New observations obtained in 2021 and 2022 are presented and used to investigate the trend of the carbonate system (including pH and aragonite saturation state, Ωar) in the southern sector of the Mozambique Channel. Using historical and new data in April–May we observed an acceleration of the acidification ranging from -0.012 TS.decade-1 in 1963–1995 to -0.027 (±0.003) TS.decade-1 in 1995–2022. Result from a neural network (FFNN) model for all seasons also suggests faster pH trend in recent decades, -0.011 TS.decade-1 over 1985–1995 and -0.018 TS.decade-1 over 1995–2022. In May 2022 we estimated Ωar of 3.49, about 0.3 lower than observed in May 1963 (Ωar = 3.86). The lowest Ωar value of 3.23 was evaluated from the FFNN model in September 2023 that corresponds to the hypothetical critical threshold value (3.25) for coral reefs. In 2025 a marine heat wave was observed in this region (sea surface temperature up to 30 °C) and data from a BGC-Argo float indicate that sea surface pH was low in January 2025 (pH = 7.95) whereas War was low in Mach 2025 (Ωar = 3.2). A projection of the CT concentrations based on observed anthropogenic CO2 in subsurface water and emissions scenario, suggests that a risky level for corals (Ωar < 3) could be reached as soon as year 2034.
Continue reading ‘New observations confirm the progressive acidification in the Mozambique Channel’Posts Tagged 'Indian'
New observations confirm the progressive acidification in the Mozambique Channel
Published 7 August 2025 Science ClosedTags: chemistry, field, Indian, modeling, regionalmodeling
Effects of different environmental stressors on marine biogenic sulfur compounds in the Northwest Pacific and Eastern Indian Oceans
Published 2 July 2025 Science ClosedTags: abundance, biogeochemistry, biological response, community composition, growth, Indian, laboratory, multiple factors, North Pacific, otherprocess, physiology, phytoplankton
Abstract
Key roles of marine dimethyl sulfoniopropionate (DMSP), dimethyl sulfide (DMS), methyl mercaptan (MeSH), and carbon disulfide (CS2) in the sulfur cycle and/or atmospheric chemistry, alongside the rapid environmental changes in marine ecosystems, underscore the need to understand their responses to dynamic ecosystem shifts. We conducted two ship-based incubation experiments in the Northwest Pacific and Eastern Indian Oceans to explore how dust deposition, ocean acidification, and microplastic exposure impact these compounds. Our results demonstrate that these stressors not only alter phytoplankton community but also modify per-cell DMSP production capacity and DMSP degradation pathways, subsequently influencing DMSP, DMS, and MeSH concentrations. CS2‘s response closely mirrors phytoplankton abundance and species. Initial physical-chemical conditions, such as carbonate system and nutrient availability, may mediate the sensitivity of phytoplankton and sulfur compounds to environmental shifts. This study enhances our understanding of biogenic sulfur responses in dynamic marine ecosystems and provides essential basis for future climate modeling.
Key Points
- External stressors alter algal communities and production and degradation of dimethyl sulfoniopropionate, thus affecting biogenic sulfides
- Response of carbon disulfide to different environmental stressors is closely linked to algal abundance
- Initial physical-chemical conditions of seawater mediate algae and biogenic sulfides’ sensitivity to environmental stressors
Plain Language Summary
Biogenic sulfur-containing compounds in the ocean, such as dimethyl sulfoniopropionate (DMSP), dimethyl sulfide (DMS), methyl mercaptan (MeSH), and carbon disulfide (CS2), play critical roles in the global sulfur cycle and have the potential to influence the Earth’s climate. For instance, DMS released from the ocean into the atmosphere contributes to cloud formation, which in turn affects weather patterns. Over recent decades, rapid environmental changes in marine ecosystems may have significantly impacted marine biogeochemical processes. To investigate how these compounds respond to such changes, we conducted two ship-based incubation experiments in the Northwest Pacific and Eastern Indian Oceans. We assessed the effects of dust deposition, ocean acidification (due to increased carbon dioxide), and microplastic pollution on the production of DMSP, DMS, MeSH, and CS2 by marine organisms. Our results demonstrate that these stressors alter phytoplankton growth and community composition and impact the pathways through which DMSP is degraded. Consequently, the concentrations of sulfur compounds in seawater are affected. Notably, changes in CS2 levels were more closely related to shifts in phytoplankton abundance. These findings enhance our understanding of how marine sulfur compounds may respond to future oceanic changes and offer valuable data for improving climate models.
Continue reading ‘Effects of different environmental stressors on marine biogenic sulfur compounds in the Northwest Pacific and Eastern Indian Oceans’Microzooplankton community dynamics under ocean acidification: key observations and insights
Published 30 April 2025 Science ClosedTags: abundance, biological response, BRcommunity, community composition, Indian, laboratory, otherprocess, phytoplankton, prokaryotes, zooplankton
Microzooplankton (MZP) community dynamics under ocean acidification were studied through pH manipulated microcosm experiments conducted in the coastal waters of the Bay of Bengal (off Vishakhapatnam) during the months of July and October 2022 (Experiment 1 and Experiment 2). The total abundance of phytoplankton and microzooplankton (MZP) communities was varied from 3.66 × 104 to 5.27 × 105 Cells. L−1 and 0.06 × 103 to 1.53 × 103 Cells. L−1, respectively, and a significant difference in phytoplankton and MZP abundance was found between the initial and final day of the entire experimental samples (control and acidified). The initial seawater samples were dominated with centric diatom species Dactyliosolen fragilissimus (Experiment 1 and Experiment 2: 72–82%) and shifted to pennate diatoms such as Pseudo-nitzschia sp. (Experiment 1: 60–68%) and Amphora sp. (Experiment 2: 80–94%) at the end of the experiments (all acidified and control samples). The initial MZP community composition consisted of four different groups LC: loricate ciliates, ALC: aloricate ciliates (heterotrophy and mixotrophy), HDS: heterotrophic dinoflagellates and copepod nauplii, and at the end of the experiments, it was shifted entirely to the dominance of aloricate ciliates (16–73%) and heterotrophic dinoflagellates (67–100%) in all the samples (control and acidified) in Experiments 1 and 2, respectively. Statistical analysis (Spearman’s rank correlation) results showed a relative and significant inverse relation of MZP with phytoplankton biomass and abundance and heterotrophic bacterial counts in all the samples (control and acidified). Besides, the LC showed a weak correlation with Chl-a, and the HDS showed a significant correlation with LC, phytoplankton biomass and abundance, and bacterial counts (picocyanobacteria and heterotrophic bacteria). These results indicate that the MZP may graze on both picocyanobacteria and heterotrophic bacteria, and also, HDS may graze on their relative community like LC. Canonical correlation analysis (CCA) revealed that prey abundance such as phytoplankton biomass (Chl-a), picocyanobacteria, and heterotrophic bacterial communities are most influencing variables on the MZP assemblages than other environmental variables such as pH, temperature, and salinity. Thus, these findings show that the MZP community dynamics under ocean acidification may vary with different species and groups due to their food availability (indirect effect) and individual competence (direct effect) to different environmental conditions, such as pH variations.
