Major perturbations in the global carbon cycle and photosymbiont-bearing planktic foraminifera during the early Eocene

Abstract

Abstract. A marked switch in the abundance of the planktic foraminiferal genera Morozovella and Acarinina occurred at low-latitude sites near the start of the Early Eocene Climatic Optimum (EECO), a multi-million-year interval when Earth surface temperatures reached their Cenozoic maximum. Stable carbon and oxygen isotope data of bulk sediment are presented from across the EECO at two locations: Possagno in northeast Italy and Deep Sea Drilling Project (DSDP) Site 577 in the northwest Pacific. Relative abundances of planktic foraminifera are presented from these two locations, as well as from Ocean Drilling Program (ODP) Site 1051 in the northwest Atlantic. All three sections have good stratigraphic markers, and the δ13C records at each section can be correlated amongst each other and to δ13C records at other locations across the globe. These records show that a series of negative carbon isotope excursions (CIEs) occurred before, during and across the EECO, which is defined here as the interval between the J event and the base of Discoaster sublodoensis. Significant though ephemeral modifications in planktic foraminiferal assemblages coincide with some of the short-term CIEs, which were marked by increases in the relative abundance of Acarinina, similar to what happened across established hyperthermal events in Tethyan settings prior to the EECO. Most crucially, a temporal link exists between the onset of the EECO, carbon cycle changes during this time and the decline in Morozovella. Possible causes are manifold and may include temperature effects on photosymbiont-bearing planktic foraminifera and changes in ocean chemistry.

Did Photosymbiont Bleaching Lead to the Demise of Planktic ForaminiferMorozovellaat the Early Eocene Climatic Optimum?

“…The symbiont‐bearing mixed‐layer genera Morozovella and Acarinina were among the most important calcifiers of early Paleogene tropical and subtropical oceans (e.g., Aze et al, ; Boersma et al, ; Pearson et al, ; Premoli Silva & Boersma, ). At multiple low‐latitude sites (Figure ), a remarkable and permanent switch in their abundance occurred close to the start of the Early Eocene Climatic Optimum (EECO; Luciani et al, ). Specifically, Morozovella abundances decreased significantly while Acarinina abundances almost doubled (Luciani et al, ).…”

“…At multiple low‐latitude sites (Figure ), a remarkable and permanent switch in their abundance occurred close to the start of the Early Eocene Climatic Optimum (EECO; Luciani et al, ). Specifically, Morozovella abundances decreased significantly while Acarinina abundances almost doubled (Luciani et al, ). This major turnover further relates to taxonomic diversity, consisting of species reduction among Morozovella and species diversification among Acarinina (Aze et al, ; Pearson et al, ).…”

“…This turnover occurred also in the temperate Southern Hemisphere setting of Atlantic Site 1263 (Luciani et al, ). The timing of the Morozovella–Acarinina switch is interesting because the EECO (~49–53 Ma; Lauretano et al, ; Luciani et al, ; Slotnick et al, , ) represents the interval of peak sustained Cenozoic warmth (Bijl et al, ; Hollis et al, ; Huber & Caballero, ; Inglis et al, ; Pross et al, ; Zachos et al, ). Consequently, the turnover might somehow relate to the onset of prolonged conditions of elevated temperature and significant change in carbon cycling.…”

Environmental stress in the northern Tethys during the Paleogene: a review of foraminiferal and geochemical records from the Polish Outer Carpathians

“…1). Af ter this cli ma tic op ti mum, short-term warm ing events oc curred un til the end of the Eocene (Bohaty and Zachos, 2003;Röhl et al, 2005;Thomas et al, 2006;Luciani et al, 2016). Futher cli mate change oc curred close the Eocene/Oligocene bound ary.…”

“…The dis tri bu tion of these or gan isms is de ter mined by ox y gen and food avail abil i ties (Gooday, 1990;Kuhnt et al, 1996;Stigter et al, 1998;Heinz et al, 2001;Thomas, 2009, 2013;Arreguín-Rodríguez et al, 2013). The ex tinc tion of spe cial ized forms with mas sive and or na mented tests, which be long to k-strat e gists, and the appear ance of low-ox y gen and acid i fi ca tion tol er ant dwarf r-strat egists can be iden ti fied as an ex am ple of adap tive ra di a tion as soci ated with dras tic eco log i cal changes that took place close to the Maastrichtian-Paleocene, Paleo cene-Eocene and EoceneOligo cene bound aries (MacLeod, 1993;Luciani et al, 2016). At the end of the Paleocene (~57 Ma), changes in hy dro ther mal activ ity and cir cu la tion in bot tom wa ters and at mo sphere, ac compa nied by global warm ing (green house ef fect), led to per tur bations in ma rine en vi ron ments that re sulted in global an oxia (Rea et al, 1990;Ken nett and Stott, 1991;Stott, 1992;Speijer et al, 1997;Bains et al, 2000;Fig.…”