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To endure, coral reefs must accumulate CaCO3 at a rate greater or equal than the sum of mechanically, biologically, and chemically mediated erosion rates. We investigated the potential role of holothurians on the CaCO3 balance of a coral reef. These deposit feeders process carbonate sand and rubble through their digestive tract and dissolve CaCO3 as part of their digestive process. In aquarium incubations with Stichopus herrmanni and Holothuria leucospilota total alkalinity increased by 97 ` 13 and 47 ` 7 mmol kg�1, respectively. This increase was due to CaCO3 dissolution, 81 ` 13 and 34 ` 6 mmol kg�1 and ammonia secretion, 16 ` 2 and 14 ` 2mmol kg�1, respectively, for these species. Surveys conducted at a long-term monitoring site of community calcification (DK13) on One Tree Reef indicated that the density of sea cucumbers was approximately 1 individual m�2. We used these data and data from surveys at Shark Alley to estimate the dissolution of CaCO3 by the sea cucumbers at both sites. At DK13 the sea cucumber population was estimated to be responsible for nearly 50% of the nighttime CaCO3 dissolution, while in Shark Alley for most of the nighttime dissolution. Thus, in a healthy reef, bioeroders dissolution of CaCO3 sediment appears to be an important component of the natural CaCO3 turnover and a substantial source of alkalinity as well. This additional alkalinity could partially buffer changes in seawater pH associated with increasing atmospheric CO2 locally, thus reducing the impact of ocean acidification on coral growth.
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... Sea cucumbers (Echinodermata: Holothuroidea) are among the most conspicuous benthic invertebrates found on coral reefs. Through their deposit-feeding processes, sea cucumbers have the potential to maintain ecosystem functioning and mitigate some of the adverse effects of human-driven ocean acidification, eutrophication, and sedimentation currently threatening coral reefs (Williamson et al. 2021, Lee et al. 2018, Schneider et al. 2011, Nestler et al. 2014). ...
... These sea cucumbers may remove sand and silt of high organic content from live corals, potentially mitigating some of the adverse effects of sedimentation on coral growth and recruitment (Nestler et al. 2014, Fabricius 2005. Finally, some sea cucumber species have been shown to increase local seawater alkalinity which might facilitate calcification processes of nearby corals, regardless of the substrate type they directly feed on, under the emerging ocean acidification (Schneider et al. 2011(Schneider et al. , 2013. ...
... Studies that have investigated the abundance of H. atra and A. mauritiana in relationship with relative substrate cover have not directly measured the substrate preference of the two species (Bellchambers et al. 2011, Eriksson et al. 2012, Massin & Doumen 1986). Instead, the species have been suggested to be associated with substrate types that dominate sites of high population densities (Bellchambers et al. 2011, Eriksson et al. 2011. This assessment of preferred substrate may be misleading if H. atra and A. mauritiana would prefer another substate type than the one of highest relative cover in the local habitat, which has been shown for other sea cucumber species (Nestler et al. 2014). ...
Research
Undergraduate Senior Capstone Project. Deposit-feeding sea cucumbers play important ecological roles on coral reefs and overexploitation has raised concern. Understanding factors that drive patterns of holothurian density and distribution is of importance to ecosystem-based management, since the ecological consequence of removing sea cucumbers by fishing likely vary from one local habitat to another. Surveys of the sea cucumbers Actinopyga mauritiana and Holothuria atra were conducted at nine shallow, currently unfished, reef sites around Oahu, Hawaii, to determine substrate preference and to what extent preferred substrate availability explains variation in species density. A. mauritiana preferred vertical and horizontal surfaces of three types of pavements while H. atra preferred two types of rubble. The density of both species increased linearly with percent preferred substrate cover across a variety of local habitat types. This finding demonstrates the importance of substrate type as a specialization component of the sea cucumber microhabitat and indicates that high density assemblages of the two species are not necessarily associated with a particular type of habitat. The present study is a step towards the understanding of how sea cucumbers influence their surrounding habitat though their feeding habits, which must be understood for successful implementation of ecosystem-based fishery management.
... Los pepinos de mar funcionan como sistemas de filtrado tanto del sustrato (p.e. arena y escombro), como en la columna de agua, permitiendo la recirculación de nutrientes, la eliminación de bacterias, e indirectamente por su actividad excavadora promueven la oxigenación del sustrato y el aumento en las concentraciones de compuestos minerales en sus formas metabolizables (Ruppert y Barnes 1996, Ambrose et al. 2001, Schneider et al. 2011. Por otro lado, los pepinos de mar tropicales protegen los arrecifes de coral de una mayor degradación debido al cambio climático. ...
