The carbonate chemistry was investigated in the semiarid eutrophic Araruama Lagoon (Brazil), one of the largest hypersaline coastal lagoons in the world. Spatial surveys during winter and summer periods were performed, in addition to a diurnal sampling in summer. The hypersaline waters have higher concentrations of total alkalinity (TA) and dissolved inorganic carbon (DIC) than the seawater that feed the lagoon, due to evaporation. However, TA and DIC concentrations were lower than those expected from evaporation. Calcium carbonate (CaCO3) precipitation partially explained these deficits. The negative correlation between the partial pressure of CO2 (pCO2) and chlorophyll a (Chl a) indicated that DIC was also consumed by primary producers. The uptake by photosynthesis contributes to 57–63% of DIC deviation from evaporation, the remaining credited to CaCO3 precipitation. Marked pCO2 undersaturation was prevalent at the innermost region with shallow, confined, and phytoplankton-dominated waters, with a strong enrichment of heavier carbon isotope (δ13C-DIC up to 5.55%), and highest pH (locally counter-acting the process of ocean acidification). Oversaturation was restricted to an urbanized region, and during night-time. The lagoon behaved as a marked CO2 sink during winter (− 15.32 to − 10.15 mmolC m−2 day−1), a moderate sink during summer (− 5.50 to − 4.67 mmolC m−2 day−1), with a net community production (NCP) of 93.7 mmolC m−2 day−1 and prevalence of net autotrophic metabolism. A decoupling between CO2 and O2 exchange rate at the air–water interface was attributed to differences in gas solubility, and high buffering capacity. The carbonate chemistry reveals simultaneous and antagonistic actions of CaCO3 precipitation and autotrophic metabolism on CO2 fluxes, and could reflect future conditions in populated and semiarid coastal ecosystems worldwide.
Continue reading ‘Eutrophication overcoming carbonate precipitation in a tropical hypersaline coastal lagoon acting as a CO2 sink (Araruama Lagoon, SE Brazil)’Posts Tagged 'South Atlantic'
Eutrophication overcoming carbonate precipitation in a tropical hypersaline coastal lagoon acting as a CO2 sink (Araruama Lagoon, SE Brazil)
Published 25 August 2021 Science ClosedTags: chemistry, field, South Atlantic
A proteomic analysis of the effect of ocean acidification on the haemocyte proteome of the South African abalone Haliotis midae
Published 17 August 2021 Science ClosedTags: biological response, laboratory, methods, mollusks, physiology, socio-economy, South Atlantic
Highlights
- 227 proteins were differentially expressed in response to ocean acidification conditions.
- Under OA conditions, H. midae underwent a metabolic shift to generate ATP via energy-efficient mechanisms.
- Haemocyte stabilisation and homeostasis in response to OA was reflected by up-regulation of oxidative stress and cytoskeletal proteins.
- An interplay between the stress and immune response was observed through up-regulation of proteins involved in protein synthesis and turnover, as well as intracellular signalling and transport.
Abstract
As a result of increasing CO2 emissions and the prevalence of global climate change, ocean acidification (OA) is becoming more pervasive, affecting many trophic levels, particularly those that rely on succinctly balanced ocean chemistry. This ultimately threatens community structures, as well as the future sustainability of the fishing/aquaculture industry. Understanding the molecular stress response of key organisms will aid in predicting their future survivability under changing environmental conditions. This study sought to elucidate the molecular stress response of the South African abalone, Haliotis midae, an understudied organism with high economic value, utilising a high throughput iTRAQ-based proteomics methodology. Adult abalone were exposed to control (pH 7.9) and experimental (pH 7.5) conditions for 12, 72 and 168 h, following which protein was isolated from sampled haemocytes and subsequently processed. iTRAQ-labelled peptides were analysed using mass spectrometry, while an array of bioinformatics tools was utilised for analysing the proteomic data. COG analysis identified “Cytoskeleton”, “Translation, ribosomal structure and biogenesis”, “Post-translational modification, protein turnover, chaperones”, and “Intracellular trafficking, secretion and vesicular transport” to be the most enriched functional classes, while statistical analysis identified a total of 33 up-regulated and 23 down-regulated effectors of OA stress in abalone. Several of the up-regulated proteins that were identified function in central metabolism (ENO1, PGK, DUOX1, GPD2), the stress/immune response (CAMKI, HSPA5/GRP78, MAPKI), and cytoskeleton, protein sorting and signal transduction (IQGAP1, MYO9B, TLN1, RDX, TCP-1/CCT, SNX6, CHMP1a, VPS13a). Protein-protein interactions were predicted using STRING DB, Cytoscape and Ingenuity Pathway Analysis, providing a model of the effects of OA on the H. midae haemocyte proteome. The data indicated that H. midae underwent a metabolic shift under OA conditions to utilize more energy-efficient mechanisms of ATP generation, while attempts at restoring haemocyte stabilisation and homeostasis were reflected by up-regulation of oxidative stress and cytoskeletal proteins. Our results support other molluscan studies that report a complex array of overlapping functions of both the stress and immune response systems. This interplay of the mounted stress and immune response is maintained and observed through the up-regulation of proteins involved in protein synthesis and turnover, as well as intracellular signalling and transport. The data presented in this study highlight the value of employing sensitive and robust -omics technologies for assessing the effects of changing environmental conditions on marine organisms.
