Posts Tagged 'Indian'

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.

Continue reading ‘The oceans and our climate’

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’

Impact of ocean acidification on the early development and escape behavior of marine medaka (Oryzias melastigma)


  • No significantly negative growth effects were observed in larvae exposed higher pCO2.
  • Eye defects and abnormal development of brain were obvious in exposed larvae.
  • Escape behavior was vulnerable to ocean acidification.


Ocean acidification is predicted to affect a wide diversity of marine organisms. However, no studies have reported the effects of ocean acidification on Indian Ocean fish. We have used the Indian Ocean medaka (Oryzias melastigma) as a model species for a marine fish that lives in coastal waters. We investigated the impact of ocean acidification on the embryonic development and the stereotyped escape behavior (mediated by the Mauthner cell) in newly hatched larvae. Newly fertilized eggs of medaka were reared in seawater at three different partial pressures of carbon dioxide (pCO2): control at 450 μatm, moderate at 1160 μatm, and high at 1783 μatm. Hatching rates, embryonic duration, and larval malformation rates were compared and were not significantly different between the treatments and the control. In the high pCO2 group, however, the yolks of larvae were significantly smaller than in the control group, and the newly hatched larvae were significantly longer than the larvae in the control. In the moderate pCO2 group, the eye distance decreased significantly. No significantly negative growth effects were observed in the larvae when exposed to pCO2 levels that are predicted as a result of ocean acidification in the next 100–200 years. Larvae reared under control conditions readily produced C-start escape behavior to mechanosensory stimuli; however, in the moderate and high pCO2 experimental groups, the probabilities of C-start were significantly lower than those of the control group. Therefore, the sensory integration needed for the C-start escape behavior appears to be vulnerable to ocean acidification. Altered behavior in marine larval fish, particularly behaviors involved in escape from predation, could have potentially negative implications to fish populations, and, further, to the marine ecosystems at the levels of CO2 projected for the future.

Continue reading ‘Impact of ocean acidification on the early development and escape behavior of marine medaka (Oryzias melastigma)’

Effect of low pH on marine mollusca at Rangbai coast, Gujarat

(…) The coastal stretches of Gujarat have several industries, which are based on salt as raw material. The saltpan activity not only provides the livelihood for a large number of unskilled workers but also provides the raw material for several such chemical industries.

The present study was conducted to know the low pH is affected by Marine Molluscan diversity from Rangbai coast. We have tried to carefully observe seasonal variation. Mainly during study observed that in December month the total number of Molluscan species is 50 while January month the number of Molluscan species is direct 28.from August to December pH was not shown any significant variation, while in January month pH was 4.3.average sea water pH is 7 to 8 neither acidic nor basic. For molluscan development, acidic sea water is not suitable for molluscan growth and development. (…)

Continue reading ‘Effect of low pH on marine mollusca at Rangbai coast, Gujarat’

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Ocean acidification in the IPCC AR5 WG II

OUP book