Work with colleagues Karl Castillo and Jack Weiss (UNC) has shown that growth rates for the reef-building coral Siderastrea siderea have changed over the past century.  However, the rate and direction of change appears to vary across reef zones, with forereef colonies exhibiting the most severe decline, nearshore colonies exhibiting a moderate decline, and backreef colonies exhibiting a moderate increase.  Most strikingly, forereef colonies, which a century ago exhibited the fastest rates of growth of the three reef zones, now exhibit the slowest rates of growth (Castillo, Ries, and Weiss, 2011). We are presently trying to determine why – READ MORE 

Biological calcification responses to CO₂-induced ocean acidification vary widely across taxa, with species exhibiting positive, threshold-positive, neutral, parabolic, threshold-negative, and negative responses (Ries et al., 2009; see below).  A generalized physicochemical model of calcifying fluid, based upon the premise that many marine calcifiers induce calcification by removing protons from their calcifying fluids, is able to generate a comparably broad range of calcification responses to CO₂-induced ocean acidification.  Measurements of the calcifying fluid of the temperate coral Astrangia poculata with pH microelectrodes reveal that the coral maintains a substantially elevated pH (~10) at the site of calcification relative to its ambient seawater (~8).  This suggests that the coral is indirectly utilizing bicarbonate (HCO₃^–) as a source of carbon in its calcification, via conversion to CO₃^2- within its high-pH calcifying fluid.  The microelectrode measurements also revealed that the coral maintained a fixed external:internal proton ratio of approximately 85:1 under both control and acidified conditions (Ries, 2011) – READ MORE

Responses of marine calcifiers to CO₂-induced ocean acidification

My work with colleagues Anne Cohen and Daniel McCorkle (WHOI) has shown that eighteen species of marine calcifiers reared under various atmospheric pCO₂ scenarios (400, 600, 900, and 2850 ppm) exhibited highly variable calcification responses to acidified seawater. Crabs, shrimp, and lobster exhibited positive responses (Ries et al., 2009).  Limpets, coralline red algae, calcareous green algae, and temperate urchins exhibited parabolic responses.  Temperate corals, pencil urchins, hard clams, and conchs exhibited threshold-negative responses.  Tube worms, periwinkles, bay scallops, oysters, whelks, and soft clams exhibited purely negative responses.  And mussels exhibited no response.  Six of the 18 species exhibited net dissolution of their shells or skeletons (i.e., shell-mass at end of 60-day experiment was less than at beginning) under the highest pCO₂ level (2850 ppm) – READ MORE

My dissertation research showed that three species of scleractinian corals reared in experimental “calcite seawater” (mMg/Ca < 2) produce up to one-third of their skeleton as the calcite, rather than the aragonite, polymorph of calcium carbonate (Ries et al., 2006) – READ MORE