Continue reading ‘A proteomic analysis of the effect of ocean acidification on the haemocyte proteome of the South African abalone Haliotis midae’Sea surface CO2 fugacity in the southwestern South Atlantic Ocean: an evaluation based on satellite-derived images
Published 13 August 2021 Science ClosedTags: chemistry, field, South Atlantic
The South Atlantic Ocean is historically less sampled than the North Atlantic Ocean. Recent efforts have improved our understanding of the carbonate system variable distribution, mainly on sea surface CO2 fugacity (fCO2). However, these studies have been regionally and temporally restricted. Hence, in this research we developed seasonal algorithms of sea surface fCO2 to investigate the CO2 dynamics along the southwestern South Atlantic Ocean during spring-summer and fall-winter periods. The studied region includes the continental shelf areas of the Abrolhos-Campos Region (an area under the influence of central water upwelling), the South Brazil Bight (a large embayment affected by the mesoscale variability in a westward boundary current), the Southern Brazilian Shelf (a coastal zone influenced by freshwater discharge from continent and water mass entrainment), and offshore waters in the open ocean domain of the southwestern South Atlantic Ocean. Monthly satellite images of sea surface temperature, salinity, and chlorophyll-a, which were concomitantly available from August 2011 to June 2015, were used to reconstruct and evaluate the sea surface fCO2 seasonal field. The predicted fields of sea surface fCO2 enabled an investigation of the main drivers that change this variable over the distinct biogeochemical provinces in the region. As expected, the sea surface temperature was the main driver of seasonal changes in sea surface fCO2, but total dissolved inorganic carbon (DIC) and total alkalinity changes were also relevant, mainly in the biogeochemical provinces under the influence of continental freshwater input or central water upwelling. The latter can play an unpredictable role in CO2 dynamics due to nutrient- and DIC-rich water transport close to the surface. Finally, the use of satellite-derived images is a powerful tool to increase biogeochemical knowledge of relatively undersampled ocean regions, while the development of seasonal sea surface fCO2 algorithms allows a better spatiotemporal comprehension of the CO2 distribution, dynamics, and drivers in the southwestern South Atlantic Ocean – a key region for improving the understanding of the global carbon cycle.
Continue reading ‘Sea surface CO2 fugacity in the southwestern South Atlantic Ocean: an evaluation based on satellite-derived images’The impacts of past, present and future ocean chemistry on predatory planktonic snails
Published 4 August 2021 Science ClosedTags: biological response, BRcommunity, calcification, laboratory, molecular biology, mollusks, morphology, physiology, reproduction, South Atlantic
The atlantid heteropods represent the only predatory, aragonite shelled zooplankton. Atlantid shell production is likely to be sensitive to ocean acidification (OA), and yet we know little about their mechanisms of calcification, or their response to changing ocean chemistry. Here, we present the first study into calcification and gene expression effects of short-term OA exposure on juvenile atlantids across three pH scenarios: mid-1960s, ambient and 2050 conditions. Calcification and gene expression indicate a distinct response to each treatment. Shell extension and shell volume were reduced from the mid-1960s to ambient conditions, suggesting that calcification is already limited in today’s South Atlantic. However, shell extension increased from ambient to 2050 conditions. Genes involved in protein synthesis were consistently upregulated, whereas genes involved in organismal development were downregulated with decreasing pH. Biomineralization genes were upregulated in the mid-1960s and 2050 conditions, suggesting that any deviation from ambient carbonate chemistry causes stress, resulting in rapid shell growth. We conclude that atlantid calcification is likely to be negatively affected by future OA. However, we also found that plentiful food increased shell extension and shell thickness, and so synergistic factors are likely to impact the resilience of atlantids in an acidifying ocean.
