New palynological, sedimentological, and geochemical records spanning the Middle Eocene climatic optimum (MECO; ca. 40 Ma) in the equatorial Atlantic Ocean indicate that peak warming was associated with upper-ocean stratification, decreased export production, and possibly harmful algal blooms, followed by slight oxygen minimum zone expansion. Combining these findings with published MECO records suggests that export production collapse and benthos starvation during the zenith of MECO warmth were widespread in the Atlantic. Furthermore, comparison to records across the Paleocene-Eocene thermal maximum (ca. 56 Ma) at the same site suggests a similar system response to warming, but with different impact on benthic communities.

Supplement to: Cramwinckel, Margot J; Van der Ploeg, Robin; Bijl, Peter K; Peterse, Francien; Bohaty, Steven M; Röhl, Ursula; Schouten, Stefan; Middelburg, Jack J; Sluijs, Appy (2019): Harmful algae and export production collapse in the equatorial Atlantic during the zenith of Middle Eocene Climatic Optimum warmth. Geology, 47(3), 247-250