Planktic foraminiferal changes in the western Mediterranean Anthropocene

Unidad de excelencia María de Maeztu CEX2019-000940-MAltres ajuts: Acord transformatiu CRUE-CSICThe increase in anthropogenic induced warming over the last two centuries is impacting marine environment. Planktic foraminifera are a globally distributed calcifying marine zooplankton responding sensitively to changes in sea surface temperatures and interacting with the food web structure. Here, we study two high resolution multicore records from two western Mediterranean Sea regions (Alboran and Balearic basins), areas highly affected by both natural climate change and anthropogenic warming. Cores cover the time interval from the Medieval Climate Anomaly to present. Reconstructed sea surface temperatures are in good agreement with other results, tracing temperature changes through the Common Era (CE) and show a clear warming emergence at about 1850 CE. Both cores show opposite abundance fluctuations of planktic foraminiferal species (Globigerina bulloides, Globorotalia inflata and Globorotalia truncatulinoides), a common group of marine calcifying zooplankton. The relative abundance changes of Globorotalia truncatulinoides plus Globorotalia inflata describe the intensity of deep winter mixing in the Balearic basin. In the Alboran Sea, Globigerina bulloides and Globorotalia inflata instead respond to local upwelling dynamics. In the pre-industrial era, changes in planktic foraminiferal productivity and species composition can be explained mainly by the natural variability of the North Atlantic Oscillation, and, to a lesser extent, by the Atlantic Multidecadal Oscillation. In the industrial era, starting from about 1800 CE, this variability is affected by anthropogenic surface warming, leading to enhanced vertical stratification of the upper water column, and resulting in a decrease of surface productivity at both sites. We found that natural planktic foraminiferal population dynamics in the western Mediterranean is already altered by enhanced anthropogenic impact in the industrial era, suggesting that in this region natural cycles are being overprinted by human influences

Anthropogenic acidification of surface waters drives decreased biogenic calcification in the Mediterranean Sea

This work contributes to the ICTA-UAB “Unit of Excellence” (FPI/MDM-2015-0552- 16-2; CEX2019-000940-M) and was funded by the Spanish Ministry of Science and Innovation, BIOCAL Project (PID2020-113526RB-I00), the EU-FP7 “Mediterranean Sea Acidification in a Changing Climate” project (MedSeA; grant agreement 265103), and the Generalitat de Catalunya (MERS, 2021 SGR 00640). J.W.B.R. acknowledges the European Research Council under the European Union’s Horizon 2020 research and innovation program (grant agreement 805246) and B.M the Severo Ochoa grant CEX2018-000794-S and CSIC LINKA20102. G.L. acknowledges funding from the Spanish Ministry of Universities through a Maria Zambrano grant.Anthropogenic carbon dioxide emissions directly or indirectly drive ocean acidification, warming and enhanced stratification. The combined effects of these processes on marine planktic calcifiers at decadal to centennial timescales are poorly understood. Here, we analyze size normalized planktic foraminiferal shell weight, shell geochemistry, and supporting proxies from 3 sediment cores in the Mediterranean Sea spanning several centuries. Our results allow us to investigate the response of surface-dwelling planktic foraminifera to increases in atmospheric carbon dioxide. We find that increased anthropogenic carbon dioxide levels led to basin wide reductions in size normalized weights by modulating foraminiferal calcification. Carbon (δ13C) and boron (δ11B) isotopic compositions also indicate the increasing influence of fossil fuel derived carbon dioxide and decreasing pH, respectively. Alkenone concentrations and test accumulation rates indicate that warming and changes in biological productivity are insufficient to offset acidification effects. We suggest that further increases in atmospheric carbon dioxide will drive ongoing reductions in marine biogenic calcification in the Mediterranean Sea.Publisher PDFPeer reviewe

Pelagic calcium carbonate production and shallow dissolution in the North Pacific Ocean

