Dissolution: The Achilles’ Heel of the Triton Shell in an Acidifying Ocean

Abstract

Ocean acidification is expected to negatively impact many calcifying marine organisms by impairing their ability to build their protective shells and skeletons, and by causing dissolution and erosion. Here we investigated the large predatory "triton shell" gastropod Charonia lampas in acidified conditions near CO 2 seeps off Shikine-jima (Japan) and compared them with individuals from an adjacent bay with seawater pH at present-day levels (outside the influence of the CO 2 seep). By using computed tomography we show that acidification negatively impacts their thickness, density, and shell structure, causing visible deterioration to the shell surface. Periods of aragonite undersaturation caused the loss of the apex region and exposing body tissues. While gross calcification rates were likely reduced near CO 2 seeps, the corrosive effects of acidification were far more pronounced around the oldest parts of the shell. As a result, the capacity of C. lampas to maintain their shells under ocean acidification may be strongly driven by abiotic dissolution and erosion, and not under biological control of the calcification process. Understanding the response of marine calcifying organisms and their ability to build and maintain their protective shells and skeletons will be important for our understanding of future marine ecosystems.

Validation of carbon isotope fractionation in algal lipids as a <i>p</i>CO<sub>2</sub> proxy using a natural CO<sub>2</sub> seep (Shikine Island, Japan)

“…The reconstructed pCO 2 values derived from the δ 13 C of general algal biomarkers closely match the actual measured pCO 2 values of the control (Fig. 5), i.e., 309±46 µatm Harvey et al, 2018), when considering the uncertainty in the reconstructed estimations. However, the proxies underestimate the absolute values measured at the elevated pCO 2 sites ( Fig.…”

“…However, the proxies underestimate the absolute values measured at the elevated pCO 2 sites ( Fig. 5; Table S3), i.e., 460±40 µatm at the mid-pCO 2 site and 769 ± 225 µatm at the high-pCO 2 site Harvey et al, 2018). There are several possible explanations as to why there is an underestimation.…”

“…Reconstructed pCO 2 from general algal biomarkers. pCO 2 reconstructed from the δ 13 C of loliolide (triangle), phytol (circle), and cholesterol (square) in June-collected sediments versus the actual pCO 2 measured at each location Harvey et al, 2018). shifts in a similar manner to the other two biomarkers with 244 + 67/ − 54, 266 + 77/ − 61, and 358 + 136/ − 90 µatm, respectively. These reconstructed values closely match each other and trend in the same direction as the actual values.…”

“…1). pCO 2 estimates are based on the carbonate chemistry parameters (pH NBS , temperature, salinity, and total alkalinity) of water in the bay and calculated using the program CO2sys Harvey et al, 2018). Temperature (annual range ca.…”

“…When this phototrophic biomass is preserved in the geologic record, the δ 13 C of sedimentary organic matter can be used to reconstruct pCO 2 (Hayes et al, 1999). The largely mixed contributions and diagenetic processes on bulk organic matter can, however, mask this signal (Hayes, 1993;Hayes et al, 1999). Thus, isotope analysis of specific biomarker lipids is preferred in order to better define the source of the δ 13 C signal (Jasper and Hayes, 1990;Pagani, 2002).…”