Posts Tagged 'Indian'

Dealing with the effects of ocean acidification on coral reefs in the Indian Ocean and Asia

Shallow coral reefs provide food, income, well-being and coastal protection to countries around the Indian Ocean and Asia. These reefs are under threat due to many anthropogenic stressors including pollution, sedimentation, overfishing, sea surface warming and habitat destruction. Ocean acidification interacts with these factors to exacerbate stress on coral reefs. Effective solutions in tackling the impact of ocean acidification require a thorough understanding of the current adaptive capacity of each nation to deal with the consequences. Here, we aim to help the decision-making process for policy makers in dealing with these future challenges at the regional and national levels. We recommend that a series of evaluations be made to understand the current status of each nation in this region in dealing with ocean acidification impacts by assessing the climate policy, education, policy coherence, related research activities, adaptive capacity of reef-dependent economic sectors and local management. Indonesia and Thailand, are selected as case studies. We also highlight general recommendations on mitigation and adaptation to ocean acidification impacts on coral reefs and propose well-designed research program would be necessary for developing a more targeted policy agenda in this region.

Continue reading ‘Dealing with the effects of ocean acidification on coral reefs in the Indian Ocean and Asia’

Environmental and physiochemical controls on coral calcification along a latitudinal temperature gradient in Western Australia

The processes that occur at the micro‐scale site of calcification are fundamental to understanding the response of coral growth in a changing world. However, our mechanistic understanding of chemical processes driving calcification is still evolving. Here, we report the results of a long‐term in situ study of coral calcification rates, photo‐physiology, and calcifying fluid (cf) carbonate chemistry (using boron isotopes, elemental systematics, and Raman spectroscopy) for seven species (four genera) of symbiotic corals growing in their natural environments at tropical, subtropical, and temperate locations in Western Australia (latitudinal range of ~11°). We find that changes in net coral calcification rates are primarily driven by pHcf and carbonate ion concentration []cf in conjunction with temperature and DICcf. Coral pHcf varies with latitudinal and seasonal changes in temperature and works together with the seasonally varying DICcf to optimize []cf at species‐dependent levels. Our results indicate that corals shift their pHcf to adapt and/or acclimatize to their localized thermal regimes. This biological response is likely to have critical implications for predicting the future of coral reefs under CO2‐driven warming and acidification.

Continue reading ‘Environmental and physiochemical controls on coral calcification along a latitudinal temperature gradient in Western Australia’

Physical factors affecting oyster diversity and distribution in southern Thailand

Aim : Studies on oyster population dynamic is essential for effective oyster aquaculture.Bandon Bay in Southern Thailand is a major shellfish aquaculture site of high commercial value. The aim of this study was to evaluate the influence of environmental factors on oyster diversity and their distribution in Bandon Bay. Methodology: Adult oysters were collected from eight aquaculture sites during low tide and their body sizes were measured. Monthly, transparency, salinity, pH, dissolved oxygen, biochemical oxygen demand, alkalinity, ammonium (NH4-N),nitrite, nitrate and phosphate were recorded from Surat Thani Coastal Fisheries Research and Development Centre, Department of Fisheries. Results : Three oyster species were observed: Crassostrea belcheri, Crassostrea lugubris and Saccostrea forskalii, however, C. belcheri was most abundant at most locations. Oyster density in Bandon Bay was mostly influenced by alkalinity, followed by salinity, pH, NO3and NH4-N. Interpretation : Since oyster reproduction, survival and shell development depend on environmental factors, thus studies on relationships between environmental factors and oyster occurrence/density may provide a better understanding about the community structures and spatial dynamics of oysters, as well as how oysters respond to environmental changes.

Continue reading ‘Physical factors affecting oyster diversity and distribution in southern Thailand’

Variability, trend and controlling factors of ocean acidification over Western Arabian Sea upwelling region

Highlights

  • The factors controlling the seasonal variability and trend in pH over the Western Arabian Sea upwelling region are studied.
  • DIC and SST are the major driving factors of seasonal variability in pH and they act in opposite directions.
  • DIC and ALK contribute up to 73% to the net trend and SST warming alone contributes another 16%.

