Calcium carbonate composition and other measures of vulnerability of the skeletons and shells of echinoderms and gastropods challenged by ocean acidification or climate warming

Marine invertebrate calcium carbonate (CaCO3) composition will likely be impacted by climate warming and ocean acidification (OA). Elevated temperature alters physiological processes that can induce stress, and OA alters the ability of calcareous marine invertebrates to maintain acid-base balances, calcify, and repair skeletal dissolution. The first of three chapters of this dissertation exploits a natural CO2 seep to evaluate impacts of chronic exposure to OA on the shells of four gastropods: the limpets Patella caerulea and P. rustica, top-shell snail Osilinus turbinatus, and whelk Hexaplex trunculus. All four gastropods experienced shell dissolution to various degrees and reduced shell integrity as pH decreased. The limpet P. rustica demonstrated altered CaCO3 composition of the shell with reduced pH, and there was evidence of altered shell microstructure in both limpets. The second chapter documents the variability of CaCO3 composition of skeletal components of high latitude Antarctic echinoderms to further evaluate the hypothesis that skeletal magnesium content is inversely correlated with latitude in the Echinodermata. Significant inverse correlations were observed in echinoderms collected between 62° and 76°S, but not when the correlation analysis was restricted to those collected south of 70°S where seawater temperature is comparatively constant. This suggests that temperature may be an important factor driving this global relationship in echinoderms. This also suggests that climate warming may lead to increasing levels of magnesium in skeletal components, rendering them more susceptible to dissolution under conditions of OA. The third chapter examines variability of the CaCO3 composition of skeletal components of the model sea urchin Lytechinus variegatus exposed to ambient and near-future seawater temperature. Over the 90-day experiment, there was no increase in skeletal magnesium content in the test, spines, or Aristotle’s lantern in the elevated temperature treatment. This result was likely related to thermal stress and individuals allocating their resources elsewhere. It appears that elevated temperatures may not alter CaCO3 composition or impact skeletal solubility in L. variegatus as OA intensifies. The mineralogy of gastropods and echinoderms investigated herein exemplifies the variable nature of susceptibility to OA and the difficulty of predicting impacts of climate change without a focus at the species level.

Duquette A., 2016. Calcium carbonate composition and other measures of vulnerability of the skeletons and shells of echinoderms and gastropods challenged by ocean acidification or climate warming. Ph.D thesis, The University of Alabama at Birmingham, 140 p. Thesis (restricted access).

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