... Por otro lado, los pepinos de mar tropicales protegen los arrecifes de coral de una mayor degradación debido al cambio climático. Ellos, al digerir la arena, producen carbonato de calcio (un componente clave para la conformación de corales), además de que sus procesos digestivos naturales también aumentan los niveles de pH del agua (Schneider et al. 2011). ...
... Los pepinos de mar funcionan como sistemas de filtrado tanto del sustrato (p.e. arena y escombro), como en la columna de agua, permitiendo la recirculación de nutrientes, la eliminación de bacterias, e indirectamente por su actividad excavadora promueven la oxigenación del sustrato y el aumento en las concentraciones de compuestos minerales en sus formas metabolizables , Ambrose et al. 2001, Schneider et al. 2011). Por otro lado, los pepinos de mar tropicales protegen los arrecifes de coral de una mayor degradación debido al cambio climático. ...
... Por otro lado, los pepinos de mar tropicales protegen los arrecifes de coral de una mayor degradación debido al cambio climático. Ellos, al digerir la arena, producen carbonato de calcio (un componente clave para la conformación de corales), además de que sus procesos digestivos naturales también aumentan los niveles de pH del agua (Schneider et al. 2011). ...
... Via their feeding activity, sea cucumbers enhance the productivity of their surrounding ecosystems (Uthicke & Klumpp, 1998;MacTavish et al., 2012;Wolkenhauer et al., 2010). Furthermore, sea cucumbers are even suggested to be crucial for buffering local ocean acidification by increasing the pH through ammonia discharge (Uthicke, 2001a;Schneider et al., 2011Schneider et al., , 2013. Finally, sea cucumbers often host many symbiotic species (Purcell et al., 2016;Eeckhaut et al., 2004;Hamamoto & Reimer, in press) and hence contribute to local marine biodiversity. ...
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Sea cucumbers are important ecological engineers in marine ecosystems. However, the fishery demand of some species, especially large-epifaunal and commercially used (LEC) sea cucumbers, has risen drastically, resulting in serious depletion of local populations for many species. Despite this problem, basic ecological data on sea cucumbers, such as population densities and preferred habitats, are often still insufficient. Here, we report on the population densities of multiple LEC sea cucumber species, and their ambient benthic communities at eight sites around Okinawa Islands. Further, we discuss the correspondence between sea cucumber densities and the surrounding coral communities. Our results show two sites within national or quasi-national parks, Aka and Manza, where stricter rules have been placed on fisheries and land reclamation compared to other areas, had the highest and third highest sea cucumber population densities among sites, respectively. Holothuria atra was observed at all survey sites and made up the majority of sea cucumber populations at all sites except for Chatan and Sesoko, where Holothuria leucospilota and Stichopus chloronotus were most abundant, respectively. Regarding the relationships between benthic composition and LEC sea cucumber species, S. chloronotus was significantly correlated with dead corals, scleractinian corals, and coralline algae. As well, H . leucospilota had significant correlations with rubble. Although there were no significant correlations between any specific scleractinian coral genus and sea cucumber densities, S. chloronotus was marginally insignificant with Platygyra and Psammocora . Notably, medium- to highly valued species were sparse in our surveys, and most of them appeared at only one site. Additionally, at one site (Odo), only three LEC sea cucumber individuals were observed. Combining these facts with relatively low population densities around the Okinawa Islands compared to densities reported in previous research from the Indo-West Pacific Ocean region, we conclude that Okinawan LEC sea cucumber populations have been and are being impacted by high levels of direct ( e.g ., overexploitation, as well as coastal development) and indirect anthropogenic pressure ( e.g ., decreasing water quality). To address the current situation, repeated monitoring and more detailed investigations to reveal the drivers that determine LEC sea cucumber species aggregations and population densities are urgently needed, along with more robust management of remaining LEC sea cucumber populations.
... The sea cucumber typically feeds on sediments rich in organic carbons. It possesses a powerful digestive tract that efficiently degrades organic carbons, concomitantly reducing biocontamination and promoting local pH balance of seawater (4,5). Thus, H. leucospilota serves as a seabed scavenger vital to the health and biodiversity of nearshore marine ecosystems, and has been prized for their roles in the restoration of injured coral reefs. ...