Abstract

Western Arabian Sea (WAS) is subjected to strong bio-physical forcings which results in significant variability in biological productivity and intense CO2 emission at different timescales. The study aims to understand the major physical factors controlling seasonal variability and trend in pH over WAS. Two sets of sensitivity experiments are carried out in order to delineate the individual factors such as Sea Surface Temperature (SST), Dissolved Inorganic Carbon (DIC), Alkalinity (ALK) and Salinity (S) which control the pH seasonal variability and its trend. The first set of sensitivity experiments extract the major controlling factors of pH seasonal variability and the second set identifies the major contributors to the trend in pH over WAS. The results show that DIC and SST are the principal drivers of seasonal variability of pH and they act in opposite directions. Seasonal warming and cooling have significant effect in pH variability during pre-monsoon and post-monsoon period, respectively. DIC plays a major role in pH seasonality during the monsoon period. WAS has been acidified from a pH of 8.12 (in 1960) to a pH of 8.05 (in 2010). The trend in pH over WAS is due to contributions from DIC and SST of 109% and 16%, respectively. The effect of ALK is to buffer the existing trend in pH by −36% while S contribution is only 7%. Collectively, DIC and ALK contribute up to 73% to the net pH trend. SST warming alone contributes another 16%. pH shows a decreasing trend of −0.0091 for 50 years for October to December and − 0.0039 for July to August with a correlation of 0.374 and 0.244 with increasing trend in SST for the corresponding period, respectively. The study raises a red flag since this region is warming rapidly which is only exacerbating acidification.

Continue reading ‘Variability, trend and controlling factors of ocean acidification over Western Arabian Sea upwelling region’

The ocean-atmospheric condition around Pieh Islands – Western Sumatra, Indonesia and its role on coral reef resilience

Pieh Islands located at the Western Sumatra is one of the most affected areas by massive coral bleaching during 2015-2016. The persistence warming or cooling of sea surface temperature due to regional climate phenomena such as El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) put the coral reef into stress condition leading into coral bleaching. However, corals have an ability to recover from such bleaching condition into normal state by reducing its stressors. A suitable oceanographic condition such as normal range of temperature and salinity, low nutrient concentration, and low sedimentation rate could support corals recovery process. This study aims to understand the variability of the ocean and atmospheric data and its role in coral reef recovery. Data gained from in situ measurements of water quality at Pieh Marine Conservation Area (PMCA) on June 2018. Several historical ocean-atmospheric data were collected to analyze their temporal variability. It is confirmed that the bleaching event was caused by positive IOD and El Niño condition in 2015-2016. However, there is the sign of coral reef recovery during 2017-2018 which is suggested due to the relatively normal condition of the ocean and atmospheric parameters in Pieh Islands.

Continue reading ‘The ocean-atmospheric condition around Pieh Islands – Western Sumatra, Indonesia and its role on coral reef resilience’

The invisible carbon footprint as a hidden impact of peatland degradation inducing marine carbonate dissolution in Sumatra, Indonesia

In Indonesia, land use change (LUC) in the form of peatland degradation induces carbon loss through direct CO2 emissions, but also via soil leaching of which circa 50% is decomposed and emitted as CO2 from the rivers. However, the fate of the remaining exported leached carbon is uncertain. Here, we show that the majority of this carbon is respired in the estuaries and emitted to the atmosphere. However, a portion is adsorbed into the marine carbon pool where it favors CaCO3 dissolution and can therefore be seen as the invisible carbon footprint. We conclude that the effects of LUC stretch beyond the terrestrial realm and are not limited to CO2 emissions, but also affect marine ecosystems. Considering the ecological and economical importance of these ecosystems, it is important that this so far invisible carbon footprint, as well as the aquatic and marine CO2 emissions, are included in climate mitigation strategies.

Continue reading ‘The invisible carbon footprint as a hidden impact of peatland degradation inducing marine carbonate dissolution in Sumatra, Indonesia’

Performance and herbivory of the tropical topshell Trochus histrio under short-term temperature increase and high CO2

Highlights

• Tropical algae-herbivore interactions were studied under a climate change scenario.

• Survival of topshells did not vary but body fitness declined under high CO2.

• Elevated temperature resulted in better physical condition and stimulated herbivory.

• Dynamic index was temperature- and pCO2-interactively dependent.

• Dominance of bottom-up control (i.e. lower grazing pressure) under high CO2.

Abstract

Within tropical environments, short-term impacts of increased seawater temperature and pCO2 on algae-herbivore interactions remain poorly understood. We investigated the isolated and combined 7-day effects of increased temperature (+4 °C) and pCO2 (~1000 μatm) on the trophic interaction Ulva sp./Trochus histrio, by assessing: i) topshells’ survival and condition index; ii) grazer consumption rates, nutritional composition and interaction strength expressed as a dynamic index. No survival differences were observed whilst body condition varied significantly. Topshells under high pCO2 displayed poor performance, concomitant with lower consumption of macroalgae. Individuals exposed to increased temperature had better physical condition, thus stimulating herbivory, which in turn was negatively correlated with carbon and nitrogen contents. The dynamic index was temperature- and pCO2- interactively dependent, suggesting lower grazing pressure under single acidification. Despite some limitations inherent to a short-term exposure, this study provides new insights to accurately predict tropical species’ phenotypic responses in a changing ocean.

Continue reading ‘Performance and herbivory of the tropical topshell Trochus histrio under short-term temperature increase and high CO2’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book