Descriptive statistics of oceanographic observations from each location.

<p>The number of observations (<i>n</i>) varies between sites (Hut Point: for Temperature and pH, <i>n</i> = 935, for Salinity and Density, <i>n</i> = 875; Cape Evans: <i>n</i> = 768; New Harbor: <i>n</i> = 420).</p><p>Descriptive statistics of oceanographic observations from each location.</p

Water mass properties observed during spring in McMurdo Sound.

<p>Locations are indicated by color: Hut Point (blue), Cape Evans (red), and New Harbor (green).</p

Photosynthesis-irradiance model parameters.

<p>Algal-specific values are presented for sea ice algae (ia), <i>Phyllophora antarctica</i> (fr), and crustose coralline (cc).</p>1<p>Mean value calculated from sea ice algae chlorophyll <i>a</i> measurements by <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107239#pone.0107239-Ryan1" target="_blank">[34]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107239#pone.0107239-McMinn3" target="_blank">[43]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107239#pone.0107239-Trenerry1" target="_blank">[44]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107239#pone.0107239-McMinn6" target="_blank">[69]</a> at Cape Evans.</p><p>Photosynthesis-irradiance model parameters.</p

Spectra for pH, tide, and surface irradiance from eastern McMurdo Sound.

<p>pH spectra (A) for Hut Point (blue) and Cape Evans (red). Tide spectra (B) are from Cape Evans. Surface irradiance spectra (C) were measured at Arrival Heights. Frequency is in the units of cycles per day.</p

Relationship between pH and tides observed at Cape Evans.

<p>Panels show pH and tidal height (A), tidal exchange rate (B), and ebb versus flood stage (C).</p

Model estimates of surface PAR (A) and hourly O₂ production rate by algal functional groups over a 24 h period.

<p>Algal groups include foliose red (B), crustose coralline (C), and sea ice algae (D). Colored lines indicate estimated O₂ production at different depths.</p

Model estimates of pH effect due to photosynthesis by algal community over a 24 h period in relation to sea ice algal biomass.

<p>Model estimates of pH effect due to photosynthesis by algal community over a 24 h period in relation to sea ice algal biomass.</p

Sensitivity analyses of model parameters for the light environment, algal biomass, and ocean carbonate system.

<p>Values represent the percent change in estimated pH in response to an increase/decrease of each parameter value by 5%. Null value of each parameter is listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107239#pone-0107239-t002" target="_blank">Table 2</a>.</p><p>Sensitivity analyses of model parameters for the light environment, algal biomass, and ocean carbonate system.</p

Results of image analyses on Calcification Acidification Units (CAUs).

<p>a) Percent cover of the various ecological functional groups. Green bands = ‘fleshy’ invertebrate and algae species. The mineralogy for calcifying species is indicated in the figure legend. b) Original variable vectors of the CAP analysis overlaid as a bi-plot (Spearman Rank correlations >0.5) for both the biological and physio-chemical data from each site. The biological vector colors correspond to functional groups listed in (a).</p

Relationship between net calcification or percent cover analyses on CAUs and relevant pH metrics.

<p>a) Means (± SE) of net reef calcification for total CaCO₃ and each polymorph of CaCO₃ against mean (± SE) daily ∑ pH·hrs above pH_csl. Both total net accretion (<i>Y = </i>6.86<i>x</i> +0.96; <i>F</i> = 7.78, <i>R</i> = 0.813, P = 0.0444) and high Mg calcite calcification rate (<i>Y = </i>7.75<i>x</i> +0.47; <i>F</i> = 12.26, <i>R</i> = 0.868, P = 0.0249) are related to mean daily ∑ pH·hrs above pH_csl. b) Percent cover of all calcifiers and for each polymorph of CaCO₃ against mean (± SE) daily ∑ pH·hrs above pH_csl. Only the percent cover of high Mg calcite is positively related to ∑ pH·hrs above pH_csl (<i>Y = </i>83.81<i>x</i> +48.52; <i>F</i> = 12.747, <i>R</i> = 0.872, P = 0.0234). Percent cover of calcitic organisms is negatively related to ∑ pH·hrs above pH_csl (<i>Y = </i>14.85–29.21<i>x</i>; <i>F</i> = 17.502, <i>R</i> = −0.902, P = 0.0139).</p