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Heavy-metal pollution has increasingly jeopardized the habitats of marine organisms including the sea cucumber, a seafloor scavenger vital to seawater bio-decontamination, ocean de-acidification and coral-reef protection. Normal physiology including immune functions of sea cucumbers is toxicologically modulated by marine metal pollutants such as cadmium (Cd). The processes underpinning Cd’s toxic effects on immune systems in the sea cucumber, Holothuria leucospilota, are still poorly understood. To this end, we cloned and characterized a full-length caspase-9 (Hl-CASP9) cDNA in the sea cucumber, Holothuria leucospilota. Hl-CASP9 mRNA levels evolved dynamically during embryonic development. Coelomocytes, a type of phagocytic immune effectors central to H. leucospilota immunity, were found to express Hl-CASP9 mRNA most abundantly. Hl-CASP9 protein structurally resembles caspases-2 and -9 in both invertebrate and vertebrate species, comprising a CARD domain and a CASc domain. Remarkably, Hl-CASP9 was transcriptionally sensitive to abiotic oxidative stress inducers including hydrogen peroxide (H2O2), nitric oxide (•NO) and cadmium (Cd), but insensitive to immunostimulants including lipopolysaccharide (LPS), and poly(I:C). Overexpression of Hl-CASP9 augmented mitochondria-dependent apoptosis in HEK293T cells, while knock-down of Hl-CASP9 blunted Cd-induced coelomocyte apoptosis in vivo. Overall, we illustrate that an evolutionarily ancient caspase-9-dependent pathway exists to sensitize coelomocytes to premature cell death precipitated by heavy metal pollutants, with important implications for negative modulation of organismal immune response in marine invertebrates.
... Finding out the seasonal changes in the preferred habitat of sea cucumbers can help us analyze the seasonal changes of its ability to restore a specifi c coral reef ecosystem and assess the importance of sea cucumbers as an ecological restoration species. Sea cucumbers play a key role in bioturbation and turnover of sediments (Mangion et al., 2004), the deposit fecal can enhance coral calcifi cation and provide a buff er against ocean acidifi cation (Schneider et al., 2011). The seasonal changes of sea cucumber's preferred habitat are closely related to its ecological adaptability, but the precision of previous studies is low on the time scale, so it is diffi cult to refl ect the fi ne changes of sea cucumber ecological adaptability. ...
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Different sea cucumbers have different preferred habitats and seasonal changes, which is still lack of detailed research. This study selects two common tropical sea cucumbers (Holothuria edulis and Stichopus chloronotus) to explore the reasons that affect their habitat selection and seasonal changes, so as to provide support for the spatial planning of sea cucumbers reserve in coral reef area. The study area is a compound distribution area of living coral reefs and sandy bottom in the north of Wuzhizhou Island. The survey time is January, April–September, 2019. Three fixed transects (G, H, and Q) were selected to reveal the population ecological characteristics of them in the typical dry season (January, April, May, and June) and rainy season (July, August, and September). The variation range of density for H. edulis and S. chloronotus were 2.0–8.9 inds./10 m2 and 0.2–0.7 inds./10 m2, respectively. The population density in rainy season was significantly higher than that in dry season (P<0.05). H. edulis tends to be distributed in deeper water. The distribution of H. edulis was significant positively correlated with the sand coverage and sand continuity in G transect (P<0.05), and significant negatively correlated with live coral coverage in three transects (P<0.01). The shift from dry season to rainy season is a key factor affecting their habitat preference. In dry season, the preferred habitats of S. chloronotus are small rock (SR), sand (S), and small coral reef (SCR), while the H. edulis is S, SR, and dead coral rubbles (DCR). In rainy season, the preferred habitats of S. chloronotus are shift to SCR and SR, while the H. edulis is SCR, DCR, and sand.
... shown that Holothuria atra has no buffering capacity of seawater due to CO 2 production. Several other studies have shown that some species of sea cucumbers can increase the alkalinity of seawater by releasing alkaline ammonia-rich faeces (Purcell et al., 2016;Schneider et al., 2011). The nitrate level increased during the experimental period; this is could be related to the transformation of sea cucumbers faecal ammonia to nitrate. ...