Planktonic calcifying organisms play a key role in regulating ocean carbonate chemistry and atmospheric CO 2 . Surprisingly, references to the absolute and relative contribution of these organisms to calcium carbonate production are lacking. Here we report quantification of pelagic calcium carbonate produc- tion in the North Pacific, providing new insights on the contribution of the three main planktonic calcifying groups. Our results show that coccolitho- phores dominate the living calcium carbonate (CaCO 3 ) standing stock, with coccolithophore calcite comprising ~90% of total CaCO 3 production, and pteropods and foraminifera playing a secondary role. We show that pelagic CaCO 3 production is higher than the sinking flux of CaCO 3 at 150 and 200 m at ocean stations ALOHA and PAPA, implying that a large portion of pelagic calcium carbonate is remineralised within the photic zone; this extensive shallow dissolution explains the apparent discrepancy between previous estimates of CaCO 3 production derived from satellite observations/biogeo- chemical modeling versus estimates from shallow sediment traps. We suggest future changes in the CaCO 3 cycle and its impact on atmospheric CO 2 will largely depend on how the poorly-understood processes that determine whether CaCO 3 is remineralised in the photic zone or exported to depth respond to anthropogenic warming and acidification

Pelagic calcium carbonate production and shallow dissolution in the North Pacific Ocean

Funding was provided by NSF Grants OCE1220600 and OCE1220302 awarded to JA and WB, respectively, MINECO PID2020-113526RB-I00, the Generalitat de Catalunya MERS (#2017 SGR-1588) awarded to PZ and NERC grant NE/N011716/1 awarded to JR.Planktonic calcifying organisms play a key role in regulating ocean carbonate chemistry and atmospheric CO2. Surprisingly, references to the absolute and relative contribution of these organisms to calcium carbonate production are lacking. Here we report quantification of pelagic calcium carbonate production in the North Pacific, providing new insights on the contribution of the three main planktonic calcifying groups. Our results show that coccolithophores dominate the living calcium carbonate (CaCO3) standing stock, with coccolithophore calcite comprising ~90% of total CaCO3 production, and pteropods and foraminifera playing a secondary role. We show that pelagic CaCO3 production is higher than the sinking flux of CaCO3 at 150 and 200 m at ocean stations ALOHA and PAPA, implying that a large portion of pelagic calcium carbonate is remineralised within the photic zone; this extensive shallow dissolution explains the apparent discrepancy between previous estimates of CaCO3 production derived from satellite observations/biogeochemical modeling versus estimates from shallow sediment traps. We suggest future changes in the CaCO3 cycle and its impact on atmospheric CO2 will largely depend on how the poorly-understood processes that determine whether CaCO3 is remineralised in the photic zone or exported to depth respond to anthropogenic warming and acidification.Publisher PDFPeer reviewe

Pelagic calcium carbonate production and shallow dissolution in the North Pacific Ocean

Planktonic calcifying organisms play a key role in regulating ocean carbonate chemistry and atmospheric CO2. Surprisingly, references to the absolute and relative contribution of these organisms to calcium carbonate production are lacking. Here we report quantification of pelagic calcium carbonate production in the North Pacific, providing new insights on the contribution of the three main planktonic calcifying groups. Our results show that coccolithophores dominate the living calcium carbonate (CaCO3) standing stock, with coccolithophore calcite comprising ~90% of total CaCO3 production, and pteropods and foraminifera playing a secondary role. We show that pelagic CaCO3 production is higher than the sinking flux of CaCO3 at 150 and 200 m at ocean stations ALOHA and PAPA, implying that a large portion of pelagic calcium carbonate is remineralised within the photic zone; this extensive shallow dissolution explains the apparent discrepancy between previous estimates of CaCO3 production derived from satellite observations/biogeochemical modeling versus estimates from shallow sediment traps. We suggest future changes in the CaCO3 cycle and its impact on atmospheric CO2 will largely depend on how the poorly-understood processes that determine whether CaCO3 is remineralised in the photic zone or exported to depth respond to anthropogenic warming and acidification

