scholarly journals Ocean acidification affects coral growth by reducing skeletal density

2018 ◽  
Vol 115 (8) ◽  
pp. 1754-1759 ◽  
Author(s):  
Nathaniel R. Mollica ◽  
Weifu Guo ◽  
Anne L. Cohen ◽  
Kuo-Fang Huang ◽  
Gavin L. Foster ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Skeletal Growth ◽  
Ion Concentration ◽  
Skeletal Density ◽  
Carbonate Ion ◽  
Carbonate Ions ◽  
Coral Reef Ecosystems ◽  
Upward Growth ◽  
Seawater Environment ◽  
The Impact

Ocean acidification (OA) is considered an important threat to coral reef ecosystems, because it reduces the availability of carbonate ions that reef-building corals need to produce their skeletons. However, while theory predicts that coral calcification rates decline as carbonate ion concentrations decrease, this prediction is not consistently borne out in laboratory manipulation experiments or in studies of corals inhabiting naturally low-pH reefs today. The skeletal growth of corals consists of two distinct processes: extension (upward growth) and densification (lateral thickening). Here, we show that skeletal density is directly sensitive to changes in seawater carbonate ion concentration and thus, to OA, whereas extension is not. We present a numerical model of Porites skeletal growth that links skeletal density with the external seawater environment via its influence on the chemistry of coral calcifying fluid. We validate the model using existing coral skeletal datasets from six Porites species collected across five reef sites and use this framework to project the impact of 21st century OA on Porites skeletal density across the global tropics. Our model predicts that OA alone will drive up to 20.3 ± 5.4% decline in the skeletal density of reef-building Porites corals.

scholarly journals Effect of ocean acidification on the benthic foraminifera <i>Ammonia</i> sp. is caused by a decrease in carbonate ion concentration

2013 ◽  
Vol 10 (1) ◽  
pp. 1147-1176 ◽  
Author(s):  
N. Keul ◽  
G. Langer ◽  
L. J. de Nooijer ◽  
J. Bijma
Keyword(s):  
Ocean Acidification ◽  
State Of The Art ◽  
Ion Concentration ◽  
Benthic Foraminifer ◽  
Carbonate System ◽  
Surface Ocean ◽  
Important Group ◽  
Carbonate Ion ◽  
Carbonate Ions ◽  
Ca 50

Abstract. About 30% of the anthropogenically released CO2 is taken up by the oceans, which causes surface ocean pH to decrease and is commonly referred to as Ocean Acidification (OA). Foraminifera are one of the most abundant groups of marine calcifiers, estimated to precipitate ca. 50% of biogenic calcium carbonate in the open oceans. We have compiled the state of the art of OA effects on foraminifera, because the majority of OA research on this group was published within the last 3 yr. Disparate responses of this important group of marine calcifiers to OA were reported, highlighting the importance of a process based understanding of OA effects on foraminifera. The benthic foraminifer Ammonia sp. was cultured using two carbonate chemistry manipulation approaches: While pH and carbonate ions where varied in one, pH was kept constant in the other while carbonate ion concentration varied. This allows the identification of teh parameter of the parameter of the carbonate system causing observed effects. This parameter identification is the first step towards a process based understanding. We argue that [CO32−] is the parameter affecting foraminiferal size normalized weights (SNW) and growth rates and based on the presented data we can confirm the strong potential of foraminiferal SNW as a [CO32−] proxy.

scholarly journals Sensitivity of pelagic CaCO<sub>3</sub> dissolution to ocean acidification in an ocean biogeochemical model

2013 ◽  
Vol 10 (7) ◽  
pp. 11343-11373
Author(s):  
A. Regenberg ◽  
B. Schneider ◽  
R. Gangst&amp;oslash;
Keyword(s):  
Ocean Acidification ◽  
Ion Concentration ◽  
Biogeochemical Model ◽  
Saturation State ◽  
Saturation Concentration ◽  
Carbonate Ion ◽  
Biogeochemical Models ◽  
Wide Range ◽  
The Impact

