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Paneled bar plots show species-specific average rates of dark (left bar, darker shade) and light (right bar, lighter shade) metabolism. Photosynthesis
Source publication
Coral reef metabolism underpins ecosystem function and is defined by the processes of photosynthesis, respiration, calcification, and calcium carbonate dissolution. However, the relationships between these physiological processes at the organismal level and their interactions with light remain unclear. We examined metabolic rates across a range of...
Contexts in source publication
Context 1
... test; Supporting Information Table S5). As O. faveolata, P. astreoides, and S. siderea had consistently similar rates, we refer to this grouping as the "massive corals" herein. We report rates as mean AE SD unless otherwise indicated. Overall, metabolic rates were higher in the massive corals than both A. cervicornis and CCA over a diurnal cycle (Fig. 4). Night metabolism followed a similar grouping as the daytime measurements: respiration was greater in the massive corals (R DO = À0.75 AE 0.23 μmol cm À2 h À1 , R DIC = À0.85 AE 0.35 μmol cm À2 h À1 ), than in A. cervicornis (R DO = À0.32 AE 0.05, R DIC = 0.38 AE 0.08 μmol cm À2 h À1 ) and CCA (R DO = À0.31 AE 0.14 μmol cm À2 h À1 , R ...
Context 2
... on community metabolism than branching A. cervicornis and encrusting CCA because of the relative benthic cover and architectural complexity of each species found in nature. Given the distinct ecological function and life-history traits within the massive coral grouping ( Darling et al. 2012), the similarity in their metabolic rates was unexpected (Fig. 4). P. astreoides is Linear relationships between (a) mean average respiration (R DIC ) and dark calcification (G dark ) for each species, (b) maximum metabolic rates derived from model coefficients for photosynthesis-and calcification-irradiance curves (P max and G max ) and (c) individually measured photosynthesis (P DIC ) and ...
Citations
... El efecto de la intensidad interlumínica en las características de crecimiento esqueletal y la morfología de los corales hermatípicos ha sido estudiado anteriormente (Graus y Macintyre 1982, Hubbard y Scature 1985, Carricart-Ganivet et al. 2007, Todd 2008, Gutiérrez-Estrada 2017, Mallon et al. 2022. Sin embargo, el efecto del trasplante de corales entre profundidades con condiciones lumínicas ambientales diferentes ha sido poco explorado. ...
Massive corals of the genus Orbicella are key organisms that help maintain the physical structure of Caribbean reefs. However, they are currently threatened by environmental changes, such as increased nutrient loads and pollution, which affect the optical properties of seawater and, consequently, limit reef development. Thus, analyzing the responses in the growth of coral species to changes in light environments can help us improve mitigation and conservation strategies for coral reefs. The objective of this study was to evaluate the effect of changes in environmental light conditions on the growth rate of Orbicella faveolata by comparing fragments transplanted from 9 m to 3 m depth and control fragments that were transplanted under the same light conditions (3 m). The fragments of both treatments showed similar growth (16–3%), as well as comparable extension and diameter values. The annual growth rate for the control fragments and transplantation treatment fragments was 1.04 ± 0.18 cm·y–1 and 1.11 ± 0.23 cm·y–1, respectively. The results of this study reveal that the coral O. faveolata can physiologically acclimate to new environmental light conditions after being transplanted from a deep environment to a shallow environment in the short-term (1–9 months). This suggests great potential for the use of O. faveolata in restoration strategies and management programs that aim to maintain the populations and structural framework of coral reefs in the Caribbean region.
... In contrast, inconsistent expression patterns of genes involved in the four processes were observed in A. fragilissima ( Fig. 5 A , Lower ). Analysis of a range of reef calcifiers indicates that calcification rates are linked to energy production at the organismal level ( 93 ). It is likely therefore that H. opuntia , with its semienclosed IUS, may require more energy to continuously maintain CaCO 3 oversaturation. ...
Algae mostly occur either as unicellular (microalgae) or multicellular (macroalgae) species,
both being uninucleate. There are important exceptions, however, as some unicellular
algae are multinucleate and macroscopic, some of which inhabit tropical seas and
contribute to biocalcification and coral reef robustness. The evolutionary mechanisms
and ecological significance of multinucleation and associated traits (e.g., rapid wound
healing) are poorly understood. Here, we report the genome of Halimeda opuntia, a
giant multinucleate unicellular chlorophyte characterized by interutricular calcification.
We achieve a high-quality
genome assembly that shows segregation into four subgenomes,
with evidence for polyploidization concomitant with historical sea level and
climate changes. We further find myosin VIII missing in H. opuntia and three other
unicellular multinucleate chlorophytes, suggesting a potential mechanism that may
underpin multinucleation. Genome analysis provides clues about how the unicellular
alga could survive fragmentation and regenerate, as well as potential signatures for extracellular
calcification and the coupling of calcification with photosynthesis. In addition,
proteomic alkalinity shifts were found to potentially confer plasticity of H. opuntia to
ocean acidification (OA). Our study provides crucial genetic information necessary for
understanding multinucleation, cell regeneration, plasticity to OA, and different modes
of calcification in algae and other organisms, which has important implications in reef
conservation and bioengineering.
