seabove7/Bove2020_GVC_CoralReefs

Data and code accompanying the Coral GVC manuscript (Bove et al 2020; DOI: https://doi.org/10.1007/s00338-020-01995-7)

Bove2020_GVC_CoralReefs

GitHub repository containing data and code accompanying the Coral GVC manuscript (Bove et al 2020)

Repository DOI:

Title: Responses of coral gastrovascular cavity pH during light and dark incubations to reduced seawater pH suggest species-specific responses to the effects of ocean acidification on calcification

Authors: Colleen B. Bove, Robert F. Whitehead & Alina M. Szmant

Abstract: Coral polyps have a fluid-filled internal compartment, the gastrovascular cavity (GVC). Respiration and photosynthesis cause large daily excursions in GVC oxygen concentration (O₂) and pH, but few studies have examined how this correlates with calcification rates. We hypothesized that GVC chemistry can mediate and ameliorate the effects of decreasing seawater pH (pH_SW) on coral calcification. Microelectrodes were used to monitor O₂ and pH within the GVC of Montastraea cavernosa and Duncanopsammia axifuga (pH only) in both the light and the dark, and three pH_SW levels (8.2, 7.9, and 7.6). At pH_SW 8.2, GVC O₂ ranged from ca. 0 to over 400% saturation in the dark and light, respectively, with transitions from low to high (and vice versa) within minutes of turning the light on or off. For all three pH_SW treatments and both species, pH_GVC was always significantly above and below pH_SW in the light and dark, respectively. For M. cavernosa in the light, pH_GVC reached levels of pH 8.4–8.7 with no difference among pH_SW treatments tested; in the dark, _GVC dropped below pH_SW and even below pH 7.0 in some trials at pH_SW 7.6. For D. axifuga in both the light and the dark, pH_GVC decreased linearly as pH_SW decreased. Calcification rates were measured in the light concurrent with measurements of GVC O₂ and pH_GVC. For both species, calcification rates were similar at pH_SW 8.2 and 7.9 but were significantly lower at pH_SW 7.6. Thus, for both species, calcification was protected from seawater acidification by intrinsic coral physiology at pH_SW 7.9 but not 7.6. Calcification was not correlated with pH_GVC for M. cavernosa but was for D. axifuga. These results highlight the diverse responses of corals to changes in pH_SW, their varying abilities to control pH_GVC, and consequently their susceptibility to ocean acidification.

Citation: Bove, C.B., Whitehead, R.F. & Szmant, A.M. Responses of coral gastrovascular cavity pH during light and dark incubations to reduced seawater pH suggest species-specific responses to the effects of ocean acidification on calcification. Coral Reefs 39, 1675–1691 (2020). https://doi.org/10.1007/s00338-020-01995-7

Repository contains the following:

1. R markdown script and html output with all code and analyses included in manuscript (Coral_GVC_Analysis)
2. Data
   • Representative light/dark M. cavernosa GVC O₂ (LD_O2_mcav_20Jun17.csv)
   • Representative light/dark GVC pH of both species (LD_pH_all_20Jun17.csv)
   • Representative stepwise light/dark GVC pH of both species (LD_step_pH_all_21Jun17.csv)
   • All light/dark GVC data in different pH treatments for analyses (LD_all_data_19Sep17.csv)
   • Calcification rate and GVC O₂ of M. cavernosa only in calcification experiments (Calc_O2_mcav_17April20.csv)
   • Calcification rate and pH_GVC for all calcification experiments (Calc_pH_all_18April20.csv)
3. Figures
   • Fig1_polyp_diagram.png (not created in Rmarkdown script)
   • Fig2_corals_electrode_images.png (not created in Rmarkdown script)
   • Fig3_LD_O2.pdf
   • Fig4_LD_pH.pdf
   • Fig5_stepwise_pH.pdf
   • Fig6_LD_pH_summary.pdf
   • Fig7_Calcification.pdf
4. Tables
   • Cabonate data for Figure 1 and figure S1 (CarbonateSW_data_10Dec19.csv)
   • Summary in Table 2 from light/dark trials (LD_table2_30April20.csv)