Continue reading ‘Microzooplankton community dynamics under ocean acidification: key observations and insights’An improved long-term high-resolution surface pCO2 data product for the Indian Ocean using machine learning
Published 16 April 2025 Science ClosedTags: chemistry, Indian, modeling, regionalmodeling
Accurate estimation of surface ocean pCO2 is crucial for understanding the ocean’s role in the global carbon cycle and its response to climate change. In this study, we employ a machine learning algorithm to correct the deviations in high-resolution (1/12°) model simulations of surface pCO2 from the INCOIS-BIO-ROMS model (pCO2model) for the period 1980–2019, using available observations (pCO2obs). We train the XGBoost model to generate spatio-temporal deviations (pCO2obs − pCO2model) of pCO2model. The interannually and climatologically varying deviations are then added back to the original model separately, which results in an improved surface pCO2 data product. A comparison of our surface pCO2 data product with moored observations, gridded SOCAT, CMEMS-LSCE-FFNN, and OceanSODA demonstrates an improvement by approximately 40% ± 3.31% in RMSE. Further analysis reveals that adding climatological deviations to pCO2model results in greater improvements than adding interannual deviations. This analysis underscores the ability of machine learning algorithms to enhance the accuracy of model-simulated surface pCO2 outputs.
Continue reading ‘An improved long-term high-resolution surface pCO2 data product for the Indian Ocean using machine learning’Warmer oceans, acidification endanger Sri Lanka’s maritime heritage
Published 8 April 2025 Media coverage ClosedTags: Indian
Sri Lanka’s waters are home to over 200 shipwrecks, each holding a unique story of trade, war, and maritime heritage. Among the most significant are the Godawaya Shipwreck, which dates back over 2,000 years, and HMS Hermes, the world’s first purpose-built aircraft carrier built by British and sunk by Japanese dive bombers during World War II (1931-1945).
Over time, these shipwrecks have transformed into artificial reefs, supporting marine biodiversity and playing a crucial role in ocean ecosystems. However, climate change is now emerging as a major threat to their survival, potentially shortening their lifespan.
“Shipwrecks face multiple threats from climate change,” says Prof. Sevvandi Jayakody of the Department of Aquaculture and Fisheries at Wayamba University of Sri Lanka. “These include extreme weather events, ocean acidification, invasive species, and rising sea temperatures, all of which can accelerate the degradation of wrecks.”
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Human-induced climate change, driven by greenhouse gas emissions such as carbon dioxide (CO₂), not only warms the planet but also increases ocean acidity when the ocean absorbs carbon dioxide from the atmosphere, which lowers the ocean’s pH.
“Globally, research has shown that ocean acidification speeds up the corrosion rate of iron and steel wrecks,” notes Prof. Jayakody. “This is especially concerning for wrecks like HMS Hermes, which may still contain live ammunition. As the metal weakens, there is a risk of explosive materials being exposed.”
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Although ocean acidification studies in Sri Lanka are still in their early stages, the National Aquatic Resources Research and Development Agency (NARA) is monitoring pH levels in coastal waters.
“We take regular measurements from stations on both the east and west coasts,” says Dr. Kanapathipillai Arulananthan director general of NARA. “Additionally, the Norwegian research vessel Nansen is expected to provide further insights into changing ocean parameters in the Northern Indian Ocean.”
Another hidden threat is the rise of invasive species that could now establish in different areas due to warming waters. Changes in ocean temperature and acidity alter microbial activity, leads to faster decomposition of wooden shipwrecks according to research.
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Ballast water from ships can introduce these invasive species to new environments. While differences in salinity, temperature, and acidity once prevented their survival, climate change is making new habitats more suitable for these species, increasing the risk of bioerosion.
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As climate change intensifies, Sri Lanka’s shipwrecks face an uncertain future. Without proactive measures, these historical and ecological treasures could deteriorate beyond recognition, taking with them invaluable insights into the past —and a crucial refuge for marine life in the present.
Mr. Mutukumarana said every shipwreck is unique and when one disintegrates so goes its story, too. The only way forward would be to reduce the rate of global warming.
Continue reading ‘Warmer oceans, acidification endanger Sri Lanka’s maritime heritage’Safeguarding South-East Asia’s marine ecosystems from ocean acidification threats
Published 28 March 2025 Newsletters and reports ClosedTags: Indian, policy, South Pacific
The increasing carbon dioxide emissions from human activities are being absorbed by the oceans, leading to a decrease in seawater pH levels worldwide. South-East Asia is particularly vulnerable to this problem, as the projected trend of ocean acidification severely threatens marine life in the region, as well as marine industry productivity and food safety. Urgent action must be taken by the Association of Southeast Asian Nations (ASEAN) Secretariat and its Member States to sustain coastal populations’ livelihoods and economic prosperity.