... The HI84502 mini titrator (HANNA Instruments, Woonsocket, RI, USA) was employed to perform titrations on seawater for the determination of total alkalinity (TA). As coral calcification is a light-enhanced process (Mallon et al., 2022), the change in total alkalinity during light conditions was utilized to calculate the calcification rate, employing the equation outlined by Cohen, Dubinsky & Erez (2016). The equation is as follows: ...
Background
Low oxygen in marine environments, intensified by climate change and local pollution, poses a substantial threat to global marine ecosystems, especially impacting vulnerable coral reefs and causing metabolic crises and bleaching-induced mortality. Yet, our understanding of the potential impacts in tropical regions is incomplete. Furthermore, uncertainty surrounds the physiological responses of corals to hypoxia and anoxia conditions.
Methods
We initially monitored in situ dissolved oxygen (DO) levels at Kham Island in the lower Gulf of Thailand. Subsequently, we conducted a 72-hour experimental exposure of corals with different morphologies— Pocillopora acuta , Porites lutea , and Turbinaria mesenterina —to low oxygen conditions, while following a 12/12-hour dark/light cycle. Three distinct DO conditions were employed: ambient (DO 6.0 ± 0.5 mg L ⁻¹ ), hypoxia (DO 2.0 ± 0.5 mg L ⁻¹ ), and anoxia (DO < 0.5 mg L ⁻¹ ). We measured and compared photosynthetic efficiency, Symbiodiniaceae density, chlorophyll concentration, respiratory rates, primary production, and calcification across the various treatments.
Results
Persistent hypoxia was observed at the study site. Subsequent experiments revealed that low oxygen levels led to a notable decrease in the maximum quantum yield over time in all the species tested, accompanied by declining rates of respiration and calcification. Our findings reveal the sensitivity of corals to both hypoxia and anoxia, particularly affecting processes crucial to energy balance and structural integrity. Notably, P. lutea and T. mesenterina exhibited no mortality over the 72-hour period under hypoxia and anoxia conditions, while P. acuta , exposed to anoxia, experienced mortality with tissue loss within 24 hours. This study underscores species-specific variations in susceptibility associated with different morphologies under low oxygen conditions. The results demonstrate the substantial impact of deoxygenation on coral growth and health, with the compounded challenges of climate change and coastal pollution exacerbating oxygen availability, leading to increasingly significant implications for coral ecosystems.
... In contrast, inconsistent expression patterns of genes involved in the four processes were observed in A. fragilissima ( Fig. 5 A , Lower ). Analysis of a range of reef calcifiers indicates that calcification rates are linked to energy production at the organismal level ( 93 ). It is likely therefore that H. opuntia , with its semienclosed IUS, may require more energy to continuously maintain CaCO 3 oversaturation. ...
Algae mostly occur either as unicellular (microalgae) or multicellular (macroalgae) species, both being uninucleate. There are important exceptions, however, as some unicellular algae are multinucleate and macroscopic, some of which inhabit tropical seas and contribute to biocalcification and coral reef robustness. The evolutionary mechanisms and ecological significance of multinucleation and associated traits (e.g., rapid wound healing) are poorly understood. Here, we report the genome of Halimeda opuntia , a giant multinucleate unicellular chlorophyte characterized by interutricular calcification. We achieve a high-quality genome assembly that shows segregation into four subgenomes, with evidence for polyploidization concomitant with historical sea level and climate changes. We further find myosin VIII missing in H. opuntia and three other unicellular multinucleate chlorophytes, suggesting a potential mechanism that may underpin multinucleation. Genome analysis provides clues about how the unicellular alga could survive fragmentation and regenerate, as well as potential signatures for extracellular calcification and the coupling of calcification with photosynthesis. In addition, proteomic alkalinity shifts were found to potentially confer plasticity of H. opuntia to ocean acidification (OA). Our study provides crucial genetic information necessary for understanding multinucleation, cell regeneration, plasticity to OA, and different modes of calcification in algae and other organisms, which has important implications in reef conservation and bioengineering.
... Therefore, photosynthesis appeared to have a predominant effect on skeletal growth, although other mechanisms also control it. Mallon et al. (2022) examined the interspecies relationships between photosynthesis, respiration, and calcification using photosynthesizing calcifiers in the Caribbean, including A. cervicornis and P. astreoides. Their results showed that calcification rates were linked to energy production at the organismal level and that the species-specific ratios of net calcification to photosynthesis varied with light over a diurnal cycle. ...
