22 Aug 2022
22 Aug 2022
Status: this preprint is open for discussion.

Calcification response of planktic foraminifera to environmental change in the Western Mediterranean Sea during the industrial era

Thibauld M. Béjard1, Andrés S. Rigual-Hernández1, José A. Flores1, Javier P. Tarruella1, Xavier Durrieu de Madron2, Isabel Cacho3, Neghar Haghipour4, Timothy Eglinton4, and Francisco J. Sierro1 Thibauld M. Béjard et al.
  • 1Área de Paleontología, Departamento de Geología, Universidad de Salamanca, 37008 Salamanca, Spain
  • 2Université de Perpignan Via Domitia, CNRS, CEFREM, Perpignan, France
  • 3GRC Geociè ncies Marines, Departament de Dinà mica de la Terra i de l’Oceà , Facultat de Ciè ncies de la Terra, Universitat de Barcelona, Barcelona, Spain
  • 4Earth Sciences Department, ETH Zurich, Zurich, 8092, Switzerland

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.

Thibauld M. Béjard et al.

Status: open (until 19 Oct 2022)

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  • RC1: 'Comment on egusphere-2022-711', Anonymous Referee #1, 24 Aug 2022 reply

Thibauld M. Béjard et al.

Thibauld M. Béjard et al.


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Short summary
The Mediterranean Sea is undergoing a rapid and unprecedented environmental change. Planktic foraminifera calcification is affected on different time scales. On seasonal and interannual scales, calcification trends differ according to the species and are linked mainly to Sea Surface Temperatures and carbonate system parameters; while comparison with pre-industrial assemblages shows that all 3 species have reduced their calcification between 20 to 35 % according to the species.