Recommendations:
- Improve marine protected areas (MPAs) by applying science-based design and grass-roots community participation
- Establish a regional task force and collaborative funding
- Increase public awareness and implement marine educational programmes through curriculum integration
Carbonate chemistry and CO2 dynamics in the Persian Gulf
Published 14 March 2025 Science ClosedTags: chemistry, field, Indian
Highlights
- The T-S diagram identifies four distinct water types in the Persian Gulf study area.
- Alkalinity loss equals 31 Mt. CaCO3 or 3.72 Mt. inorganic carbon deposited annually.
- A ΔOrgC:ΔCaCO3 ratio of 2.6:1 indicates higher photosynthesis over calcification.
- Dissolved inorganic carbon and total alkalinity, dominate the pCO2 distribution.
- 85 % of surface waters of the Persian Gulf acted as CO2 sinks in late summer.
Abstract
This study examines the carbonate chemistry of the Persian Gulf within the Iranian Exclusive Economic Zone, using datasets collected during the PGE2102 expedition in September 2021. The water column was stratified, with a warm, oxic upper layer (0–25 m: 33.2 °C, salinity 38.9 psu, O2 177 μmol/kg) and a cooler, low-oxygen deep layer (> 25 m: 24.4 °C, salinity 40.2 psu, O2 94.3 μmol/kg). Four water types were identified: Indian Ocean Surface Water (IOSW), Surface Persian Gulf Water (Surface-PG), Deep Persian Gulf Water (Deep-PG), and Northwest Persian Gulf Water (NW-PG). The lowest normalized alkalinity (NAT) was found in NW-PG (2427 ± 29 μmol/kg), suggesting alkalinity loss, while IOSW exhibited the highest NAT (2551 ± 9 μmol/kg). Deep-PG had lower NAT (2460 ± 18 μmol/kg) than surface waters, with surface NAT decreasing westward. Organic matter decomposition in Deep-PG resulted in the lowest pH (7.924 ± 0.030) and highest pCO2 (592.8 ± 47 μatm). Surface waters showed reduced dissolved inorganic carbon (DIC ~2047 μmol/kg) and undersaturated pCO2 (403.9 ± 69 μatm) due to photosynthesis. Hypoxic zones in western and central areas exhibited elevated DIC (up to 2305.6 μmol/kg) and the lowest pH (7.832), reflecting remineralization. Calcium carbonate precipitation contributed to significant alkalinity losses (66.2 μmol/kg), translating to 31 million tons of annual deposition. A ΔOrgC:ΔCaCO3 ratio of 2.6:1 in surface waters suggests higher photosynthetic activity relative to calcification. Despite localized pCO2 hotspots, 85 % of surface waters acted as CO2 sinks, highlighting unique carbonate dynamics shaped by stratification, biogeochemical processes and regional conditions.
Continue reading ‘Carbonate chemistry and CO2 dynamics in the Persian Gulf’Effect of thermal and non-thermal processes on the variability of ocean surface pCO2 and buffering capacity in the North Indian Ocean
Published 24 February 2025 Science ClosedTags: biogeochemistry, chemistry, Indian, modeling, regionalmodeling
Highlights
- A coupled atmosphere–ocean-biogeochemistry model is customised for NIO.
- High surface pCO2 in upwelling regions of NIO are controlled by non-thermal processes.
- Surface pCO2 changes in upwelling regions of NIO are more sensitive to changes in DIC.
- Diffusion, CO2 flux and Phytoplankton uptake primarily control DIC variability in NIO.
Abstract
The oceans have absorbed nearly 30% of the anthropogenic CO2 that alters the ocean carbon chemistry. The oceanic processes are highly complex, which mandate approaches that couple its physical, chemical and biological states. Here, we use a coupled atmosphere–ocean-biogeochemistry model, incorporating spatially and temporally varying atmospheric CO2 to simulate the north Indian Ocean (NIO) carbon dynamics for the period 2013–2020. We assess the seasonal variability of Dissolved Inorganic Carbon (DIC), total Alkalinity (ALK), ocean surface pCO2 and buffering capacity. To assess the mechanisms that control carbon dynamics in the region, we segregate the ocean surface pCO2 into temperature-driven (thermal) and bio-physical processes induced (non-thermal) pCO2. We find that the thermally driven pCO2 is dominant in summer (June, July, August and September; JJAS), but the non-thermal component in winter (December, January and February; DJF) in the northern Arabian Sea (AS). The northern AS is characterised by a deep mixed layer and convection-induced vertical mixing during winter. DIC from the subsurface layer is uplifted to the surface, which results in high ocean surface pCO2 in winter. Off the Oman coast, the non-thermal processes control the surface pCO2 in summer. In the northern bay, the thermal component of pCO2 is dominant in summer and non-thermal component is prominent in winter as in northern AS, but their magnitudes are lower due to large riverine flux. The budget analysis reveals strong influence of diffusion, CO2 flux and biological processes in controlling DIC variability in NIO. Low buffering capacity in upwelling regions indicates that pCO2 changes are more sensitive to changes in DIC, primarily due to the upwelled DIC-rich surface waters. Therefore, it results in a reduced ability to absorb CO2. This warrants the need to address recent changes in carbon dynamics in response to the increased levels of atmospheric CO2.
