Episodes of intensified biological productivity in the subtropical Atlantic Ocean during the termination of the Middle Eocene Climatic Optimum (MECO)

Abstract

The Middle Eocene Climatic Optimum (MECO) is an~500 kyr interval of pronounced global warming from which the climate system recovered in <50 kyr. The deep-sea sedimentary record can provide valuable insight on the marine ecosystem response to this protracted global warming event and consequently on the ecological changes during this time. Here we present new benthic foraminiferal assemblage data from Ocean Drilling Program Site 1051 in the subtropical North Atlantic, spanning the MECO and post-MECO interval (41.1 to 39.5 Ma). We find little change in the species composition of benthic foraminiferal assemblages during the studied interval, suggesting that the rate of environmental change was gradual enough that these organisms were able to adapt. However, we identify two transient intervals associated with peak warming (higher-productivity interval (HPI)-1; 40.07-39.96 Ma) and shortly after the MECO (HPI-2; 39.68-39.55 Ma), where benthic foraminiferal accumulation rates increase by an order of magnitude. These HPIs at Site 1051 appear to coincide with intervals of strengthened productivity in the Tethys, Southern Ocean, and South Atlantic, and we suggest that an intensified hydrological cycle during the climatic warmth of the MECO was responsible for eutrophication of marine shelf and slope environments.

Did Photosymbiont Bleaching Lead to the Demise of Planktic Foraminifer Morozovella at the Early Eocene Climatic Optimum?

“…Surface‐water eutrophy during the EECO at the studied site seems also supported by the early Eocene calcareous nannofossil assemblages that were dominated by Coccolithus pelagicus (Mita, ), a taxon with affinities to warm and eutrophic surface waters (e.g., Agnini et al, , , ; Dedert et al, ; Fornaciari et al, ; Newsam et al, ; Perch‐Nielsen, ; Tremolada & Bralower, ). Interestingly, high‐productivity intervals characterized by increased in siliceous plankton were recorded at Site 1051 (Moebius et al, ; Witkowski et al, ) at the peak of Middle Eocene Climatic Optimum, a longer‐lived warming event of ~500 kyr that occurred at ~40 Ma (e.g., Bohaty & Zachos, ; Bohaty et al, ). The eutrophication in the slope of the adjacent North American continental margin has been considered as triggered by intensified hydrological cycle during the climatic warmth of the Middle Eocene Climatic Optimum, leading to an increase in riverine input into the ocean (Moebius et al, ; Witkowski et al, ).…”

“…Interestingly, high-productivity intervals characterized by increased in siliceous plankton were recorded at Site 1051 (Moebius et al, 2015;Witkowski et al, 2014) at the peak of Middle Eocene Climatic Optimum, a longer-lived warming event of~500 kyr that occurred at~40 Ma (e.g., Bohaty & Zachos, 2003;Bohaty et al, 2009). The eutrophication in the slope of the adjacent North American continental margin has been considered as triggered by intensified hydrological cycle during the climatic warmth of the Middle Eocene Climatic Optimum, leading to an increase in riverine input into the ocean (Moebius et al, 2015;Witkowski et al, 2014). We can speculate that also the intense warming at the EECO may have lead to similar conditions at Site 1051.…”

X Conferencias y Seminarios del Doctorado en Geología

“…Records from a number of sites and sections, studied in different ocean basins and at different latitudes support this hypothesis (Boscolo-Galazzo et al 2013Moebius et al 2014Moebius et al , 2015Rivero-Cuesta et al 2018). Despite its comparable magnitude, the longer duration of MECO warming phase (ca.…”

“…This mechanism continued after peak conditions, leading to the deposition of organic rich layers and eventually hypoxic conditions. (Moebius et al, 2015) is located in the NW Atlantic (Blake Nose), and its estimated depositional setting lies between 1000 to 2000 m paleodepth. Similar to Site 1263, it corresponds to an open ocean (pelagic) environment and its benthic foraminiferal response to the MECO event is also similar to that at Site 1263: largely unchanged faunal composition.…”

“…Despite its comparable magnitude, the longer duration of MECO warming phase (ca. 500 kyr) could have been the key difference with the PETM, being slow enough to allow adaptation of the benthic fauna (Moebius et al, 2015).…”