Morphological Properties of Gastropod Shells in a Warmer and More Acidic Future Ocean Using 3D Micro-Computed Tomography

Abstract

The increased absorption of atmospheric CO2 by the ocean reduces pH and affects the carbonate chemistry of seawater, thus interfering with the shell formation processes of marine calcifiers. The present study aims to examine the effects of ocean acidification and warming on the shell morphological properties of two intertidal gastropod species, Nassarius nitidus and Columbella rustica. The experimental treatments lasted for 3 months and combined a temperature increase of 3°C and a pH reduction of 0.3 units. The selected treatments reflected the high emissions (RCP 8.5) “business as usual” scenario of the Intergovernmental Panel on Climate Change models for eastern Mediterranean. The morphological and architectural properties of the shell, such as density, thickness and porosity were examined using 3D micro-computed tomography, which is a technique giving the advantage of calculating values for the total shell (not only at specific points) and at the same time leaving the shells intact. Nassarius nitidus had a lower shell density and thickness and a higher porosity when the pH was reduced at ambient temperature, but the combination of reduced pH and increased temperature did not have a noticeable effect in comparison to the control. The shell of Columbella rustica was less dense, thinner and more porous under acidic and warm conditions, but when the temperature was increased under ambient pH the shells were thicker and denser than the control. Under low pH and ambient temperature, shells showed no differences compared to the control. The vulnerability of calcareous shells to ocean acidification and warming appears to be variable among species. Plasticity of shell building organisms as an acclimation action toward a continuously changing marine environment needs to be further investigated focusing on species or shell region specific adaptation mechanisms.

Is Ocean Acidification Really a Threat to Marine Calcifiers? A Systematic Review and Meta‐Analysis of 980+ Studies Spanning Two Decades

“…From a structural perspective, calcareous shells or skeletons are made of hierarchically arranged CaCO 3 crystals embedded in organic matrix. [12,103] Acidified seawater is expected to dissolve and weaken these structures, rendering them more fragile due to the looser package of CaCO 3 crystals (i.e., lower density or higher porosity [104][105][106] ). Contrary to this expectation, structural integrity and mechanical strength of CaCO 3 minerals remain unchanged in some calcifiers inhabiting the natural CO 2 -acidified environment, [14,107,108] implying their adaptability to ocean acidification.…”

Oyster Reef Surfaces in the Central Wadden Sea: Intra-Reef Classification and Comprehensive Statistical Description

“…Influences of the micro-roughness scale on the hydraulic roughness development could be addressed in future research. Micro-computed tomography (Micro-CT) investigations of singular shells could be applied to resolve surfaces up to several µm (Chatzinikolaou et al, 2021;Keklikoglou et al, 2021). Despite this limitation, it is assumed that the provided topographical parameters represent the key factors that influence the hydraulic roughness.…”

Shark teeth can resist ocean acidification

“…increased elastic modulus). How warming led to these changes in mechanical properties of teeth remains unclear, but could be associated with the changes in porosity, organic matter content, microstructures, mineral arrangement or energy budget for biomineralization that deserve further investigations (Barclay et al, 2020; Chatzinikolaou et al, 2021; Di Santo, 2016, 2019; Gervais et al, 2021; Leung et al, 2020a, 2020b; Lübke et al, 2015; Marcus et al, 2017). Regardless of the underlying mechanisms, we found that the mechanical resilience of teeth increased when combined with ocean acidification (Temp vs. OA × Temp) due to the decrease in elastic modulus (i.e.…”