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Impact of extreme warmth, excess of CO2 pressure abd carbon cycle perturbations on marine biota: planktic foraminiferal resilience to the early Eocene climatic optimum (EECO, 53-49 MA)
No full textI foraminiferi planctonici sono protisti marini con gusci di carbonato di calcio. La loro abbondanza ed evoluzione sono correlate ai cambiamenti paleoceanografici e climatici, rendendoli importanti indicatori per la ricostruzione degli ambienti passati. L’ Early Eocene Climatic Optimum (EECO, ~53–49 Ma) è l’intervallo più caldo del Cenozoico. Durante l’EECO si sono verificati anche eventi di riscaldamento globale di breve durata (<200 kyr), noti come 'ipertermali'. Questo intervallo offre quindi l' opportunità di studiare la resilienza del biota marino al riscaldamento estremo, considerando una prospettiva sia a lungo che a breve termine.
Studi recenti sui foraminiferi planctonici documentano che i due generi portatori di simbionti, Morozovella e Acarinina, predominanti nel mixed layer di oceani tropicali e subtropicali dell’inizio del Paleogene, hanno subito un cambiamento permanente in abbondanza e diversità negli oceani Atlantico e Tetide all’inizio dell’EECO (evento J). Inoltre, tutte le specie di Morozovella hanno modificato la direzione di avvolgimento del guscio (coiling) da destrorso a sinistrorso (specie criptiche) entro l’EECO, < 200 kyr dopo l’evento K/X. Un altro cambiamento significativo nell’ Atlantico è stata la quasi scomparsa del genere Chiloguembelina dall’evento K/X.
Lo scopo di questa ricerca è di estendere l'analisi dei foraminiferi planctonici a contesti paleoceanografici al di fuori dell’Atlantico e della Tetide, concentrandosi sui sites 1209–1210 (Shatsky Rise, Pacifico), Hole 762C (Oceano Indiano) e Site U1510 (Mar di Tasmania).
Dai risultati emerge che l’abbondanza di Morozovella è diminuita a 53.28 Ma, all’inizio dell’EECO, nel Pacifico subtropicale, confermando i dati atlantici. Nonostante le aspettative di una ridotta produzione di foraminiferi, la dimensione dei gusci nell’assemblage è leggermente aumentata. Lo species replacement all'interno delle comunità evidenzia la resilienza della produzione carbonatica pelagica, sottolineando il ruolo critico dei foraminiferi planctonici nella regolazione della rete alimentare marina e del ciclo globale del carbonio (Capitolo 1).
Anche nel Pacifico subtropicale si è verificato lo switch nell’abbondanza relativa tra Morozovella e Acarinina. La dimensione dei gusci di Morozovella è inaspettatamente aumentata, mentre quella di Acarinina è diminuita. Valori minori di δ13C in Acarinina suggeriscono una sua migrazione in profondità per evitare le alte temperature superficiali. Tuttavia, la riduzione di luce potrebbe aver indebolito la simbiosi, limitando la dimensione delle taglie. Morozovella, rimanendo in superficie, ha mantenuto la simbiosi e una dimensione maggiore, ma con una flessibilità ecologica limitata (Capitolo 2).
Alle alte latitudini meridionali (Oceano Indiano e Mar di Tasmania), Morozovella non è diminuita, indicando che condizioni più fredde potrebbero aver fornito rifugio. Tuttavia, Acarinina ha dominato globalmente, confermando la sua maggiore adattabilità. La scomparsa globale di Chiloguembelina dall’evento K/X suggerisce una risposta alla riduzione di nutrienti nel termoclino (Capitolo 3).
Lo switch nel coiling di Morozovella da destrorso a sinistrorso, <200 kyr dopo l’evento K/X, è stato registrato in tutti i sites, mentre Acarinina non mostra una preferenza nell’avvolgimento. Il declino di Morozovella può essere interpretato come la diminuzione delle forme destrorse, che, con valori di δ13C minori, indicano un habitat più profondo e una simbiosi ridotta. Questa strategia ecologica, più accentuata in Acarinina, ha favorito questo genere durante l’EECO, con la sopravvivenza parziale di Morovella sinistrorse, sopravvissute ai morfotipi destrorsi, ma in piccole quantità (Capitolo 4). Questi risultati forniscono preziose informazioni sull'adattamento dei foraminiferi planctonici al caldo estremo, con implicazioni rilevanti per le proiezioni climatiche future.Planktic foraminifera are marine protists with calcium carbonate shells. Their abundance and evolution correlate with paleoceanographic and climatic changes, making them valuable environmental indicators. The Early Eocene Climatic Optimum (EECO, ~53–49 Ma) was the warmest long-term interval of the Cenozoic. In addition, several short-term (< 200 kyr) global warming events, the hyperthermals, occurred before and during this interval. The EECO provides indeed an exceptional opportunity to explore the marine biota resilience to extreme warmth through a long- and short-term perspective.
Recent studies on planktic foraminiferal response to the EECO record that the two symbiont-bearing mixed layer genera Morozovella and Acarinina, dominating early Paleogene tropical and subtropical surface oceans, permanently switched their abundance and diversity in the Atlantic and Tethys oceans close to the EECO onset (J event). This change began at equatorial latitudes and gradually spread to tropical and temperate regions. In addition, at tropical, equatorial, and southern temperate Atlantic sites, all the Morozovella species modify their coiling direction from preferentially dextral to sinistral coiling (probably cryptic species) within the EECO, <200 kyr after the K/X event. Another major change from the Atlantic Ocean is the virtual disappearance of the genus Chiloguembelina from the K/X event.