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In this work, we investigated the potential benefits of Holothuria (Roweothuria) poli Delle chiaje, 1824, in the bioremediation of aquaculture farm effluents in the Mediterranean Sea as well as the impact of mechanical, chemical and hypoxic stress conditions on the process of evisceration. The usefulness of H. poli as an effective candidate for fish farm effluent bioremediation was tested by placing 14 sea cucumbers in aquaria with 50 L of aquaculture wastewater for 21 days and examining the physicochemical parameters of this wastewater at fixed times (0, 7, 14 and 21 days). Interestingly, the results clearly showed that the addition of H. poli reduces chemical oxygen demand (COD), total organic carbon (TOC) and suspended matter (SM). In the second part of this work, we examined the exposure of H. poli to mechanical, chemical and hypoxic stimuli under controlled laboratory conditions. The results showed that the evisceration was strongly induced by potassium chloride (KCl) and sodium hydroxide (NaOH), compared with magnesium chloride (MgCl2), sodium chloride (NaCl), sodium sulphate (Na2SO4) and sodium bicarbonate (NaHCO3). In addition, high mechanical pressure and hypoxia (exposure to ambient air) also resulted in the evisceration of H. poli. In conclusion, the sea cucumber H. poli is an effective candidate for the fish farm effluent bioremediation in the Mediterranean and is useful for sustainable integrative multitrophic aquaculture.
... Aspidochirotids are also important in nutrient cycling in oligotrophic coral reef waters increasing productivity and enhancing coral growth (Uthicke and Klumpp, 1998;Uthicke, 1999Uthicke, , 2001. Recent research points to the contribution of tropical sea cucumbers in local buffering of the carbonate coral reef environment with the potential to aid calcification processes (Schneider et al., 2011;Schneider et al., 2013;Wolfe et al., 2018). In addition to these roles in ecosystem functioning, sea cucumbers also provide direct habitat for a plethora of associated species that live in or on their bodies, with over 200 species of symbionts, parasites and commensals reported (Eeckhaut et al., 2004;Purcell et al., 2016a). ...
Article
Tropical sea cucumbers are in peril due to overharvest. Sixteen species are endangered or vulnerable (IUCN) with high-value teatfish recently listed on CITES Appendix II. In light of these listings, we review the Queensland Sea Cucumber Fishery, which harvests CITES-listed black teatfish (Holothuria whitmaei) and white teatfish (H. fuscogilva), and other IUCN-species, from the Great Barrier Reef (GBR), Australia. Teatfish harvest on the GBR has experienced serial catch reductions and fishery closure due to local depletion, a trend observed globally for sea cucumbers and of concern for the at-risk GBR World Heritage Area. We provide the first case study for teatfish while their trade continues, and highlight other species of concern. The major target species of the fishery, Actinopyga spinea (~ 50% of total catch), is not a traditional species in the global trade. With over one million individuals harvested annually, its fishery and its ecological consequences require attention. We synthesise knowledge on teatfish population parameters, identify knowledge gaps and suggest measures to reduce fishery impacts. Continued global exploitation of at-risk marine invertebrate species, coupled with scientific uncertainties, emphasise the urgent need for targeted research and to apply the precautionary principle to avoid detrimental outcomes in their conservation status.
... Sea cucumbers play an important role in marine ecosystem functionality through nutrient recycling, bioturbation, benthic productivity, and meiofauna population dynamics (Schneider et al., 2011;MacTavish et al., 2012;Oh et al., 2017). To date, more than 1,250 species of sea cucumbers have been identified in benthic areas of both shallow and deep seas world-wide and approximately 20 of them are known to be edible (Jo and Park, 2016). ...
