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Schematic illustration of the AMOC and thermocline hypothesis. Environmental conditions are expressed as changes in the relative temperature (solid line) and the chlorophyll concentration (dashed line) with increasing depth. (a) Relatively strong AMOC and thermocline. A thin mixed layer consists of relatively warm water, while the subsurface layer is cooler. It causes a strong temperature gradient and thus a strong thermocline. This results in an increased accumulation of organic matter (marine snow) and a high concentration of chlorophyll within the thermocline. The concentration of food and the physical conditions may favour the test growth of G. menardii. (b) A relatively cool and deep mixed layer and a warm subsurface layer develop a weak thermocline. In comparison to strong thermocline conditions, the accumulation of chlorophyll and organic matter is low. The physical conditions may also contribute to a reduction in the test growth of G. menardii. Illustration modified by Brown (2007).
Source publication
The mean test size of planktonic foraminifera (PF) is
known to have increased especially during the last 12 Myr, probably in terms
of an adaptive response to an intensification of the surface-water
stratification. On geologically short timescales, the test size in PF is
related to environmental conditions. In an optimal species-specific
environment...
Citations
... AgC retroflection eddies (rings) of warmer and saline waters then leak into the BUS, moving northwest (Petrick et al., 2015). This 120 influx of AgC waters from the Indian Ocean is known as Agulhas leakage (Fine et al., 1988;Petrick et al., 2015;Friesenhagen, 2022). A greater input of the Indian Ocean subtropical waters is induced by the increase in strength of the BOC . ...
... The Agulhas leakage represents an inflow of warm and saline waters from the Indian Ocean to the southeastern Atlantic Ocean 250 (Fine et al., 1988;Petrick et al., 2015;Friesenhagen, 2022). To evaluate the capability of the possible water exchanges between the Indian and the Atlantic Ocean (Tables S3-S4 and Fig. 5), we calculated the Agulhas Leakage Efficiency (ALE) Index (Caley et al., 2014). ...
... Caley et al., 2012;Villar et al., 2015) hypothesized that the tropical fauna in the southeastern Atlantic represents a reseeding population from the Indian Ocean. Specifically, giant eddies of warm water from the Agulhas current can access the Benguela region according to a mechanism known as the Agulhas leakage (Fine et al., 1988;Petrick et al., 2015;Friesenhagen, 2022). ...
The Benguela Upwelling System (BUS), located in the southeastern Atlantic Ocean, represents one of the world’s most productive regions. This system is delimited to the south by the Agulhas retroflection region. The northern boundary of the BUS is, instead, represented by the Angola Benguela Front (ABF), which is a thermal feature separating warm waters of the Angola Basin (including the South Atlantic Central Waters; SACW) from the cooler Benguela Oceanic Current (BOC). We performed statistical analyses on planktonic foraminiferal assemblages in 94 samples from Holes U1575A and U1576A, cored during International Ocean Discovery Program (IODP) Expedition 391. Drilled sites are located along the Tristan-Gough-Walvis Ridge (TGW) seamount track in the northern sector of the BUS (offshore the Namibian continental margin). The analyzed stratigraphic intervals span the Early-Late Pleistocene, marked by the Early-Middle Pleistocene Transition (EMPT; 1.40–0.40 Myr), during which important glacial-interglacial sea surface temperature (SST) variabilities occurred. This work provides novel insights on the local paleoceanographic evolution of the northern BUS and associated thermocline variability based on the ecological significance of the foraminiferal assemblages. Specifically, variations in the assemblage content allowed to characterize the different water masses (BOC, SACW, Agulhas waters) and reconstruct their interactions during the Quaternary. The interplay of the previously mentioned water masses induced perturbations in the BUS (ABF latitudinal shifts and input of tropical waters from the Agulhas retroflection region). Furthermore, we investigated the possible link between changes in the paleoceanographic conditions and climatic events (e.g., Benguela Niño/Niña-like phases and deglaciation stages) recorded since the EMPT.
... The first occurrence of the small-size morphotype of B. balkhanica in the Upper Valanginian could be interpreted as primitive form, evolving from smaller to larger sized species such as B. balkhanica arenaceous morphotype and B. balkhanica sensu stricto ( Fig. 3 ). This trend of increasing size has also been demonstrated for other foraminifera such as larger discoid foraminifera of porcelaneous and microgranularagglutinated (e.g., Song et al., 1994 ;Septfontaine, 1988Septfontaine, , 2020, deepsea benthic foraminifera (e.g., Kaiho, 1999 ), planktic foraminifera (e.g., Arnold et al., 1995 ;Schmidt et al., 2004 ;Friesenhagen, 2022 ). The Upper Valanginian to Upper Hauterivian B. balkhanica small-size morphotype are represented by microspheric forms only, probably because the megalospheric forms were small and thus difficult to observe and/or to preserve in the sedimentary record (see Table 1 ). ...
