Depth-habitat reorganization of planktonic foraminifera across the Albian/Cenomanian boundary

New mid-Cretaceous stable isotope (δ18O and δ13C) records of multiple planktonic foraminiferal species and coexisting coccoliths from Blake Nose (western North Atlantic) document a major depth-ecology reorganization of planktonic foraminifera. Across the Albian/Cenomanian boundary, deep-dwellingPraeglobotruncana stephaniandRotalipora globotruncanoidesadapted to living at a shallower depth, while, at the same time, the population of surface-dwellingParacostellagerina libycadeclined. Subsequently, the opportunistic speciesHedbergella delrioensisshifted to a deep environment, and the deep-dwelling formsRotalipora montsalvensisandRotalipora reichelifirst appeared. The primary paleoenvironmental cause of the observed changes in planktonic adaptive strategies is uncertain, yet their coincidence with an earliest Cenomanian cooling trend reported elsewhere implicates the importance of reduced upper-ocean stratification. Although there has been an implicit assumption that the species-specific depth habitats of fossil planktonic foraminifera were invariant through time, planktonic paleoecology is a potential variable. Accordingly, the possibility of evolutionary changes in planktonic foraminiferal depth ecology should be a primary consideration (along with other environmental parameters) in paleoceanographic interpretations of foraminiferal stable isotope data.

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Factors controlling the depth habitat of planktonic foraminifera in the subtropical eastern North Atlantic

Biogeosciences ◽

10.5194/bg-14-827-2017 ◽

2017 ◽

Vol 14 (4) ◽

pp. 827-859 ◽

Cited By ~ 50

Author(s):

Andreia Rebotim ◽

Antje H. L. Voelker ◽

Lukas Jonkers ◽

Joanna J. Waniek ◽

Helge Meggers ◽

...

Keyword(s):

Water Column ◽

Chlorophyll A ◽

Mixed Layer ◽

North Atlantic ◽

Planktonic Foraminifera ◽

Individual Species ◽

Habitat Depth ◽

Chlorophyll A Concentration ◽

Eastern North Atlantic ◽

Species Specific

Abstract. Planktonic foraminifera preserved in marine sediments archive the physical and chemical conditions under which they built their shells. To interpret the paleoceanographic information contained in fossil foraminifera, the recorded proxy signals have to be attributed to the habitat and life cycle characteristics of individual species. Much of our knowledge on habitat depth is based on indirect methods, which reconstruct the depth at which the largest portion of the shell has been calcified. However, habitat depth can be best studied by direct observations in stratified plankton nets. Here we present a synthesis of living planktonic foraminifera abundance data in vertically resolved plankton net hauls taken in the eastern North Atlantic during 12 oceanographic campaigns between 1995 and 2012. Live (cytoplasm-bearing) specimens were counted for each depth interval and the vertical habitat at each station was expressed as average living depth (ALD). This allows us to differentiate species showing an ALD consistently in the upper 100 m (e.g., Globigerinoides ruber white and pink), indicating a shallow habitat; species occurring from the surface to the subsurface (e.g., Globigerina bulloides, Globorotalia inflata, Globorotalia truncatulinoides); and species inhabiting the subsurface (e.g., Globorotalia scitula and Globorotalia hirsuta). For 17 species with variable ALD, we assessed whether their depth habitat at a given station could be predicted by mixed layer (ML) depth, temperature in the ML and chlorophyll a concentration in the ML. The influence of seasonal and lunar cycle on the depth habitat was also tested using periodic regression. In 11 out of the 17 tested species, ALD variation appears to have a predictable component. All of the tested parameters were significant in at least one case, with both seasonal and lunar cyclicity as well as the environmental parameters explaining up to > 50 % of the variance. Thus, G. truncatulinoides, G. hirsuta and G. scitula appear to descend in the water column towards the summer, whereas populations of Trilobatus sacculifer appear to descend in the water column towards the new moon. In all other species, properties of the mixed layer explained more of the observed variance than the periodic models. Chlorophyll a concentration seems least important for ALD, whilst shoaling of the habitat with deepening of the ML is observed most frequently. We observe both shoaling and deepening of species habitat with increasing temperature. Further, we observe that temperature and seawater density at the depth of the ALD were not equally variable among the studied species, and their variability showed no consistent relationship with depth habitat. According to our results, depth habitat of individual species changes in response to different environmental and ontogenetic factors and consequently planktonic foraminifera exhibit not only species-specific mean habitat depths but also species-specific changes in habitat depth.