Geohistorical insights into marine functional connectivity

This is the final version. Available from Oxford University Press via the DOI in this record. Data availability: All data produced for this work have been made available within the main manuscript or in the supplementary material.Marine functional connectivity (MFC) refers to the flows of organic matter, genes, and energy that are caused by the active and passive movements of marine organisms. Occurring at various temporal and spatial scales, MFC is a dynamic, constantly evolving global ecological process, part of overall ecological connectivity, but with its own distinct and specific patterns. Geological and historical archives of changes in the distributions, life histories, and migration of species can provide baselines for deciphering the long-term trends (decadal to millions of years) and variability of MFC. In this food-for-thought paper, we identify the different types of geohistorical data that can be used to study past MFC. We propose resources that are available for such work. Finally, we offer a roadmap outlining the most appropriate approaches for analysing and interpreting these data, the biases and limitations involved, and what we consider to be the primary themes for future research in this field. Overall, we demonstrate how, despite differences in norms and limitations between disciplines, valuable data on ecological and societal change can be extracted from geological and historical archives, and be used to understand changes of MFC through time.Austrian Science Fund (FWF)Natural Environment Research Council (NERC)European Union’s Horizon 2020European Research CouncilEuropean Research CouncilFundação para a Ciência e a Tecnologia (FCT)Axencia Galega de Innovación (GAIN)—Xunta de Galici

Geohistorical insights into marine functional connectivity

Marine functional connectivity (MFC) refers to the flows of organic matter, genes, and energy that are caused by the active and passive movements of marine organisms. Occurring at various temporal and spatial scales, MFC is a dynamic, constantly evolving global ecological process, part of overall ecological connectivity, but with its own distinct and specific patterns. Geological and historical archives of changes in the distributions, life histories, and migration of species can provide baselines for deciphering the long-term trends (decadal to millions of years) and variability of MFC. In this food-for-thought paper, we identify the different types of geohistorical data that can be used to study past MFC. We propose resources that are available for such work. Finally, we offer a roadmap outlining the most appropriate approaches for analysing and interpreting these data, the biases and limitations involved, and what we consider to be the primary themes for future research in this field. Overall, we demonstrate how, despite differences in norms and limitations between disciplines, valuable data on ecological and societal change can be extracted from geological and historical archives, and be used to understand changes of MFC through time

The Trident of Climate Change Impacts on Marine Ecosystems: Warming, Acidification and Deoxygenation - Insights from Mediterranean sedimentary records

