Posts Tagged 'Indian'



A study on the impact of acidification on the morphometry, photosynthesis, and biochemical composition of phytoplankton

Many marine organisms are affected by ocean acidification, particularly those with shells and skeletons built from calcium carbonate; e.g., corals, oysters, clams, mussels, snails, and phytoplankton and zooplankton—the tiny plants and animals that form the base of the marine food web. These “marine calcifiers” face two potential problems associated with ocean acidification. The first one is that their shells and skeletons may dissolve as the ocean pH decreases; as CO2 is dissolved in seawater it becomes more corrosive, and the water chemistry undergoes major changes, such that fewer carbonate ions, the primary building blocks of marine organisms, are accessible for uptake to shells and skeletons. To build their shells or skeletons, marine organisms generally undergo an internal chemical process that converts bicarbonate to carbonate in the form of calcium carbonate. Exactly how ocean acidification slows calcification or shell formation is not yet completely understood, but various mechanisms are being studied. Most investigations of this corrosive environment focus on the evolutionary defense mechanisms that organisms must have in order to build and maintain their calcium carbonate shells and skeletons in an increasingly acidified environment. In such environments, these organisms can be subject to greater energy expenditure and environmental stressors such as ocean temperature increases, low oxygen accessibility, disease, and habitat loss.

Continue reading ‘A study on the impact of acidification on the morphometry, photosynthesis, and biochemical composition of phytoplankton’

A microcosm study on the impact of acidification on feeding, survival, nauplii production rate, post-embryonic development and nutritional composition of marine copepod

Ocean acidification is the ongoing decrease in the pH of the oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. Increased carbon dioxide (CO2) from the burning of fossil fuels and other human activities continues to affect our atmosphere, resulting in global warming and climate change. Less well known is that this carbon dioxide is altering the chemistry of the surface oceans and causing them to become more acidic. From scientists and marine resource managers to policy- and decision-makers, there is a growing concern that the process called ocean acidification could have significant consequences on marine organisms which may alter species composition, disrupt marine food webs and ecosystems and potentially damage fishing, tourism and other human activities connected to the seas.

Continue reading ‘A microcosm study on the impact of acidification on feeding, survival, nauplii production rate, post-embryonic development and nutritional composition of marine copepod’

Mechanisms and seasonal drivers of calcification in the temperate coral Turbinaria reniformis at its latitudinal limits

High-latitude coral reefs provide natural laboratories for investigating the mechanisms and limits of coral calcification. While the calcification processes of tropical corals have been studied intensively, little is known about how their temperate counterparts grow under much lower temperature and light conditions. Here, we report the results of a long-term (2-year) study of seasonal changes in calcification rates, photo-physiology and calcifying fluid (cf) chemistry (using boron isotope systematics and Raman spectroscopy) for the coral Turbinaria reniformis growing near its latitudinal limits (34.5° S) along the southern coast of Western Australia. In contrast with tropical corals, calcification rates were found to be threefold higher during winter (16 to 17° C) compared with summer (approx. 21° C), and negatively correlated with light, but lacking any correlation with temperature. These unexpected findings are attributed to a combination of higher chlorophyll a, and hence increased heterotrophy during winter compared with summer, together with the corals’ ability to seasonally modulate pHcf, with carbonate ion concentration [CO32-]cf  being the main controller of calcification rates. Conversely, calcium ion concentration [Ca2+]cf declined with increasing calcification rates, resulting in aragonite saturation states Ωcf that were stable yet elevated fourfold above seawater values. Our results show that corals growing near their latitudinal limits exert strong physiological control over their cf in order to maintain year-round calcification rates that are insensitive to the unfavourable temperature regimes typical of high-latitude reefs.
Continue reading ‘Mechanisms and seasonal drivers of calcification in the temperate coral Turbinaria reniformis at its latitudinal limits’

Water quality study at Tuticorin Harbour

The rapid population growth and increasing industrial activities including marine activities have resulted in increasing water pollution, which is considered as one of the primary issue of environmental pollution in coastal region of developing countries including Tuticorin in India. The study area map of Tuticorin harbour is collected. Seawater samples were collected from three different sampling points in Tuticorin coastal to study physico-chemical characteristics and parameters such as temperature, pH, salinity, nitrite, ammonia, silicates, dissolved oxygen and inorganic phosphate were studied using various analytical techniques. The studies reveal that the physical and chemical composition of all the samples collected from the sites mainly depends on discharge from the sources of pollutants.

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Ocean changes to come

Key messages

  • Oceans are key to the climate system’s carbon, heat and freshwater cycles.
  • Oceans are changing, and further physical, chemical and biological changes are projected for Australian waters this century.
  • Ocean warming, acidification, deoxygenation and sea-level rise have important implications for marine ecosystems and the ocean services on which humans depend.
  • Climate models are essential tools for exploring mitigation options and integrating climate predictions with human systems such as agriculture and fisheries.

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The oceans and our climate

Key messages

  • The oceans are a major influence on global and Australian climate.
  • The oceans currently store over 93% of increased heat accumulating in the
    Earth’s climate system.
  • Warming oceans and loss of mass from glaciers and ice sheets are causing sea
    level to rise.
  • Ocean acidification is an inevitable consequence of rising atmospheric
    carbon dioxide.
  • Ocean warming and acidification have significant negative implications for
    marine environments and ecosystem services.

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Variability in the phytoplankton community of Kavaratti reef ecosystem (northern Indian Ocean) during peak and waning periods of El Niño 2016

El Niño, an interannual climate event characterized by elevated oceanic temperature, is a prime threat for coral reef ecosystems worldwide, owing to their thermal threshold sensitivity. Phytoplankton plays a crucial role in the sustenance of reef trophodynamics. The cell size of the phytoplankton forms the “master morphological trait” with implications for growth, resource acquisition, and adaptability to nutrients. In the context of a strong El Niño prediction for 2015–2016, the present study was undertaken to evaluate the variations in the size-structured phytoplankton of Kavaratti reef waters, a major coral atoll along the southeast coast of India. The present study witnessed a remarkable change in the physicochemical environment of the reef water and massive coral bleaching with the progression of El Niño 2015–2016 from its peak to waning phase. The fluctuations observed in sea surface temperature, pH, and nutrient concentration of the reef water with the El Niño progression resulted in a remarkable shift in phytoplankton size structure, abundance, and community composition of the reef waters. Though low nutrient concentration of the waning phase resulted in lower phytoplankton biomass and abundance, the diazotroph Trichodesmium erythraeum predominated the reef waters, owing to its capability of the atmospheric nitrogen fixation and dissolved organic phosphate utilization.

Continue reading ‘Variability in the phytoplankton community of Kavaratti reef ecosystem (northern Indian Ocean) during peak and waning periods of El Niño 2016’


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Ocean acidification in the IPCC AR5 WG II

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