Article
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Significant increases in global sea surface temperatures are expected with climate change and may cause a serious challenge for marine organisms cultured in aquatic environments that are characterized by short and long-term fluctuations in water temperatures. Apostichopus japonicus , a sea cucumber with high nutritional value and pharmacological properties, is an important economic species that is widely raised in aquaculture in China. In recent years, continuous extreme high temperatures (up to 30°C) have occurred frequently in summer leading to mass mortality of sea cucumbers cultured in semi-open shallow regions seriously restricting the sustainable development of sea cucumber aquaculture. In the present study, we combined RNA-seq and PacBio single-molecular real-time (SMRT) sequencing technology to unveil the potential mechanisms of response to acute heat stress in A. japonicus coelomocytes. A total of 1,375 differentially expressed genes (DEGs) were identified in a comparison of control and 48 h heat stress (HS) groups. Pathway enrichment analysis indicated that nine important pathways induced by HS were significantly enriched ( q -value < 0.05) and mostly fell into four classes: folding, sorting, and degradation, immune and infectious diseases, signal transduction, and post-transcriptional regulation. Among them, all 41 genes connected with protein processing in endoplasmic reticulum were significantly up-regulated, and 12 of these were selected and validated via qPCR. Furthermore, changes in alternative splicing (AS) were also identified in sea cucumbers following HS. A total of 1,224 and 1,251 differential alternative splicing (DAS) events were identified using splice junction counts (JC only) and reads on target and junction counts (JCEC) as the input for rMATS in CO-HS comparison. We further found that the RNA splicing-related genes were enriched in the spliceosome pathway and showed DAS in control versus heat-stressed animals. In particular, we compared and confirmed that the hsfs1 gene, the master regulator of the heat shock response, showed differentially spliced exons in response to HS. This is the first comprehensive study showing that transcriptional and post-transcriptional (AS) controls are involved in the acute heat stress response of sea cucumber coelomocytes and provides novel insights into the molecular mechanisms of echinoderm adaptation to environmental stress.
... Most sea cucumbers are deposit-feeders and classic example of bioturbators. They enhance the productivity and maintain the marine ecosystems by blending sediments, reintegrating nutrients, triggering algal growth, and controlling both the pH and the carbonate content in water (Purcell 2004;Wolkenhauer et al. 2010;Schneider et al. 2011). ...
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The population structure and growth parameters of the commercially important species of sea cucumber Holothuria arguinensis in Moroccan waters was studied, being the first study reported along these waters. We collected 455 individuals of H. arguinensis at Skhirat, and 209 at Souiria K’dima, Northern and center Atlantic of Morocco. To avoid deviation from the accurate measurements in sea cucumber related to statistical estimation because of the elasticity of the body wall, we used a compound index which merged length and width to give the SLW index (square root of length multiplied by width) and its related modifications such as Le (recalculated length) were assessed and different morphometric relationships were also explored, the results indicate that recalculated length appears to be more valuable and helpful in obtaining an accurate length of sea cucumber. The student’s t-test revealed that H. arguinensis has allometric growth (b ≠ 1 or b ≠ 3, P < 0.05). The von Bertalanffy growth function including L∞, K and t0 were estimated to be L∞ = 25.96 cm, K = 0.17 yr.−1, t0 = –1.55 year at Skhirat, and L∞ = 25.44 cm, K = 0.29 yr⁻¹, t0 = –1.02 year at Souiria K’dima. The longevity in H. arguinensis was high (8.51 years at Skhirat and 6.81 years at Souiria k’dima) and the estimated natural mortality of H. arguinensis was low (0.47 year⁻¹ at Skhirat and 0.67 year⁻¹ at Souiria k’dima) when analyzed against other sea cucumber species, which indicated that this organism might be resistant to predation. Similarly, these findings will be used to establish a sustainable management strategy to exploit this marine resource and support the fishery development plans and aquaculture.
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The question at once arises, how is it that even the stoutest corals, resting with broad base upon the ground, and doubly secure from their spreading proportions, become so easily a prey to the action of the same sea which they met shortly before with such effectual resistance? The solution of this enigma is to be found in the mode of growth of the corals themselves. Living in communities, death begins first at the base or centre of the group, while the surface or tips still continue to grow, so that it resembles a dying centennial tree, rotten at the heart, but still apparently green and flourishing without, till the first heavy gale of wind snaps the hollow trunk, and betrays its decay. Again, innumerable boring animals establish themselves in the lifeless stem, piercing holes in all directions into its interior, like so many augurs, dissolving its solid connexion with the ground, and even penetrating far into the living portion of these compact communities. --L. Agassiz, 1852 4.1 INTRODUCTION Coral reefs are among the Earth's most biologically diverse ecosystems, and many of the organisms contributing to the high species diversity of reefs normally weaken them and convert massive reef structures to rubble, sand and silt. The various activities of those reef species that cause coral and coralline algal erosion are collectively termed bioerosion, a name coined by Neumann (1966). A bioeroder is any organism that, through its assorted activities, erodes and weakens the calcareous skeletons of reef-building species. Although an extensive terminology has been adopted only during the past three decades, bioerosion has been recognized as an important process in reef development and maturation for more than a century (e.g., Darwin, 1842; Agassiz, 1852). Traces of biologically-induced erosion in ancient reef structures indicate that bioerosion has probably had some effect on reef carbonate budgets since Precambrian and Cambrian times (Vogel, 1993).
