32 research outputs found
The Paleozoic δ88/86Sr record of marine carbonates – Implications to ocean carbonate chemistry and mass extinction events
Calcitization of aragonitic bryozoans in Cenozoic tropical carbonates from East Kalimantan, Indonesia
© The Author(s) 2016. Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The file attached is the published version of the article
The Impact of Global Warming and Anoxia on Marine Benthic Community Dynamics: an Example from the Toarcian (Early Jurassic)
The Pliensbachian-Toarcian (Early Jurassic) fossil record is an archive of natural data of benthic community response to global warming and marine long-term hypoxia and anoxia. In the early Toarcian mean temperatures increased by the same order of magnitude as that predicted for the near future; laminated, organic-rich, black shales were deposited in many shallow water epicontinental basins; and a biotic crisis occurred in the marine realm, with the extinction of approximately 5% of families and 26% of genera. High-resolution quantitative abundance data of benthic invertebrates were collected from the Cleveland Basin (North Yorkshire, UK), and analysed with multivariate statistical methods to detect how the fauna responded to environmental changes during the early Toarcian. Twelve biofacies were identified. Their changes through time closely resemble the pattern of faunal degradation and recovery observed in modern habitats affected by anoxia. All four successional stages of community structure recorded in modern studies are recognised in the fossil data (i.e. Stage III: climax; II: transitional; I: pioneer; 0: highly disturbed). Two main faunal turnover events occurred: (i) at the onset of anoxia, with the extinction of most benthic species and the survival of a few adapted to thrive in low-oxygen conditions (Stages I to 0) and (ii) in the recovery, when newly evolved species colonized the re-oxygenated soft sediments and the path of recovery did not retrace of pattern of ecological degradation (Stages I to II). The ordination of samples coupled with sedimentological and palaeotemperature proxy data indicate that the onset of anoxia and the extinction horizon coincide with both a rise in temperature and sea level. Our study of how faunal associations co-vary with long and short term sea level and temperature changes has implications for predicting the long-term effects of “dead zones” in modern oceans
Gauging benthic recovery from 20th century pollution on the southern California continental shelf using bivalves from sediment cores
Radiocarbon dating supports bivalve-fish age coupling along a bathymetric gradient in high-resolution paleoenvironmental studies
Studies of paleocommunities and trophic webs assume that multispecies assemblages consist of species that coexisted in the same habitat over the duration of time averaging. However, even species with similar durability can differ in age within a single fossil assemblage. Here, we tested whether skeletal remains of different phyla and trophic guilds, the most abundant infaunal bivalve shells and nektobenthic fish otoliths, differed in radiocarbon age in surficial sediments along a depth gradient from 10 to 40 m on the warm-temperate Israeli shelf, and we modeled their dynamics of taphonomic loss. We found that, in spite of the higher potential of fishes for out-of-habitat transport after death, differences in age structure within depths were smaller by almost an order of magnitude than differences between depths. Shell and otolith assemblages underwent depth-specific burial pathways independent of taxon identity, generating death assemblages with comparable time averaging, and supporting the assumption of temporal and spatial co-occurrence of mollusks and fishes. © 2020 The Authors. Gold Open Access
Revisiting mid-Paleozoic ocean chemistry with the combined measurement of 87Sr/86Sr and δ88/86Sr on Silurian brachiopods
Anthropogenically induced environmental changes in the northeastern Adriatic Sea in the last 500 years (Panzano Bay, Gulf of Trieste)
Shallow and sheltered marine embayments in urbanized areas are
prone to the accumulation of pollutants, but little is known about the
historical baselines of such marine ecosystems. Here we study foraminiferal
assemblages, geochemical proxies and sedimentological data from 1.6 m long
sediment cores to uncover ∼ 500 years of anthropogenic pressure
from mining, port and industrial activities in the Gulf of Trieste, Italy.
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From 1600 to 1900 AD, normalized element concentrations and foraminiferal
assemblages point to negligible effects of agricultural activities. The only
significant anthropogenic activity during this period was mercury mining in
the hinterlands of the gulf, releasing high amounts of mercury into the bay
and significantly exceeding the standards on the effects of trace elements
on benthic organisms. Nonetheless, the fluctuations in the concentrations of
mercury do not correlate with changes in the composition and diversity of
foraminiferal assemblages due to its non-bioavailability. Intensified
agricultural and maricultural activities in the first half of the 20th
century caused slight nutrient enrichment and a minor increase in
foraminiferal diversity. Intensified port and industrial activities in the
second half of 20th century increased the normalized trace
element concentrations and persistent organic pollutants (PAH, PCB) in the
topmost part of the core. This increase caused only minor changes in the
foraminiferal community because foraminifera in Panzano Bay have a long
history of adaptation to elevated trace element concentrations.
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Our study underlines the importance of using an integrated,
multidisciplinary approach in reconstructing the history of environmental
and anthropogenic changes in marine systems. Given the prolonged human
impacts in coastal areas like the Gulf of Trieste, such long-term baseline
data are crucial for interpreting the present state of marine ecosystems
Intertidal Death Assemblages as Proxies of Marine Biodiversity: An Example from Northern Patagonia, Argentina
Marine conservation biologists have identified mollusks as one of the appropriate surrogate taxa for characterizing marine benthic diversity. In turn, live/dead comparison studies have overwhelmingly demonstrated that mollusk remains are faithful proxies of the mollusk composition of the living communities from which they come, with positive consequences for the paleoecological evaluation of fossil assemblages. In this contribution, we evaluate the way in which mollusk biodiversity is distributed along the lower intertidal to supratidal (high water mark) dead shell assemblages accumulated on a northern Patagonian rocky shore, in order to explore the usefulness of these assemblages as paleontological proxies and potential surrogates of regional biodiversity. A diversity gradient from the lower intertidal to the supratidal was identified which is probably associated with vertical transport, although the influence of gradients of the living community should be tested to confirm this. The outstanding result of this study is the discovery of high levels of diversity among dead shells (31 bivalves and 39 gastropod species) in a single locality and with a moderate sampling effort. The supratidal death assemblage has higher species richness than expected, possibly caused by stranding of the fauna after storms. Nevertheless, this level shows the lowest level of evenness and a strong bias when samples are not sieved through a fine mesh. The record of marine benthic diversity in death assemblages is a promising area of research that deserves to be explored in depth.Fil: Archuby, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Roche, Andrea. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; Argentina. Universidad Nacional del Comahue. Escuela de Ciencias Marinas; Argentin