising of atmospheric CO2 have been widely studied. In particular, the potential effects of a lowering pH on tropical coral reefs have received special attention. However, only a few studies have focused on testing the effects of ocean a...

Two experiments were conducted in winter 2010 and summer 2011, MST_W and MST_S, respectively to examine the dynamics of microbial communities and organic matter under different pH conditions and different nutrient levels. Natural seawater from the Blanes Bay Microbial Observatory, NW Mediterranean was enclosed in eight 200 L tanks and maintained in...

A large part of the CO2 released to the atmosphere due to human activities is taken up by the oceans, raising the amount of total inorganic carbon dissolved in the upper layers, thus affecting the chemical balances of the CO2 system in seawater. In addition to the estimation of the anthropogenic carbon inventory, establishing the rate at which ocea...

In recent years, some of the ramifications of the ocean acidification problematic derived from the anthropogenic rising of atmospheric CO2 have been widely studied. In particular, the potential effects of a lowering pH on tropical coral reefs have received special attention. However, only a few studies have focused on testing the effects of ocean a...

The Catalan Sea, located between the eastern Iberian coast and the Balearic Islands, is a representative portion of the western Mediterranean basin and provides a valuable case study for climate change effects on Mediterranean ecosystems. Global warming is reflected regionally by a rise in sea level over the last century, an increase in surface tem...

CATAGIFT is the acronym of the project supported by the Catalan Government (trough the AGAUR agency) to support the activities of the EGU Committee on Education in Catalonia. The objective of this project is two-fold: 1) To establish a coordinated action to support the participation of three Catalan science teachers of primary and secondary schools...

ODP Site 1240 from the Eastern Equatorial Pacific (EEP) provides a unique archive to explore, at high resolution, the role of low latitude oceanographic systems in past global climate changes. A combination of both inorganic and organic geochemical proxies is applied to reconstruct temperature and salinity changes in surface and thermocline layers....

Past hydrographical conditions in the Eastern Equatorial Pacific (EEP) are analysed throughout the multi- proxy study of the long sediment core ODP Site 1240, located at the Panama Basin (0°01.311"N, 86°27.758"W, 2921mbsl). The combination of different geochemical proxies (delta18O, delta13C and Mg/Ca) in two different foraminifera species with div...

1] The advent of new microanalytical techniques such as electron microprobe mapping (EMP) and laser ablation microsamplers coupled to mass spectrometers (LA-ICP-MS) provides a new array of possibilities to explore in great detail the trace elements distribution in foraminiferal carbonates. Here we apply these techniques to characterize diagenetic p...

Since the Industrial Revolution, the CO2 concentration in the atmosphere has increased substantially, enhancing the greenhouse effect, which is very much related to current global warming. Fortunately, the Earth has a series of reservoirs, especially its oceans, which trap a significant amount of the excess CO2. This marine absorption of CO2, howev...

Comparison of ice cores from Greenland and Antarctica shows an asynchronous two-step warming at these high latitudes during the Last Termination. However, the question whether this asynchrony extends to lower latitudes is unclear mainly due to the scarcity of paleorecords from the Southern Hemisphere. New data from a marine core collected off South...

We compile and compare data for the last 150,000 years from four deep-sea cores in the midlatitude zone of the Southern Hemisphere. We recalculate sea surface temperature estimates derived from foraminifera and compare these with estimates derived from alkenones and magnesium/calcium ratios in foraminiferal carbonate and with accompanying sedimento...

Low resolution (5-year) Sr/Ca and δ18O samples, extending back to 1708 A.D., were analysed from a Porites coral core collected from Flinders Reef, an offshore reef on the Queensland Plateau in the western Coral Sea (17.5° S, 148.3° E). Using the Sr/Ca ratio as a proxy for sea surface temperature (SST), we deconvolved a salinity record by subtractin...

We compile and compare data for the last 150,000 years from four deep-sea cores in the midlatitude zone of the Southern Hemisphere. We recalculate sea surface temperature estimates derived from foraminifera and compare these with estimates derived from alkenones and magnesium/calcium ratios in foraminiferal carbonate and with accompanying sedimento...

Book review of: Elderfield, H. (ed.). 2006 – The Oceans and Marine Geochemistry. Paperback. Elsevier. Volume 6 of the Treatise on Geochemistry, H.D. Holland and K.K. Turekian (eds). Amsterdam, 646 pp. This book is the sixth of a collection of nine volumes (plus a complete index) that make up the monumental ‘Treatise on Geochemistry’, envisioned as...

Coral reefs are exceptional environments where changes in calcification, photosynthesis, and respiration induce large temporal variations of pH. We argue that boron isotopic variations in corals provide a robust proxy for paleo-pH which, together with the likely concomitant changes in the reconstructed partial pressure of CO2 (PCO2) calculated by M...

Alkenone palaeothermometry has demonstrated a wide spatial and temporal applicability for the reconstruction of sea-surface temperatures (SST). Some oceanic realms, however, remain poorly studied. We document U37K' index data for two sediment cores retrieved from the South Tasman Sea, one west of New Zealand (SO136-GC3) and the other southeast of T...

