In vivo pH measurement at the site of calcification in an octocoral

Abstract

Calcareous octocorals are ecologically important calcifiers, but little is known about their biomineralization physiology, relative to scleractinian corals. Many marine calcifiers promote calcification by up-regulating pH at calcification sites against the surrounding seawater. Here, we investigated pH in the red octocoral Corallium rubrum which forms sclerites and an axial skeleton. To achieve this, we cultured microcolonies on coverslips facilitating microscopy of calcification sites of sclerites and axial skeleton. Initially we conducted extensive characterisation of the structural arrangement of biominerals and calcifying cells in context with other tissues, and then measured pH by live tissue imaging. Our results reveal that developing sclerites are enveloped by two scleroblasts and an extracellular calcifying medium of pH 7.97 ± 0.15. Similarly, axial skeleton crystals are surrounded by cells and a calcifying medium of pH 7.89 ± 0.09. In both cases, calcifying media are more alkaline compared to calcifying cells and fluids in gastrovascular canals, but importantly they are not pH up-regulated with respect to the surrounding seawater, contrary to what is observed in scleractinians. This points to a potential vulnerability of this species to decrease in seawater pH and is consistent with reports that red coral calcification is sensitive to ocean acidification.

A high biodiversity mitigates the impact of ocean acidification on hard-bottom ecosystems

“…These results confirm the negative impact of acidification on the red corals when incubated alone 2,82 . Indeed, we found that the acidification treatment caused decalcification of C. rubrum calcium carbonate sclerites (57 ± 6% of damaged sclerites compared to no damages in the controls; p < 0.01; Fig.…”

A high biodiversity mitigates the impact of ocean acidification on hard-bottom ecosystems

“…These results confirm the negative impact of acidification on the red corals when incubated alone 2,82 . Indeed, we found that the acidification treatment caused decalcification of C. rubrum calcium carbonate sclerites (57 ± 6% of damaged sclerites compared to no damages in the controls; p < 0.01; Fig.…”

3D Photogrammetry Modeling Highlights Efficient Reserve Effect Apparition After 5 Years and Stillness After 40 for Red Coral (Corallium rubrum) Conservation in French MPAs

“…South Riou populations (RRS_20 and RRS_40) showed growth rates overpassing what is known in the wild. Previous studies already shown very high fertility on this site (Garrabou and Harmelin, 2002) and equivalent growth rates have already been obtained in a controlled environment (Goff et al, 2017). Local environmental conditions might explain these observed growth rates: little light and low temperatures [around 13 • C in February; and 20 • C in August (Vielzeuf et al, 2013)], proximity to a major coastal upwelling zone (Millot and Wald, 1980), influencing the diversity of organisms on the substrate (Oscarella spp., Reniera fulva, Crella mollior, Aplysina cavernicola as well as overpulids and bryozoa), lack of competition (Montero-Serra et al, 2018) as well as the composition of the microbiome TABLE 4 | Results of permutation analyzes of variance (PERMANOVA) in the Cerbère-Banyuls reserve (A) and the Calanques national park (B) via a design incorporating the year and protection factor (year as a fixed factor with 2 modalities; protection as a fixed factor with three modalities; interaction protection * year) for the multivariate matrix (maximum size; basal diameter; number of branches) and each univariate matrix.…”

Activation Profile Analysis of CruCA4, an α-Carbonic Anhydrase Involved in Skeleton Formation of the Mediterranean Red Coral, Corallium rubrum

“…Intriguingly, as demonstrated by our groups, even if CruCA4 was expressed at very low levels with respect to the other isoforms, it was the only isoenzyme expressed in the tissue-calcifying fraction [ 37 , 38 ]. Thus, CruCA4 attracted our attention as the main coral α-CA involved in the biomineralization process.…”

A high biodiversity mitigates the impact of ocean acidification on hard-bottom ecosystems

“…These results confirm the negative impact of acidification on the red corals when incubated alone 2,82 . Indeed, we found that the acidification treatment caused decalcification of C. rubrum calcium carbonate sclerites (57 ± 6% of damaged sclerites compared to no damages in the controls; p < 0.01; Fig.…”