... This is consistent with the findings observed from P. australiensis. Although Mallon et al. (2022) suggested the importance of considering natural variations in light for all reef metabolism studies, light intensity in this study (120-140 mmol/m 2 /s) was relatively low. This light condition would produce low calcification rates for both species, and the temperature sensitivities would differ from those obtained using corals from the field. ...
Although biogenic carbonates, such as foraminifera and coccolithophorids, are valuable tools for reconstructing past environments, scleractinian corals also offer environmental data from tropical to subtropical regions with a higher time resolution. For example, oxygen isotopes (δ¹⁸O) and strontium-calcium (Sr/Ca) ratios have been utilized to reconstruct sea surface temperatures and salinity, primarily through the use of massive-type Porites sp. from the Pacific, as well as corals like Diploria and Montastrea from the Atlantic. While a few types of corals other than Porites have been utilized in paleoclimate studies, comprehensive evaluations of their geochemical tracers as temperature proxies have not been thoroughly conducted. Therefore, in this study, we focused on branching-type Acropora, which are found worldwide and are often present in fossil corals. We conducted a comparison of the chemical compositions (δ¹⁸O, δ¹³C, Sr/Ca, U/Ca, Mg/Ca, and Ba/Ca) of Acropora digitifera and Porites australiensis through temperature-controlled culture experiments. The validity of using the chemical components of A. digitifera as temperature proxies was then evaluated. Three colonies of A. digitifera and P. australiensis were collected for culture experiments on Sesoko Island, Okinawa, Japan. We reared coral samples in seawater with five different temperature settings (18, 21, 24, 27, 30°). The calcification rate and photosynthesis efficiency (Fv/Fm) of each nubbin were measured during the experimental period. After the culture experiment for 77 days, chemical components in skeletal parts grown during the experiment were then measured. Consequently, the mean growth rates and Fv/Fm throughout the experiment were higher for A. digitifera (0.22%/d and 0.63 for growth rate and Fv/Fm) compared to those for P. australiensis (0.11%/d and 0.38 for growth rate and Fv/Fm). This suggests that the higher efficiency of photosynthesis in A. digitifera would promote greater calcification compared to P. australiensis. Regarding the potential use as temperature proxies, A. digitifera exhibited a strong negative correlation, on average, between δ¹⁸O and the water temperature (r = 0.95, p< 0.001). The temperature dependency was found to be comparable to that reported in Porites corals (-0.11 and -0.17 ‰/°C for P. australiensis and A. digitifera, respectively). Thus, the δ¹⁸O of A. digitifera appeared to be a useful temperature proxy, although it was also slightly influenced by skeletal growth rate at the same temperature. A strong negative correlation was also observed between the mean Sr/Ca ratio and temperature in A. digitifera (r = 0.61, p< 0.001) as well as P. australiensis (r = 0.56, p< 0.001), without a clear influence from the skeletal growth rate. Therefore, the skeletal Sr/Ca ratio in corals may have been primarily influenced by water temperature, although large deviations in Sr/Ca were observed in A. digitifera, even at the same temperature settings. This deviation can be reduced by subsampling an apical part of a polyp including the axis of skeletal growth. The U/Ca ratio of A. digitifera appeared to be affected by internal pH variation within the corals, especially at 30°C. Similar to U/Ca ratios, metabolic and kinetic effects on corals were observed in δ¹³C of A. digitifera at 18 and 30°C. In addition, considering the variation pattern of both U/Ca and δ¹³C of A. digitifera at 30°C, it has been suggested that respirations may overwhelm photosynthesis for coral samples at 30°C. Therefore, the U/Ca and δ¹³C of A. digitifera could potentially be used as proxies of biomineralization processes, whereas the δ¹⁸O and Sr/Ca displayed a high possibility of acting as temperature proxies.
... Temperature and daylight seasonality in the subtropical FRC are relatively high compared to tropical reefs. Both temperature and light are known to exert substantial effects on the metabolic processes of corals and primary producers, including calcification and photosynthesis rates (Fourqurean & Zieman, 1991;Gattuso et al., 1999;Mallon et al., 2022). In the FCR, months with colder temperatures generally coincide with shorter daylight hours, and vice versa. ...
