Unexpected increase in structural integrity caused by thermally induced dwarfism in large benthic foraminifera.

Climate change is predicted to negatively impact calcification and change the structural integrity of biogenic carbonates, influencing their protective function. We assess the impacts of warming on the morphology and crystallography of Amphistegina lobifera, an abundant benthic foraminifera species in shallow environments. Specimens from a thermally disturbed field area, mimicking future warming, are about 50% smaller compared with a control location. Differences in the position of the ν1 Raman mode of shells between the sites, which serves as a proxy for Mg content and calcification temperature, indicate that calcification is negatively impacted when temperatures are below the thermal range facilitating calcification. To test the impact of thermal stress on the Young's modulus of calcite which contributes to structural integrity, we quantify elasticity changes in large benthic foraminifera by applying atomic force microscopy to a different genus, Operculina ammonoides, cultured under optimal and high temperatures. Building on these observations of size and the sensitivity analysis for temperature-induced change in elasticity, we used finite element analysis to show that structural integrity is increased with reduced size and is largely insensitive to calcite elasticity. Our results indicate that warming-induced dwarfism creates shells that are more resistant to fracture because they are smaller.

Using Museum collections to assess the impact of industrialization on mussel (Mytilus edulis) calcification.

Mytilus edulis is a commercially and ecologically important species found along the east coast of the United States. Ecologically, M. edulis improves water quality through filtration feeding and provides habitat formation and coastal protection through reef formation. Like many marine calcifiers, ocean warming, and acidification are a growing threat to these organisms-impacting their morphology and function. Museum collections are useful in assessing long-term environmental impacts on organisms in a natural multi-stressor environment, where acclimation and adaptation can be considered. Using the American Museum of Natural History collections ranging from the early 1900s until now, we show that shell porosity changes through time. Shells collected today are significantly more porous than shells collected in the 1960s and, at some sites, than shells collected from the early 1900s. The disparity between porosity changes matches well with the warming that occurred over the last 130 years in the north Atlantic suggesting that warming is causing porosity changes. However, more work is required to discern local environmental impacts and to fully identify porosity drivers. Since, porosity is known to affect structural integrity, porosity increasing through time could have negative consequences for mussel reef structural integrity and hence habitat formation and storm defenses.

Environmental impacts on the structural integrity of British rhodoliths.

Coralline algae form complex habitats which are biodiversity hotspots. Experimental studies suggest that climate change will decrease coralline algal structural integrity. These experiments, however, lack information on local morphological variability and how much structural change would be needed to threaten habitat formation. Here, using finite element modelling, we assess variability in cellular structure and chemical composition of the carbonate skeleton of four coralline algal species from Britain in contemporary and historical specimens collected over the last 130 years. Cellular and mineral properties are highly variable within species, between sites and through time, with structurally weaker cells in the southern species and contemporary material compared to northern taxa and historical material. Yet, temporal differences in strength were smaller than spatial differences. Our work supports long term experiments which show the adaptation potential of this group. Our results suggest that future anthropogenic climate change may lead to loss of habitat complexity in the south and expansion of structurally weaker southern species into northern sites.

Selective chemical degradation of silica sinters of the Taupo Volcanic Zone (New Zealand). Implications for early Earth and Astrobiology.

Most organic matter (OM) on Earth occurs as kerogen-like materials, that is naturally formed macromolecules insoluble with standard organic solvents. The formation of this insoluble organic matter (IOM) is a topic of much interest, especially when it limits the detection of compounds of geomicrobiological interest. For example, studies that search for biomarker evidence of life on early Earth or other planets usually use solvent-based extractions. This leaves behind a pool of OM as unexplored post-extraction residues, potentially containing diagnostic biomarkers. Since the IOM has an enhanced potential for preservation compared to soluble OM, analysing IOM-released biomarkers can also provide even deeper insights into the ecology of ancient settings, with implications for early Earth and Astrobiology investigations. Here, we analyse the prokaryotic lipid biosignature within soluble and IOM of the Taupo Volcanic Zone (TVZ) silica sinters, which are key analogues in the search for life. We apply sequential solvent extractions and a selective chemical degradation upon the post-solvent extraction residue. Moreover, we compare the IOM from TVZ sinters to analogous studies on peat and marine sediments to assess patterns in OM insolubilisation across the geosphere. Consistent with previous work, we find significant but variable proportions-1%-45% of the total prokaryotic lipids recovered-associated with IOM fractions. This occurs even in recently formed silica sinters, likely indicating inherent cell insolubility. Moreover, archaeal lipids seem more prone to insolubilisation as compared to the bacterial analogues, which might enhance their preservation and also bias overall biomarkers interpretation. These observations are similar to those observed in other settings, confirming that even in a setting where the OM derives predominantly from prokaryotic sources, patterns of IOM formation/occurrence are conserved. Differences with other settings, however, such as the occurrence of archaeol in IOM fractions, could be indicative of different mechanisms for IOM formation that merit further exploration.