Continue reading ‘The impacts of past, present and future ocean chemistry on predatory planktonic snails’Efeitos biológicos da orfenadrina sob diferentes cenários de acidificação oceânica (in Portuguese)
Published 30 July 2021 Science ClosedTags: biological response, BRcommunity, echinoderms, laboratory, mollusks, multiple factors, physiology, reproduction, sediment, South Atlantic, toxicants
O aumento das emissões de gás carbônico atmosférico proveniente de atividades antrópicas desde a Revolução Industrial teve como consequência uma maior participação de águas superficiais no processo de sequestro de dióxido de carbono, a fim de amenizar o efeito estufa. A principal consequência do aumento de captura de gás carbônico pelos oceanos é um fenômeno denominado acidificação oceânica. Alguns poluentes presentes na água, como por exemplo fármacos e produtos de cuidados pessoais (FPCPs) podem sofrer alterações na sua mobilidade e biodisponibilidade por conta da diminuição do pH do meio. Atualmente a quantidade de dados sobre os efeitos e o risco ambiental de FPCPs em organismos marinhos ainda é escassa. Diante deste cenário o presente estudo teve como objetivo analisar a ocorrência, o comportamento e a biodisponibilidade do fármaco orfenadrina frente a diferentes cenários de acidificação oceânica. O fármaco orfenadrina, empregado como relaxante muscular e amplamente consumido foi observado em todos os pontos de amostragem das áreas de influência dos emissários submarinos de Santos e Guarujá – SP, com concentrações que variaram LOQ a 0,5 ng/g em sedimentos. Os resultados do ensaio de toxicidade com água empregando ouriços do mar (Echinometra lucunter) nos diferentes pHs 8,0; 7,6; 7,3 apresentaram valores de CEO de 0,05mg/L e o EpH50 foi estabelecido em 7,30. Quanto aos ensaios com mexilhões Perna perna foram observados efeitos em concentrações ambientalmente relevantes, com CEO de 200 ng/g. Os resultados dos ensaios feitos para a avaliação do desenvolvimento embriolarval em água indicaram que tanto o processo de acidificação quanto o aumento da concentração afetam o desenvolvimento dos embriões de ouriço do mar. Já nos ensaios com P. perna foi possível verificar ainda que a presença do fármaco de caráter básico reduziu os efeitos da acidificação oceânica. Os resultados da análise de bioacumulação detectaram a presença da orfenadrina em todos os tecidos analisados. A análise dos ensaios de citotoxicidade nesta ocasião refutou a hipótese inicial do estudo, visto que a presença do fármaco de caráter básico reduziu os efeitos da acidificação oceânica. Neste sentido, fica evidente necessidade de se aprofundar os estudos sobre toxicologia relacionada a fármacos sob cenários de acidificação em ambiente marinho.
Continue reading ‘Efeitos biológicos da orfenadrina sob diferentes cenários de acidificação oceânica (in Portuguese)’The sensitivity of the marine carbonate system to regional ocean alkalinity enhancement
Published 9 July 2021 Science ClosedTags: Arctic, chemistry, globalmodeling, Indian, mitigation, modeling, North Atlantic, North Pacific, regionalmodeling, South Atlantic, South Pacific
Ocean Alkalinity Enhancement (OAE) simultaneously mitigates atmospheric concentrations of CO2 and ocean acidification; however, no previous studies have investigated the response of the non-linear marine carbonate system sensitivity to alkalinity enhancement on regional scales. We hypothesise that regional implementations of OAE can sequester more atmospheric CO2 than a global implementation. To address this, we investigate physical regimes and alkalinity sensitivity as drivers of the carbon-uptake potential response to global and different regional simulations of OAE. In this idealised ocean-only set-up, total alkalinity is enhanced at a rate of 0.25 Pmol a-1 in 75-year simulations using the Max Planck Institute Ocean Model coupled to the HAMburg Ocean Carbon Cycle model with pre-industrial atmospheric forcing. Alkalinity is enhanced globally and in eight regions: the Subpolar and Subtropical Atlantic and Pacific gyres, the Indian Ocean and the Southern Ocean. This study reveals that regional alkalinity enhancement has the capacity to exceed carbon uptake by global OAE. We find that 82–175 Pg more carbon is sequestered into the ocean when alkalinity is enhanced regionally and 156 PgC when enhanced globally, compared with the background-state. The Southern Ocean application is most efficient, sequestering 12% more carbon than the Global experiment despite OAE being applied across a surface area 40 times smaller. For the first time, we find that different carbon-uptake potentials are driven by the surface pattern of total alkalinity redistributed by physical regimes across areas of different carbon-uptake efficiencies. We also show that, while the marine carbonate system becomes less sensitive to alkalinity enhancement in all experiments globally, regional responses to enhanced alkalinity vary depending upon the background concentrations of dissolved inorganic carbon and total alkalinity. Furthermore, the Subpolar North Atlantic displays a previously unexpected alkalinity sensitivity increase in response to high total alkalinity concentrations.
Continue reading ‘The sensitivity of the marine carbonate system to regional ocean alkalinity enhancement’Physiology, niche characteristics and extreme events: current and future habitat suitability of a rhodolith-forming species in the Southwestern Atlantic
Published 18 June 2021 Science ClosedTags: algae, biological response, individualmodeling, laboratory, modeling, mortality, multiple factors, nutrients, performance, photosynthesis, physiology, policy, reproduction, South Atlantic, temperature
Highlights
- Global climate change and local stressors are the main threats to reef-building organisms and habitats they build, such as rhodolith beds.
- Through an experimental essay and ecological niche modelling, we were able to determine the environmental factors that determine the distribution and affect the physiology of an important rhodolith-forming species in the southwestern Atlantic.
- Our results raise the possibility of some rhodolith-forming species being resilient to future environmental change based on our current understanding of their distributions, a perspective that will need to be further explored by future studies.
- This information is helpful in informing policies for the conservation of priority areas, aiding the preservation of marine biodiversity in the South Atlantic.