Continue reading ‘Effect of thermal and non-thermal processes on the variability of ocean surface pCO2 and buffering capacity in the North Indian Ocean’Carbon dioxide–induced acidification enhances short-lived brominated hydrocarbons production in oligotrophic oceans
Published 18 February 2025 Science ClosedTags: biogeochemistry, biological response, community composition, field, Indian, multiple factors, nutrients, otherprocess, physiology, phytoplankton, South Atlantic
Oceanic emission is a primary source of brominated very short-lived substances (BrVSLs) to the atmosphere, which have important effects on stratospheric ozone chemistry. Marine biogeochemical processes regulating BrVSLs are often sensitive to ocean acidification. Yet, the response of BrVSLs production to acidification remains poorly understood. Herein, the effects of acidification on the production of two main BrVSLs, dibromomethane (CH2Br2) and tribromomethane (CHBr3), were studied by ship-based incubation experiments at three stations in the South Atlantic and Indian Oceans. The average CH2Br2 and CHBr3 concentrations increased by 17.2–58.7% and 14.3–80.3% due to acidification under the in situ nutrient conditions with nutrient and/or iron limitation at the three stations, but the mechanisms driving these increases varied among different regions. The increased bromoperoxidase (BrPO) activity caused by acidification facilitated BrVSLs release in the Eastern Tropical Indian Ocean, where diatoms were dominant. CHBr3 increased due to acidification as a result of enhanced reactivity of dissolved organic matter (DOM) in the Eastern Tropical Atlantic, where dinoflagellates were dominant. Brominated very short-lived substances increased due to acidification as a result of a combined effect of the above two mechanisms in the Benguela Current Coastal with high phytoplankton abundance. Under the nutrient and/or iron addition conditions with nutrient and iron sufficiency, however, acidification did not promote BrVSLs production due to its only minor effect on the BrPO activity and reactivity of DOM, partly because the effect of increased oxidative stress was offset by that of changed phytoplankton composition. Our study provided a basis for future modeling on the impact of acidification on global BrVSLs emissions.
Continue reading ‘Carbon dioxide–induced acidification enhances short-lived brominated hydrocarbons production in oligotrophic oceans’Submarine groundwater discharge impacts on coastal waters of southeastern Arabian Sea: changes to carbonate chemistry and plankton communities
Published 5 February 2025 Science ClosedTags: biological response, chemistry, community composition, field, Indian, laboratory, otherprocess, phytoplankton
Highlights
- Submarine groundwater discharge impacts on tropical coastal waters were studied.
- Nutrient sourced SGD input stimulate the growth of diatoms in the coastal waters.
- Acidification may alter the balance between plankton communities.
- Long term monitoring studies of interactive effects of potential drivers needed.
Abstract
Submarine groundwater discharge (SGD) is a significant contributor to effect phytoplankton community shift and marine ecosystem changes, yet little information is available about its influence in the Indian coastal waters. This microcosm study assessed the impact of groundwater input on carbonate chemistry changes, plankton community structuring and marine ecosystem dynamics in coastal waters off Kochi, southeastern Arabian Sea (SEAS), southwest India. The relatively high nutrient content (nitrate and silicate) and low nitrate to silicate ratio (N/Si < 1) in the groundwater favoured the growth and fast abundance of diatom species (Thalassiosira sp.). The increased growth rate of diatoms in coastal groundwater additions shifts the community composition towards higher microphytoplankton relative to picoplankton proportion. Increased heterotrophic thecate dinoflagellates such as Protoperidinium species with SGD might become the significant consumers of bloom forming diatoms in the coastal waters. The SGD driven acidification with increased nutrient supply may alter the balance between autotrophic and heterotrophic plankton communities, which becomes intense with the effective increase in atmospheric aerosols and anthropogenic inputs, amplifying the scope of coastal ocean acidification.
Continue reading ‘Submarine groundwater discharge impacts on coastal waters of southeastern Arabian Sea: changes to carbonate chemistry and plankton communities’Contrasting trends of the ocean CO2 sink and pH in the Agulhas current system and the Mozambique Basin, South-Western Indian Ocean (1963-2023)
Published 28 January 2025 Science ClosedTags: chemistry, field, Indian
Highlights
- Ocean acidification estimated in the Mozambique Basin and the African coastal zone.
- These regions act as a CO2 sink
- The decrease of pH was faster in recent decade
- It was driven by anthropogenic CO2 uptake with about 10% due to the ocean warming
Abstract
We describe new observations of the oceanic carbonate system in the South-Western Indian Ocean obtained in January 2021 (OISO-31 cruise) and May 2022 (RESILIENCE cruise). To evaluate the decadal trends and drivers of fugacity of CO2 (fCO2), air-sea CO2 fluxes, dissolved inorganic carbon (CT) and pH, we used available data in this region over 1963-2023 and compared the results in the Mozambique Basin and in the Agulhas region near the African coast. Over 1995-2023, we found a faster fCO2 increase in the Mozambique basin (2.03 ±0.07 μatm.yr-1) compared to the coastal zone (1.37 ±0.07 μatm.yr-1). The temporal change of anthropogenic CO2 concentrations estimated in subsurface enables to reconstruct the carbonate system properties since the 1960s. In the Mozambique Basin the CO2 sink increased slightly over 1960-2022 with a maximum observed in May 2022 (-2.4 mmolC.m-2.d-1). In the coastal zone, the ocean CO2 sink increased from near equilibrium in the 1960s to a maximum observed in May 2022 (-4.2 mmolC.m-2.d-1). In both regions, we found a decrease of pH, most pronounced in the open ocean zone (-0.020 ±0.001.decade-1 over 1995-2023). The lowest pH of 8.04 was observed in January 2021, 0.11 lower than in the 1960s. The increase of the CO2 sink and the decrease of pH were mainly driven by anthropogenic CO2 uptake, with about 10% due to the ocean warming.
Continue reading ‘Contrasting trends of the ocean CO2 sink and pH in the Agulhas current system and the Mozambique Basin, South-Western Indian Ocean (1963-2023)’Satellite-derived ocean color data for monitoring pCO2 dynamics in the North Indian Ocean
Published 27 January 2025 Science ClosedTags: chemistry, Indian, modeling, regionalmodeling
Highlights
- A Multiparametric Linear Regression (MLR) model was developed using in-situ and satellite observations to accurately estimate pCO2 in the NIO region.
