Abstract. The Mediterranean Sea sustains a rich and fragile ecosystem currently threatened by multiple anthropogenic impacts that include, among others, warming, pollution, and changes in seawater carbonate speciation associated to increasing uptake of atmospheric CO2. This environmental change represents a major risk for marine calcifiers such as planktonic foraminifera, key components of pelagic Mediterranean ecosystems and major exporters of calcium carbonate to the sea floor, thereby playing a major role in the marine carbon cycle. In this study, we investigate the response of planktic foraminifera calcification in the northwestern Mediterranean Sea on different timescales across the industrial era. This study is based on data from a 12-year-long sediment trap record retrieved in the in the Gulf of Lions and seabed sediment samples from the Gulf of Lions and the promontory of Menorca. Three different planktic foraminifera species were selected based on their different ecology and abundance: Globigerina bulloides, Neogloboquadrina incompta, and Globorotalia truncatulinoides. A total of 273 samples were weighted in both sediment trap and seabed samples. The results of our study suggest substantial different seasonal calcification patterns across species: G. bulloides shows a slight calcification increase during the high productivity period, while both N. incompta and G. truncatulinoides display a higher calcification during the low productivity period. The comparison of these patterns with environmental parameters indicate that controls on seasonal calcification are species-specific. Interannual analysis suggests that both G. bulloides and N. incompta did not significantly reduce their calcification between 1994 and 2005, while G. truncatulinoides exhibited a constant and pronounced increase in its calcification that translated in an increase of 20 % of its shell weight. The comparison of these patterns with environmental data reveals that optimum growth conditions affect positively and negatively G. bulloides and G. truncatulinoides calcification, respectively. Sea surface temperatures (SSTs) have a positive influence on N. incompta and G. truncatulinoides calcification, while carbonate system parameters appear to affect positively the calcification of three species in the Gulf of Lions throughout the 12-year time series. Finally, comparison between sediment trap data and seabed sediments allowed us to assess the changes of planktic foraminifera calcification during the late Holocene, including the pre-industrial era. Several lines of evidence indicate that selective dissolution did not bias the results in any of our data sets. Our results showed a weight reduction between pre-industrial and post-industrial Holocene and recent data, with G. truncatulinoides experiencing the largest weight loss (32 %–40 %) followed by G. bulloides (18 %–24 %) and N. incompta (9 %–18 %). Overall, our results provide evidence of a decrease in planktic foraminifera calcification in the western Mediterranean, most likely associated with ongoing ocean acidification and regional SST trends, a feature consistent with previous observations in other settings of the world's oceans.

Los microfósiles son una herramienta excepcional para hacer reconstrucciones climáticas y oceanográficas en sedimentos marinos debido a su alta abundancia, y a que muchos grupos permiten hacer estudios geoquímicos, especialmente los que presentan conchas de carbonato cálcico. En particular, las asociaciones de foraminíferos planctónicos han sido ampliamente utilizadas en ese sentido, ya que en el océano actual la distribución de las diferentes especies está íntimamente ligada a las condiciones climáticas y oceanográficas. La rápida respuesta de este grupo de microorganismos a los cambios climáticos nos permite utilizarlos para identificar eventos climáticos en un registro sedimentario y asociar esos eventos a sus equivalentes en registros de referencia bien datados. Esta práctica se conoce como eventoestratigrafía y nos permite obtener dataciones precisas y que pueden llegar a tener una resolución muy alta, por ejemplo, cuando se compara con los registros de los testigos de hielo de Groenlandia. Además, los análisis geoquímicos realizados en conchas de foraminíferos, como los isótopos de oxígeno (δ18O), también nos sirven para realizar eventoestratigrafía a diferentes escalas temporales. En este artículo, mostramos varios ejemplos de cómo se ha reconstruido el marco cronológico en secuencias sedimentarias marinas cercanas a la península ibérica a partir de abundancias relativas de foraminíferos planctónicos, paleotemperatura, o δ18O comparando los eventos climáticos del testigo de sedimento marino con los de un registro de referencia.