Expanding from previous works, this research aimed to extend the analysis of planktic foraminifera to other paleoceanographic settings outside the Atlantic Ocean and Tethys, focusing on Pacific ODP Sites 1209–1210 (Shatsky Rise), Hole 762C (Indian Ocean), and Site U1510 (Tasman Sea).
Results show that Morozovella abundance in the subtropical Pacific declined at 53.28 Ma, EECO onset, coupled by Acarinina increase, confirming Atlantic findings. Despite expectations of reduced foraminiferal production, assemblage test size slightly increased. Species replacement within communities highlights the resilience of pelagic carbonate production, emphasizing the critical role of planktic foraminifera in regulating the marine food web and global carbon cycling (Chapter 1)
The Morozovella/Acarinina abundance switch prompts investigation into environmental triggers. Unexpectedly, Morozovella test size increased, while Acarinina’s decreased. Lower δ13C values in Acarinina suggest this genus likely evaded the higher temperatures at the surface by migrating to deeper layers. However, reduced light likely weakened its symbiosis, limiting test size. In contrast, Morozovella remained shallower in the mixed layer, sustaining symbiosis and larger size but with limited ecological flexibility (Chapter 2).
At southern high latitudes (Exmouth Plateau, Indian Ocean; Tasman Sea, Pacific), Morozovella did not decline, indicating cooler conditions may have provided refugia. Conversey, Acarinina dominated globally, confirming its ecological adaptability (Chapter 3). The global disappearance of Chiloguembelina from the K/X hyperthermal through the EECO suggests a response to food supply reduction and thermocline changes, including enhanced oxygenation (Chapters 1-3).
Additionally, the switch in Morozovella coiling from dextral to sinistral <200 kyr after the K/X event was recorded at all sites whereas Acarinina lacks preferential coiling. This suggests that Morozovella decline can be read as dextral morphotypes drop. The survivors’ dextral forms show slightly lower δ13C values than dextrals, indicating a deeper habitat and reduced symbiosis. This ecological strategy, more pronounced in Acarinina, favoured this genus, allowing it to thrive during the EECO, and only partially the sinistral morozovellids forms, which survived with respect to dextral morphotypes but only in small abundance (Chapter 4).
These findings provide critical insights into planktic foraminiferal adaptation to extreme warmth, relevant for future climate projections
Planktic foraminiferal response to the Early Eocene Climatic Optimum (EECO) from southern mid-to-high latitudes
No full textThe Early Eocene Climatic Optimum (EECO; ~53–49 Ma) records the warmest long-term global average tem- perature and CO2 levels of the Cenozoic and is punctuated by multiple transient global warming events (hyperthermals), providing a significant opportunity to investigate the impact of extreme heat on planktic foraminifera, a key group of marine calcifiers highly sensitive to paleoenvironmental changes. Studies on Atlantic and Pacific Oceans documented a dramatic decline in abundance and diversity of the symbiont-bearing genus Morozovella close to the EECO onset (J event), and a corresponding permanent increase in the abundance of Acarinina. We extend the record to southern high-latitude locations on the Australia margin to provide a global perspective on planktic foraminiferal resilience to the EECO. We present planktic foraminiferal biostratigraphy, quantitative abundance and dissolution from Hole 762C (Exmouth Plateau, Indian Ocean) and Site U1510 (Tasman Sea, Pacific Ocean). Despite core breaks, these sites record multiple hyperthermals within the EECO. Our results suggest that cooler conditions at higher latitudes may have mitigated the decline of Morozovella observed at Atlantic and tropical Pacific sites. At Hole 762C and Site U1510, Acarinina dominates the assemblage, demonstrating the greatest ecological flexibility. The disappearance of the genus Chiloguembelina from the K/X hyperthermal through the EECO in the studied sites may represent a global event as it occurred at the same level in the Atlantic and tropical Pacific. This study from higher southern latitudes enhances our understanding of global planktic foraminiferal resilience to the EECO underlying similarities and differences constrained by the diverse geological settings
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Contrasting response in test size and abundance of planktic foraminifera <i>Morozovella </i>and <i>Acarinina </i>to the EECO in the subtropical Pacific Ocean
No full textThe EECO (∼53–49 Ma) is characterized by the highest global average temperature and CO2 levels of the Cenozoic, providing the opportunity to explore the interplay between prolonged warmth, potential physiological stress, and marine planktic ecosystems, of which planktic foraminifera are a component. Previous studies have documented a dramatic decline in the dominant planktic foraminiferal genus Morozovella and a concurrent increase in Acarinina abundances at the onset of the EECO in the Atlantic, Tethys and Pacific Oceans. This study aims to investigate how extreme climatic conditions during the EECO influenced the abundance, size, and ecological strategies of planktic foraminifera, focusing on the response of the symbiont-bearing mixed-layer dweller Morozovella and Acarinina at Ocean Drilling Program (ODP) sites 1209–1210 Shatsky Rise, in the subtropical Pacific Ocean. We present species abundances, test size and δ13C data of Morozovella. Acarinina test size and δ13C data were quantified to assess whether observed changes affected all mixed-layer dwellers or were specific to Morozovella. Our results show a temporary increase in Morozovella test size at the EECO onset, partially linked to the dominance of larger species such as M. crater and M. aragonensis. In contrast, Acarinina displays a reduction in test size. The generally lower δ13C values across the EECO in Acarinina suggest a deeper habitat in the mixed-layer and/or reduced symbiosis relative to Morozovella. We speculate that Acarinina evaded the high temperatures by moving deeper in the mixed layer. The reduced symbiosis relationship due to diminished light in the deeper water column might have led to a smaller test size. In contrast, Morozovella maintained a shallower position in the mixed layer allowing it to sustain efficient symbiosis and larger size. However, the limited ecological flexibility of this taxon may have impeded its ability to adapt and maintain high abundance across the EECO.</p
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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