Environmental changes in the East Equatorial Pacific during the Mid Pleistocene Transition and implications for the Last Global Extinction of benthic foraminifera

Benthic foraminifera are important indicators for ecological studies. The assemblage composition of local communities can be used to analyze influences of environmental variables such as temperature, salinity, pH, and others. In recent years, the experimental propagule method has emerged as an effective tool to evaluate the influence of these variables on assemblage dynamics of benthic foraminifera. Propagules (tiny juveniles) of benthic foraminifera are widespread and can survive outside of a species&#8217; natural distribution range. Their ability to become dormant and be re-activated once local conditions become suitable, is an important driver behind the capacity of foraminiferal assemblages to react quickly to environmental changes. In the laboratory, the propagules are first separated from the coarser fractions by sieving and then cultured under different conditions.In the present study, we analyzed the effect of ocean pH on the composition of shallow-water assemblages from Corfu Island (Greece). Like other calcifying organisms, assemblages of foraminifera are susceptible to pH variations and have revealed compositional shifts along natural or experimental pH gradients. Our experimental set-up included four pH treatments between 6.5 and 8.5 at constant temperature and salinity (22&#176;C and 38 ppt) for 5 weeks.At the conclusion of the cultivation experiment, we found high numbers of grown specimens (825&#8211;1564 per replicate) and a high survivability rate throughout all treatments (78&#8211;87%). Higher pH (7.8 and 8.5) resulted in assemblages that were dominated by monothalamous and porcelaneous species, whereas lower pH (6.5 and 7.2) lead to a reduction in porcelaneous and an increase in agglutinated species. Several taxa showed significant positive or negative correlations with decreasing pH values.Our results are congruent with previous findings that reported compositional shifts from calcareous to agglutinated taxa with decreasing pH (both from culture and field observations). Our study also indicates that the activation of propagules is an important mechanism behind assemblage dynamics in shallow-water foraminifera. As such, it offers an improved insight into potential resilience and recovery mechanisms of foraminiferal assemblages with regard to local or seasonal pH variations as well as ongoing ocean acidification.

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Carbon and nitrogen budgets and respiration rates of selected foraminifera of the Gullmar Fjord in Sweden

10.5194/egusphere-egu21-12003 ◽

2021 ◽

Author(s):

Julia Wukovits ◽

Nicolaas Glock ◽

Johanna Nachbagauer ◽

Petra Heinz ◽

Wolfgang Wanek ◽

...

Keyword(s):

Benthic Foraminifera ◽

Environmental Changes ◽

Microscopy Imaging ◽

Test Volume ◽

Nitrogen Budgets ◽

Carbon And Nitrogen ◽

Respiration Rates ◽

Feeding Experiments ◽

Nitrogen Intake ◽

Oxygen Concentrations

Benthic foraminifera are highly abundant, ubiquitous&#160;marine protists, with many species feeding on microalgae or phytodetritus. Knowledge about carbon and nitrogen budgets and metabolic activities of benthic foraminifera can help to increase our understanding about their ecology and their role in aquatic biogeochemistry at the sediment-water interface. This can further increase their application as proxies for&#160;environmental changes. Shifts in the benthic foraminiferal communities of the Swedish Gullmars Fjord document the shift from well oxygenated bottom waters to seasonal hypoxia at its deepest location the Alsb&#228;ck Deep (125 m), during the last century.So far there are only investigations available relating foraminiferal community composition with increased primary productivity and resulting hypoxia in this Fjord. In contrast, studies about&#160;the species-specific feeding ecology or food derived foraminiferal carbon and nitrogen fluxes are scarce.Therefore, laboratory feeding experiments and respiration rate measurements were carried out with Bulimina marginata, Cassidulina laevigata&#160;and Globobulima turgida,&#160;abundant foraminifera in such environments, collected in August 2017.Experiments were conducted&#160;to evaluate the carbon and nitrogen intake and turnover of dual (13C and 15N) isotope labelled Phaeodactylum tricornutum&#160;detritus;&#160;detritus of a common diatom in the Gullmar Fjord. For the feeding experiments, foraminifera were incubated at 9.1&#176;C in the dark, in sterile filtered seawater at ambient oxygen concentrations. The foraminifera were fed for a period of 24 hours and subsequently incubated without food for&#160;another 24 hours. After each incubation cycle, foraminiferal respiration rates were measured. The individuals were analyzed via Elemental Analyzer-Isotope Ratio Mass Spectroscopy to evaluate 13C/12C and 15N/14N ratios and their bulk content of organic carbon and nitrogen.Additionally, we present carbon&#160;and nitrogen to volume ratios for the foraminifera B. marginata, C. laevigata, G. turgida, G. auriculata&#160;and Nonionella turgida,&#160;as derived from elemental analysis and light microscopy imaging.The results show, that B. marginata, an opportunistic species associated with high fluxes of organic matter, had the highest rate of specific carbon and nitrogen intake and turnover. Cassidulina laevigata,&#160;a species&#160;that co-occurs&#160;with fresh phytodetritus&#160;and&#160;does not tolerate very low oxygen concentrations, showed lower carbon and nitrogen intake rates. Globobulima turgida,&#160;a denitrifying infaunal species that thrives under hypoxia, showed the lowest specific carbon and nitrogen intake and turnover rates. Respiration rates of all species did not depend on incubation with or without a food source.&#160;The foraminifera showed similar carbon and nitrogen densities per test volume across all species.Overall this study helps to improve the knowledge on the nutritional ecology of the investigated species, demonstrating the close relation between feeding/metabolic rates and their environmental niche&#160;and highlighting the need to introduce foraminiferal data in future marine carbon and nitrogen flux models.

