Ocean acidification (OA) caused by rising atmospheric CO2 concentration and solar ultraviolet radiation (UVR) resulting from ozone depletion may affect marine organisms, but little is known regarding how unicellular Rhodosorus sp. SCSIO-45730, an excellent species resource containing various biological-active compounds, responds to OA and UVR. Therefore, we conducted a factorial coupling experiment to unravel the combined effects of OA and UVR on the growth, photosynthetic performances, biochemical compositions and enzyme activities of Rhodosorus sp. SCSIO-45730, which were exposed to two levels of CO2 (LC, 400 μatm, current CO2 level; HC, 1000 μatm, future CO2 level) and three levels of UVR (photosynthetically active radiation (PAR), PAR plus UVA, PAR plus UVB) treatments in all combinations, respectively. Compared to LC treatment, HC stimulated the relative growth rate (RGR) due to higher optimum and effective quantum yields, photosynthetic efficiency, maximum electron transport rates and photosynthetic pigments contents regardless of UVR. However, the presence of UVA had no significant effect but UVB markedly reduced the RGR. Additionally, higher carbohydrate content and lower protein and lipid contents were observed when Rhodosorus sp. SCSIO-45730 was cultured under HC due to the ample HCO−3HCO3− applications and active stimulation of metabolic enzymes of carbonic anhydrase and nitrate reductase, thus resulting in higher TC/TN. OA also triggered the production of reactive oxygen species (ROS), and the increase of ROS coincided approximately with superoxide dismutase and catalase activities, as well as phenols contents. However, UVR induced photochemical inhibition and damaged macromolecules, making algal cells need more energy for self-protection. Generally, these results revealed that OA counteracted UVR-related inhibition on Rhodosorus sp. SCSIO-45730, adding our understanding of the red algae responding to future global climate changes.
Continue reading ‘Effects of seawater acidification and solar ultraviolet radiation on photosynthetic performances and biochemical compositions of Rhodosorus sp. SCSIO-45730’Posts Tagged 'algae'
Effects of seawater acidification and solar ultraviolet radiation on photosynthetic performances and biochemical compositions of Rhodosorus sp. SCSIO-45730
Published 6 January 2023 Science ClosedTags: algae, biological response, growth, laboratory, light, multiple factors, North Pacific, photosynthesis, physiology
Decreased salinity offsets the stimulation of elevated pCO2 on photosynthesis and synergistically inhibits the growth of juvenile sporophyte of Saccharina japonica (Laminariaceae, Phaeophyta)
Published 12 December 2022 Science ClosedTags: algae, biological response, growth, laboratory, multiple factors, North Pacific, photosynthesis, physiology, salinity
The combined effect of elevated pCO2 (Partial Pressure of Carbon Dioxide) and decreased salinity, which is mainly caused by freshwater input, on the growth and physiological traits of algae has been poorly assessed. In order to investigate their individual and interactive effects on the development of commercially farmed algae, the juvenile sporophytes of Saccharina japonica were cultivated under different levels of salinity (30, 25 and 20 psu) and pCO2 (400 and 1000 µatm). Individually, decreased salinity significantly reduced the growth rate and pigments of S. japonica, indicating that the alga was low-salinity stressed. The maximum quantum yield, Fv/Fm, declined at low salinities independent of pCO2, suggesting that the hyposalinity showed the main effect. Unexpectedly, the higher pCO2 enhanced the maximum relative electron transport rate (rETRmax) but decreased the growth rate, pigments and soluble carbohydrates contents. This implies a decoupling between the photosynthesis and growth of this alga, which may be linked to an energetic reallocation among the different metabolic processes. Interactively and previously untested, the decreased salinity offset the improvement of rETRmax and aggravated the declines of growth rate and pigment content caused by the elevated pCO2. These behaviors could be associated with the additionally decreased pH that was induced by the low salinity. Our data, therefore, unveils that the decreased salinity may increase the risks of future CO2-induced ocean acidification on the production of S. japonica.