En un món amb alt CO2, l'escalfament oceànic (OW), l'acidificació (OA) i la desoxigenació (OD) induïts pels humans constitueixen una amenaça important per als ecosistemes marins. Per tal d'investigar els canvis ambientals marins deguts a l'increment de la temperatura i l'acidificació, induïts per l'humà, es reconstrueixen els canvis en el registre fòssil de foraminífers durant els darrers 2.000 anys al mar Mediterrani occidental. Els foraminífers planctònics estan distribuïts globalment, formen part del zooplàncton marí calcificant i el seu registre fòssil permet quantificar canvis fisicoquímics i biològics a la superfície del mar. Encara es desconeix fins a quin punt aquests organismes clau són sensibles a les interaccions dels efectes del canvi climàtic a escales temporals anteriors als registres observacionals. Dos capítols d'aquesta tesi es dediquen a analitzar els canvis en la composició, abundància i calcificació dels foraminífers planctònics, juntament amb diversos paleo-indicadors de tres testimonis d'alta resolució recollits al Mar d'Alboran, al Mar Balear i a l'Estret de Sicília. Els resultats suggereixen que durant l'era preindustrial els canvis en la productivitat dels foraminífers planctònics i la composició d'espècies s'expliquen principalment a través de la variabilitat climàtica natural. Però a partir del 1800e.c. la dinàmica dels foraminífers està relacionada amb l'escalfament accelerat de la temperatura de la superfície del mar, cosa que indica una disminució de la productivitat marina a causa de l'estratificació de la columna d'aigua induïda, també, per l'augment de la temperatura. La reducció de les closques dels foraminífers implica que el CO2 antropogènic ja ha afectat la calcificació dels foraminífers planctònics durant el segle XX, corroborat amb dades d'isòtops de carboni i bor que indiquen una millor absorció de CO2 antropogènic i una disminució del pH a la zona d'estudi. Aquestes registres de sediments de la Mediterrània occidental evidencien una empremta en tota la conca degut a l'absorció de CO2 antropogènic. La tesi també ofereix una visió de com l'increment de la desoxigenació marina pot afectar l'ecologia dels peixos. Es planteja la hipòtesi que la desoxigenació de l'oceà obert suposa amenaces greus específicament per a la comunitat de peixos mesopelàgics, augmentant l'estrès físic, desplaçant el seu hàbitat òptim a la zona fòtica i per tant, canviant les relacions presa-depredador amb efectes negatius per a la seva abundància i composició. Els peixos mesopelàgics són actors clau a les xarxes tròfiques oceàniques, un recurs nutritiu abundant per a l'aqüicultura i els mercats nutracèutics i de màxima importància per a la mitigació del canvi climàtic ja que transporten carboni des de la superfície en profunditat. En el tercer capítol, s'investiguen els impactes de la hipòxia oceànica en la comunitat de peixos utilitzant otòlits de l'Holocè d'un testimoni de sediments de la Mediterrània oriental. Es detecten abundàncies globals extremadament baixes d'otòlits, entre 7 i 11 ka, quan les aigües de fons i intermèdies eren anòxiques i les aigües superficials eren notablement productives. Durant aquest temps, la composició dels otòlits està dominada per peixos adaptats a la zona epipelàgica, mentre que les espècies mesopelàgiques són gairebé absents. Després de la reoxigenació, des de fa uns 6 ka fins a l'actualitat, els otòlits d'espècies de peixos mesopelàgics dominen el registre fòssil. Els resultats suggereixen una probable resposta negativa dels peixos d'aigua mitjana a la intensificació i expansió contínua de les zones mínimes d'oxigen durant els propers segles que suposen impactes importants en la pesca marina, la conservació, l'estructura de la xarxa tròfica i la capacitat d'emmagatzematge de carboni.Para investigar los efectos de los cambios ambientales antropogénicos como el incremento de la temperatura y la acidificación, reconstruimos los cambios en las comunidades de foraminíferos planctónicos a través de su registro fósil y a lo largo de los últimos 2.000 años en el Mediterráneo occidental. Los foraminíferos planctónicos tienen una distribución global, forman parte del zooplancton marino calcificador y su registro fósil se puede utilizar para estudiar los cambios fisicoquímicos y biológicos en la superficie del mar. Aún se desconoce hasta qué punto estos organismos clave son sensibles a la interacción de los estresores del cambio climático a escalas de tiempo anteriores a los registros observacionales. Dos capítulos de esta tesis están dedicados a analizar los cambios en la composición, abundancia y calcificación de los foraminíferos planctónicos, junto con diversos paleo-indicadores de tres testigos de sedimento de alta resolución recogidos en el Mar de Alborán, el Mar Balear y el Estrecho de Sicilia. Nuestros resultados sugieren que durante la era preindustrial los cambios en la productividad de los foraminíferos planctónicos y en la composición de las especies pueden explicarse principalmente a través de la variabilidad climática natural. Aproximadamente a partir de 1800 e.c., la dinámica de los foraminíferos está relacionada con el aumento acelerado de la temperatura de la superficie del mar, lo que también se refleja en una disminución de la productividad marina debido a la estratificación de la columna de agua. La reducción en el peso de los esqueletos calcáreos de los foraminíferos planctónicos indica que el CO2 antropogénico ya ha afectado su calcificación durante el siglo XX, lo que también se corrobora con los análisis de isótopos de carbono y boro, que indican una mayor absorción antropogénica de CO2 y una disminución del pH en el lugar de estudio. Estos registros sedimentarios del Mediterráneo occidental reflejan la huella antropogénica en toda la cuenca inducida por el aumento de CO2. La tesis también permite vislumbrar cómo puede afectar el aumento de