Comparison of Mediterranean Pteropod Shell Biometrics and Ultrastructure from Historical (1910 and 1921) and Present Day (2012) Samples Provides Baseline for Monitoring Effects of Global Change

• Published in: PloS one Vol. 12; no. 1; p. e0167891
• Main Authors: Howes, Ella L, Eagle, Robert A, Gattuso, Jean-Pierre, Bijma, Jelle
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.01.2017; Public Library of Science (PLoS)
• Subjects: Acidification; Alkalinity; Animal Shells - metabolism; Animal Shells - ultrastructure; Animals; Anthropogenic factors; Aragonite; Basins; Biodiversity and Ecology; Biology and Life Sciences; Biometrics; Calcium carbonate; Calcium Carbonate - chemistry; Carbon dioxide; Carbon Dioxide - chemistry; Carbon Dioxide - history; Carbon dioxide atmospheric concentrations; Carbon dioxide concentration; Cavolinia inflexa; Chemical analysis; Climate change; Climate Change - history; Climate effects; Climate monitoring; Computed tomography; Earth Sciences; Electron microscopy; Empirical analysis; Environmental Sciences; Gastropoda - anatomy & histology; Gastropoda - metabolism; Global temperatures; High resolution; History, 20th Century; History, 21st Century; Hydrogen ions; Hydrogen-Ion Concentration; Ice core data; Ice cores; Medicine and Health Sciences; Mediterranean Sea; Microscopy, Electron, Scanning; Models, Statistical; Monitoring; Morphology; Mytilus edulis; Ocean acidification; Ocean basins; Ocean, Atmosphere; Oceanography; Oceans; Ontogeny; pH effects; Physical Sciences; Research and Analysis Methods; Salinity; Scanning electron microscopy; Sciences of the Universe; Seawater; Seawater pH; Secretion; Shells; Styliola subula; Temperature; Time series; Trends; Ultrastructure; Water analysis; ANTHROPOGENIC CO2; CARBON; TEMPERATURES; DYNAMICS; ACL; IMPACTS; OCEAN ACIDIFICATION; ARAGONITE
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0167891

Anthropogenic carbon perturbation has caused decreases in seawater pH and increases in global temperatures since the start of the 20th century. The subsequent lowering of the saturation state of CaCO3 may make the secretion of skeletons more problematic for marine calcifiers. As organisms that precipitate thin aragonite shells, thecosome pteropods have been identified as being particularly vulnerable to climate change effects. Coupled with their global distribution, this makes them ideal for use as sentinel organisms. Recent studies have highlighted shell dissolution as a potential indicator of ocean acidification; however, this metric is not applicable for monitoring pH changes in supersaturated basins. In this study, the novel approach of high resolution computed tomography (CT) scanning was used to produce quantitative 3-dimensional renderings pteropod shells to assess the potential of using this method to monitor small changes in shell biometrics that may be driven by climate change drivers. An ontogenetic analysis of the shells of Cavolinia inflexa and Styliola subula collected from the Mediterranean was used to identify suitable monitoring metrics. Modern samples were then compared to historical samples of the same species, collected during the Mediterranean leg of the Thor (1910) and Dana (1921) cruises to assess whether any empirical differences could be detected. Shell densities were calculated and scanning electron microscopy was used to compare the aragonite crystal morphology. pH for the collection years was hind-cast using temperature and salinity time series with atmospheric CO2 concentrations from ice core data. Historical samples of S. subula were thicker than S. subula shells of the same size from 2012 and C. inflexa shells collected in 1910 were significantly denser than those from 2012. These results provide a baseline for future work to develop monitoring techniques for climate change in the oceans using the novel approach of high-resolution CT scanning.