Posts Tagged 'Indian'

Variation in calcification rate of Acropora downingi relative to seasonal changes in environmental conditions in the northeastern Persian Gulf

There is a strong interest in understanding how coral calcification varies with changing environmental conditions, especially given the projected changes in temperature and aragonite saturation due to climate change. This study explores in situ variation in calcification rates of Acropora downingi in the northeastern Persian Gulf relative to seasonal changes in temperature, irradiance and aragonite saturation state (Ωarag). Calcification rates of A. downingi were highest in the spring and lowest in the winter, and intra-annual variation in calcification rate was significantly related to temperature (r2 = 0.30) and irradiance (r2 = 0.36), but not Ωarag (r2 = 0.02). Seasonal differences in temperature are obviously confounded by differences in other environmental conditions and vice versa. Therefore, we used published relationships from experimental studies to establish which environmental parameter(s) (temperature, irradiance, and/or Ωarag) placed greatest constraints on calcification rate (relative to the maximum spring rate) in each season. Variation in calcification rates was largely attributable to seasonal changes in irradiance and temperature (possibly ~57.4 and 39.7% respectively). Therefore, we predict that ocean warming may lead to increased rates of calcification during winter, but decelerate calcification during spring, fall and especially summer, resulting in net deceleration of calcification for A. downingi in the Persian Gulf.

Continue reading ‘Variation in calcification rate of Acropora downingi relative to seasonal changes in environmental conditions in the northeastern Persian Gulf’

Variation in carbonate system and air-water CO2 flux during summer in the Mahanadi Estuary, India

The carbonate system of water of the inner estuary and near shore in the Mahanadi estuary, Bay of Bengal, India was studied in summer season of 2014. Physicochemical parameters like temperature, pH, salinity, total alkalinity (TA), dissolved inorganic carbon (DIC), total organic carbon (TOC) and chlorophyll a (chl a) were measured in order to study their role in controlling the CO2 flux. The estuary acted as a sink for atmospheric CO2 triggered by the allochthonous organic carbon input. The average CO2 flux was recorded as -0.36±13.29 μmol/m2h in inner estuary and -10.36±2.00 μmol/m2h in near shore region. The temperature and salinity were found to be significantly and positively correlated with fCO2 (water) indicating their deterministic role in influencing air-water CO2 flux.

Continue reading ‘Variation in carbonate system and air-water CO2 flux during summer in the Mahanadi Estuary, India’

Biomarker response of climate change-induced ocean acidification and hypercapnia studies on brachyurian crab Portunus pelagicus

A laboratory level microcosm analysis of the impacts of ocean acidification on the environmental stress biomarkers in Portunus pelagicus (Linneaus 1758)exposed to a series of pH regimes expected in the year 2100 (pH 7.5 and 7.0) and leakage from a sub-seabed carbon dioxide storage site (pH 6.5 – 5.5) was carried out. Levels of the antioxidant enzyme catalase, the phase II detoxification enzyme, glutathione S. transferase, the lipid peroxidation biomarker, malondialdehyde, acetylcholinesterase, and reduced glutathione were estimated in the tissues of the exposed animals to validate theses enzymes as biomarkers of Hypercapnia. The integrated biomarkers indicated a stress full environment in all animals except those exposed to the control seawater (pH 8.1). The reducing pH was also observed to be highly lethal to the animals exposed to lower pH levels which were obvious from the rate of mortality in a short term of exposure. The present study substantiates the role of biomarkers as an early warning of ocean acidification at a sub-lethal level.

Continue reading ‘Biomarker response of climate change-induced ocean acidification and hypercapnia studies on brachyurian crab Portunus pelagicus’

Coral reefs and people in a high-CO2 world: where can science make a difference to people?

Reefs and People at Risk

Increasing levels of carbon dioxide in the atmosphere put shallow, warm-water coral reef ecosystems, and the people who depend upon them at risk from two key global environmental stresses: 1) elevated sea surface temperature (that can cause coral bleaching and related mortality), and 2) ocean acidification. These global stressors: cannot be avoided by local management, compound local stressors, and hasten the loss of ecosystem services. Impacts to people will be most grave where a) human dependence on coral reef ecosystems is high, b) sea surface temperature reaches critical levels soonest, and c) ocean acidification levels are most severe. Where these elements align, swift action will be needed to protect people’s lives and livelihoods, but such action must be informed by data and science.

An Indicator Approach

Designing policies to offset potential harm to coral reef ecosystems and people requires a better understanding of where CO2-related global environmental stresses could cause the most severe impacts. Mapping indicators has been proposed as a way of combining natural and social science data to identify policy actions even when the needed science is relatively nascent. To identify where people are at risk and where more science is needed, we map indicators of biological, physical and social science factors to understand how human dependence on coral reef ecosystems will be affected by globally-driven threats to corals expected in a high-CO2 world. Western Mexico, Micronesia, Indonesia and parts of Australia have high human dependence and will likely face severe combined threats. As a region, Southeast Asia is particularly at risk. Many of the countries most dependent upon coral reef ecosystems are places for which we have the least robust data on ocean acidification. These areas require new data and interdisciplinary scientific research to help coral reef-dependent human communities better prepare for a high CO2 world.

