Publication Date:
2024-03-15
Description:
Corals exert a strong biological control over their calcification processes, but there is a lack of knowledge on their capability of long-term acclimatization to ocean acidification (OA). We used a dual geochemical proxy approach to estimate the calcifying fluid pH (pHcf) and carbonate chemistry of a Mediterranean coral (Balanophyllia europaea) naturally growing along a pH gradient (range: pHTS 8.07–7.74). The pHcf derived from skeletal boron isotopic composition (δ11B) was 0.3–0.6 units above seawater values and homogeneous along the gradient (mean +/- SEM: Site 1 = 8.39 +/- 0.03, Site 2 = 8.34 +/- 0.03, Site 3 = 8.34 +/- 0.02). Also carbonate ion concentration derived from B/Ca was homogeneous [mean +/- SEM (μmol /kg): Site 1 = 579 +/- 34, Site 2 = 541 +/- 27, Site 3 = 568 +/- 30] regardless of seawater pH. Furthermore, gross calcification rate (GCR, mass of CaCO3 deposited on the skeletal unit area per unit of time), estimated by a “bio-inorganic model” (IpHRAC), was homogeneous with decreasing pH. The homogeneous GCR, internal pH and carbonate chemistry confirm that the features of the “building blocks” – the fundamental structural components – produced by the biomineralization process were substantially unaffected by increased acidification. Furthermore, the pH up-regulation observed in this study could potentially explain the previous hypothesis that less “building blocks” are produced with increasing acidification ultimately leading to increased skeletal porosity and to reduced net calcification rate computed by including the total volume of the pore space. In fact, assuming that the available energy at the three sites is the same, this energy at the low pH sites could be partitioned among fewer calicoblastic cells that consume more energy given the larger difference between external and internal pH compared to the control, leading to the production of less building blocks (i.e., formation of pores inside the skeleton structure, determining increased porosity). However, we cannot exclude that also dissolution may play a role in increasing porosity. Thus, the ability of scleractinian corals to maintain elevated pHcf relative to ambient seawater might not always be sufficient to counteract declines in net calcification under OA scenarios.
Keywords:
Acid-base regulation; Alkalinity, total; Animalia; Aragonite saturation state; Balanophyllia europaea; Benthic animals; Benthos; Bicarbonate ion; Boron/Calcium ratio; Boron/Calcium ratio, standard error; Calcification/Dissolution; Calcification rate of calcium carbonate; Calcifying fluid, aragonite saturation state; Calcifying fluid, carbonate ion; Calcifying fluid, carbonate ion, standard error; Calcifying fluid, dissolved inorganic carbon; Calcifying fluid, dissolved inorganic carbon, standard error; Calcifying fluid, pH; Calcifying fluid, pH, standard error; Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Cnidaria; CO2 vent; Coast and continental shelf; Field observation; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gross calcification rate, relative; Gross calcification rate of calcium carbonate; Mediterranean Sea; Net calcification rate, relative; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; pH change; pH change, standard error; Ratio; Ratio, standard error; Registration number of species; Salinity; Single species; Site; Species; Temperate; Temperature, water; Type; Uniform resource locator/link to reference; δ11B; δ11B, standard deviation
Type:
Dataset
Format:
text/tab-separated-values, 1459 data points
Permalink