- Validation of the MLR model showed significant low errors (MRE = 0.08, MNB = 0.013, RMSE = 7.26 μatm) and a high correlation coefficient (R2 = 0.96), demonstrating superior performance.
- The interannual (2012-2022) variability of pCO2 in the NIO region shows an increasing trend.
- The study reveals seasonal variability in pCO2 in the NIO, peaking pre and post-monsoon, influencing marine ecosystems.
Abstract
The partial pressure of carbon dioxide (pCO2) in the North Indian Ocean (NIO) undergoes significant variations due to factors such as biological activity, ocean circulation patterns, and atmospheric influences. Understanding these variations is crucial for assessing the ocean role in the global carbon cycle and their impact on climate change. Estimating pCO2 through in-situ platforms is challenging due to the time-consuming, expensive, and complex nature of water sample collection, particularly under rough oceanic conditions. Conversely, remote sensing technology offers high spatiotemporal resolution data over extensive synoptic scales, making it a valuable tool for pCO2 estimation. Current models for estimating pCO2 in the NIO region are limited due to the improper selection of model parameters and the scarcity of in-situ measurements, highlighting the need for a more accurate approach. This study develops a Multiparametric Linear Regression (MLR) method, integrating satellite and in-situ observations of sea surface temperature (SST), sea surface salinity (SSS), and chlorophyll-a (Chla) concentration. To develop and validate this model, in-situ data were sourced from the Global Ocean Data Analysis Project (GLODAP). Validation results showed that the proposed MLR approach outperformed existing global models, achieving low mean relative error (MRE = 0.08), mean normalized bias (MNB = 0.013), and root mean square error (RMSE = 7.26 μatm), with a high correlation coefficient (R2 = 0.96). This study has the potential to improve understanding of carbon dynamics in the NIO region and its contribution to the global carbon cycle. The pCO2 maps generated in this study improve climate modeling and monitoring, supporting predictions and mitigation efforts. This accurate model also aids policy-making, environmental management, and ecological assessments.
Continue reading ‘Satellite-derived ocean color data for monitoring pCO2 dynamics in the North Indian Ocean’Ocean acidification a murky phenomenon with little research done, say scientists
Published 14 January 2025 Media coverage ClosedTags: Indian
Ocean acidification—a critical yet understudied issue in Sri Lanka—results from increased atmospheric CO2 levels dissolving into the ocean, altering its chemistry. This phenomenon poses significant threats to marine biodiversity and ecosystems, yet research efforts remain constrained by limited data, coordination, and resources.
“Four years ago, NARA established two permanent stations to measure and monitor pH levels—one off the western coast of Sri Lanka, covering the Arabian Sea, and the other off Trincomalee, for the Bay of Bengal,” says Dr K. Arulananthan, Director General of the National Aquatic Resources Research and Development Agency (NARA). These stations aim to collect long-term data to understand oceanic changes better.
“The Sri Lankan government has funded these initiatives through the Treasury. While we’ve observed strong seasonal variations in pH levels, such fluctuations—lower during the rainy season and higher during dry periods—are natural and normal,” he explains. However, Dr. Arulananthan notes that four years of data is insufficient to establish definitive trends.
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Dr. Arulananthan emphasised the interconnectedness of pH levels and carbon dioxide. “Acidification is directly related to CO2. While Sri Lanka’s emissions are negligible, making us not a major contributor, the responsibility lies with big emitters. However, we do have significant ecosystems, such as mangroves, that help absorb CO2. Replanting mangroves is a major step forward,” he notes.
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“Measuring pH and observing its changes is a very basic analysis that alone cannot reflect acidification. To establish a trend and study the impact, we need data from multiple locations over a long period,” says Prof. Terney Pradeep Kumara, Professor of Oceanography at the University of Ruhuna, Sri Lanka.
According to Prof. Terney, the lack of proper coordination in data collection and processing is a major obstacle to understanding ocean acidification trends in Sri Lanka. “Data collection happens, but the information is not collated well enough, and we don’t have sufficient trend records to quantify acidification. However, there is evidence to suggest that changes are occurring,” he notes.
The professor highlighted the absence of state-of-the-art technology as another critical challenge. “We need more advanced tools, such as data loggers on reefs and rocks, to analyse long-term trends. Right now, no reliable data is being created,” he says.
While global scenarios of ocean acidification have been studied extensively, Prof. Terney pointed out the gap in localised research. “We don’t have our own data, so we can’t conclusively say what the impact is. Theoretically, we can assume coral growth rates are changing, but we haven’t connected those changes to acidification. We haven’t calculated calcification rates,” he explains.
Globally, scientists have not observed clear trends linking acidification to coral growth rates, but Prof. Terney emphasised the importance of monitoring Sri Lanka’s unique conditions. “Different parts of the ocean around Sri Lanka exhibit varying pH levels due to local factors such as river discharges. For example, Trincomalee’s deep channel is influenced by the Mahaweli River, so it cannot serve as the focal point for data extraction,” he says.
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“The root cause of acidification is climate change because the increase of CO2 in our atmosphere leads to ocean acidification,” says Dr. Sivakumaran Sivaramanan, Environmental Assessor at the Central Environmental Authority (CEA). According to Dr Sivaramanan, addressing climate change is essential to mitigating ocean acidification. “Global and local attempts to tackle global warming will naturally reduce acidification. But any meaningful climate effort—whether in research, mitigation, or adaptation—usually takes about a decade of consistent work to yield results,” he explains.
Dr. Sivaramanan highlights the challenges in advancing research locally. “Research in this area is moving slowly because it demands significant time and funding. You need to measure everything consistently to gain actionable insights,” he says. While awareness programs are being conducted, mitigation strategies require robust data and consistent action. “The only permanent solution is to resolve the climate crisis,” he emphasises.