Continue reading ‘Coral reefs and people in a high-CO2 world: where can science make a difference to people?’

Ocean acidification: assessing the vulnerability of socioeconomic systems in Small Island Developing States

Ocean acidification poses an increasing threat to marine ecosystems and also interacts with other anthropogenic environmental drivers. A planned response strategy could minimize exposure of socioeconomic systems to potential hazards and may even offer wider advantages. Response strategies can be informed by understanding the hazards, assessing exposure and assessing risks and opportunities. This paper assesses exposure of key socioeconomic systems to the hazards of ocean acidification and analyzes the risks and opportunities of this exposure from Small Island Developing States (SIDS) perspectives. Key socioeconomic systems that are likely to be affected by ocean acidification are identified. A risk analysis matrix is developed to evaluate the risks or opportunities arising from ocean acidification. Analysis of the matrix reveals similarities and differences in potential adaptive responses at global and regional levels. For example, while ocean acidification poses significant threats to SIDS from more frequent toxic wild-caught seafood events and, potentially destruction of coral reef structure and habitat, SIDS may have a relative advantage in aquaculture and an important role to play in global marine ecosystem conservation.

Continue reading ‘Ocean acidification: assessing the vulnerability of socioeconomic systems in Small Island Developing States’

A first look at factors affecting aragonite compensation depth in the eastern Arabian Sea

Water column measurements suggest shoaling of aragonite saturation depths (ASD) throughout the world oceans, due to increase in greenhouse gas concentration. Past records of aragonite saturation state under different climatic conditions are required to assess the impact of climatic changes on shoaling/deepening of ASD. The preservation state of organisms having aragonite skeletons, is used to assess the past changes in aragonite saturation depths, with respect to the modern ASD. Here for the first time, we delineate and discuss the factors that affect the modern aragonite compensation depth (ACD) in the eastern Arabian Sea by using pteropod abundance in the surface sediments. A total of 78 spade core-top samples collected along seven latitudinal transects, covering the continental shelf, slope and abyssal region of the eastern Arabian Sea were used. Pteropods were picked from coarse fraction (≥ 63 μm). Based on the pteropod preservation, we report that in the eastern Arabian Sea, ACD lies at a water depth of ≤ 525 m, which matches with the chemically defined aragonite saturation depth. We further report that the ACD shoals from north to south. The zone of high pteropod abundance coincides with low %Corg. The increase in pteropod abundance in the outer shelf region coincides with the drop in dissolved oxygen concentration. The deeper limit of pteropod abundance lies in the center of the oxygen minimum zone with higher %Corg. Therefore, we suggest that the pteropod abundance in the eastern Arabian Sea is not always related with the lower dissolved oxygen, but is strongly influenced by %Corg. This first report of the pteropod based aragonite compensation depth estimates from the eastern Arabian Sea will help in assessing future changes in ACD under the influence of anthropogenic green-house gas emissions.

Continue reading ‘A first look at factors affecting aragonite compensation depth in the eastern Arabian Sea’

Using present-day observations to detect when anthropogenic change forces surface ocean carbonate chemistry outside preindustrial bounds (update)

One of the major challenges to assessing the impact of ocean acidification on marine life is detecting and interpreting long-term change in the context of natural variability. This study addresses this need through a global synthesis of monthly pH and aragonite saturation state (Ωarag) climatologies for 12 open ocean, coastal, and coral reef locations using 3-hourly moored observations of surface seawater partial pressure of CO2 and pH collected together since as early as 2010. Mooring observations suggest open ocean subtropical and subarctic sites experience present-day surface pH and Ωarag conditions outside the bounds of preindustrial variability throughout most, if not all, of the year. In general, coastal mooring sites experience more natural variability and thus, more overlap with preindustrial conditions; however, present-day Ωarag conditions surpass biologically relevant thresholds associated with ocean acidification impacts on Mytilus californianus (Ωarag < 1.8) and Crassostrea gigas (Ωarag < 2.0) larvae in the California Current Ecosystem (CCE) and Mya arenaria larvae in the Gulf of Maine (Ωarag < 1.6). At the most variable mooring locations in coastal systems of the CCE, subseasonal conditions approached Ωarag =  1. Global and regional models and data syntheses of ship-based observations tended to underestimate seasonal variability compared to mooring observations. Efforts such as this to characterize all patterns of pH and Ωarag variability and change at key locations are fundamental to assessing present-day biological impacts of ocean acidification, further improving experimental design to interrogate organism response under real-world conditions, and improving predictive models and vulnerability assessments seeking to quantify the broader impacts of ocean acidification.

Continue reading ‘Using present-day observations to detect when anthropogenic change forces surface ocean carbonate chemistry outside preindustrial bounds (update)’


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