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The behavior of the ocean carbon cycle has been, and will continue to be, modified by the increase in atmospheric CO2 due to fossil fuel combustion and land-use emissions of this gas. The consequences of a high-CO2 world and increasing riverine transport of organic matter and nutrients arising from human activities were investigated by means of two biogeochemical box models. Model numerical simulations ranging from the year 1700 to 2300 show that the global coastal ocean changes from a net source to a net sink of atmospheric CO2 over time; in the 18th and 19th centuries, the direction of the CO2 flux was from coastal surface waters to the atmosphere, whereas at present or in the near future the net CO2 flux is into coastal surface waters. These results agree well with recent syntheses of measurements of air-sea CO2 exchange fluxes from various coastal ocean environments. The model calculations also show that coastal ocean surface water carbonate saturation state would decrease 46 percent by the year 2100 and 73 percent by 2300. Observational evidence from the Pacific and Atlantic Oceans shows that the carbonate saturation state of surface ocean waters has already declined during recent decades. For atolls and other semi-enclosed carbonate systems, the rate of decline depends strongly on the residence time of the water in the system. Based on the experimentally observed positive relationship between saturation state and calcification rate for many calcifying organisms, biogenic production of CaCO3 may decrease by 42 percent by the year 2100 and by 85 to 90 percent by 2300 relative to its value of about 24 × 1012 moles C/yr in the year 2000. If the predicted change in carbonate production were to occur along with rising temperatures, it would make it difficult for coral reef and other carbonate systems, to exist as we know them now into future centuries. Because high-latitude, cold-water carbonates presently occur in waters closer to saturation with respect to carbonate minerals than the more strongly supersaturated waters of the lower latitudes, it might be anticipated that the cool-water carbonate systems might feel the effects of rising atmospheric CO2 (and temperature) before those at lower latitudes. In addition, modeling results show that the carbonate saturation state of coastal sediment pore water will decrease in the future owing to a decreasing pore water pH and increasing CO2 concentrations attributable to greater deposition and remineralization of land-derived and in situ produced organic matter in sediments. The lowered carbonate saturation state drives selective dissolution of metastable carbonate minerals while a metastable equilibrium is maintained between the pore water and the most soluble carbonate phase present in the sediments. In the future, the average composition of carbonate sediments and cements may change as the more soluble Mg-calcites and aragonite are preferentially dissolved and phases of lower solubility, such as calcites with lower magnesium content, increase in percentage abundance in the sediments.
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In this study we investigated the relations between community calcification of an entire coral reef in the northern Red Sea and annual changes in temperature, aragonite saturation and nutrient loading over a two year period. Summer (April–October) and winter (November–March) average calcification rates varied between 60 ± 20 and 30 ± 20 mmol·m−2·d−1, respectively. In general, calcification increased with temperature and aragonite saturation state of reef water with an apparent effect of nutrients, which is in agreement with most laboratory studies and in situ measurements of single coral growth rates. The calcification rates we measured in the reef correlated remarkably well with precipitation rates of inorganic aragonite calculated for the same temperature and degree of saturation ranges using empirical equations from the literature. This is a very significant finding considering that only a minute portion of reef calcification is inorganic. Hence, these relations could be used to predict the response of coral reefs to ocean acidification and warming.
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Model predictions suggest that the saturation state of surface ocean waters with respect to carbonate minerals will decline during the twenty-first century owing to increased invasion of atmospheric CO2. As a result, calcareous organisms may have difficulty calcifying, leading to production of weaker skeletons and greater vulnerability to erosion. Alternatively, it has been suggested that there will be no significant impact on coral reef ecosystems because any changes in saturation state and pH will be restored by dissolution of metastable carbonate minerals. To resolve this controversy, we employ a physical-biogeochemical box model representative of the shallow-water ocean environment. Numerical simulations demonstrate that the carbonate saturation state of surface waters could significantly decrease and hamper the biogenic production of CaCO3 during the twenty-first century. Similarly, the average saturation state of marine pore waters could decline significantly, inducing dissolution of metastable carbonate phases within the pore-water sediment system. Such dissolution could buffer the carbon chemistry of the pore waters, but overlying surface waters of reefs and other shallow-water carbonate environments will not accumulate sufficient alkalinity to buffer pH or carbonate saturation state changes owing to invasion of atmospheric CO2.