Abstract
Given the ecological and biogeochemical importance of rhodolith beds, it is necessary to investigate how future environmental conditions will affect these organisms. We investigated the impacts of increased nutrient concentrations, acidification, and marine heatwaves on the performance of the rhodolith-forming species Lithothamnion crispatum in a short-term experiment, including the recovery of individuals after stressor removal. Furthermore, we developed an ecological niche model to establish which environmental conditions determine its current distribution along the Brazilian coast and to project responses to future climate scenarios. Although L. crispatum suffered a reduction in photosynthetic performance when exposed to stressors, they returned to pre-experiment values following the return of individuals to control conditions. The model showed that the most important variables in explaining the current distribution of L. crispatum on the Brazilian coast were maximum nitrate and temperature. In future ocean conditions, the model predicted a range expansion of habitat suitability for this species of approximately 58.5% under RCP 8.5. Physiological responses to experimental future environmental conditions corroborated model predictions of the expansion of this species’ habitat suitability in the future. This study, therefore, demonstrates the benefits of applying combined approaches to examine potential species responses to climate-change drivers from multiple angles.
Continue reading ‘Physiology, niche characteristics and extreme events: current and future habitat suitability of a rhodolith-forming species in the Southwestern Atlantic’Coastal pH variability and the eco-physiological and behavioural response of a coastal fish species in light of future ocean acidification
Published 5 May 2021 Science ClosedTags: biological response, chemistry, field, fish, laboratory, performance, physiology, respiration, South Atlantic
Ocean acidification (OA) is a global phenomenon referring to a decrease in ocean pH and a perturbation of the seawater carbonate system due to ever-increasing atmospheric CO2 concentrations. In coastal environments, identifying the impacts of OA is complex due to the multiple contributors to pH variability by coastal processes, such as freshwater inflow, upwelling, hydrodynamic processes, and biological activity. The aim of this PhD study was to quantify the local processes occurring in a temperate coastal embayment, Algoa Bay in South Africa, that contribute to pH and carbonate chemistry variability over time (monthly and 24-hour) and space (~10 km) and examine how this variability impacts a local fish species, Diplodus capensis, also commonly known as ‘blacktail’. Algoa Bay, known for its complex oceanography, is an interesting location in which to quantify carbonate chemistry variability. To assess this variability, monitoring sites were selected to coincide with the Algoa Bay Sentinel Site long-term ecological research (LTER) and continuous monitoring (CMP) programmes. The average pH at offshore sites in the bay was 8.03 ± 0.07 and at inshore sites was 8.04 ± 0.15. High pH variability (~0.55–0.61 pH units) was recorded at both offshore (>10 m depth) and inshore sites (intertidal surf zones). Many sites in the bay, especially the atypical site at Cape Recife, exhibit higher than the average pH levels (>8.04), suggesting that pH variability may be biologically driven. This is further evidenced by high diurnal variability in pH (~0.55 pH units). Although the specific drivers of the high pH variability in Algoa Bay could not be identified, baseline carbonate chemistry conditions were identified, which is necessary information to design and interpret biological experiments. Long-term, continuous monitoring is required to improve understanding of the drivers of pH variability in understudied coastal regions, like Algoa Bay.
Continue reading ‘Coastal pH variability and the eco-physiological and behavioural response of a coastal fish species in light of future ocean acidification’Tidal action and macroalgal photosynthetic activity prevent coastal acidification in an eutrophic system within a semi-desert region
Published 3 May 2021 Science ClosedTags: abundance, algae, biogeochemistry, biological response, BRcommunity, laboratory, otherprocess, photosynthesis, South Atlantic
Highlights
- Macroalgal photosynthesis (MP) controls daily pH variability during low tide.
- Environmental factors control pH variability at seasonal scale.
- Ulva lactuca photosynthetic activity increased the pH of seawater.
- Macrotidal action and MP prevent coastal acidification in an eutrophic system.
Abstract
Nutrient input drive macroalgal blooms and increases in photosynthetic activity in coastal ecosystems. An intense macroalgal photosynthetic activity can increase the surrounding pH and it could prevent the acidification that often follows an eutrophication process. We tested this hypothesis with field sampling and experiments in a macrotidal (up to 9 m in amplitude) coastal system within a semi-desert region with contrasting eutrophic conditions and Ulva lactuca blooms in the northern Argentinean Patagonia (San Antonio Bay). Our results indicate that daily pH variability during low tide could be controlled by the photosynthetic activity of Ulva lactuca under eutrophic conditions. At seasonal scale, the pH variations were related to environmental features, particularly seawater temperature. Both environmental (i.e. high solar radiation, negligible freshwater inputs and, large tidal action) and anthropogenic nutrient inputs into the studied area promote the Ulva lactuca blooms, which in turn increases the surrounding pH in well oxygenated seawater through the intense photosynthetic activity. Our study shows that eutrophication instead of being a driver of acidification, could contribute to its prevention in well oxygenated marine coastal systems located within semi-desert regions.
