Abstract

Anthropogenic CO2 is a major driver of change in most marine ecosystems, as the consequent ocean acidification is threatening marine calcifying organisms. In this respect, long-term analyses on ocean acidification effects on marine ecosystems acclimated to high pCO₂, as found around CO₂ vents, are needed. Here we tackle mollusk assemblages from acidified shallow marine settings off the Aeolian archipelago (Central Mediterranean). The detected gradient manifests along a 34 m long transect (9.6 m and 11.4 m water depth), mostly in a Posidonia oceanica matte from normal (site 1) to high levels (site 3) of pCO₂ (405 μatm, pH 8.1 and 715 μatm, pH 7.8; respectively). The strongest acidified condition at the vent crater (site 4, pCO₂ 1110 μatm, pH 7.7). At the vent site gaseous emissions are characterized by ~99% in volume of CO₂ and ~0.6% of H₂S. However, water dissolved H₂S was below detection limit and the sulphate content along the transect does not show significant variations with respect to normal seawater values. Preliminary paleoecologic surveys on diversity structure (diversity profiles) and taphonomic degradation (NMDS, z scored % values) were conducted on mollusk remains collected along the natural pH gradient (sites 1-4). Along the P. oceanica matte (sites 1-3), overall mollusk taxon diversity (alpha and beta) decreased, mollusk in site 3 were mostly juveniles and had higher overall taphonomic damages than those retrieved at normal pH conditions. Within the vent crater only fewer and highly taphonomically altered gastropod specimens were retrieved on the pebbly seafloor, suggesting a very short residence time of shell material and rapid dissolution. Even if vents are not exact predictors of the anthropogenic-designed future of marine settings, due to their limited spatial and temporal extent, they can act as natural laboratories where to evaluate the output of ecosystem processes under rising pCO₂ and the effects on the creation of the future fossil record.

Keywords: mollusk, conservation paleobiology, taphonomy, ocean acidification, Tyrrhenian Sea

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Scarponi, D. A. Mancuso, S. Goffredo, and M. Kowalewski, 2023. Mollusk response under ocean acidification in shallow marine settings of Sicily (Central Mediterranean). In: Abstracts of the 2^nd Conservation Paleobiology Symposium. Bulletin of the Florida Museum of Natural History 60(2):113. https://doi.org/10.58782/flmnh.tbsm5836