Continue reading ‘Decreased salinity offsets the stimulation of elevated pCO2 on photosynthesis and synergistically inhibits the growth of juvenile sporophyte of Saccharina japonica (Laminariaceae, Phaeophyta)’Responses of the macroalga Ulva prolifera Müller to ocean acidification revealed by complementary NMR- and MS-based omics approaches
Published 9 December 2022 Science ClosedTags: algae, biological response, laboratory, Mediterranean, molecular biology, physiology
Ocean acidification (OA) is a dramatic perturbation of seawater environments due to increasing anthropogenic emissions of CO2. Several studies indicated that OA frequently induces marine biota stress and a reduction of biodiversity. Here, we adopted the macroalga Ulva prolifera as a model and applied a complementary multi-omics approach to investigate the metabolic profiles under normal and acidified conditions. Our results show that U. prolifera grows at higher rates in acidified environments. Consistently, we observed lower sucrose and phosphocreatine concentrations in response to a higher demand of energy for growth and a higher availability of essential amino acids, likely related to increased protein biosynthesis. In addition, pathways leading to signaling and deterrent compounds appeared perturbed. Finally, a remarkable shift was observed here for the first time in the fatty acid composition of triglycerides, with a decrease in the relative abundance of PUFAs towards an appreciable increase of palmitic acid, thus suggesting a remodeling in lipid biosynthesis. Overall, our studies revealed modulation of several biosynthetic pathways under OA conditions in which, besides the possible effects on the marine ecosystem, the metabolic changes of the alga should be taken into account considering its potential nutraceutical applications.
Continue reading ‘Responses of the macroalga Ulva prolifera Müller to ocean acidification revealed by complementary NMR- and MS-based omics approaches’Global decrease in heavy metal concentrations in brown algae in the last 90 years
Published 5 December 2022 Science ClosedTags: algae, biological response, chemistry, metals, multiple factors, review, salinity, temperature, toxicants
Highlights
- A decline in metal pollution in algae is widespread in coastal ecosystems worldwide.
- Decrease in algae concentrations may not also occur in seawater but in bioavailability.
- Decreases began from 70’s coinciding with the implementation of environmental policies.
- Legislation and ocean acidification can impact on the heavy metal content in algae.
Abstract
In the current scenario of global change, heavy metal pollution is of major concern because of its associated toxic effects and the persistence of these pollutants in the environment. This study is the first to evaluate the changes in heavy metal concentrations worldwide in brown algae over the last 90 years (>15,700 data across the globe reported from 1933 to 2020). The study findings revealed significant decreases in the concentrations of Cd, Co, Cr, Cu, Fe, Hg, Mn, Pb and Zn of around 60–84% (ca. 2% annual) in brown algae tissues. The decreases were consistent across the different families considered (Dictyotaceae, Fucaceae, Laminariaceae, Sargassaceae and Others), and began between 1970 and 1990. In addition, strong relationships between these trends and pH, SST and heat content were detected. Although the observed metal declines could be partially explained by these strong correlations, or by adaptions in the algae, other evidences suggest an actual reduction in metal concentrations in oceans because of the implementation of environmental policies. In any case, this study shows a reduction in metal concentrations in brown algae over the last 50 years, which is important in itself, as brown algae form the basis of many marine food webs and are therefore potential distributors of pollutants.
Continue reading ‘Global decrease in heavy metal concentrations in brown algae in the last 90 years’Coral reef carbonate accretion rates track stable gradients in seawater carbonate chemistry across the U.S. Pacific Islands
Published 1 December 2022 Science ClosedTags: algae, biological response, BRcommunity, calcification, chemistry, community composition, corals, field, methods, North Pacific, otherprocess
The U.S. Pacific Islands span a dramatic natural gradient in climate and oceanographic conditions, and benthic community states vary significantly across the region’s coral reefs. Here we leverage a decade of integrated ecosystem monitoring data from American Samoa, the Mariana Archipelago, the main and Northwestern Hawaiian Islands, and the U.S. Pacific Remote Island Areas to evaluate coral reef community structure and reef processes across a strong natural gradient in pH and aragonite saturation state (Ωar). We assess spatial patterns and temporal trends in carbonate chemistry measured in situ at 37 islands and atolls between 2010 and 2019, and evaluate the relationship between long-term mean Ωar and benthic community cover and composition (benthic cover, coral genera, coral morphology) and reef process (net calcium carbonate accretion rates). We find that net carbonate accretion rates demonstrate significant sensitivity to declining Ωar, while most benthic ecological metrics show fewer direct responses to lower-Ωar conditions. These results indicate that metrics of coral reef net carbonate accretion provide a critical tool for monitoring the long-term impacts of ocean acidification that may not be visible by assessing benthic cover and composition alone. The perspectives gained from our long-term, in situ, and co-located coral reef environmental and ecological data sets provide unique insights into effective monitoring practices to identify potential for reef resilience to future ocean acidification and inform effective ecosystem-based management strategies under 21st century global change.