... Unfortunately, only limited effort has been made to track morphological transitions between succeeding species within a suspected lineage. Particularly for the G. menardii lineage, temperature, salinity, and stratification have been implicated as the primary drivers of its size shifts documented over both the Neogene and Quaternary [25,[73][74][75]. ...
... Undoubtedly, strong temperature-or salinity-driven upper water-mass stratification changes could lead to a relatively large variation in the G. menardii size, reflecting the changing patterns of ecological niches within the thermocline [74,75]. The preference of such graduated micro-niches in the upper water column may also confirm their biostratigraphic significance over the Late Miocene. ...
... Proportional small productivity changes preceding the Tortonian-Messinian boundary, due to reduced freshwater inputs, can be inferred given the ultra-oligotrophic nature of the study area. For the Atlantic and Pacific Oceans, the test-size evolution of G. menardii during the Late Miocene [74,75] has shown that the larger sizes possibly preferred shallower water levels within the thermocline, due to a stronger chlorophyll maximum developed at the boundary between the surface and subsurface layer where the marine snow accumulates [80]. The increased concentrations of degrading particulate organic matter occurred in that specific layer [81] and the subsequent settlement of G. menardii shells may have led to the optimum test growth and development of larger shells. ...
The Tortonian-Messinian transition is associated with important climatic and oceanographic changes in the Mediterranean Basin, which have shaped both the biotic and abiotic nature of this setting. The morphological variability of the planktonic foraminifera Globorotalia menardii, a species that is highly sensitive to water column structure, has been investigated from the sedimen-tary archive of three Cretan sections across a west-east transect covering the Tortonian-Messinian Boundary. The present work explicitly focuses on test-size and coiling direction changes occurring during the 7.36-7.24 Ma time slice. On such a short timescale, the most important morphological differentiation accounts for the average size of G. menardii, which is mostly associated with evolutionary adaptation to new ecological niches during the latest Tortonian as a response to the environmental perturbations and ecological stress conditions preceding the Tortonian-Messinian Boundary. A combined thermal and/or salinity-driven stratification and thermocline development hypothesis has been suggested to explain the observed size variability. To ameliorate the accuracy of the proposed model and further determine which environmental parameter reflects the optimum conditions of the analysed species, additional sea surface temperature and salinity data derived from the same sampling intervals of the studied or additional Mediterranean sites are needed. The coiling direction of this species within the study time interval remained constant and not environmentally controlled.
... Their calcareous skeletons, or tests, preserve not only their entire life history, but also a biogeochemical expression of the surrounding water column (e.g., Edgar et al., 2017). These features allow for high-resolution species-specific quantification of physiological and ecological adaptation through periods of climate variability (e.g., Knappertsbusch, 2007;Wade et al., , 2016Hull and Norris, 2009;Wade and Olsson, 2009;Edgar et al., 2013a;Aze et al., 2014;Pearson and Ezard, 2014;Weinkauf et al., 2014Weinkauf et al., , 2019Brombacher et al., 2017aBrombacher et al., , 2021Falzoni et al., 2018;Si and Aubry, 2018;Fox et al., 2020;Todd et al., 2020;Kearns et al., 2021Kearns et al., , 2022Pearson and Penny, 2021;Shaw et al., 2021;Woodhouse et al., 2021;Friesenhagen, 2022;Hupp et al., 2022;Woodhouse and Swain et al., 2023). ...
... Despite the reduction in morphospecies diversity from ∼ 3 Ma, the late Cenozoic closure of the Tethyan and Central American Seaways (Crame and Rosen, 2002;Brierly and Fedorov, 2010;Hamon et al., 2013;Matthews et al., 2016) may have contributed to the notable rise in diversity through the Neogene Ezard et al., 2011;Peters et al., 2013;Fraass et al., 2015;Lowery et al., 2020), due to a significantly more heterogenous ocean structure via longitudinal obstruction of tropical-subtropical waters by continental reconfiguration, and latitudinal partitioning caused by the steepening of global meridional temperature gradients (Haug et al., 2001;Schmidt et al., 2004a, b;Knappertsbusch, 2016;Ford et al., 2022;Friesenhagen, 2022;Gaskell et al., 2022). Moreover, this intensified, heterogenous icehouse climate may have played a significant role in shaping the incredible diversity observed within modern planktonic foraminiferal cryptic genotypes (Darling and Aurahs et al., 2009;Morard et al., 2009Morard et al., , 2013Morard et al., , 2019Ujiié et al., 2010;Norris and Hull, 2012;Weiner et al., 2012Weiner et al., , 2014André et al., 2014;Ujiié and Ishitani, 2016), though further work is required on the quantification of planktonic foraminiferal cryptic diversity within deep time (André et al., 2013). ...