Abstract. In ocean biogeochemical models pelagic CaCO3 dissolution is usually calculated as R = k * Sn, where k is the dissolution rate constant transforming S, the degree of (under-) saturation of seawater with respect to CaCO3, into a time dependent rate R, and n is the reaction rate order. Generally, there are two ways to define the saturation state of seawater with respect to CaCO3: (1) Δ[CO32−], which reflects the difference between the in-situ carbonate ion concentration and the saturation concentration, and (2) Ω, which is approximated by the ratio of in-situ carbonate ion concentration over the saturation concentration. Although describing the same phenomenon, the deviation from equilibrium, both expressions are not equally applicable for the calculation of CaCO3 dissolution in the ocean across pressure gradients, as they differ in their sensitivity to ocean acidification (change of [CO32−]) over depth. In the present study we use a marine biogeochemical model to test the sensitivity of pelagic CaCO3 dissolution to ocean acidification (1–4 × CO2 + stabilization), exploring the possible parameter space for CaCO3 dissolution kinetics as given in the literature. We find that at the millennial time scale there is a wide range of CaCO3 particle flux attenuation into the ocean interior (e.g. a reduction of −55 to −85% at 1000 m depth), which means that there are significant differences in the impact on particle ballasting, depending on the kinetic expression applied.

scholarly journals Effects of ocean acidification on calcification of symbiont-bearing reef foraminifers

2011 ◽  
Vol 8 (1) ◽  
pp. 1809-1829 ◽  
Author(s):  
K. Fujita ◽  
M. Hikami ◽  
A. Suzuki ◽  
A. Kuroyanagi ◽  
H. Kawahata
Keyword(s):  
Coral Reefs ◽  
Ocean Acidification ◽  
Ion Concentration ◽  
Saturation State ◽  
Benthic Foraminifers ◽  
Carbonate Ion ◽  
Algal Symbiont ◽  
Coral Reef Ecosystems ◽  
Flow Through ◽  
Carbonate Species

Abstract. Ocean acidification (decreases in carbonate ion concentration and pH) in response to rising atmospheric pCO2 is generally expected to reduce rates of calcification by reef calcifying organisms, with potentially severe implications for coral reef ecosystems. Large, algal symbiont-bearing benthic foraminifers, which are important primary and carbonate producers in coral reefs, produce high-Mg calcite shells, whose solubility can exceed that of aragonite produced by corals, making them the "first responder" in coral reefs to the decreasing carbonate saturation state of seawater. Here we report results of culture experiments performed to assess the effects of ongoing ocean acidification on the calcification of symbiont-bearing reef foraminifers using a high-precision pCO2 control system. Living clone individuals of three foraminiferal species (Baculogypsina sphaerulata, Calcarina gaudichaudii, and Amphisorus hemprichii) were subjected to seawater at five pCO2 levels from 260 to 970 μatm. Cultured individuals were maintained for about 12 weeks in an indoor flow-through system under constant water temperature, light intensity, and photoperiod. After the experiments, the shell diameter and weight of each cultured specimen were measured. Net calcification of Baculogypsina and Calcarina, which secrete a hyaline shell and host diatom symbionts, increased under intermediate levels of pCO2 (580 and/or 770 μatm) and decreased at a higher pCO2 level (970 μatm). Net calcification of Amphisorus, which secretes a porcelaneous shell and hosts dinoflagellate symbionts, tended to decrease at elevated pCO2. These different responses among the three species are possibly due to differences in calcification mechanisms (in particular, the specific carbonate species used for calcification) between hyaline and porcelaneous taxa, and to links between calcification by the foraminiferal hosts and photosynthesis by the algal endosymbionts. Our findings suggest that ongoing ocean acidification might favor symbiont-bearing reef foraminifers with hyaline shells at intermediate pCO2 levels (580 to 770 μatm) but be unfavorable to those with either hyaline or porcelaneous shells at higher pCO2 levels (near 1000 μatm).

The coral reef-dwelling Peneroplis spp. shows calcification resilience to ocean acidification conditions - results from culture experiments

2021 ◽  
Author(s):  
Laurie Charrieau ◽  
Katsunori Kimoto ◽  
Delphine Dissard ◽  
Beatrice Below ◽  
Kazuhiko Fujita ◽  
...  
Keyword(s):  
Coral Reefs ◽  
Ocean Acidification ◽  
Sea Water ◽  
General Structure ◽  
Ion Concentration ◽  
Large Benthic Foraminifera ◽  
Carbonate Ion ◽  
Short Period

