Posts Tagged 'Indian'

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.

Continue reading ‘Ocean changes to come’

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’

CO2 induced growth response in a diatom dominated phytoplankton community from SW Bay of Bengal coastal water

The ongoing increase in surface seawater CO2 level could potentially impact phytoplankton primary production in coastal waters; however, CO2 sensitivity studies on tropical coastal phytoplankton assemblages are rare. The present study investigated the interactive impacts of variable CO2 level, light and zinc addition on the diatom dominated phytoplankton assemblages from the western coastal Bay of Bengal. Increased CO2supply enhanced particulate organic matter (POC) production; a concomitant depletion in δ13CPOM values at elevated CO2 suggested increased CO2 diffusive influx inside the cell. Trace amount of Zn added under low CO2 level accelerated growth probably by accelerating Zn-Carbonic Anhydrase activity which helps in converting bicarbonate ion to CO2. Almost identical values of δ13CPOM in the low CO2 treated cells grown with and without Zn indicated a low discrimination between 13C and 12C probably due to bicarbonate uptake. These evidences collectively indicated the existence of the carbon concentration mechanisms (CCMs) at low CO2. A minimum growth rate was observed at low CO2 and light limited condition indicating light dependence of CCMs activity. Upon the increase of light and CO2 level, growth response was maximum. The cells grown in the low CO2 levels showed higher light stress (higher values of both diatoxanthin index and the ratio of photo-protective to light-harvesting pigments) that was alleviated by both increasing CO2 supply and Zn addition (probably by efficient light energy utilization in presence of adequate CO2). This is likely that the diatom dominated phytoplankton communities benefited from the increasing CO2 supply and thus may enhance primary production in response to any further increase in coastal water CO2 levels and can have large biogeochemical consequences in the study area.

Continue reading ‘CO2 induced growth response in a diatom dominated phytoplankton community from SW Bay of Bengal coastal water’

Intra-annual variability of CO2 flux in the Mahanadi Estuary – a tropical estuarine system, India

The inorganic carbon dynamics and the CO2 flux of estuarine system are strongly influenced by the productivity and nutrient regime of water. This study provides full seasonal coverage of assessment of the physicochemical variables of Mahanadi estuary, mainly focusing on the carbonate system through the measurement of pH, Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), both aqueous and air fCO2, Dissolved Oxygen (DO) and chlorophyll a (chl a). The relationship of TA and DIC were found conservative throughout the study period. The estuary was found to be over-saturated with CO2 and acted as a net source. However, the magnitude of flux varied from season to season with a range between -8.14 to 58.09 μmol m-2 h-1 indicating ephemeral sink phase in the estuary. The air-water CO2 flux was primarily governed by fCO2 (water) although other factors such as temperature, pH, salinity, total alkalinity, wind speed and fCO2 (air) noticeably affected CO2 flux. A strong positive correlation was observed between temperature and inorganic nutrients during the study period. The study of net ecosystem metabolism justifies the heterotrophic nature of Mahanadi estuarine system.

Continue reading ‘Intra-annual variability of CO2 flux in the Mahanadi Estuary – a tropical estuarine system, India’

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Ocean acidification in the IPCC AR5 WG II

OUP book