Continue reading ‘Tidal action and macroalgal photosynthetic activity prevent coastal acidification in an eutrophic system within a semi-desert region’Impact of increased nutrients and lowered pH on photosynthesis and growth of three marine phytoplankton communities from the coastal South West Atlantic (Patagonia, Argentina)
Published 25 March 2021 Science ClosedTags: biological response, BRcommunity, community composition, growth, laboratory, multiple factors, nutrients, photosynthesis, phytoplankton, South Atlantic, zooplankton
Effect of global change variables on the structure and photosynthesis of phytoplankton communities was evaluated in three different sites of the Patagonian coast of Argentina: enclosed bay (Puerto Madryn, PM), estuarine (Playa Unión, PU), and open waters (Isla Escondida, IE). We exposed samples to two contrasting scenarios: Present (nutrients at in situ levels) vs. Future (with lowered pH and higher nutrients inputs), and determined growth and photosynthetic responses after 2 days of acclimation. Under the Future condition phytoplankton growth was higher in the estuarine site compared to those in PM and IE. This effect was the most pronounced on large diatoms. While the increase of photosynthetic activity was not always observed in the Future scenario, the lower photosynthetic electron requirement for carbon fixation (Φe,C = ETR/PmB) in this scenario compared to the Present, suggests a more effective energy utilization. Long-term experiments were also conducted to assess the responses along a 4 days acclimation period in PU. Diatoms benefited from the Future conditions and had significantly higher growth rates than in the Present. In addition, Φe,C was lower after the acclimation period in the Future scenario, compared to the Present. Our results suggest that the availability, frequency and amount of nutrients play a key role when evaluating the effects of global change on natural phytoplankton communities. The observed changes in diatom growth under the Future scenario in PU and IE and photosynthesis may have implications in the local trophodynamics by bottom up control.
Continue reading ‘Impact of increased nutrients and lowered pH on photosynthesis and growth of three marine phytoplankton communities from the coastal South West Atlantic (Patagonia, Argentina)’Multiple-stressor effects of warming and acidification on the embryonic development of an estuarine fiddler crab
Published 22 March 2021 Science ClosedTags: biological response, chemistry, crustaceans, field, laboratory, morphology, mortality, multiple factors, reproduction, South Atlantic, temperature
Highlights
- Elevated temperature accelerated early and late embryonic development.
- Reduced pH accelerated late embryonic development.
- Elevated temperature reduced survivorship in later stages.
- A negative synergetic effect between pH and temperature was evidenced in egg volume.
- > 70% of embryos well-developed under elevated temperature and reduced pH.
Abstract
Predicted effects of anthropogenic climate change on estuarine and coastal organisms are complex, and early life history stages of calcified ectotherms are amongst the most sensitive groups. Despite the importance of understanding their vulnerability, we lack information on the effects of multiple stressors on the embryonic development of estuarine and burrowing organisms, mainly mangrove-associated species. Here, we determined the combined effects of elevated temperature and decreased pH on the embryonic development of the estuarine fiddler crab Leptuca thayeri. Initially, the microhabitat (burrow) of ovigerous (egg-bearing) females was measured for temperature, pH, and salinity, which provided control values in our laboratory experiment. Embryos at the early stage of development were subjected to cross-factored treatments of predicted temperature and pH and evaluated for development rate, survivorship, and volume until their later embryonic stage. Embryo development was faster at early and later stages of development, and survivorship was lower under elevated temperature. Embryos under reduced pH showed advanced embryonic stages at their late development stage. Higher egg volume was observed in a warmer and acidified environment, and lower volume in warmer and non-acidified conditions, indicating that embryo development is synergistically affected by warming and acidification. More than 70% of embryos developed until late stages under the multiple-stressors treatment, giving insights on the effects of a warm and acidified environment on burrowing estuarine organisms and their early stages of development.
Continue reading ‘Multiple-stressor effects of warming and acidification on the embryonic development of an estuarine fiddler crab’Anthropogenic CO2 and ocean acidification in Argentine Basin water masses over almost five decades of observations
Published 19 March 2021 Science ClosedTags: chemistry, field, South Atlantic
Highlights
- In the Argentine Basin there is an increase in anthropogenic carbon at all depths.
- Acidification by carbon uptake is being enhanced by natural processes.
- The loss of carbonate affects upper and intermediate water masses: SACW, SAMW, AAIW
- The imminent carbonate undersaturation in AAIW is virtually unavoidable.
Abstract
The chemical conditions of the Argentine Basin (western South Atlantic Ocean) water masses are evaluated with measurements from eleven hydrographic cruises to detect and quantify anthropogenic and natural stressors in the ocean carbon system. The database covers almost half-century (1972-2019), a time-span where the mean annual atmospheric carbon dioxide concentration (CO2atm) increased from 325 to 408 parts per million of volume (ppm). This increase of atmospheric CO2 (83 ppm, the 64% of the total anthropogenic signal in the atmosphere) leads to an increase in anthropogenic carbon (Cant) across all the water column and the consequent ocean acidification: a decrease in excess carbonate that is unequivocal in the upper (South Atlantic Central Water, SACW) and intermediate water masses (Sub Antarctic Mode Water, SAMW and Antarctic Intermediate Water, AAIW). For each additional ppm in CO2atm the water masses SACW, SAMW and AAIW lose excess carbonate at a rate of 0.39±0.04, 0.47±0.05 and 0.23±0.03 μmol·kg-1·ppm-1 respectively. Modal and intermediate water masses in the Argentine Basin are very sensitive to carbon increases due low buffering capacity. The large rate of AAIW acidification is the synergic effect of carbon uptake combined with deoxygenation and increased remineralization of organic matter. If CO2 emissions follows the path of business-as-usual emissions (SSP 5.85), SACW would become undersaturated with respect to aragonite at the end of the century. The undersaturation in AAIW is virtually unavoidable.
