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Abstract: A global foraminiferal model was used to determine the seasonal imprint of planktonic foraminifera on the sedimentary record. The model provides monthly concentrations of five planktonic foraminiferal species used in paleoceanographic reconstructions including N. pachyderma (sin. and dex.), G. bulloides, G. ruber (white) and G. sacculifer. The temperature imprint in foraminiferal shells varies according to the season of calcification, and the sedimentary records retain this seasonal imprint. Proxy records for a species will therefore be weighted towards the values during the season of maximum production for that species. Our model prediction reveals that, in general, at high latitudes, close to the geographical limit of occurrence of each species, the signal is biased towards summer conditions. In contrast, at lower latitudes the signal is biased towards winter or annual mean conditions. Temperatures derived from G. ruber (white) and G. sacculifer are most suitable for estimating annual mean SST in tropical waters, between 20° N/S, while G. ruber (white) when collected at mid-latitudes, near to 40° latitude, reflects mainly summer conditions. We carried out sensitivity experiments to study the response of planktonic foraminiferal seasonality to changes in temperature. We forced the model decreasing the temperature globally by 2 °C and 6 °C. In most of the regions, due to the cooling, the season of maximum production shifted to a warmer season. Thus, the annual species population recorded little change in the temperature. In tropical waters, where temperature seasonality is low, foraminiferal population recorded the entire temperature variation. These findings highlight the importance of considering changes in seasonality through time, specially for temperature reconstructions based on monospecific samples, such as those derived from planktonic foraminiferal isotopic and trace element composition. [Copyright &y& Elsevier]

We present a multi-year record of shell fluxes and δ 18 O of six planktonic foraminifera species ( Globigerinoides ruber pink, Globigerinoides ruber white, Trilobatus sacculifer , Orbulina universa , Neogloboquadrina dutertrei , Globorotalia menardii ) from sediment traps located in the southwestern Atlantic. Among the six species, only the fluxes of G. ruber white and N. dutertrei exhibit a significant seasonal component, with G. ruber white showing a single flux peak in austral summer, and N. dutertrei exhibiting two flux peaks in spring and autumn. To estimate calcification depths of the studied species, we then compare their measured δ 18 O to vertical δ 18 O profiles predicted for each collection time from in-situ temperature profiles and climatological salinity profiles. For the majority of the cases, the measured δ 18 O could be accounted for by in-situ calcification, assuming species-specific temperature-δ 18 O calibrations. The resulting estimates of the calcification depth imply that each species exhibits a characteristic typical mean calcification depth. The estimated calcification depths for N. dutertrei (mode 60–70 m) and G. menardii (mode 70–80 m) appear to track the depth of the thermocline in the region, whereas the calcification depths of the remaining four species correspond to conditions in the mixed layer. Among the apparent mixed-layer calcifiers, G. ruber pink and white appeared to calcify consistently shallower (mode 30–40 m) while T. sacculifer calcified deeper (mode 50–60 m). Because of the low flux seasonality, the observed oxygen isotope offsets among the species are similar to the flux-weighted mean annual δ 18 O offsets, indicating that isotopic offsets among the species in sediment samples are mainly due to different calcification depths. Since the habitat offsets among the species are consistent across seasons, δ 18 O in sedimentary shells can be used to track conditions in different parts of the water column and the difference in the oxygen-isotope composition between surface species (best represented by G. ruber pink) and thermocline species (best represented by N. dutertrei ) can be used as a proxy for stratification in the southwestern Atlantic. [ABSTRACT FROM AUTHOR]