Response of Early Jurassic (Pliensbachian-Toarcian) benthic marine faunas from south-western Europe to temperature-related stresses (EvoBiv)
Final Report Abstract
We studied the faunal change of benthic marine macroinvertebrate assemblages across the early Toarcian warming/extinction event and the concomitant Toarcian Oceanic Anoxic Event (TOAE) in two fossiliferous sections of south-western Europe. We integrated faunal data with geological proxy data and applied physiological principles to explain the correlative links between abiotic environmental change and palaeoecological dynamics. Specifically, we tested the role of ocean warming as the proximate driver of faunal change. To this end, we used the oxygen isotope ratios of shells of brachiopods and oysters to establish a high-resolution temperature curve for the studied localities. One main focus was on changes in body size, where we expected a decrease in shell sizes as response to heat stress. For the Portuguese locality near Rabaçal, the mean shell size of brachiopod-bivalve communities decreased significantly before the TOAE. The underlying mechanism of size decrease were larger-sized brachiopod species becoming less abundant over time. We tentatively suggested that, at geologic time scales, a warming-induced decline in body size may serve as a precursor of imminent turnover at the community level, including local extirpations and biodiversity decrease – a hypothesis that needs further testing. In the Spanish section at Barranco de la Cañada, shell size of macrobenthic communities was overall smaller during the TOAE environmental crisis than before and afterwards. For the whole early Toarcian succession, we identified a significant negative correlation between the mean shell size of bivalve-brachiopod communities and of bivalve subcommunities with the oxygen isotope-derived temperature estimates. Again, a decline in the presence and abundance of larger-sized species, in this case bivalves, was the dominant mechanism of reduced community shell size during the TOAE. Likewise, these changes in the proportions of larger-sized bivalve species correlate negatively with temperature, supporting the interpretation that heat stress was a main cause of body size reduction. The second main focus concerned changes in the composition and ecological structure of benthic macroinvertebrate assemblages from pre-event background times, across the TOAE interval, and into post-event survival and recovery times. For the continuously fossiliferous succession at Barranco de la Cañada, we found that water temperature is significantly correlated with taxonomic and functional diversity and with shifts in ecological composition. Most ecological change occurred at the onset of the TOAE, synchronous with the increase in water temperatures, and involved declines in multiple diversity metrics, abundance, and biomass. Ecological instability during the TOAE is indicated by distinct oscillations in all diversity metrics and the relative abundance of individual modes of life, as well as the dominance by opportunistic species. Local recovery to ecologically stable and diverse post-TOAE faunal assemblages occurred rapidly at the end of the TOAE, synchronous with decreasing water temperatures. Because dysoxia–anoxia prevailed in many other regions during the TOAE, our studies suggest that multiple mechanisms can be operating simultaneously with different relative contributions in different parts of the ocean. Future studies will have to explore to which degree additional potential drivers such as ocean acidification and altered nutrient regimes may have influenced the observed faunal patterns. Considering the TOAE as a possible deep-time warming analog to assess the consequences of current and projected climate change for marine ecosystems is complicated by several uncertainties. Still, we tentatively consider the identified faunal changes across the TOAE hyperthermal – taxonomic and ecological reorganisations; declines in diversity, abundance, and biomass; long-term ecological instability with predominance of opportunistic species; and reductions in community size structure – to also be plausible threats to presentday shallow-water benthic communities.
Publications
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2017. Body size trends of brachiopods and bivalves at the early Toarcian (Early Jurassic) extinction event in the Lusitanian Basin, Portugal. – In: Reolid, M. (ed.). International Workshop on the Toarcian Oceanic Anoxic Event, IGCP-655: 87–89; Universidad de Jaén
Piazza, V., Aberhan, M. & Duarte, L.V.
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2017. Declines in the body size of benthic macroinvertebrates as a harbinger of the Early Toarcian (Early Jurassic) extinction event in the Lusitanian Basin, Portugal. – Geological Society of America Abstracts with Programs, vol. 49, no. 6
Aberhan, M., Piazza, V. & Duarte, L.V.
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2018. Ecological change within assemblages of brachiopods and molluscs across the Early Toarcian (Early Jurassic) extinction event in the Lusitanian Basin, Portugal. – Paleontolgía Mexicana Nùmero Especial 3, 10th International Congress on the Jurassic System: 3–4
Aberhan, M., Piazza, V. & Duarte, L.V.
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2018. Selectivity of temperature-related stresses towards brachiopods across the Early Toarcian (Early Jurassic) extinction event in Neo-Tethys. – Permophiles 66, Supplement 1, 8th International Brachiopod Congress, Abstract Volume: 87–88
Piazza, V. & Aberhan, M.
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2018. Trends in body size of brachiopods and bivalves across the early Toarcian (Early Jurassic) extinction event in the NW-Tethys. – In: Dunhill, A. et al. (eds.). Crossing the Palaeontological-Ecological Gap (CPEG), Abstracts: 11–12; Leeds
Piazza, V. & Aberhan, M.
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2019. Reductions in body size of benthic macroinvertebrates as a precursor of the Early Toarcian (Early Jurassic) extinction event in the Lusitanian Basin, Portugal. – Paleobiology 45: 296–316
Piazza, V., Duarte, L.V., Renaudie, J. & Aberhan, M.
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2020. Ocean warming affected faunal dynamics of benthic invertebrate assemblages across the Toarcian Oceanic Anoxic Event in the Iberian Basin (Spain). – PLoS ONE 15(12): e0242331
Piazza, V., Ullmann, C.V. & Aberhan, M.
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2020. Temperature-related body size change of marine benthic macroinvertebrates across the Early Toarcian Anoxic Event. – Scientific Reports 10: 4675
Piazza, V., Ullmann, C.V. & Aberhan, M.
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2020. Warm afterglow from the Toarcian Oceanic Anoxic Event drives the success of deep-adapted brachiopods. – Scientific Reports 10: 6549
Ullmann, C.V., Boyle, R., Duarte, L.V., Hesselbo, S.P., Kasemann, S., Klein, T., Lenton, T., Piazza, V. & Aberhan, M.