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<p>IODP Site U1389 recovered a thick contouritic drift sequence deposited on the main branch of the Mediterranean Overflow Water in the gulf of Cadiz. That allows high resolution core recoveries for Quaternary period. In this study a high-resolution SST record was obtained by modern analogues method, using planktic foraminifer assemblages and Artificial Neural Networks. Seawater oxygen isotope composition was inferred by using the <em>Globigerina bulloides</em> δ<sup>18</sup>O record and the new SST data.</p><p>During MIS-3 the average amplitude of the SST change between Greenland stadials and interstadials is in the order of 2 to 4 °C. Foraminifer taxa that best reflects these minor changes is <em>Globigeririnita glutinata</em>. Heinrich stadial periods are represented by abrupt SST drops of about 8 °C compared to Interstadial values, and high abundance of polar and subpolar species <em>Neogloboquadrina pachyderma</em> <em>sin </em>and <em>Turborotalita quinqueloba</em>. During MIS-2 and MIS-4, SST is higher than expected for glacial maxima, with some subtropical species occurrence except in Heinrich events. Seawater δ<sup>18</sup>O also shows millennial variability, with higher values during Greenland Interstadials and the most pronounced drops or freshening in Heinrich stadial events. During glacial maxima stadials δ<sup>18</sup>O reaches its highest values, that reflects together with the high SST potential subtropical influence.</p><p>SST and seawater δ<sup>18</sup>O changes along the record precisely reflect the impact of the Greenland stadial-interstadial events and Heinrich events on sea surface conditions. Minor event Heinrich 2.2 (2b) has been identified by SST drop but not by water freshening. Otherwise, Greenland stadial 15, which corresponds to C-14 IRD event in North Atlantic shows Heinrich-like behavior according to both sea surface proxies.</p>

Abstract. The aim of this work is to investigate the variability of planktic foraminifera calcification in the northwestern Mediterranean Sea on seasonal, interannual and pre-industrial Holocene time scales. This study is based on data from a 12-year-long sediment trap record retrieved in the in the Gulf of Lions and seabed sediment samples from the Gulf of Lions and the promontory of Menorca. Three different planktic foraminifera species were selected based on their different ecology and abundance: Globigerina bulloides, Neogloboquadrina incompta, and Globorotalia truncatulinoides. A total of 273 samples were weighted in both sediment trap and seabed samples. As the traditionally used sieve fractions method is considered unreliable because of the effect of morphometric parameters on the foraminifera weight, we measured area and diameter to constrain the effect of these parameters. The results of our study show substantial different seasonal calcification patterns across species: G. bulloides showed a slight calcification increase during the high productivity period, while both N. incompta and G. truncatulinoides display a higher calcification during the low productivity period. The comparison of these patterns with environmental parameters revealed that Optimum Growth Conditions temperature and carbonate system parameters are the most likely to influence seasonal calcification in the Gulf of Lions. Interannual analysis suggest that both G. bulloides and N. incompta slightly reduced their calcification between 1994 and 2005, while G. truncatulinoides exhibited a constant and pronounced increase in its calcification that translated in an increase of 20 % of its shell weight for the 400–500 µm narrow size class. While our data suggest that carbonate system parameters are the most likely environmental parameter driving foraminifera calcification changes over the years. Finally, comparison between sediment trap data and seabed sediments allowed us to assess the changes of planktic foraminifera calcification during the late Holocene, including the preindustrial era. Several lines of evidence strongly indicate that selective dissolution did not bias the results in any of our data sets. Our results showed a clear calcification reduction between pre-industrial Holocene and recent data with G. truncatulinoides experiencing the largest calcification decrease (32–40 %) followed by N. incompta (20–27 %) and G. bulloides (18–24 %). Overall, our results provide evidence of clear reduction in planktic foraminifera calcification in the Mediterranean most likely associated with ongoing ocean acidification and consistent with previous observations in other settings of the world’s oceans.