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Factors controlling the depth habitat of planktonic foraminifera in the subtropical eastern North Atlantic

10.5194/bg-2016-348 ◽

2016 ◽

Cited By ~ 3

Author(s):

Andreia Rebotim ◽

Antje H. L. Voelker ◽

Lukas Jonkers ◽

Joanna J. Waniek ◽

Helge Meggers ◽

...

Keyword(s):

Chlorophyll A ◽

Mixed Layer ◽

North Atlantic ◽

Planktonic Foraminifera ◽

Depth Interval ◽

Individual Species ◽

Habitat Depth ◽

Chlorophyll A Concentration ◽

Eastern North Atlantic ◽

Species Specific

Abstract. Planktonic foraminifera preserved in marine sediments archive the physical and chemical conditions under which they built their shells. To interpret the paleoceanographic information contained in fossil foraminifera, the proxy signals have to be attributed to the habitat of individual species. Much of our knowledge on habitat depth is based on indirect methods, which reconstruct the depth at which the largest portion of the shell has been calcified. However, habitat depth can be best studied by direct observations in stratified plankton nets. Here we present a synthesis of living planktonic foraminifera abundance data in vertically resolved plankton net hauls taken in the eastern North Atlantic during twelve oceanographic campaigns between 1995 and 2012. Live (cytoplasm-bearing) specimens were counted for each depth interval and the vertical habitat at each station was expressed as average living depth (ALD). This allows us to differentiate species showing an ALD consistently above 100 m (e.g. Globigerinoides ruber white and pink), indicating a shallow habitat; species occurring from the surface to the subsurface (e.g. Globigerina bulloides, Globorotalia inflata, Globorotalia truncatulinoides); and species inhabiting the subsurface (e.g. Globorotalia scitula and Globorotalia hirsuta). For 17 species with variable ALD, we assessed whether their depth habitat at a given station could be predicted by mixed layer (ML) depth, temperature in the ML and chlorophyll a concentration in the ML. The influence of seasonal and lunar cycle on the depth habitat was also tested using periodic regression. In 11 out of the 17 tested species, ALD variation appears to have a predictable component. All of the tested parameters were significant at least in one case, with both seasonal and lunar cyclicity as well as the environmental parameters being able to explain up to > 50 % of the variance. Whereas G. truncatulinoides, G. hirsuta and G. scitula appear to deepen their living depth towards the summer, populations of Trilobatus sacculifer appears to descend in the water column towards the new moon. In all other species, properties of the mixed layer explained more of the observed variance. Chlorophyll a concentration seems least important for ALD, whilst shoaling of the habitat with deepening of the ML is observed most frequently. We observe both shoaling and deepening of species habitat with increasing temperature. Further, we observe that temperature and seawater density at the depth of the ALD were not equally variable among the studied species, and their variability showed no consistent relationship with depth habitat. According to our results, depth habitat of individual species changes in response to different environmental and ontogenetic factors and consequently planktonic foraminifera exhibit not only species-specific mean habitat depths but also species-specific changes in habitat depth.

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Variability in Neogloboquadrina pachyderma stable isotope ratios from isothermal conditions: implications for individual foraminifera analysis

10.5194/cp-2021-87 ◽

2021 ◽

Author(s):

Lukas Jonkers ◽

Geert-Jan A. Brummer ◽

Julie Meilland ◽

Jeroen Groeneveld ◽

Michal Kucera

Keyword(s):

Stable Isotope ◽

North Atlantic ◽

Environmental Variability ◽

Seasonal Pattern ◽

Planktonic Foraminifera ◽

Population Level ◽

Excess Noise ◽

Neogloboquadrina Pachyderma ◽

Stable Isotope Data ◽

Δ18o And Δ13c

Abstract. Individual foraminifera analysis (IFA) holds promise to reconstruct seasonal to interannual oceanographic variability. Even though planktonic foraminifera are reliable recorders of environmental conditions on a population level, whether they also are on the level of individuals is unknown. Yet, one of the main assumptions underlying IFA is that each specimen records ocean conditions with negligible noise. Here we test this assumption using stable isotope data measured on groups of four shells of Neogloboquadrina pachyderma from a 16–19 days resolution sediment trap time series from the subpolar North Atlantic. We find a within-sample variability of 0.11 and 0.10 ‰ for δ18O and δ13C respectively that show no seasonal pattern and exceed water column variability in spring when conditions are homogeneous down to 100s of metres. We assess the possible effect of life cycle characteristics and delay due to settling on foraminifera δ18O variability with simulations using temperature and δ18Oseawater as input. These simulations indicate that the observed δ18O variability can partially be explained by environmental variability. Individual N. pachyderma are thus imperfect recorders of temperature and δ18Oseawater. We estimate the excess noise on δ18O to be 0.11 ± 0.06 ‰. The origin and nature of the recording imprecision require further work, but our analyses highlight the need to take such excess noise into account when interpreting the geochemical variability among individual foraminifera.