&lt;p&gt;Ocean acidification is a consequence of current anthropogenic climate changes.&amp;#160;The concomitant decrease in pH and carbonate ion concentration in sea water may have severe impacts on calcifying organisms. Coral reefs are among the first ecosystems recognized vulnerable to ocean acidification. Within&amp;#160;coral reefs, large benthic foraminifera (LBF) are major calcium carbonate producers.&lt;/p&gt;&lt;p&gt;The aim of this study was to evaluate the effects of varying&amp;#160;pH on&amp;#160;survival and calcification of the&amp;#160;symbiont-bearing LBF species &lt;em&gt;Peneroplis&lt;/em&gt; spp.&amp;#160;We performed culture experiments to study their&amp;#160;resistance to ocean acidification conditions,&amp;#160;as well as their resilience once placed back under open ocean pH (7.9).&lt;/p&gt;&lt;p&gt;After three&amp;#160;days, small signs of test decalcification were observed on specimens kept at pH 7.4, and severe test decalcification was observed on specimens kept at pH 6.9, with the inner organic lining clearly appearing.&amp;#160;After 32 days under pH 7.4, similar strongly decalcified specimens were observed. All the specimens were alive&amp;#160;at the end of the experiment. This result demonstrates the&amp;#160;resistance of &lt;em&gt;Peneroplis &lt;/em&gt;spp.&amp;#160;to an acidified pH, at least on a short period of time.&lt;/p&gt;&lt;p&gt;After being partially decalcified, some of the living specimens were placed back at pH 7.9. After one month, the majority of the specimens showed recalcification&amp;#160;features, mostly by addition of new chambers.&amp;#160;The trace elements concentrations of the newly formed chambers were analysed by LA-ICPMS. Interestingly, more chambers were added when food was given, which&amp;#160;highlights the crucial role of energy source in the&amp;#160;recalcification process. Moreover, the newly formed chambers were most of the time abnormal, and the general structure&amp;#160;of the tests was altered, with potential impacts on reproduction and in situ survival. In conclusion, if symbiont-bearing LBF show some resistance and resilience to&amp;#160;lowered pH&amp;#160;conditions, they&amp;#160;will remain&amp;#160;strongly affected by ocean acidification.&lt;/p&gt;

scholarly journals Predicting the impact of ocean acidification on coral reefs: evaluating the assumptions involved

2015 ◽  
Vol 73 (3) ◽  
pp. 550-557 ◽  
Author(s):  
Paul L. Jokiel
Keyword(s):  
Coral Reefs ◽  
Ocean Acidification ◽  
Bulk Water ◽  
Ion Concentration ◽  
Calcification Rate ◽  
Saturation State ◽  
Simplifying Assumptions ◽  
Reef Decline ◽  
Highly Correlated ◽  
The Impact

Abstract Predictions of future impact of climate change on coral reefs indicate that bleaching mortality due to higher temperature will be the major factor in the decline of coral reefs. Ocean acidification (OA) is increasingly considered to be an important contributing factor, but estimates of its importance vary widely in the literature. Models of future reef decline due to OA generally involve four simplifying assumptions that can lead to contradictions. The assumptions are: (i) Oceanic conditions of Ωarag control or are at least highly correlated with net calcification rate (Gnet) on coral reefs. (ii) Calcification rate is driven by bulk water carbonate ion concentration [CO32−] expressed as Ωarag. (iii) Changes in coral calcification rate can be used to estimate future changes in coral reef calcification rate. (iv) The impact of OA is additive and not synergistic with other environmental factors such as increased temperature. The assumption that aragonite saturation state (Ωarag) of seawater drives calcification is the most widely used and needs to be further evaluated. An alternate hypothesis is that calcification is limited by the ability of the system to rid itself of the protons generated by calcification. Recent studies allow further testing of the assumptions and point the way to resolving shortcomings in our understanding of how OA impacts coral reefs.

scholarly journals Skeletal mineralogy of coral recruits under high temperature and <i>p</i>CO<sub>2</sub>

2016 ◽  
Vol 13 (5) ◽  
pp. 1717-1722 ◽  
Author(s):  
T. Foster ◽  
P. L. Clode
Keyword(s):  
High Temperature ◽  
Ocean Acidification ◽  
High Pco2 ◽  
X Ray Diffraction ◽  
Calcite Precipitation ◽  
Ambient Seawater ◽  
The Past ◽  
Coral Reef Ecosystems ◽  
Combined Impact ◽  
The Impact

