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Coral response to climate change
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
Modeling the calcification response to ocean acidification
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 CO32-
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
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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
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Sulfur isotope biogeochemistry
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My work with colleagues David Fike
(Washington University), Tim Lyons (UC Riverside), Lisa Pratt (Indiana
University), and John Grotzinger (Cal Tech) has found that sulfur
isotopes from Namibian carbonates suggest that low seawater sulfate
conditions (and thus low atmospheric oxygen) persisted into terminal
neoproterozoic time, just prior to the Cambrian radiation of animal
life (Ries et al., 2009) - READ MORE
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Mg-fractionation in
biogenic calcite
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My colleagues
and I have shown that
most high-Mg calcite secreting marine organisms
incorporate Mg into their skeletal calcite in proportion to the
concentration of Mg in their ambient seawater (Stanley, Hardie, & Ries, 2010;
Ries et al., 2008; Ries et al., 2006; Ries, 2006; Stanley, Ries, &
Hardie, 2005; Ries, 2004; Stanley, Ries & Hardie, 2002). This finding
supports the use of Mg/Ca ratios in fossil calcitic organisms to
reconstruct ancient seawater Mg/Ca ratios and suggests that most modern
high-Mg calcite secreting taxa produced low-Mg calcite during calcite
sea intervals of the geologic past - READ
MORE
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