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Stable-isotope studies of planktonic foraminifera in North Atlantic core tops

Palaeogeography Palaeoclimatology Palaeoecology ◽

10.1016/0031-0182(81)90036-5 ◽

1981 ◽

Vol 33 (1-3) ◽

pp. 157-172 ◽

Cited By ~ 42

Author(s):

Joseph T. Durazzi

Keyword(s):

Stable Isotope ◽

North Atlantic ◽

Planktonic Foraminifera ◽

Isotope Studies ◽

Atlantic Core

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Ecology of Recent Planktonic Foraminifera: Part I: Areal Distribution in the Western North Atlantic

Micropaleontology ◽

10.2307/1484157 ◽

1959 ◽

Vol 5 (1) ◽

pp. 77 ◽

Cited By ~ 42

Author(s):

Allan W. H. Be

Keyword(s):

North Atlantic ◽

Planktonic Foraminifera ◽

Areal Distribution

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Energetic Submesoscales Maintain Strong Mixed Layer Stratification during an Autumn Storm

Journal of Physical Oceanography ◽

10.1175/jpo-d-17-0130.1 ◽

2017 ◽

Vol 47 (10) ◽

pp. 2419-2427 ◽

Cited By ~ 18

Author(s):

Daniel B. Whitt ◽

John R. Taylor

Keyword(s):

Mixed Layer ◽

North Atlantic ◽

Small Scale ◽

Upper Ocean ◽

Ocean Mixed Layer ◽

Ocean Stratification ◽

The North ◽

Large Eddy ◽

The Mean ◽

Scale Turbulence

AbstractAtmospheric storms are an important driver of changes in upper-ocean stratification and small-scale (1–100 m) turbulence. Yet, the modifying effects of submesoscale (0.1–10 km) motions in the ocean mixed layer on stratification and small-scale turbulence during a storm are not well understood. Here, large-eddy simulations are used to study the coupled response of submesoscale and small-scale turbulence to the passage of an idealized autumn storm, with a wind stress representative of a storm observed in the North Atlantic above the Porcupine Abyssal Plain. Because of a relatively shallow mixed layer and a strong downfront wind, existing scaling theory predicts that submesoscales should be unable to restratify the mixed layer during the storm. In contrast, the simulations reveal a persistent and strong mean stratification in the mixed layer both during and after the storm. In addition, the mean dissipation rate remains elevated throughout the mixed layer during the storm, despite the strong mean stratification. These results are attributed to strong spatial variability in stratification and small-scale turbulence at the submesoscale and have important implications for sampling and modeling submesoscales and their effects on stratification and turbulence in the upper ocean.

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Nyitni vagy nem nyitni? – Pilisi barlangok szellőzöttsége a geokémiai adatok tükrében

Földrajzi Közlemények ◽

10.32643/fk.145.3.3 ◽

2021 ◽

Vol 145 (3) ◽

pp. 224-231

Keyword(s):

Stable Isotope ◽

Environmental Conditions ◽

Isotope Fractionation ◽

Environmental Parameters ◽

Basic Research ◽

Geochemical Analysis ◽

Cave System ◽

Cave Environment ◽

Carbonate Formations ◽

The Given

Speleothem formations are one of the most important and informative objects in paleoclimatological research. However, in order to interpret the data that reflect environmental conditions, we have to know the operation of the given cave, and it should be determined how the composition of the carbonate formed at the given site is related to the changes in the environmental parameters. The study presents the results of stable isotope geochemical analysis of speleothem formations and carbonate precipitated on glass plates collected in the Vacska Cave (Pilis Hills). The youngest layer of carbonate formations, formed in the last 1-2 decades, shows an isotope fractionation sign indicating strong ventilation, with the exception of a single site farthest from the entrance to the cave. The isotope shift was also accompanied by a change in carbonate fabric. Preceding the fabric change, the carbonate of the speleothem formations did not show ventilation-related shifts in the isotope compositions, suggesting that the exploration and opening of the cave areas may have caused the change. Based on this, we recommend the installation of local closures in the Vacska Cave and in the entire Ariadne cave system. The study provides a good example of how the results of basic research can be utilized in practical environmental protection, in the preservation of a strictly protected cave environment.

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