la desoxigenación a la ecología de los peces. La desoxigenación del océano abierto supone graves amenazas, específicamente a la comunidad de peces mesopelágicos, aumentando su estrés físico, desplazando su hábitat hacia la superficie y modificando la relación depredador-presa, con efectos negativos para su abundancia y composición. Los peces mesopelágicos son especies clave en las redes tróficas oceánicas, un recurso nutricional abundante para la acuicultura y los mercados nutracéuticos y de suma importancia para la mitigación del cambio climático, ya que transportan carbono de la superficie a las profundidades marinas. En el tercer capítulo, se investigan los efectos de la hipoxia oceánica en la comunidad de peces de aguas intermedias utilizando otolitos del Holoceno procedentes de un testimonio de sedimentos del Mediterráneo oriental. Detectando abundancias globales extremadamente bajas de otolitos entre hace 7 y 11 ka cuando el fondo y las aguas intermedias eran altamente anóxicas, y las aguas superficiales eran notablemente productivas. Durante esta época, la composición de los otolitos está dominada por peces adaptados a la zona epipelágica, mientras que las especies mesopelágicas están casi ausentes. Tras la reoxigenación desde hace unos 6 ka hasta la actualidad, los otolitos de especies de peces mesopelágicos dominan el registro. Nuestros resultados sugieren una probable respuesta negativa de los peces de aguas medias a la intensificación y expansión continuas de las zonas de oxígeno mínimo en los próximos siglos, lo que tendría importantes repercusiones en la pesca marina, la conservación marina, la estructura de la red trófica oceánica y la capacidad de almacenamiento de carbono.In a high CO2 world, human induced ocean warming (OW), acidification (OA) and deoxygenation (OD) forms a major threat to marine ecosystems. By means of our long-term records, we capture the complex natural environment throughout periods of diverse intensity of human and naturally induced climate pressure. This allows us to assess the impact of OW, OA and OD on the ecology and calcification of planktic foraminifera, and on midwater fish dynamics, both key groups of organisms being highly important for structure and functioning of global marine ecosystem services and food web. The main objective of this thesis is to contribute to the understanding of the ocean in high CO2 conditions by reconstructing marine ecosystem dynamics beyond the temporal scale of instrumental records, to place recent observations into the context of past climate change, when human influence was minor or even absent. Our findings may help to better project future ocean food web dynamics and will serve to facilitate marine policy decision making. To investigate marine environmental changes as a response to human induced OW and OA, we reconstruct fossil planktic foraminiferal changes through the last 2k years in the western Mediterranean Sea. Planktic foraminifera are globally distributed, calcifying marine zooplankton and susceptible recorders of physicochemical and biological changes at the sea surface. How sensitive those key organisms are to the combined effects of climate change drivers on timescales beyond observational records is still unknown. Two chapters of this thesis are dedicated to analyzing changes of planktic foraminifera composition, abundance, and test calcification along with multi-proxy data from the same three high resolution multicores, collected in the Alboran Sea, Balearic Sea and the Strait of Sicily. Our findings suggest that in the pre-industrial era changes in planktic foraminiferal productivity and species composition can be mainly explained through natural climate variability. Starting from about 1800 CE, foraminiferal dynamics are linked to accelerated sea surface temperature warming, indicating decreased marine productivity due to thermally induced water column stratification. Reduced test weights imply that anthropogenic CO2 has already affected planktic foraminiferal calcification during the 20th century, corroborated by carbon and boron isotope data indicating enhanced anthropogenic CO2 uptake and decreasing pH at our study sites. Our studies detect a basin-wide imprint of anthropogenically CO2 induced changes in western Mediterranean sediment records. Moreover, the thesis provides a glimpse on how future ocean deoxygenation may impact oceanic fish ecology. Open ocean deoxygenation is hypothesized to pose severe threats specifically to the mesopelagic fish community by enhancing physical stress, shifting their habitat into the photic zone, and so changing prey-predator relationships, with negative effects for their abundance and composition. Mesopelagic fish are key players in ocean food webs, an abundant nutritional resource for aquaculture and nutraceutical markets and of highest importance for climate change mitigation as they transport carbon from the surface to the deep sea. In a third chapter, we investigate the impacts of ocean hypoxia on midwater fish community by using Holocene otoliths from an Eastern Mediterranean sediment core. Extremely low overall abundances of otoliths are detected between 7 and 11 ka ago, when bottom to mid-waters were highly anoxic, and surface waters were remarkably productive. During that time otolith composition is dominated by fish adapted to the epipelagic zone, while mesopelagic species are nearly absent. After reoxygenation at about 6 ka ago until present, mesopelagic fish species dominate the otolith record. Our results suggest a likely negative response of midwater fish to ongoing intensification and expansion of Oxygen Minimum Zones (OMZs) over coming centuries, which would have major impacts on marine fisheries, marine conservation, ocean food web structure and carbon storage capacity.Universitat Autònoma de Barcelona. Programa de Doctorat en Ciència i Tecnologia Ambiental