Continue reading ‘Coral reef carbonate accretion rates track stable gradients in seawater carbonate chemistry across the U.S. Pacific Islands’Evaluation of growth, primary productivity, nutritional composition, redox state, and antimicrobial activity of red seaweeds Gracilaria debilis and Gracilaria foliifera under pCO2-induced seawater acidification
Published 14 November 2022 Science ClosedTags: algae, biological response, growth, laboratory, photosynthesis, physiology
Highlights
- Seawater acidification improved primary productivity, pigments, and carbon storage.
- No sign of oxidative stress under acidification
- Improved antimicrobial activities in acidified samples
- Possible benefits in the future high pCO2 conditions
Abstract
The genus Gracilaria is an economically important group of seaweeds as several species are utilized for various products such as agar, used in medicines, human diets, and poultry feed. Hence, it is imperative to understand their response to predicted ocean acidification conditions. In the present work, we have evaluated the response of Gracilaria foliifera and Gracilaria debilis to carbon dioxide (pCO2) induced seawater acidification (pH 7.7) for two weeks in a controlled laboratory conditions. As a response variable, we have measured growth, productivity, redox state, primary and secondary metabolites, and mineral compositions. We found a general increase in the daily growth rate, primary productivity, and tissue chemical composition (such as pigments, soluble and insoluble sugars, amino acids, and fatty acids), but a decrease in the mineral contents under the acidified condition. Under acidification, there was a decrease in malondialdehyde. However, there were no significant changes in the total antioxidant capacity and a majority of enzymatic and non-enzymatic antioxidants, except for an increase in tocopherols, ascorbate and glutathione-s-transferase in G. foliifera. These results indicate that elevated pCO2 will benefit the growth of the studied species. No sign of oxidative stress markers indicating the acclimatory response of these seaweeds towards lowered pH conditions. Besides, we also found increased antimicrobial activities of acidified samples against several of the tested food pathogens. Based on these observations, we suggest that Gracilaria spp. will be benefitted from the predicted future acidified ocean.
Continue reading ‘Evaluation of growth, primary productivity, nutritional composition, redox state, and antimicrobial activity of red seaweeds Gracilaria debilis and Gracilaria foliifera under pCO2-induced seawater acidification’Impact of climate change on Arctic macroalgal communities
Published 4 November 2022 Science ClosedTags: algae, Arctic, biological response, light, multiple factors, phanerogams, review, salinity, temperature
The Arctic region faces a warming rate that is more than twice the global average. Seaice loss, increase in precipitation and freshwater discharge, changes in underwater light, and amplification of ocean acidification modify benthic habitats and the communities they host. Here we synthesize existing information on the impacts of climate change on the macroalgal communities of Arctic coasts. We review the shortand long-term changes in environmental characteristics of shallow hard-bottomed Arctic coasts, the floristics of Arctic macroalgae (description, distribution, life-cycle, adaptations), the responses of their biological and ecological processes to climate change, the resulting winning and losing species, and the effects on ecosystem functioning. The focus of this review is on fucoid species, kelps, and coralline algae which are key ecosystem engineers in hard-bottom shallow areas of the Arctic, providing food, substrate, shelter, and nursery ground for many species. Changes in seasonality, benthic functional diversity, food-web structure, and carbon cycle are already occurring and are reshaping Arctic benthic ecosystems. Shallow communities are projected to shift from invertebrate-to algal-dominated communities. Fucoid and several kelp species are expected to largely spread and dominate the area with possible extinctions of native species. A considerable amount of functional diversity could be lost impacting the processing of land-derived nutrients and organic matter and significantly altering trophic structure and energy flow up to the apex consumers. However, many factors are not well understood yet, making it difficult to appreciate the current situation and predict the future coastal Arctic ecosystem. Efforts must be made to improve knowledge in key regions with proper seasonal coverage, taking into account interactions between stressors and across species.