Continue reading ‘Anthropogenic CO2 and ocean acidification in Argentine Basin water masses over almost five decades of observations’Primary, secondary, and tertiary stress responses of juvenile seahorse Hippocampus reidi exposed to acute acid stress in brackish and seawater
Published 18 March 2021 Science ClosedTags: biological response, fish, laboratory, mortality, multiple factors, physiology, salinity, South Atlantic
Highlights
• Activity of antioxidant enzymes was harmed in seahorse juveniles exposed to acidic environment in brackish water.
• Lower tolerance for acidification in brackish water triggered lipid peroxidation in seahorse juveniles.
• Seahorse juvenile survival was not influenced by pH neither in brackish nor in sea water.
Abstract
Seahorse Hippocampus reidi is a vulnerable species, inhabiting estuarine and coastal waters. The safety of acidic environments for fish has been considered in terms of ocean acidification in nature and decreasing pH in intensive aquaculture systems. This study aimed to investigate the effects of acute exposition (96 h) of juvenile seahorses to different pH (5, 6, 7, and 8) in brackish (BW – salinity 11) or seawater (SW – salinity 33). For that, we studied the responses of cortisol, oxidative stress, and survival, thus covering primary, secondary, and tertiary stress responses. In SW, cortisol levels were not altered for fish maintained at pH 5 and 8. However, in BW, cortisol was higher for fish kept at pH 5. Regarding secondary stress responses, only GST activity increased with acidification in SW. However, acidification in BW caused biochemical alterations at enzymatic level (SOD, GST, GPx) and glutathione metabolism, accompanied by reduction of antioxidant capacity (TEAC) and increased lipid peroxidation (TBARS). Survival was always above 90% and it did not differ significantly among pH levels. Our results suggest that H. reidi juveniles are more vulnerable to acidic exposure in BW than in SW.
Continue reading ‘Primary, secondary, and tertiary stress responses of juvenile seahorse Hippocampus reidi exposed to acute acid stress in brackish and seawater’Influence of acidification and warming of seawater on biofouling by bacteria grown over API 5L steel
Published 24 February 2021 Science ClosedTags: abundance, biological response, BRcommunity, community composition, laboratory, mesocosms, molecular biology, multiple factors, otherprocess, prokaryotes, protists, South Atlantic, temperature
The acidification and warming of seawater have several impacts on marine organisms, including over microorganisms. The influence of acidification and warming of seawater on biofilms grown on API 5L steel surfaces was evaluated by sequencing the 16S ribosomal gene. For this, three microcosms were designed, the first simulating the natural marine environment (MCC), the second with a decrease in pH from 8.1 to 7.9, and an increase in temperature by 2 °C (MMS), and the third with pH in around 7.7 and an increase in temperature of 4 °C (MES). The results showed that MCC was dominated by the Gammaproteobacteria class, mainly members of the Alteromonadales Order. The second most abundant group was Alphaproteobacteria, with a predominance of Rhodobacterales and Oceanospirillales. In the MMS system there was a balance between representatives of the Gammaproteobacteria and Alphaproteobacteria classes. In MES there was an inversion in the representations of the most prevalent classes previously described in MCC. In this condition, there was a predominance of members of the Alphaproteobacteria Class, in contrast to the decrease in the abundance of Gammaproteobacteria members. These results suggest that possible future climate changes may influence the dynamics of the biofouling process in surface metals.
Continue reading ‘Influence of acidification and warming of seawater on biofouling by bacteria grown over API 5L steel’Ocean circulation drives the variability of the carbon system in the Eastern Tropical Atlantic
Published 12 February 2021 Science ClosedTags: chemistry, North Atlantic, South Atlantic
The carbon system in the eastern tropical Atlantic remains poorly known. The variability and drivers of the carbon system are assessed using surface dissolved inorganic carbon (DIC), alkalinity (TA) and fugacity of CO2 (fCO2) measured in the 12° N–12° S, 12° W–12° E region from 2005 to 2019. A relationship linking DIC to temperature, salinity and year has been determined, with salinity being the strongest predictor. The seasonal variations of DIC, ranging from 80 to 120 mol kg−1, are more important than the year-to-year variability that is less than 50 mol kg−1 over the 2010–2019 period. DIC and TA concentrations are lower in the northern part of the basin where surface waters are fresher and warmer. Carbon supply dominates over biological carbon uptake during the productive upwelling period from July to September. The lowest DIC and TA are located in the Congo plume. The influence of the Congo is still observed at the mooring at 6° S, 8° E as shown by large salinity and chlorophyll variations. Nevertheless, this site is a source of CO2 emissions into the atmosphere.