3D Photogrammetry Modeling Highlights Efficient Reserve Effect Apparition After 5 Years and Stillness After 40 for Red Coral (Corallium rubrum) Conservation in French MPAs

“…South Riou populations (RRS_20 and RRS_40) showed growth rates overpassing what is known in the wild. Previous studies already shown very high fertility on this site (Garrabou and Harmelin, 2002) and equivalent growth rates have already been obtained in a controlled environment (Goff et al, 2017). Local environmental conditions might explain these observed growth rates: little light and low temperatures [around 13 • C in February; and 20 • C in August (Vielzeuf et al, 2013)], proximity to a major coastal upwelling zone (Millot and Wald, 1980), influencing the diversity of organisms on the substrate (Oscarella spp., Reniera fulva, Crella mollior, Aplysina cavernicola as well as overpulids and bryozoa), lack of competition (Montero-Serra et al, 2018) as well as the composition of the microbiome TABLE 4 | Results of permutation analyzes of variance (PERMANOVA) in the Cerbère-Banyuls reserve (A) and the Calanques national park (B) via a design incorporating the year and protection factor (year as a fixed factor with 2 modalities; protection as a fixed factor with three modalities; interaction protection * year) for the multivariate matrix (maximum size; basal diameter; number of branches) and each univariate matrix.…”

Activation Profile Analysis of CruCA4, an α-Carbonic Anhydrase Involved in Skeleton Formation of the Mediterranean Red Coral, Corallium rubrum

“…Intriguingly, as demonstrated by our groups, even if CruCA4 was expressed at very low levels with respect to the other isoforms, it was the only isoenzyme expressed in the tissue-calcifying fraction [ 37 , 38 ]. Thus, CruCA4 attracted our attention as the main coral α-CA involved in the biomineralization process.…”

A high biodiversity mitigates the impact of ocean acidification on hard-bottom ecosystems

“…These results confirm the negative impact of acidification on the red corals when incubated alone 2,82 . Indeed, we found that the acidification treatment caused decalcification of C. rubrum calcium carbonate sclerites (57 ± 6% of damaged sclerites compared to no damages in the controls; p < 0.01; Fig.…”

3D Photogrammetry Modeling Highlights Efficient Reserve Effect Apparition After 5 Years and Stillness After 40 for Red Coral (Corallium rubrum) Conservation in French MPAs

“…South Riou populations (RRS_20 and RRS_40) showed growth rates overpassing what is known in the wild. Previous studies already shown very high fertility on this site (Garrabou and Harmelin, 2002) and equivalent growth rates have already been obtained in a controlled environment (Goff et al, 2017). Local environmental conditions might explain these observed growth rates: little light and low temperatures [around 13 • C in February; and 20 • C in August (Vielzeuf et al, 2013)], proximity to a major coastal upwelling zone (Millot and Wald, 1980), influencing the diversity of organisms on the substrate (Oscarella spp., Reniera fulva, Crella mollior, Aplysina cavernicola as well as overpulids and bryozoa), lack of competition (Montero-Serra et al, 2018) as well as the composition of the microbiome TABLE 4 | Results of permutation analyzes of variance (PERMANOVA) in the Cerbère-Banyuls reserve (A) and the Calanques national park (B) via a design incorporating the year and protection factor (year as a fixed factor with 2 modalities; protection as a fixed factor with three modalities; interaction protection * year) for the multivariate matrix (maximum size; basal diameter; number of branches) and each univariate matrix.…”

Activation Profile Analysis of CruCA4, an α-Carbonic Anhydrase Involved in Skeleton Formation of the Mediterranean Red Coral, Corallium rubrum

“…Intriguingly, as demonstrated by our groups, even if CruCA4 was expressed at very low levels with respect to the other isoforms, it was the only isoenzyme expressed in the tissue-calcifying fraction [ 37 , 38 ]. Thus, CruCA4 attracted our attention as the main coral α-CA involved in the biomineralization process.…”