Continue reading ‘Impact of climate change on Arctic macroalgal communities’A look to the future acidified ocean through the eyes of the alien and invasive alga Caulerpa cylindracea (Chlorophyta, Ulvophyceae)
Published 18 October 2022 Science ClosedTags: adaptation, algae, biological response, field, morphology, otherprocess, photosynthesis, physiology, vents
Underwater CO2 vents represent natural laboratories where the responses of marine organisms to ocean acidification can be tested. In a such context, we investigated the changes in the physiology, anatomy, and ultrastructure of the non-indigenous algal species Caulerpa cylindracea growing along a natural pH/CO2 gradient, by conducting a reciprocal transplant experiment between two populations from an acidified vs a non-acidified site. Stress effects in transplants from current to lowered pH conditions resulted in a decrease in the number of active chloroplasts together with an increased number of dilatations between thylakoid membranes and a higher amount of plastoglobules. These changes were consistent with a decrease in the chlorophyll content and in photosynthetic efficiency, matched by an increase in carotenoid content and non-photochemical yields. On the opposite side, transplants from low to current pH showed a recovery to original conditions. Unexpectedly, no significant difference was recorded between wild populations living at current and lowered pH. These results suggest an ongoing acclimation process to lowered pH in the C. cylindracea populations growing in the vent area. This confirms the high plasticity of this invasive species, able to cope not only with different light and temperature conditions but even with a new acidified scenario.
Continue reading ‘A look to the future acidified ocean through the eyes of the alien and invasive alga Caulerpa cylindracea (Chlorophyta, Ulvophyceae)’Mastocarpus papillatus and Porphyra lanceolata differ in stress-induced bleaching depending on morphological factors
Published 12 October 2022 Science ClosedTags: algae, biological response, laboratory, morphology, multiple factors, temperature
Climate change has caused a rapid increase in ocean acidification and sea surface temperature. As anthropogenic effects continue, marine ecosystems must cope with continued shifts in ocean properties. Already, marine organisms have shown evidence of stress-induced responses through the form of bleaching, which is the loss of photosynthetic pigment. Research has largely focused on the bleaching of coral and calcified macroalgae which are more susceptible to changes in carbonate chemistry; however, the ecological importance of fleshy macroalgae necessitates further research as calcified macroalgal responses to climate change may not be representative of other forms of algae. In this study, we subject Porphyra lanceolata and Mastocarpus papillatus, intertidal fleshy macroalga of the Rhodophyta phylum, to the projected effects of climate change by manipulating water temperature and pH. We also investigated how the morphological structures of P. lanceolata and M. papillatus may play a role in mitigating bleaching. We eliminated overall morphology by excising small portions of algae and comparing these excised samples to intact samples. We found that an increase in temperature and a decrease in pH did not affect the amount of bleaching in both species. We also found that Intact samples of P. lanceolata showed a lower amount of bleaching as compared to excised samples while there was no difference in the amount of bleaching between intact and excised samples of M. papillatus. The ruffled, foliose morphology of P. lanceolata may help prevent bleaching while the simple, bladed morphology of M. papillatus may not. These functional morphological differences may give insight into how different species of algae can combat the effects of climate change on a morphological level.
Continue reading ‘Mastocarpus papillatus and Porphyra lanceolata differ in stress-induced bleaching depending on morphological factors’Acidification of seawater attenuates the allelopathic effects of Ulva pertusa on Karenia mikimotoi
Published 9 September 2022 Science ClosedTags: algae, biological response, BRcommunity, laboratory, morphology, photosynthesis, physiology, phytoplankton
Acidification of seawater resulting from absorption of excessive carbon dioxide from the atmosphere is posing a serious threat to marine ecosystem. In this study, we hypothesized that acidified seawater attenuates allelopathic effects of macroalgae on red tide algae because the increase of dissolved carbon dioxide benefits algal growth, and investigated the allelopathic effects of Ulva pertusa on Karenia mikimotoi in response to seawater acidification by determining cell density, photosynthetic pigment content, chlorophyll fluorescence parameters, and chloroplast structure of K. mikimotoi under U. pertusa stress in original (pH=8.2) and acidified (pH=7.8) seawater. U. pertusa inhibited the growth of K. mikimotoi in the original and acidizing seawater, and the inhibition rate was positively correlated with treatment time and concentration of U. pertusa. However, acidizing condition significantly weakened the inhibition degree of U. pertusa on K. mikimotoi (P < 0.05), with the inhibition rates decreased from 51.85 to 43.16% at 10 gFW/L U. pertusa for 96 h. U. pertusa reduced contents of chlorophyll a, chlorophyll c, and carotenoid, maximum photochemical quantum yield (Fv/Fm), actual quantum yield, maximum relative electron transfer efficiency (rETRmax) of PSII, real-time fluorescence value (F), and maximum fluorescence value (Fm′) of PSII of K. mikimotoi under original and acidified conditions. And, the inhibition degree of U. pertusa under acidizing condition was significantly lower than that of original seawater group. Furthermore, the damage degree of chloroplast structure of K. mikimotoi under U. pertusa stress was more serious under original seawater condition. These results indicate that acidification of seawater attenuates the allelopathic effects of U. pertusa on K. mikimotoi.