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The initial impacts of acidification, he notes, will primarily affect marine biodiversity. “Fish migration patterns will change as the Indian Ocean, particularly around Sri Lanka, is a biodiversity hotspot. Large marine animals like whales will also feel the effects. It’s a chain reaction—corals are affected first, followed by species dependent on them, and the impacts ripple through the ecosystem,” he says.
Dr. Sivaramanan also addresses misconceptions about acidification. “Some assume that eutrophication leads to acidification because nutrient-induced algal blooms block sunlight, slowing photosynthesis and creating anoxic conditions. While this must be mitigated, it does not cause acidification directly,” he clarifies. “The root cause is climate change.”
Continue reading ‘Ocean acidification a murky phenomenon with little research done, say scientists’Vulnerability of the Bay of Bengal to ocean acidification: challenges and adaptation strategies
Published 3 January 2025 Media coverage ClosedTags: Indian
Impact of Ocean Acidification on Marine Life
Ocean acidification directly affects marine organisms, especially those that rely on calcium carbonate to build their shells and skeletons. These organisms include corals, oysters, clams, mussels, and snails, many of which support valuable commercial and recreational fisheries. The Bay of Bengal, which hosts a rich array of marine life, is particularly vulnerable to these changes.
Saint Martin’s Island, located in the Bay of Bengal, is the only coral-bearing island in Bangladesh. Studies have shown a significant decline in coral species around this island. In 1997, 66 coral species were recorded, but by 2008, only 40 species remained. If the current trends continue, an additional 26 species may be lost within the next decade. Ocean acidification is largely responsible for coral bleaching, stunted growth, and the loss of coral species diversity. These changes threaten not only the coral reefs but also the entire marine ecosystem, which supports a variety of subsistence, recreational, and commercial fisheries.
Coral reefs, which cover less than 1% of the ocean floor, are home to about 25% of all marine species. Their destruction would result in the loss of crucial habitats for numerous fish and invertebrates, ultimately leading to a decline in fishery productivity. The economic value of coral reef services has been estimated at $30 billion per year globally, with potential losses of up to $870 billion by the year 2100 if ocean acidification continues unabated.
Implications for Fisheries and Livelihoods
Ocean acidification poses a significant threat to the global fishing industry, which is vital for the food security and livelihoods of millions of people, especially in developing countries. In 2006, global marine capture fisheries and aquaculture provided 110 million metric tons of food, with a commercial value of $170 billion. The Bay of Bengal is no exception, as it supports a major fishery sector that is heavily dependent on the health of its marine ecosystems.
Acidification can affect fish species directly by altering their survival, reproduction, and growth patterns, as well as indirectly through changes in predator-prey relationships and nutrient recycling. In addition, acidification can have detrimental effects on mangrove ecosystems, which are crucial for the coastal food chain and act as breeding and nursery grounds for many marine species. Lowered soil pH in mangrove forests can harm the respiratory roots of these plants, leading to their mortality and further exacerbating coastal erosion and habitat loss.
The damage to marine habitats and fisheries in the Bay of Bengal would have severe socioeconomic consequences. Coastal communities, particularly those relying on fishing, shrimp farming, and other marine-related industries, would face a decline in incomes and jobs. This could lead to increased poverty, food insecurity, and mental health challenges, as well as reduced resilience to extreme natural events like cyclones and flooding.
Research and Monitoring Efforts in Bangladesh
In Bangladesh, several organizations, including the Institute of Marine Sciences and Fisheries (IMSF) at Chittagong University, have been actively researching the effects of ocean acidification on coastal and marine ecosystems. The Bangladesh Navy, the Bangladesh Inland Water Transport Authority, and the Coast Guard have also contributed to the monitoring of the Bay of Bengal’s shelf waters, providing valuable hydrographical data.
To address the challenges posed by ocean acidification, it is crucial to improve monitoring and data collection. Real-time sensors installed in sensitive areas of the Bay of Bengal would allow for the continuous monitoring of changing water conditions, helping researchers develop models to predict future impacts and costs associated with ocean acidification.
National and Global Adaptation Strategies
The impacts of ocean acidification are already being felt in Bangladesh, and the government has recognized the need for urgent action. The Ministry of Environment and Forests, in collaboration with other agencies, has developed policy documents to address climate change, including ocean acidification. The National Adaptation Programme of Action (NAPA), introduced in 2005, outlines priority activities such as awareness-raising, capacity building, and the implementation of projects to reduce the impact of climate change in vulnerable regions.
The Bangladesh Climate Change Strategy and Action Plan (BCCSAP), developed in 2009, further emphasizes the importance of building resilience through the development of adaptive infrastructures, such as cyclone-resistant houses and roads, as well as promoting sustainable practices in agriculture and fisheries. Efforts to develop coastal plantations, restore coral reefs, and establish living shorelines are promising adaptation strategies that could help protect coastal ecosystems and the livelihoods of coastal communities.
At the international level, the United Nations Framework Convention on Climate Change (UNFCCC) has focused on addressing loss and damage due to ocean acidification and other climate impacts. The UNFCCC’s National Adaptation Plans (NAPs) provide a framework for developing countries to strengthen their resilience to climate change through strategic planning, policy dialogue, and financial support.
Conclusion
The vulnerability of the Bay of Bengal to ocean acidification is a pressing concern, with far-reaching consequences for marine biodiversity, fisheries, food security, and the livelihoods of coastal communities. Addressing this challenge requires concerted efforts at local, national, and international levels, including enhanced research, monitoring, and adaptation strategies. Reducing CO2 emissions is essential to mitigating the worst effects of ocean acidification, but proactive measures such as improved infrastructure, ecosystem restoration, and climate-resilient practices are critical to safeguarding the Bay of Bengal’s marine resources and the people who depend on them.
