Microsensor studies on Padina from a natural CO2 seep: implications of morphology on acclimation to low pH

• Main Authors: Hofmann, Laurie C, Fink, Artur, Bischof, Kai, de Beer, Dirk
• Format: Dataset
• Language: English
• Published: PANGAEA 2015
• Subjects: Alkalinity; total; Aragonite saturation state; Benthos; Bicarbonate ion; BIOACID; Biological Impacts of Ocean Acidification; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyta; Chromista; CO2 vent; Coast and continental shelf; Distance; Field experiment; Figure; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gross photosynthesis rate; oxygen; Identification; Location; Macroalgae; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; standard error; Padina australis; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; Potentiometric; Primary production/Photosynthesis; Registration number of species; Replicate; Run Date/Time; Salinity; Single species; Site; South Pacific; Species; Temperate; Temperature; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.860218; https://doi.org/10.1594/PANGAEA.860218

Low seawater pH can be harmful to many calcifying marine organisms, but the calcifying macroalgae Padina spp. flourish at natural submarine carbon dioxide seeps where seawater pH is low. We show that the microenvironment created by the rolled thallus margin of Padina australis facilitates supersaturation of CaCO3 and calcifi-cation via photosynthesis-induced elevated pH. Using microsensors to investigate oxygen and pH dynamics in the microenvironment of P. australis at a shallow CO2 seep, we found that, under saturating light, the pH inside the microenvironment (pHME) was higher than the external seawater (pHSW) at all pHSW levels investigated, and the difference (i.e., pHME-pHSW) increased with decreasing pHSW (0.9 units at pHSW 7.0). Gross photosynthesis (Pg) inside the microenvironment increased with decreasing pHSW, but algae from the control site reached a threshold at pH 6.5. Seep algae showed no pH threshold with respect to Pg within the pHSW range investigated. The external carbonic anhydrase (CA) inhibitor, acetazolamide, strongly inhibited Pg of P. australis at pHSW 8.2, but the effect was diminished under low pHSW (6.4-7.5), suggesting a greater dependence on membrane-bound CA for the dehydration of HCO3- ions during dissolved inorganic carbon uptake at the higher pHSW. In comparison, a calcifying green alga, Halimeda cuneata f. digitata, was not inhibited by AZ, suggesting efficient bicarbonate transport. The ability of P. australis to elevate pHME at the site of calcification and its strong dependence on CA may explain why it can thrive at low pHSW.