Abstract
Understanding how marine taxa will respond to near-future climate changes is one of the main challenges for management of coastal ecosystem services. Ecological studies that investigate relationships between the environment and shell properties of commercially important marine species are commonly restricted to latitudinal gradients or small-scale laboratory experiments. This paper aimed to explore the variations in shell features and growth of the edible bivalve Chamelea gallina from the Holocene sedimentary succession to present-day thanatocoenosis of the Po Plain-Adriatic Sea system (Italy). Comparing the Holocene sub-fossil record to modern thanatocoenoses allowed obtaining an insight of shell variations dynamics on a millennial temporal scale. Five shoreface-related assemblages rich in C. gallina were considered: two from the Middle Holocene, when regional sea surface temperatures were higher than today, representing a possible analogue for the near-future global warming, one from the Late Holocene and two from the present-day. We investigated shell biometry and skeletal properties in relation to the valve length of C. gallina. Juveniles were found to be more porous than adults in all horizons. This suggested that C. gallina promoted an accelerated shell accretion with a higher porosity and lower density at the expense of mechanically fragile shells. A positive correlation between sea surface temperature and both micro-density and bulk density were found, with modern specimens being less dense, likely due to lower aragonite saturation state at lower temperature, which could ultimately increase the energetic costs of shell formation. Since no variation was observed in shell CaCO3 polymorphism (100% aragonite) or in compositional parameters among the analyzed horizons, the observed dynamics in skeletal parameters are likely not driven by a diagenetic recrystallization of the shell mineral phase. This study contributes to understand the response of C. gallina to climate-driven environmental shifts and offers insights for assessing anthropogenic impacts on this economic relevant species.
Highlights
Evaluating how marine ecosystems could respond to near-future global warming is critical to design proper conservation and management strategies, especially in coastal areas with increasing urbanization and resource overexploitation.In the marine realm, calcifying macroinvertebrates such as corals, brachiopods and mollusks produce hard structures for support and protection that constitute high-resolution archives recording the environmental conditions that have prevailed during their life [1, 2]
This study aimed to investigate the variations in skeletal features of C. gallina assemblages during the last 8000 years from shoreface deposits and active shoreface settings of the Po-Adriatic system (Italy)
According to the data reported for the Gulf of Lion, estimated and measured Sea surface temperature (SST) appeared to cool down gradually moving from the oldest horizon (CO1, 18.6 ̊C) to nowadays setting (MCE, 17.3 and MGO, 17.2 ̊C) (Kruskal-Wallis test, df = 4, p < 0.001; Table 1)
Summary
Evaluating how marine ecosystems could respond to near-future global warming is critical to design proper conservation and management strategies, especially in coastal areas with increasing urbanization and resource overexploitation.In the marine realm, calcifying macroinvertebrates such as corals, brachiopods and mollusks produce hard structures for support and protection that constitute high-resolution archives recording the environmental conditions that have prevailed during their life [1, 2]. Through the control exerted by intraskeletal macromolecules, mollusks can exert imprints on calcium carbonate biomineralization [3], influencing the polymorphism, morphology and chemistry of the shell in response to environmental changes [4,5,6] Those biogenic structures can be useful tools to reconstruct the historical effects of climate change on marine organisms, allowing a better understanding of near-future dynamics. Quantifying the effect of near future climate change on marine calcifying organisms requires long-term multi-generational studies for assessing their adaptability to changing environmental conditions [7]. A complementary approach is to investigate the recent fossil record This line of research gives access to an archive of ecological responses to past climate transitions that could elucidate near-future scenarios of marine ecosystems under global warming [9, 10]
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