Ocean acidification (OA) threatens coral reef persistence by decreasing calcification and accelerating the dissolution of reef frameworks. The carbonate chemistry of coastal areas where many reefs exist is strongly influenced by the metabolic activity of the underlying benthic community, contributing to high spatiotemporal variability. While characterizing this variability is difficult, it has important implications for the progression of OA and the persistence of the ecosystems. Here, we characterized the carbonate chemistry at 38 permanent stations located along 10 inshore‐offshore transects spanning 250 km of the Florida Coral Reef (FCR), which encompass four major biogeographic regions (Biscayne Bay, Upper Keys, Middle Keys, and Lower Keys) and four shelf zones (inshore, mid‐channel, offshore, and oceanic). Data have been collected since 2010, with approximately bi‐monthly periodicity starting in 2015. Increasing OA, driven by increasing DIC, was detected in the mid‐channel, offshore, and oceanic zones in every biogeographic region. In the inshore zone, however, increasing TA counteracted any measurable OA trend. Strong seasonal variability occurred at inshore sites and included periods of both exacerbated and mitigated OA. Seasonality was region‐dependent, with greater variability in the Lower and Middle Keys. Elevated pH and aragonite saturation states (ΩAr) were observed in the Upper and Middle Keys, which could favor reef habitat persistence in these regions. Offshore reefs in the FCR could be more susceptible to global OA by experiencing open‐ocean‐like water chemistry conditions. By contrast, higher seasonal variability at inshore reefs could offer a temporary OA refuge during periods of enhanced primary production.
Coral calcification is critical for reef growth and highly dependent on environmental conditions. Yet, little is known about how corals calcify under sub-optimal conditions (e.g., turbid waters, high nutrients, sedimentation) or coral growth in understudied regions such as the Colombian Caribbean. We therefore assessed the calcification and linear extension rates of five coral species across an inshore-to-offshore gradient in the Colombian Caribbean. A suite of environmental variables (temperature, light intensity, visibility, pH, nutrients) measured during the rainy season (May – November 2022) demonstrated more sub-optimal conditions inshore compared to offshore. Across all species, calcification rates were 59% and 37% lower inshore compared to the offshore and midshore sites, respectively. Across all sites, massive corals calcified up to 92% more than branching species but were more susceptible to heat stress and sub-optimal inshore conditions. However, branching species had reduced survival due to extreme climatic events (i.e., bleaching, hurricanes). A comparison with published rates for the wider Caribbean revealed that massive species in the Colombian Caribbean grow up to 11 times more than those in the wider Caribbean while branching species generally have similar growth rates, but this finding may have been influenced by fragment size and/or heat stress. Our findings indicate that present-day environmental conditions, coupled with more frequent extreme climatic events, will favor massive over branching species in midshore areas of the Colombian Caribbean. This suggests a possible shift towards faster calcifying massive species in future coral communities, possibly exacerbating the ongoing regional decline in branching species over the last decades.
Coral reefs are at risk due to various global and local anthropogenic stressors that impact the health of reef ecosystems worldwide. The most recent climate models predict that climate change will increase the frequency and intensity of tropical storms. This increased storm occurrence and strength will likely compromise coral reef structures and habitats for reefdwelling organisms, including across the Florida Keys Reef Tract (FKRT), the most extensive tropical reef system along the US coast. While several recent studies reveal the chronic impacts of tropical storms on corals, relatively little is known about the effects of major storm events on coral growth and how these effects vary over spatiotemporal scales. Here, I characterize the skeletal growth of two common Caribbean reef-building coral species, Siderastrea siderea and Pseudodiploria strigosa, before and after Hurricane Irma, to investigate the storm's impact on coral skeletal growth on inner and outer reefs of the FKRT. Coral cores were extracted from both species at four inner and four outer reef sites in May 2015, before Hurricane Irma struck the Florida Keys in September 2017. Subsequently, 33 micro-cores were collected in May 2019, two years after the storm traversed our previously cored coral colonies. A three-way ANOVA model with storm, species, and reef location as the three factors was used to assess the impact of the storm on each of three growth parameters: skeletal density, linear extension, and calcification rates. Results reveal no difference in the coral annual skeletal growth parameters pre- and post-Hurricane Irma, although previously quantified differences in these growth parameters across species and location were observed. However, analysis of the “yearly” change in annual skeletal growth parameters showed significant differences in skeletal density across groups before and after Hurricane Irma, but not for linear extension and calcification rates. Our findings improve an understanding of the impacts of tropical storms on coral skeletal growth and offer new insights into how we can employ corals’ innate growth capacities to help conserve coral reefs under climate change.
Calcification is vital to marine organisms that produce calcium carbonate shells and skeletons. However, how calcification is impacted by ongoing environmental changes, including ocean acidification, remains incompletely understood due to complex relationships among the carbonate system variables hypothesized to drive calcification. Here, we experimentally decouple these drivers in an exploration of shell formation in adult marine mussels, Mytilus californianus. In contrast to models that focus on single parameters like calcium carbonate saturation state, our results implicate two independent factors, bicarbonate concentration and seawater pH, in governing calcification. While qualitatively similar to ideas embodied in the related substrate-inhibitor ratio (bicarbonate divided by hydrogen ion concentration), our data highlight that merging bicarbonate ion and hydrogen ion concentrations into a simple quotient obscures important features of calcification. Considering a dual-parameter framework improves mechanistic understanding of how calcifiers interact with complex and changing chemical conditions.