Continue reading ‘Ocean circulation drives the variability of the carbon system in the Eastern Tropical Atlantic’Effects of ocean acidification on growth, pigment contents and antioxidant potential of the subtropical Atlantic red alga Hypnea pseudomusciformis Nauer, Cassano & M.C. Oliveira (Gigartinales) in laboratory
Published 25 January 2021 Science ClosedTags: algae, biological response, laboratory, morphology, photosynthesis, physiology, South Atlantic
Marine ecosystems are subject to several modifications due to anthropogenic impacts, including ocean acidification caused by the absorption of excessive CO2 present in the atmosphere. Perspectives are for dramatic modifications in seawater pH and more than 60% of the ocean surface impacted over the next 100 years by global change. In this study, ocean acidification scenarios were simulated by CO2 enrichment into seawater in three pH levels (8.0, 7.6 and 7.2) using a bioreactor system in laboratory conditions. Experimental evaluation was performed with Hypnea pseudomusciformis Nauer, Cassano & M.C. Oliveira due to its great importance in coastal marine ecosystems for primary production and commercial interest. Contrary to our initial hypothesis, the growth rate of H. pseudomusciformis decreased significantly with decreased pH conditions, even with increased availability of CO2. The maximum quantum yield and chlorophyll a content were also negatively affected by the pH reduction, while an increase in antioxidant activity was observed, indicating physiological stress. The physiological responses to decreased pH conditions reflect the importance of species-level studies and corroborate the changes caused by the ocean acidification on the macroalgal species.
Continue reading ‘Effects of ocean acidification on growth, pigment contents and antioxidant potential of the subtropical Atlantic red alga Hypnea pseudomusciformis Nauer, Cassano & M.C. Oliveira (Gigartinales) in laboratory’Photoprotection and antioxidative metabolism in Ulva lactuca exposed to coastal oceanic acidification scenarios in the presence of Irgarol
Published 7 December 2020 Science ClosedTags: algae, biological response, laboratory, multiple factors, otherprocess, photosynthesis, physiology, South Atlantic, toxicants
Highlights
- Photosynthetic yield is affected by low pH in assays with and without Irgarol.
- Membrane damage and antioxidant activities increased in low pH added to Irgarol.
- H2O2 content and lipid peroxidation were not affected by low pH isolated.
- U.lactuca is tolerant to low pH by triggering photoprotector mechanisms.
- Protective mechanisms could not avoid the simultaneous effects of low pH and Irgarol.
Abstract
Anthropogenic changes such as ocean acidification, eutrophication, and the release of hazardous chemicals affect coastal environments and aquatic organisms. We investigated the effects of seawater pH (7.4 and 8.2) isolated and in combination with Irgarol on Ulva lactuca. Stress indicators such as membrane damage, lipid peroxidation, and hydrogen peroxide content were assessed. In addition, chlorophyll fluorescence and antioxidant enzyme activities were measured. The photosynthetic yield was affected by low pH in assays with and without Irgarol. However, the combination of low pH and Irgarol promoted photoinhibition, besides the induction of non-photochemical quenching (NPQ) and changes in photosynthetic pigment contents. The induction of NPQ was directly influenced by low pH. The membrane damage was increased in low pH with and without Irgarol exposure. Total soluble protein and carbohydrate contents decreased in low pH, and in presence of Irgarol. The H2O2 content and lipid peroxidation were not affected by low pH. In contrast, Irgarol exposure strongly increased lipid peroxidation in both pHs, suggesting a possible synergistic effect. To avoid the harmful effects of high H2O2, U. lactuca increased antioxidant enzyme activities in treatments under low pH and in presence of Irgarol. Our results indicate that U. lactuca is tolerant to low pH by inducing NPQ, changing pigment contents, and increasing antioxidant defenses. In contrast, these protective mechanisms could not avoid the harmful effects of the combination with Irgarol.
Continue reading ‘Photoprotection and antioxidative metabolism in Ulva lactuca exposed to coastal oceanic acidification scenarios in the presence of Irgarol’Autonomous measurement of seawater total alkalinity as an enhancement of ocean carbon observations: from performance characterization to long-term field deployment
Published 30 October 2020 Science ClosedTags: chemistry, field, methods, North Atlantic, South Atlantic
Since around the mid of the 18th century, the global atmospheric carbon dioxide (CO2) concentration has significantly increased due to anthropogenic activities. For 2018, around 11.5 GtC yr−1 were emitted by fossil fuel combustion and cement production, and land use changes. A sink for the atmospheric CO2 is the ocean, which has taken up around 2.6 GtC yr−1 in 2018. The relative good understanding of the current global mean oceanic uptake of anthropogenic CO2 is contrasted by a lack of knowledge how the natural carbon cycle will respond regionally to changes introduced by anthropogenic CO2 emissions, like global warming, ocean acidification or ocean deoxygenation. In view of the central role of the oceanic CO2 sink and its vulnerability to these changes, extensive ocean carbon observations are necessary. Over several years, the Ships of Opportunity (SOOP) network provides high-quality CO2 partial pressure (p(CO2)) data of the surface ocean, and, therefore, forms the backbone of the global observation system for the oceanic CO2 sink. However, to get full insight into the marine CO2 system, at least two of the four measurable carbonate variables are required, which are p(CO2), total alkalinity (AT), dissolved inorganic carbon (CT) and pH. The so far common workaround is the prediction of AT by using established temperature-salinity based parameterizations. However, compared with direct measurements, this procedure leads to higher uncertainties and spatiotemporal biases. Therefore, autonomous SOOP-based AT measurements are of great interest and, in the end, should enhance ocean carbon observations. In order to achieve this enhancement, this thesis goals to provide an example of a successful implementation of a novel autonomous analyzer for seawater AT, the CONTROS HydroFIA TA (-4H-JENA engineering GmbH, Germany), on a Carbon-SOOP station operating in the subpolar North Atlantic (together with fundamental guidelines and recommendations leading to high-quality AT data).