Continue reading ‘Acidification of seawater attenuates the allelopathic effects of Ulva pertusa on Karenia mikimotoi‘Ocean acidification but not nutrient enrichment reduces grazing and alters diet preference in Littorina littorea
Published 30 August 2022 Science ClosedTags: algae, biological response, laboratory, mollusks, multiple factors, nutrients, performance
Ocean acidification and eutrophication have direct, positive effects on the growth of many marine macroalgae, potentially resulting in macroalgal blooms and shifts in ecosystem structure and function. Enhanced growth of macroalgae, however, may be controlled by the presence of grazers. While grazing under ocean acidification and eutrophication conditions has variable responses, there is evidence of these factors indirectly increasing consumption. We tested whether a common marine herbivorous snail, Littorina littorea, would increase consumption rates of macroalgae (Ulva and Fucus) under ocean acidification (increased pCO2) and/or eutrophication conditions, via feeding trials on live and reconstituted algal thalli. We found that increased pCO2 resulted in reduced grazing rates on live thalli, with snails feeding almost exclusively on Ulva. However, eutrophication did not impact consumption rates of live tissues. In addition, similarity in consumption of reconstituted Ulva and Fucus tissues across all treatments indicated that physical characteristics of algal tissues, rather than tissue chemistry, may drive dietary shifts in a changing climate. In this system, decreased consumption, coupled with increased growth of macroalgae, may ultimately enhance algal growth and spread.
Continue reading ‘Ocean acidification but not nutrient enrichment reduces grazing and alters diet preference in Littorina littorea‘A regional view of the response to climate change: a meta-analysis of European benthic organisms’ responses
Published 4 July 2022 Science ClosedTags: algae, biological response, BRcommunity, corals, crustaceans, echinoderms, field, Mediterranean, mollusks, mortality, multiple factors, North Atlantic, phanerogams, photosynthesis, physiology, reproduction, temperature
Climate change is impacting organisms in every region of the world ocean by acting though on individuals in response to their local environments. Given projected future risks derived from these changes, it is becoming increasingly important to understand regional signals of how organisms respond to facilitate their governance and protection. Benthic organisms structure ecological compositions and ecosystem dynamics, therefore not only providing insights into their own response to climate change but also how ecosystems might respond to future conditions. European seas are transitional areas including boreal, warm-temperate, and subarctic waters with organisms frequently at limits of their distributions. Here, we use a meta-analytical approach to assess how calcification, growth, metabolism, photosynthesis, reproduction, and survival in European benthic organisms respond to ocean acidification and warming. Using meta-regression, we examine how study design factors influence effect-size outcomes. Longer experimental periods generally amplified the effects of climate change on taxonomic groupings and related physiological traits and against expectation do not result in acclimation. In agreement with global studies, we find that impacts vary considerably on different taxonomic groupings and their physiological traits. We found calcifying organisms are an at-risk taxon in European waters, with climate stressors decreasing growth rates, reproduction, and survival rates. Fleshy algal species demonstrate resilience to climate stressors, suggesting future European benthic ecosystems will undergo restructuring based on current climate emission pathways.
Continue reading ‘A regional view of the response to climate change: a meta-analysis of European benthic organisms’ responses’Systematic review and meta-analysis of ocean acidification effects in Halimeda: implications for algal carbonate production
Published 24 June 2022 Science ClosedTags: algae, biological response, calcification, light, morphology, multiple factors, nutrients, physiology, review, temperature
Highlights
- Calcification responses to OA vary widely among Halimeda species (neutral, negative).
- For some species, these responses also seem to be region-dependent.
- Experimental evidence suggests future declines in Halimeda-derived CaCO3 production.
- Occurrence and magnitude of declines will be determined by community composition.