Continue reading ‘Vulnerability of the Bay of Bengal to ocean acidification: challenges and adaptation strategies’Environmental determinants of reef fish community structure in Sempu Strait, East Java, Indonesia
Published 31 December 2024 Science ClosedTags: chemistry, community composition, field, fish, Indian, otherprocess
The Rumah Apung located in Sempu Strait, Malang District, East Java, Indonesia, is home to diverse coral reef ecosystems that provide vital ecological services and support local livelihoods. However, these ecosystems face significant threats from both natural environmental changes and anthropogenic activities. Understanding how environmental factors influence reef fish communities is critical to inform effective conservation strategies. This study investigated the influence of environmental factors on the community structure of coral reef fish in the Sempu Strait waters, East Java, using Underwater Visual Census (UVC) and Principal Component Analysis (PCA). Conducted from August 2023 to May 2024 at the Sempu Strait Floating House Station, this study aimed to assess the impact of water quality, substrate type, and food availability on the diversity and abundance of coral reef fish. The main results revealed a significant correlation between the community structure of coral reef fish and environmental variables such as water clarity, salinity (r=0.65, p<0.01), pH (r=0.55, p<0.05), dissolved oxygen (r=0.70, p<0.01), and sediment type. Seasonal variations significantly affected water quality, with cold nutrient-rich water during the east monsoon increasing fish biomass by about 30%. Human activities, especially recreational diving and fishing activities, were correlated with a 20% decline in coral reef fish populations, highlighting the anthropogenic pressure on this ecosystem. PCA provides insight into the complex interdependencies within coral reef ecosystems, illustrating how multiple environmental factors combine to influence reef fish dynamics. The study concludes that effective management and conservation strategies,such as establishing marine protected areas, implementing community-based monitoring programs, and promoting sustainable tourism practices, are essential, supported by regular environmental monitoring, are essential to maintain the biodiversity and ecological integrity of coral reefs in the Sempu Strait. These strategies should address both natural environmental changes and anthropogenic impacts to mitigate their adverse effects on coral reef ecosystem conditions.
Continue reading ‘Environmental determinants of reef fish community structure in Sempu Strait, East Java, Indonesia’Addressing the impact of ocean acidification on coral reefs and marine life: a risk assessment for SDG 14 (life below water)
Published 10 December 2024 Science ClosedTags: biological response, corals, Indian, mitigation, review
One of the main issues emerging from environmental change with significant ramifications for marine life is Ocean acidification. It alludes to the cycle by which the sea turns out to be more acidic because of expansion in the concentration of carbon dioxide in the environment. As carbon dioxide levels ascend in climate a critical part is consumed by the sea which prompts a progression of redox responses that decline the pH of ocean water. This peculiarity has broad ramifications for marine life, especially for coral reefs, which are among the most miscellaneous and monetarily significant biological ecosystems in the world. The purpose of this review is to address and assess the impact of ocean acidification on coral reefs and marine life in order to conserve and sustain marine life below water thus fulfilling Sustainable Development Goal 14 (Life below water).
Continue reading ‘Addressing the impact of ocean acidification on coral reefs and marine life: a risk assessment for SDG 14 (life below water)’The influence of macrophytes on diurnal pH variability in subtropical estuaries: a mesocosm study
Published 4 December 2024 Science ClosedTags: algae, biological response, BRcommunity, chemistry, Indian, laboratory, mesocosms, phanerogams
Highlights
- Macrophytes influence estuary water column pH levels.
- Floating macrophytes decrease pH and submerged macrophytes increase pH.
- Diurnal pH variability is more pronounced in submerged macroalgae.
- Floating macrophytes exhibit lower diurnal variability.
Abstract
Coastal ecosystems are increasingly threatened by anthropogenic impacts, particularly from land-based activities that drive eutrophication. This research investigated eutrophication and the unique challenges facing southern hemisphere coastal ecosystems. We used a mesocosm study to measure the influence of a macroalga (Rhizoclonium riparium) and a floating macrophyte (Pistia stratiotes), on diurnal pH variability. Diurnal pH variability was more pronounced in the presence of macroalgae due to the direct release of metabolic byproducts into the water column during photosynthesis and respiration. In contrast, floating macrophyte treatments had lower diurnal pH variability, as metabolic byproducts are released into the atmosphere through floating foliage. Floating macrophytes influenced overall water column pH levels, resulting in an acidification effect, becoming more pronounced as macrophyte biomass increased. The study highlighted the importance of nutrient management and its association with macrophytes, to preserve the delicate balance of estuaries, and ensure the sustainable functioning of these critical ecosystems. Further in situ research is recommended to validate and expand on the mesocosm findings.
Continue reading ‘The influence of macrophytes on diurnal pH variability in subtropical estuaries: a mesocosm study’Drivers of biological diversity and responses to global changes in marine invertebrates
Published 12 November 2024 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, corals, echinoderms, Indian, laboratory, molecular biology, otherprocess, reproduction
Human activities, in particular global changes (e.g., ocean warming – OW and ocean acidification – OA) are projected to drive some marine species to extinction within the coming decades. Marine invertebrates are amongst the most vulnerable to these changes due to the increased energetic cost to maintain intracellular pH homeostasis. To mitigate extinction, organisms may migrate, acclimate or adapt genetically. While these mechanisms are increasingly documented, they are not fully understood. This knowledge is critical for assessment of extinction risks, an important index for effective conservation and management of marine biodiversity. This thesis aims to increase our understanding on the drivers of biological diversity and sensitivity of marine invertebrates to OW and OA. Specifically, I assess (1) the quality of inferences on adaptive evolution in recent publications on responses of marine invertebrates to OW or OA and summarize the current knowledge and identify the gaps (Paper I); (2) the drivers of genetic diversity, structure, connectivity among Acropora austera populations across Mozambique coral reefs (Paper II); (3) the sensitivity to low pH in larvae of the sea urchin, Tripneustes gratilla, from subtidal and intertidal seagrass meadows with contrasting pH variability at Inhaca Island, Mozambique (Paper III); (4) the role of natural fluctuation in pH on the response of larvae of the sea urchin Echinus esculentus to low pH (Paper IV). Field genome scans surveys, laboratory experiments and systematic literature review were used. My systematic literature review (Paper I) highlights that publication on adaptive responses of marine invertebrates to OW or OA used more frequently strong methods for inferences of genetic change, such as common garden experiments and molecular genetic analysis. Methods for weaker inferences, such as comparison to model prediction, were less frequently used. On the other hand, reciprocal transplants, the stronger method for inferring adaptive change was less used in comparison with weaker methods such as phenotypic and genotypic selection. I also showed different levels of genetic variability and connectivity between populations of corals along the Mozambique coast. These geographic differences in levels of genetic diversity and connectivity may be explained by oceanographic factors and mode of reproduction of the corals (Paper II). Larvae of the sea urchin T. gratilla from Inhaca Island had reduced fitness when exposed to low pH. Moreover, larvae from adults collected in an intertidal habitat were more sensitive to low pH as compared to larvae from adults collected in a subtidal population. This result reveals population specific responses to low pH and challenges current theories that predict higher tolerance in individuals living in habitats with higher pH range (Paper III). Under present day natural variability in pH, the extreme low pH does not appear to be the main driver of biological responses in larvae of the sea urchin E. esculentus and adaptation to such conditions might be associated with a cost of plasticity but not a cost of canalization (Paper IV). Overall, this thesis shows that oceanographic factors and natural variability in pH influence the levels of genetic diversity and biological sensitivity in populations of marine invertebrates. These parameters should be considered to better evaluate the ability of marine invertebrates to withstand environmental changes and to sustain the provision of ecological functions, and guide conservation strategies.
