"Effects of Ocean Acidification on Marine organisms"  is a heavy weight phrase in modern marine research. Marine organisms are numerous and there is not a single effect on them. hence this is not a valid question in fact. Neither oceans are becoming  only acidic, but warmer and oligotrophic, means multi-stressors and effects are also combined  The main reason is the changing carbonate chemistry for dissolving more CO2 in the surface seawater resulting in: increasing CO2, hydrogen ion and bicarbonate ion concentrations  and decreasing pH and carbonate ion concentrations. There are huge literature on each component of marine ecosystems and their responses to ocean acidification, starting from bacteria, phytoplankton, calcifying, non-calcifying phytoplankton, macroalgae, corals, microzooplankton, mesozooplankton, fish, fish larvae and so on . Each component expressed unique responses to changing carbon chemistry parameters. the effects on ecosystem levels would be a combined one and not really an easy job for the marine ecologists.

There were three international symposiums only on "Ocean in a high CO2 world", a special issue was published in Biogeosciences and several publications in Nature Climate change and Nature Geo Science. some are given bellow"

1. Lessons learned from ocean acidification research, Ulf Riebesell  & Jean-Pierre Gattuso, Nature Climate Change, 5,12–14(2015) doi:10.1038/nclimate2456

2.Scott C. Doney, Victoria J. Fabry, Richard A. Feely, and Joan A. Kleypas, Ocean Acidification: The Other CO2 Problem Annual Review of Marine Science

Vol. 1: 169-192 (Volume publication date January 2009) 

3. Broadgate, W. et al. Ocean Acidification Summary for Policymakers: Third Symposium on the Ocean in a High-CO2 World (International Geosphere-Biosphere Programme, 2013). 

4. Schlüter, L., Lohbeck, K. T., Gutowska, M. A., Gröger, J. P., Riebesell, U. and Reusch, T. B. H. (2014) Adaptation of a globally important coccolithophore to ocean warming and acidification Nature Climate Change, 4 (11). pp. 1024-1030. DOI 10.1038/NCLIMATE2379. 

5.Lohbeck, K. T., Riebesell, U. and Reusch, T. B. H. (2012) Adaptive evolution of a key phytoplankton species to ocean acidification Nature Geoscience, 5 . pp. 346-351. DOI 10.1038/ngeo1441. 

6.Turley, C., Eby, M., Ridgwell, A. J., Schmidt, D. N., Findlay, H. S., Brownlee, C., Riebesell, U., Fabry, V. J., Feely, R. A. and Gattuso, J. P. (2010) The societal challenge of ocean acidification,  Marine Pollution Bulletin, 60 (6). pp. 787-792. DOI 10.1016/j.marpolbul.2010.05.006. 

Ocean acidification reduces the pH of the aquatic system and the seas..

The calcium carbonate is depleted from coral reefs and as a result coral bleaching takes place..

Hi Sufia, your explanation is having some technical error, the term "Ocean Acidification" does not reduce the pH of the aquatic systems and the seas. The term "Ocean Acidification" is exclusively to define the drop of pH towards acidic range from 8.2 average to further 0.1 unit drop in the global oceans. Acidification does not mean that the pH of the oceans are going >7 pH which is ideally an acidic range, nevertheless, we define this issue as ocean acidification because the concentration of hydrogen ion is increasing and hence the pH shift is towards acidic range. This is mainly because of dissolving atmospheric CO2 in to the surface ocean. Other aquatic system pH drop does not come under "Ocean Acidification" and the reason may not be the same. Last but not the least, this is true that Calcium carbonate saturation is decreasing from global oceans but not from coral reefs (reefs are hard structures),  which impeding the formation of calcium carbonate skeleton in calcifying organisms. However, corals are not only calcifying organisms in the oceans, there are several, the entire molluscan groups and coraline algae, coccolithophores, pteropods and so on come under calcifiers. We should be precise and careful while answering such kind of sensitive question in this kind of science forum.

The acidification may be in the coastal part, if the mixing of ocean water is more this problem won't rise. Many parts of the ocean, water circulation dilute the pollutants, the impact may be near coastal part or enclosed areas like brackish water lakes. Due to acidification the marine molluscs can not form the shells ultimately they will be destroyed.  

Dr. Rajaguru, I do not agree with you since the chances of mixing in the oceans will be reduced due to warmer temperature in the future oceans (Raven et al 2005) and hence would not solve the problem. CO2 is not a pollutant like other pollutants in the sea and is used by the marine primary producers. Coastal waters have always high fluctuations in pH and CO2 levels due to natural reasons like fresh water input which also acidifies the waters. However, ocean acidification we are concerned about is mostly due to the dissolution on atmospheric CO2 where open oceans are not excluded. oceans in the temperature parts, Arctic and Antarctic  are more vulnerable to pH drop because of higher solubility of CO2 in cold temperature. Moreover, about dissolution of Molluscs, it may not be such simple. Already research outcomes are there where scientist reported a growing resistance of calcifier under high CO2 levels during long term  experiment (Lohbeck et al. 2012) and it is also possible that they develop some mechanism to survive under high CO2 levels. Lots of molluscs also live in the seabed where CO2 levels are usually high and also close to the hydrothermal vents. Hence some groups are having natural power to resist under such condition. Hence the community may shift. Last but not the least, global oceans already experienced huge change in pH over the multimillion year scale, however those changes were slow over several 1000 years and the change we are facing now is within very short time scale and hence a threat. Nevertheless, there are several groups globally who are working to invent some Geo-engineering designs to mitigate CO2 from the atmosphere.

Thaxs for your comments and answers

Thanks Madam Haimanti Biswas for excellent statement. I have given general statement by considering large volume of water body. I like to study more and work in this aspect. During several cruises of NIOT I have missed to study the acidification problems. Thank you.

You can go through this book, where about 15 case studies on the effect of acidification on molluscs and corals have been discussed in details.