Abstract
Ocean acidification (OA) has been identified as one of the major climate-change related threats, mainly due to its significant impacts on marine calcifiers. Among those are the calcareous green algae of the genus Halimeda that are known to be major carbonate producers in shallow tropical and subtropical seas. Hence, any negative OA impacts on these organisms may translate into significant declines in regional and global carbonate production. In this study, we compiled the available information regarding Halimeda spp. responses to OA (experimental, in situ), with special focus on the calcification responses, one of the most studied response parameters in this group. Furthermore, among the compiled studies (n = 31), we selected those reporting quantitative data of OA effects on algal net calcification in an attempt to identify potential general patterns of species- and/or regional-specific OA responses and hence, impacts on carbonate production. While obtaining general patterns was largely hampered by the often scarce number of studies on individual species and/or regions, the currently available information indicates species-specific susceptibility to OA, seemingly unrelated to evolutionary lineages (and associated differences in morphology), that is often accompanied by differences in a species’ response across different regions. Thus, for projections of future declines in Halimeda-associated carbonate production, we used available regional reports of species-specific carbonate production in conjunction with experimental OA responses for the respective species and regions. Based on the available information, declines can be expected worldwide, though some regions harbouring more sensitive species might be more impacted than others.
Continue reading ‘Systematic review and meta-analysis of ocean acidification effects in Halimeda: implications for algal carbonate production’Ocean acidification induced changes in Ulva fasciata biochemistry may improve Dicentrarchus labrax aquaculture via enhanced antimicrobial activity
Published 16 June 2022 Science ClosedTags: algae, biological response, BRcommunity, fish, fisheries, morphology, mortality, physiology, reproduction
Highlights
- Ocean acidification induced changes in Ulva fasciata biochemistry.
- U. fasciata methanolic extract at pCO2–750 reduced the pathogenic bacterial community.
- Sea bass growth was also highest after being exposed methanolic extract of U. fasciata at pCO2–750.
Abstract
Changes in seawater carbonate chemistry including increased seawater carbon dioxide concentrations (pCO2), commonly known as ocean acidification (OA), can impact metabolic activities and phytochemical production in marine algae. While OA impacts typically reduce animal health, this study investigated the potential of OA-induced changes in methanol bioactivity from the macroalgae Ulva fasciata, to enhance larval European sea bass (Dicentrarchus labrax) aquaculture via increasing antimicrobial activity. After exposing U. fasciata to four pCO2 levels ~280, 550, 750 and 1050 μatm, macroalgae methanol extracts at pCO2–750 exhibited the highest total phenolic content (TPC), flavonoid content (TFC) and yielded the highest antioxidant and antimicrobial activities. After using extracts as a daily water additive for sea bass larvae, U. fasciata methanolic extract at pCO2–750 yielded the greatest reduction in pathogenic bacterial community and the highest survival rate for sea bass larvae. Sea bass larvae growth was also highest after exposure to methanolic extract of U. fasciata grown at pCO2–750, potentially due to higher TPC, TFC and polyunsaturated fatty acid levels. Such nutritional benefits may have been acquired by sea bass larvae via direct uptake or via indirect transfer, by which live feed (Brachionus or Artemia) consumed by larvae accumulated more nutrients. Our results suggest that pCO2–750 has a significant physiological impact on U. fasciata, potentially allowing macroalgae under OA conditions to function as nutritional supplements to increase the performance of sea bass aquaculture.
Continue reading ‘Ocean acidification induced changes in Ulva fasciata biochemistry may improve Dicentrarchus labrax aquaculture via enhanced antimicrobial activity’Global assessment of coralline algae mineralogy points to high vulnerability of Southwestern Atlantic reefs and rhodolith beds to ocean acidification
Published 15 June 2022 Science ClosedTags: algae, biological response, corals, dissolution, field, South Atlantic
Coralline algae constitute one of the main groups of highly vulnerable calcified benthic organisms to ocean acidification. Although damaging effects of seawater acidification on the coralline algae skeleton have been widely demonstrated, the susceptibility to dissolution varies according to the Mg2+ in the calcite lattice. Even though the Southwest Atlantic Ocean exhibits the world’s largest rhodolith beds, which occupies 20,902 km2, there is no information regarding the coralline algae species mineralogy in this area. Here, we provide mineralogical data of twenty-four coralline algae species, examine the similarity in taxonomic groups, spatial occurrence and the vulnerability of these algae to seawater acidification. Mineralogy revealed that coralline algae skeletons were mainly composed of high-Mg calcite (> 70%) with minor presence of aragonite (< 30%) and dolomite (< 3%). There were no similarities between the skeletal mineralogy of taxonomic groups and sampling regions. Remarkably, the mean Mg-substitution of encrusting coralline algae from the Brazilian Shelf was 46.3% higher than global average. Because of the higher mean Mg-substitution in calcite compared with worldwide coralline algae, these algae from Southwest Atlantic Ocean would be highly susceptible to dissolution caused by the expected near-future ocean acidification and will compromise CaCO3 net production across the Brazilian Shelf.
