What are some environmental changes in the ocean and how does it affect organisms living there?

1 Answer
Aug 7, 2017


Ocean acidification and plastics


Oceans and seas are performing a notable service to the climate system by absorbing so much #CO_2# (carbondioxide) we currently add into the atmosphere by using nonrenewable fuels (coal, natural gas, gas, etc.). The natural pH of oceans and seas (open ones) is between 8.0 and 8.3, which means they are alkaline. When dissolved carbon dioxide gas dissolves into sea water, carbonic acid and bicarbonate ions form:

#CO_2 + H_2O <=> H_2CO_3 <=> H^+ + HCO_3^-#

The bicarbonate ions ionize to some extent into hydrogen and carbonate ions:

#HCO_3^-# #<=> H^+ + CO_3^-2#

The above reactions release hydrogen ions, which make the water more acidic as carbon dioxide absorption accelerates. Studies have shown that oceans and seas already experienced a decrease in pH of 0.1 since preindustrial times. It seems possible ocean pH will drop by another 0.3 by the end of this century. If that happens, oceans and seas will be more acidic than they have been for hundreds of million years. Many creatures will probably not adopt this change. Mass extinction might be seen.

Another important issue is plastics and garbage we throw to oceans/seas. Many creatures eat them. They die when they do this sooner or later. Some wastes cause deaths of animals because of entanglement. In some areas, there are more plastics compared to fish counts. Such pollution will not only cause changes in fish populations but also harm human being since humans consume fish contaminated with microplastics.