Dire straits

Global warming will have bigger impact on oceans than thought

By Indu Mathi S
Last Updated: Saturday 04 July 2015

Coral reefs, seagrass beds and shallow soft-bottom habitats would experience the largest changes in ocean biogeochemistry due to greenhouse gases

GREENHOUSE gases will interfere with the biogeochemical reactions of ocean and affect sea-level, ocean temperature, oxygen concentration, pH levels and phytoplankton productivity by 2100. This disturbance in aquatic life will also have a socio-economic impact as the changes would influence the livelihood of people in coastal areas, says a study.

For the study, the scientists analysed the models of projected climate change developed for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change till 2100, and found that with the exception of the Antarctic and small areas in the South Pacific and North Atlantic, the rest of the world’s oceans would experience change in biogeochemical parameters. For instance, increased levels of carbon dioxide in the ocean will increase the rate of photosynthesis in the algae and alter the productivity of the system on which the entire food web of the ocean rests.

The study was conducted by the University of Hawai'i, Manoa, US, and published in PLoS Biology on October 15. “When you look at the world oceans, there are a few places that will be free of changes; (but) most will suffer the simultaneous effects of warming, acidification and reductions in oxygen and productivity,” says Camilo Mora, lead author of the study and assistant professor at the department of geography, University of Hawai'i. To understand the extent of impact of biogeochemical changes in marine habitats, the scientists compiled the global distribution of 32 marine habitats and biodiversity hot spots and found that the biggest changes will take place in shallow-water habitats like corals, rocky reefs and sea grass beds while deep-sea habitats, such as ocean floors and mountains, will undergo only minute changes.

On the vulnerability of people living in coastal areas, the results predict that under moderate carbon dioxide increase, 1.4 billion people will be exposed to medium-to-high oceanic change by 2100. Arthur J. Miller, research oceanographer and professor at Scripps Institution of Oceanography, University of California, San Diego, says, “They have methodically assessed the potential impacts of multiple biogeochemical stressors on various parts of the ecosystem to identify how complicated processes may interact to affect ocean biology. The compelling result is that the impacts are overwhelmingly detrimental to the ocean ecosystem as well as to the consequent resource usage.”

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  • The opening title "Global

    The opening title "Global warming will have bigger impact on oceans than thought" is not a correct statement. As usual people use the words like global warming and climate change as an adjective to get hype to the presentation. Recent report states that "The simultaneous occurrence of acidification, warming and de-oxygenation that is seriously affecting how productive and efficient the ocean is." Historical ocean temperature shows a cyclic variation and carbon dioxide followed this pattern -- when sea temperature is high carbon dioxide is released in to the atmosphere and when ocean temperature is low the ocean absorbs the carbon dioxide. This clearly indicate that the life in the ocean or for that matter ocean ecosystem adopted for centuries to such variations in temperature and carbon dioxide.

    As we all know the fact that in 70s the environmental movement started with pollution from chemical inputs use in green revolution agriculture technology. This causes air, water, soil and food pollution. The runoff from agriculture fields joins the oceans after contaminating rivers. In the case of Gulf of Mexico, the runoff from USA agriculture fields joins the river and that carried polluted water finally merges in ocean. This created dead zone -- no oxygen & no life -- over thousands of square kilometers in Gulf of Mexico. In addition to this, there are several other pollutants joining the oceans -- oil spills, ships discharges, industrial effluents, etc -- I discussed this in my recent article "Impacts of pollution on Environment: Myths & Realities" published in the Compendium released on the occasion of Platinum Jubilee Celebrations of Andhra Pradesh State Centre (1938-2012) of Institute of Engineers (India), on 14th November 2013.

    As per as global warming is concerned in the last more than a decade no systematic rise was evident. But, the ocean temperatures over specified zones are affected by short term cyclic variations. Yet they are not new. Southern Hemisphere temperature rise is far lower than the Northern Hemisphere. So, what we are talking as global warming is highly variable with regions. Also, the contribution to this from heat-island effect is confined to urban areas.

    Acidification is more associated with pollution entering in to ocean waters. So, the major factor affecting the ocean ecosystem is from pollution that needs control.

    Dr. S. Jeevananda Reddy

    Posted by: Anonymous | 7 years ago | Reply