Continue reading ‘Global assessment of coralline algae mineralogy points to high vulnerability of Southwestern Atlantic reefs and rhodolith beds to ocean acidification’Strategies of carbon use and photosynthetic performance of the two seaweeds Gracilaria chouae and Gracilariopsis lemaneiformis under different conditions of the carbonate system
Published 10 June 2022 Science ClosedTags: algae, biological response, light, multiple factors, photosynthesis, physiology
The use of Gracilaria chouae and Gracilariopsis lemaneiformis in aquaculture has recently been rapidly expanding owing to their bio- and eco-functions on coastal areas. However, high density cultures of these commercial seaweeds can lead to rapid changes in carbonate system even on a very short-term basis, which, in turn, effectively affects the physiology of these commercial seaweeds. To explore the regulation of mechanism of carbon use of G. chouae and Gp. lemaneiformis in different carbonate systems, this study exposed two seaweeds to natural seawater (control), and treatments of high CO2 and normal HCO3− concentrations (HC-NB), and natural CO2 and low HCO3− concentrations (NC-LB) to determine the net photosynthetic rate, pH drift, rapid light curves and chlorophyll fluorescence measurements. The results showed that net photosynthetic rates, non-photochemical quenching (NPQ), potential mechanism of relative electron transfer (rETRm) and the ability of both seaweeds to tolerate high light (Ik) increased significantly in the HC-NB treatment. Gp. lemaneiformis had significantly higher rates of photosynthesis and more dramatic changes in pH in all the treatments. Thalli were treated with an inhibitor of extracellular carbonic ahhydrase acetazolamide (AZ) and an anion exchange protein inhibitor 4,4′-disocyanostilbene-2,2′-disulfonate (DIDS), AZ was the primary inhibitor of HCO3− used for both seaweeds during first 2 h. However, after 24 h, DIDS and AZ were the primary inhibitors of G. chouae in all the treatments, and DIDS was the main inhibitor of Gp. lemaneiformis in the control and HC-NB treatments. In conclusion, the photosynthetic ability of G. chouae is greater in carbonate system manipulated seawaters and is more effective at metabolizing HCO3− by extracellular carbonic anhydrase at high pH values. The direct HCO3− use by the anion exchange transporter could be induced at high pH values and low [HCO3−] for both seaweeds. This study will provide a theoretical basis for seaweed aquaculture.
Continue reading ‘Strategies of carbon use and photosynthetic performance of the two seaweeds Gracilaria chouae and Gracilariopsis lemaneiformis under different conditions of the carbonate system’Molecular response of Sargassum vulgare to acidification at volcanic CO2 vents: insights from proteomic and metabolite analyses
Published 8 June 2022 Science ClosedTags: algae, biological response, field, Mediterranean, physiology, vents
Ocean acidification is impacting marine life all over the world. Understanding how species can cope with the changes in seawater carbonate chemistry represents a challenging issue. We addressed this topic using underwater CO2 vents that naturally acidify some marine areas off the island of Ischia. In the most acidified area of the vents, having a mean pH value of 6.7, comparable to far-future predicted acidification scenarios (by 2300), the biomass is dominated by the brown alga Sargassum vulgare. The novelty of the present study is the characterization of the S. vulgare proteome together with metabolite analyses to identify the key proteins, metabolites, and pathways affected by ocean acidification. A total of 367 and 387 proteins were identified in populations grown at pH that approximates the current global average (8.1) and acidified sites, respectively. Analysis of their relative abundance revealed that 304 proteins are present in samples from both sites: 111 proteins are either higher or exclusively present under acidified conditions, whereas 120 proteins are either lower or present only under control conditions. Functionally, under acidification, a decrease in proteins related to translation and post-translational processes and an increase of proteins involved in photosynthesis, glycolysis, oxidation-reduction processes, and protein folding were observed. In addition, small-molecule metabolism was affected, leading to a decrease of some fatty acids and antioxidant compounds under acidification. Overall, the results obtained by proteins and metabolites analyses, integrated with previous transcriptomic, physiological, and biochemical studies, allowed us to delineate the molecular strategies adopted by S. vulgare to grow in future acidified environments, including an increase of proteins involved in energetic metabolism, oxidation-reduction processes, and protein folding at the expense of proteins involved in translation and post-translational processes.
