Lisa L. Robbins Peter J. Harries Pamela Hallock Jonathan Wynn Paul O. Knorr 2015 <p><span>A common, but not universal, effect of ocean acidification on benthic foraminifera is a reduction in the growth rate. The miliolid <i>Archaias angulatus</i> is a high-Mg (&gt;4 mole% MgCO₃), symbiont-bearing, soritid benthic foraminifer that contributes to Caribbean reef carbonate sediments. A laboratory culture study assessed the effects of reduced pH on the growth of <i>A. angulatus</i>. We observed a statistically significant 50% reduction in the growth rate (p &lt; 0.01), calculated from changes in maximum diameter, from 160 &mu;m/28 days in the pH 8.0/pCO_2<i>air</i> 480 ppm control group to 80 &mu;m/28 days at a treatment level of pH 7.6/pCO_2<i>air</i> 1328 ppm. Additionally, pseudopore area, &delta;¹⁸O values, and Mg/Ca ratio all increased, albeit slightly in the latter two variables. The reduction in growth rate indicates that under a high-CO₂ setting, future <i>A. angulatus</i> populations will consist of smaller adults. A model using the results of this study estimates that at pH 7.6 <i>A. angulatus</i> carbonate production in the South Florida reef tract and Florida Bay decreases by 85%, from 0.27 Mt/yr to 0.04 Mt/yr, over an area of 9,000 km².</span></p> application/pdf 10.2113/gsjfr.45.2.109 en Cushman Foundation for Foraminiferal Research Response of the Miliolid Archaias angulatus to simulated ocean acidification article