The use of foraminiferal Mg/Ca ratios as an indicator of past temperatures in which these organisms dwelt has been widely employed by the paleoceanographic community during the last two decades. However, it was also early recognized that there are many potential contamination sources that may bias the `natural' Mg/Ca relationship within foraminifer...

1] The geochemical composition of foraminifera shells from an Ocean Drilling Program site in the Panama Basin has been analyzed by several analytical techniques (LA-ICP-MS, ICP-MS, XRD, SEM, EDX) in order to identify and evaluate the occurrence of contaminant phases which may bias paleoenvironmental reconstructions. LA-ICP-MS results on uncleaned t...

In recent years, many paleoceanographic studies have employed the foraminiferal elemental composition as a proxy of sea water paleoenvironmental conditions. In particular, the foraminiferal Mg/Ca ratio has been widely used as a sea water paleotemperature estimator. Nevertheless, this technique is still in development and special attention needs to...

An increase in iron supply associated with enhanced dust inputs could be responsible for higher marine phytoplankton production leading to the typically lower glacial atmospheric CO2 concentrations, as suggested by the “iron hypothesis.” The enhanced dust supply may also have provided the oceans with significant amounts of silica, which would have...

The combination of parallel Sr/Ca and delta 18O records in corals allows reconstruction of past changes in sea surface temperature (SST) and seawater delta 18O composition (McCulloch et al., 1994). The latter provides climatic information related to changes in the hydrologic cycle and can be interpreted as a salinity proxy. Since the delta 18O sign...

Here we present a detailed record of alkenone-derived sea surface temperature (SST) offshore western New Zealand (Core SO136-GC3; 42° 18'S, 169° 53'E, 958m water depth), covering the penultimate deglaciation and last interglacial. We focus on Marine Isotopic Stage 5e, which is characterized by three main singular features: first, maxima SSTs (18.5...

Pressurized liquid extraction has been performed on a suite of deep-sea sediments to assess its capability as an extraction technique in the analysis of molecular biomarkers used in paleoceanography. Specific compounds assessed comprise long-chain alkenones, n-alkanes, n-alcohols and, additionally, one diol and one keto-ol. These have been extracte...

A study of the C37 alkenone distributions in core MD952011 from the Norwegian Sea (about 65°N) has allowed the evaluation of the applicability of the U37K and U37K′ indexes in these cold waters. The use of the first defined U37K appears to be the most appropriate to estimate sea surface temperatures (SST) allowing a high resolution SST reconstructi...

Reconstructions of upper ocean temperature (T) during the Holocene (10–0 ka B.P.) were established using the alkenone method from seven, high accumulation sediment cores raised from the northeast Atlantic and the Mediterranean Sea (36°N–75°N). All these paleo-T records document an apparent long-term cooling during the last 10 kyr. In records with i...

Productivity changes in the central North Atlantic Ocean have been traced by means of the total C37 alkenone contents along two sediment cores located at 43°N and 37°N. Both alkenone signals revealed the occurrence of discrete productivity events every 23 kyr. Spectral analyses highlight the presence of a dominant 23-kyr periodicity in the alkenone...

The Holocene is characterized by its stable climate in the context of the last 500 kyr (McManus et al., Science, 1999). In spite of this stability short and long term changes have been identified (Grootes and Stuiver, J. Geophys. Res., 1997; Bond et al., Science, 1997; Dahl-Jensen et al., Science, 1998). Stable isotope and pollen records in contine...

The present study describes the first sea surface temperature (SST) reconstruction in the southeastern Subtropical Pacific Ocean, offshore the South American coast. The obtained record encompasses the last 400 kyr and follows the characteristic glacial/interglacial pattern defined by global ice volume. However, SST leads the delta18O isotopic recor...

Sea surface temperatures (SST) and input of continental materials have been reconstructed from the study of the long-chain alkenones and n-alkanes, respectively, in a core located in the western side of the Mid-Atlantic Ridge (MD952037, 37°05′N 32°02′W, 2630 m depth). Both the long- and short-term variability recorded by the temperatures and the pl...

Major errors (> 0.5°C) are produced in paleotemperature estimation with the C37 alkenone method when the amount of the diunsaturated or triunsaturated species, C37:2 and C37:3, respectively, approaches the limit of detection. These errors are more commonly encountered with C37:3 because of its higher adsorption to gas chromatographic (GC) columns....

Analysis of C37 alkenone mixtures by gas chromatography (GC) with flame ionization detection (FID) and GC coupled to mass spectrometry (GC/MS) in the chemical ionization mode (CI) shows that the later is useful for paleotemperature estimation when ammonia is used as reagent gas. Conversely, the use of isobutane gives rise to Uk'37 readings that are...

Sea surface temperatures (SST) and input of continental materials have been reconstructed from the study of the long-chain alkenones and n-alkanes, respectively, in a core located in the western side of the Mid-Atlantic Ridge (MD952037, 37°05'N 32°02'W, 2630 m depth). Both the long- and short-term variability recorded by the temperatures and the pl...

1] Being able to decipher paleo sea surface temperatures for warm oceanic waters is of the utmost importance to further evaluate the role of the tropics in global climate change. The U 37 K 0 index is one of such paleothermometers, although the warm range of temperatures often poses serious analytical challenges. This paper discusses and reviews se...