Continue reading ‘Molecular response of Sargassum vulgare to acidification at volcanic CO2 vents: insights from proteomic and metabolite analyses’Cessation of hardground accretion by the cold-water coralline algae Clathromorphum compactum and Clathromorphum nereostratum predicted within two centuries
Published 25 May 2022 Science ClosedTags: algae, biological response, BRcommunity, calcification, individualmodeling, laboratory, modeling, multiple factors, North Atlantic, temperature
Ocean acidification and warming are expected to disproportionately affect high-latitude calcifying species, such as crustose coralline algae. Clathromorphum nereostratum and Clathromorphum compactum are the primary builders of carbonate-hardgrounds in the Aleutians Islands of Alaska and North Atlantic shelf, respectively, providing habitat and settlement substrates for a large number of species. We exposed wild-collected specimens to 12 pCO2/T treatments (344–3322 μatm; 6.38–12.40°C) for 4 months in a factorially crossed, replicated laboratory experiment. Impacts of pCO2/T on algal calcification were quantified from linear extension and buoyant weight. Here we show that, despite belonging to the same genus, C. nereostratum exhibited greater sensitivity to thermal stress, while C. compactum exhibited greater sensitivity to pH stress. Furthermore, multivariate models of algal calcification derived from the experiment indicate that both C. nereostratum and C. compactum will commence net dissolution as early as 2120 and 2200 AD, respectively. Our results therefore indicate that near-term climate change may lead to substantial degradation of these species and loss of the critical hardground habitats that they form.
Continue reading ‘Cessation of hardground accretion by the cold-water coralline algae Clathromorphum compactum and Clathromorphum nereostratum predicted within two centuries’The potential of kelp Saccharina japonica in shielding Pacific oyster Crassostrea gigas from elevated seawater pCO2 stress
Published 20 May 2022 Science ClosedTags: algae, biological response, BRcommunity, chemistry, community composition, field, growth, laboratory, mesocosms, mitigation, mollusks, multiple factors, North Pacific, nutrients, otherprocess, photosynthesis, physiology, respiration
Ocean acidification (OA) caused by elevated atmospheric CO2 concentration is predicted to have negative impacts on marine bivalves in aquaculture. However, to date, most of our knowledge is derived from short-term laboratory-based experiments, which are difficult to scale to real-world production. Therefore, field experiments, such as this study, are critical for improving ecological relevance. Due to the ability of seaweed to absorb dissolved carbon dioxide from the surrounding seawater through photosynthesis, seaweed has gained theoretical attention as a potential partner of bivalves in integrated aquaculture to help mitigate the adverse effects of OA. Consequently, this study investigates the impact of elevated pCO2 on the physiological responses of the Pacific oyster Crassostrea gigas in the presence and absence of kelp (Saccharina japonica) using in situ mesocosms. For 30 days, mesocosms were exposed to six treatments, consisting of two pCO2 treatments (500 and 900 μatm) combined with three biotic treatments (oyster alone, kelp alone, and integrated kelp and oyster aquaculture). Results showed that the clearance rate (CR) and scope for growth (SfG) of C. gigas were significantly reduced by elevated pCO2, whereas respiration rates (MO2) and ammonium excretion rates (ER) were significantly increased. However, food absorption efficiency (AE) was not significantly affected by elevated pCO2. The presence of S. japonica changed the daytime pHNBS of experimental units by ~0.16 units in the elevated pCO2 treatment. As a consequence, CR and SfG significantly increased and MO2 and ER decreased compared to C. gigas exposed to elevated pCO2 without S. japonica. These findings indicate that the presence of S. japonica in integrated aquaculture may help shield C. gigas from the negative effects of elevated seawater pCO2.
Continue reading ‘The potential of kelp Saccharina japonica in shielding Pacific oyster Crassostrea gigas from elevated seawater pCO2 stress’