Abstract. Aragonite, which is the polymorph of CaCO3 precipitated by modern corals during skeletal formation, has a higher solubility than the more stable polymorph calcite. This higher solubility may leave animals that produce aragonitic skeletons more vulnerable to anthropogenic ocean acidification. It is therefore important to determine whether scleractinian corals have the plasticity to adapt and produce calcite in their skeletons in response to changing environmental conditions. Both high pCO2 and lower Mg ∕ Ca ratios in seawater are thought to have driven changes in the skeletal mineralogy of major marine calcifiers in the past ∼ 540 Ma. Experimentally reduced Mg ∕ Ca ratios in ambient seawater have been shown to induce some calcite precipitation in both adult and newly settled modern corals; however, the impact of high pCO2 on the mineralogy of recruits is unknown. Here we determined the skeletal mineralogy of 1-month-old Acropora spicifera coral recruits grown under high temperature (+3 °C) and pCO2 (∼ 900 µatm) conditions, using X-ray diffraction and Raman spectroscopy. We found that newly settled coral recruits produced entirely aragonitic skeletons regardless of the treatment. Our results show that elevated pCO2 alone is unlikely to drive changes in the skeletal mineralogy of young corals. Not having an ability to switch from aragonite to calcite precipitation may leave corals and ultimately coral reef ecosystems more susceptible to predicted ocean acidification. An important area for prospective research would be the investigation of the combined impact of high pCO2 and reduced Mg ∕ Ca ratio on coral skeletal mineralogy.

scholarly journals Impact of carbonate saturation on large Caribbean benthic foraminifera assemblages

2018 ◽  
Author(s):  
Ana Martinez ◽  
Laura Hernández-Terrones ◽  
Mario Rebolledo-Vieyra ◽  
Adina Paytan
Keyword(s):  
Ocean Acidification ◽  
Benthic Foraminifera ◽  
Atmospheric Carbon Dioxide ◽  
Inorganic Carbon ◽  
Low Ph ◽  
Ion Concentration ◽  
Relative Distribution ◽  
Submarine Springs ◽  
Carbonate Ion ◽  
Calcite Saturation

Abstract. Increasing atmospheric carbon dioxide and its dissolution in seawater have reduced ocean pH and carbonate ion concentration with potential implications to calcifying organisms. To assess the response of Caribbean benthic foraminifera to low carbonate saturation conditions, we analyzed benthic foraminifera abundance and relative distribution in proximity to low carbonate saturation submarine springs and at adjacent control sites. Our results show that the total abundance of benthic foraminifera is significantly lower at the low pH low calcite saturation submarine springs than at control sites, despite higher concentrations of inorganic carbon at the spring sites. The relative abundance of symbiont-bearing foraminifera and agglutinated foraminifera was higher at the low pH low calcite saturation submarine springs compared to control sites. These differences indicate that non-symbiont bearing heterotrophic calcareous foraminifera are more sensitive to the effects of ocean acidification than non-calcifying and symbiont bearing foraminifera, suggesting that future ocean acidification may impact natural benthic foraminifera populations.

scholarly journals Effect of carbonate ion concentration and irradiance on calcification in planktonic foraminifera

2010 ◽  
Vol 7 (1) ◽  
pp. 247-255 ◽  
Author(s):  
F. Lombard ◽  
R. E. da Rocha ◽  
J. Bijma ◽  
J.-P. Gattuso
Keyword(s):  
Ocean Acidification ◽  
Planktonic Foraminifera ◽  
High Light ◽  
Ion Concentration ◽  
Low Light ◽  
Calcification Rate ◽  
Shell Size ◽  
Shell Weight ◽  
Carbonate Ion ◽  
Orbulina Universa

Abstract. The effect of carbonate ion concentration ([CO32−]) on calcification rates estimated from shell size and weight was investigated in the planktonic foraminifera Orbulina universa and Globigerinoides sacculifer. Experiments on G. sacculifer were conducted under two irradiance levels (35 and 335 μmol photons m−2 s−1). Calcification was ca. 30% lower under low light than under high light, irrespective of the [CO32−]. Both O. universa and G. sacculifer exhibited reduced final shell weight and calcification rate under low [CO32−]. For the [CO32−] expected at the end of the century, the calcification rates of these two species are projected to be 6 to 13% lower than the present conditions, while the final shell weights are reduced by 20 to 27% for O. universa and by 4 to 6% for G. sacculifer. These results indicate that ocean acidification would impact on calcite production by foraminifera and may decrease the calcite flux contribution from these organisms.

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