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Shift in biotic response of abyssal benthic foraminifera since MIS 7 in the eastern equatorial Pacific Ocean

Geosciences Journal ◽

10.1007/s12303-011-0031-y ◽

2011 ◽

Vol 15 (4) ◽

pp. 417-422 ◽

Cited By ~ 2

Author(s):

Hiroyuki Takata ◽

Boo-Keun Khim ◽

Chan Min Yoo ◽

Sang-Bum Chi

Keyword(s):

Pacific Ocean ◽

Benthic Foraminifera ◽

Equatorial Pacific ◽

Equatorial Pacific Ocean ◽

Biotic Response ◽

Eastern Equatorial Pacific ◽

Eastern Equatorial Pacific Ocean

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The impact of African aridity on the isotopic signature of Atlantic deep waters across the Middle Pleistocene Transition

Quaternary Research ◽

10.1016/j.yqres.2011.09.010 ◽

2012 ◽

Vol 77 (1) ◽

pp. 182-191 ◽

Cited By ~ 4

Author(s):

Bruno Malaizé ◽

Elsa Jullien ◽

Amandine Tisserand ◽

Charlotte Skonieczny ◽

E. Francis Grousset ◽

...

Keyword(s):

Deep Water ◽

Benthic Foraminifera ◽

Environmental Changes ◽

Phase Relationship ◽

Isotopic Signature ◽

Middle Pleistocene ◽

Time Interval ◽

Deep Waters ◽

Time Period ◽

The Impact

A high resolution analysis of benthic foraminifera as well as of aeolian terrigenous proxies extracted from a 37 m-long marine core located off the Mauritanian margin spanning the last ~ 1.2 Ma, documents the possible link between major continental environmental changes with a shift in the isotopic signature of deep waters around 1.0–0.9 Ma, within the so-called Mid-Pleistocene Transition (MPT) time period. The increase in the oxygen isotopic composition of deep waters, as seen through the benthic foraminifera δ18O values, is consistent with the growth of larger ice sheets known to have occurred during this transition. Deep-water mass δ13C changes, also estimated from benthic foraminifera, show a strong depletion for the same time interval. This drastic change in δ13C values is concomitant with a worldwide 0.3‰ decrease observed in the major deep oceanic waters for the MPT time period. The phase relationship between aeolian terrigeneous signal increase and this δ13C decrease in our record, as well as in other paleorecords, supports the hypothesis of a global aridification amongst others processes to explain the deep-water masses isotopic signature changes during the MPT. In any case, the isotopic shifts imply major changes in the end-member δ18O and δ13C values of deep waters.

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Abyssal benthic foraminifera in the eastern equatorial Pacific (IODP EXP 320) during the middle Eocene

Journal of Paleontology ◽

10.1666/12-107 ◽

2013 ◽

Vol 87 (6) ◽

pp. 1160-1185 ◽

Cited By ~ 5

Author(s):

Hiroyuki Takata ◽

Ritsuo Nomura ◽

Akira Tsujimoto ◽

Boo-Keun Khim ◽

Ik Kyo Chung

Keyword(s):

Water Depth ◽

Benthic Foraminifera ◽

Middle Eocene ◽

Accumulation Rate ◽

Equatorial Pacific ◽

Equatorial Pacific Ocean ◽

Ocean Drilling Program ◽

Integrated Ocean Drilling Program ◽

Eastern Equatorial Pacific ◽

Study Interval

We report on the faunal transition of benthic foraminifera during the middle Eocene at Site U1333 (4862 m water depth, 3,560–3,720 m paleo-water depth) of Integrated Ocean Drilling Program Expedition 320 in the eastern equatorial Pacific Ocean. During the period ∼41.5–40.7 Ma, which includes carbonate accumulation event 3 (CAE-3), the benthic foraminiferal accumulation rate (BFAR) increased gradually and then it declined rapidly. In contrast, BFAR was considerably lower during ∼40.7–39.4 Ma, corresponding to the middle Eocene climatic optimum (MECO), and then it increased during ∼39.3–38.4 Ma, including CAE-4. Diversity (E [S200]) was slightly lower in the upper part of the study interval than in the lower part. The most common benthic foraminifera were Nuttallides truempyi, Oridorsalis umbonatus, and Gyroidinoides spp. in association with Globocassidulina globosa and Cibicidoides grimsdalei during the period studied. Quadrimorphina profunda occurred abundantly with N. truempyi, O. umbonatus, and G. globosa during ∼39.4–38.4 Ma, including CAE-4, although this species was also relatively common in the lower part of the study interval. Virgulinopsis navarroanus and Fursenkoina sp. A, morphologically infaunal taxa, were common during ∼38.8–38.4 Ma, corresponding to the late stage of CAE-4. Based on Q-mode cluster analysis, four sample clusters were recognized and their stratigraphic distributions were generally discriminated in the lower and upper parts of the study interval. Thus, there was only a small faunal transition in the abyssal eastern equatorial Pacific during the middle to late-middle Eocene. The faunal transition recognized in this study may be related to recovery processes following intense carbonate corrosiveness in the eastern equatorial Pacific during MECO.

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