Continue reading ‘Drivers of biological diversity and responses to global changes in marine invertebrates’Assessing the potential of macroalgae-based carbon sequestration in Indonesia
Published 11 October 2024 Science ClosedTags: algae, biological response, Indian, laboratory, mitigation
Macroalgae are being intensively explored as a nature-based solution to address climate change. Although there are still some uncertainties about recognizing macroalgae in climate mitigation, the research trend on macroalgae carbon potential continues to increase. We collected secondary data, literature reviews, and expert opinions through focus group discussions to estimate the carbon sequestration potential of macroalgae and examine its feasibility in Indonesian climate mitigation. Our analysis shows that the carbon sequestration potential of macroalgae in Indonesia is significant, estimated to range from 351.246-2.526.332 Mg C yr−1, placing macroalgae as the third largest marine carbon store after mangroves and seagrass. In addition, macroalgae have higher CO2 sequestration rates than other blue carbon habitats. Our assessment of the viability of macroalgae in the blue carbon shows that macroalgae meet the critical elements of blue carbon criteria, including carbon sequestration scale, long-term storage, anthropogenic impact, and social or environmental interventions. However, aligning it with other climate mitigation policies is essential for macroalgae to be fully recognized in blue carbon. This preliminary study suggests that macroalgae could be necessary for Indonesia’s climate mitigation action.
Continue reading ‘Assessing the potential of macroalgae-based carbon sequestration in Indonesia’Indian Ocean acidification and its driving mechanisms over the last four decades (1980–2019)
Published 16 September 2024 Science ClosedTags: chemistry, Indian
This paper aims to study the changes in the Indian Ocean seawater pH in response to the changes in sea-surface temperature, sea-surface salinity, dissolved inorganic carbon (DIC), and total alkalinity (ALK) over the period 1980–2019 and its driving mechanisms using a high-resolution regional model outputs. The analysis indicates that the rate of change of declining pH in the Arabian Sea (AS), the Bay of Bengal (BoB), and the Equatorial Indian Ocean (EIO) is −0.014 ± 0.002, −0.014 ± 0.001, and −0.015 ± 0.001 unit dec−1, respectively. Both in AS and BoB (EIO), the highest (lowest) decadal DIC trend is found during 2000–2009. The surface acidification rate has accelerated throughout the IO region during 2010–2019 compared to the previous decades. Further, our analysis indicates that El Ninõ and positive Indian Ocean Dipole events lead to an enhancement of the Indian Ocean acidification. The increasing anthropogenic CO2 uptake by the ocean dominantly controls 80% (94.5% and 85.7%) of the net pH trend (1980–2019) in AS (BoB and EIO), whereas ocean warming controls 14.4% (13.4% and 7.0%) of pH trends in AS (BoB and EIO). The changes in ALK contribute to enhancing the pH trend of AS by 5.0%. ALK dominates after DIC in the EIO and, similar to the AS, contributes to increasing the negative pH trend by 10.7%. In contrast, it has a buffering effect in the BoB, suppressing the pH trend by −5.4%.
Key Points
- The Indian Ocean pH is decreasing at an average rate of 0.015 dec−1 from 1980 to 2019
- The trend of dissolved inorganic carbon primarily drives an increasing ocean acidification trend in the Indian Ocean
- El Ninõ and positive Indian Ocean Dipole events lead to an enhancement of the Indian Ocean acidification
Plain Language Summary
The oceans play a significant role in regulating the amount of CO2 in the atmosphere. The increasing oceanic uptake of CO2 counterbalances the increase in atmospheric CO2. This uptake has a considerable impact on marine biogeochemistry, leading to pH and alkalinity imbalances in the water column, commonly referred to as ocean acidification. In an acidic ocean, excess CO2 reacts with seawater to form carbonic acid, which is highly unstable and undergoes further reduction by releasing hydrogen ions (H+) and acidifying the seawater (reduces the pH). Several studies have projected a decline of upper ocean pH by 0.3–0.4 by the end of the 21st century, which has the potential to reduce oceanic biological production considerably. The number of available observations to study Indian Ocean acidification is limited. There is a critical need to understand the status of Indian Ocean acidification and identify its key drivers. This article consolidates the current level of understanding about the Indian Ocean acidification based on the available field observations, reconstructed data sets, and model simulations.
Continue reading ‘Indian Ocean acidification and its driving mechanisms over the last four decades (1980–2019)’