The Pliocene-Recent is associated with many important climatic and paleoceanographic changes, which have shaped the biotic and abiotic nature of the modern world. The closure of the Central American Seaway and the development and intensification of Northern Hemisphere ice sheets had profound global impacts on the latitudinal and vertical structure of the oceans, triggering the extinction and radiation of many marine groups. In particular, marine calcifying planktonic foraminifera, which are highly sensitive to water column structure, exhibited a series of extinctions as global temperatures fell. By analyzing high-resolution (∼ 5 kyr) sedimentary records from the Eastern Equatorial Pacific Ocean, complemented with global records from the novel Triton dataset, we document the biotic changes in this microfossil group, within which three species displayed isochronous co-extinction, and species with cold-water affinity increased in dominance as meridional temperature gradients steepened. We suggest that these changes were associated with the terminal stages of the closure of the Central American Seaway, where following the sustained warmth of the mid-Pliocene Warm Period, bipolar ice sheet expansion initiated a world in which cold- and deep-dwelling species became increasingly more successful. Such global-scale paleoecological and macroevolutionary variations between the Pliocene and the modern icehouse climate would suggest significant deviations from pre-industrial baselines within modern and future marine plankton communities as anthropogenic climate forcing continues.
... For more information about the development of VDDs; see also Knappertsbusch and Mary (2012). Knappertsbusch, 2016Knappertsbusch, , 2022Friesenhagen, 2022) and on the planktonic foraminiferal genus Truncorotalia (Bicknell et al., 2018). Experiencing the advantages of AMOR, the desire emerged of multiplying it to a fleet of AMORs for parallel processing of samples, and the effort for duplicating it was evaluated (Scheffelmeier et al., 2014). ...
Morphometric shell measurements help to quantify the evolutionary patterns of planktonic foraminifera (marine, calcite-secreting, and floating protists). The study of shell variations of these organisms requires observations at high stratigraphic resolution, which entails morphometric measurements from thousands of specimens. The collection of such data is time-consuming because specimens need to be oriented prior to imaging. In our studies about menardiform, globorotalids through time automatic devices were developed to orientate and image specimens under incident light. A first prototype—Automated Measurement system for shell mORphology (AMOR)—was realized in 2009 and was proven to be advantageous for gathering morphometric data. AMOR consists of a motorized universal tilting stage enabling an automatic orientation of specimens in a multicellular slide under a motorized binocular microscope. After the collection of images from the oriented specimens, shell parameters can be extracted and analyzed using separate digital imaging and morphometric software. AMOR was strongly tuned to Globorotalia menardii, a species with a quasi-symmetrical biconvex geometry in a keel view and often with a non-circular periphery in an equatorial view. Improvements of the software driving AMOR now allow the orientation of spiro- and umbilico-convex profiles and with circular forms in an equatorial view such as in phylogenetically related species like Globorotalia miocenica and Globorotalia multicamerata. Program AMOR v. 3.28 was given more flexibility using a scripting language for automatic control of the Windows graphical user interface. This approach was used to allow combinations of fix orienting functions in AMOR, which released us from reprogramming of the sophisticated LabView code. Scripting of core functions enables developing “portfolios” of adapted recipes for processing the morphologies that are beyond the menardiform morphogroup. To further expand on this concept, a follow-up robot—System AMOR 2—was completed in March 2020. It integrates the modified hardware, a newer digital camera, the updated software (AMOR v. 4.2), and improved functions. The present contribution describes the development from old AMOR to its newer twin, with the perspective of building a fleet of robots for the imaging of the oriented foraminifera in parallel.
The Plio-Pleistocene is associated with many important climatic and paleoceanographic changes which have shaped the biotic and abiotic nature of the modern world. The closure of the Central American Seaway and the development and intensification of northern hemisphere icesheets had profound global impacts on the latitudinal and vertical structure of the oceans triggering the extinction and radiation of many marine groups. In particular, marine calcifying planktonic foraminifera, that are sensitive to water column structure, exhibited a series of extinctions as global temperatures fell. By analyzing high-resolution (~5 kyr) sedimentary records from the Eastern Equatorial Pacific Ocean, complimented with global records from the novel Triton dataset, we document the biotic changes in this microfossil group, within which three species displayed isochronous co-extinction, and species with cold-water affinity increase in dominance. We suggest that these changes are associated with the terminal stages of the closure of the Central American Seaway and mark the initiation of a world in which cold- and deep-dwelling species became increasingly more successful.