Continue reading ‘Autonomous measurement of seawater total alkalinity as an enhancement of ocean carbon observations: from performance characterization to long-term field deployment’The success of the fertilization and early larval development of the tropical sea urchin Echinometra lucunter (Echinodermata: Echinoidea) is affected by the pH decrease and temperature increase
Published 20 August 2020 Science ClosedTags: biological response, echinoderms, laboratory, multiple factors, reproduction, South Atlantic, temperature
Highlights
• Temperature and pH were tested on embryo-larval development of sea urchins.
• Larval development test proved to be more sensitive compared to gamete fecundity test.
• Low pH as an isolated factor exhibit significant results on fertilization and embryo-larval development.
• Extreme high temperature associated with low pH affect only sea urchin’s embryo-larval.
• Combination of low pH and high temperature causes damages in sea urchin.
Abstract
The decrease in the pH of oceans and the increase in their temperature are the two main problems observed in the marine ecosystems due to the increasing emission of CO2 in the atmosphere. Both conditions can affect the ecological processes of reproduction, recruitment and survival of the marine biota. Thus, the objective of the present study was to evaluate the effects of pH decrease and temperature increase of seawater on the fertilization success and embryo-larval development of a species of tropical sea urchin. For this purpose, fertilization success (gametes) and embryo-larval development rate were determined by exposing gametes and embryos to decreasing pH values (8.0 (control), 7.7, and 7.4) and increasing temperatures (26 (control), 28, 30, 34, and 38 °C). These conditions were tested associated with each other (in synergy). The gamete test was sensitive to all investigated scenarios, the fertilization success was significantly reduced in the conditions of increased temperature (28, 30, 34, and 38 °C) associated with the ideal pH (pH 8.0) and the conditions of reduced pH (pH 7.7, and 7.4), remaining unchanged only in the ideal condition (pH 8.0 + 26 °C). However, the embryo test displayed enhanced sensitivity in the scenarios of temperature increase (28, 30, 34, and 38 °C) associated with pH decrease conditions. A significantly reduction of 29%, 23% and 10% was observed in all tested pH values at 38 °C, when compared to the control group (80%, 79.5% and 63%, respectively). Therefore, the present study suggests that the occurrence of both scenarios may have a significant impact, in the coming years, on the population of Echinometra lucunter.
Vulnerability and resilience of tropical coastal ecosystems to ocean acidification
Published 11 August 2020 Science ClosedTags: biological response, corals, Indian, review, South Atlantic, South Pacific
Ocean acidification leads to a wide variety of responses from tropical coastal ecosystems. Coral reefs are most vulnerable with most coral species exhibiting declining calcification rates with decreasing pH and carbonate chemistry parameters. Some corals show resilience to acidification likely due to active physiological regulation of their calcifying fluid. Other calcifying organisms, such as some foraminifera and coccolithophores, exhibit negative responses, whereas some symbiont-bearing calcifiers respond positively, to increasing acidification. Seagrasses and brown macroalgae thrive under acidified conditions, with increasing rates of primary productivity. Some tropical coastal fish species are resilient, and in some species, respond positively, to acidification. Some tropical species show complex, nonlinear responses to declining pH and carbonate chemistry. Factors that influence the ability of a species to adapt to and/or resist acidification include food supply, nutrient availability, temperature, diet, interactions with symbionts and other organisms and species and community diversity. Interactive effects of ocean acidification with other climate change parameters, such as elevated temperature, play an important but poorly understood role in determining the resilience and vulnerability of tropical coastal species, communities and ecosystems. Some short-lived species can undergo acclimation and/or adaptive evolution to increase fitness in the face of acidification. Biota living in tropical estuarine and nearshore environments, such as mangroves, seagrasses and intertidal and subtidal inshore benthos, are unlikely to be significantly affected by future acidification as such environments exhibit very wide variations in water and sediment pH and carbonate chemistry. Nearly all tropical coastal environments exhibit significant CO2 efflux to the atmosphere due to pCO2 and [CO32-] oversaturation caused by high rates of respiration and factors linked to fluvial discharge. Except for coral reefs, most calcifying organisms and upwelling regions, tropical estuarine and inshore ecosystems unaffected by eutrophication and other anthropogenic problems should be resilient to future acidification.
