Sharks are a major part of the earth's marine ecosystem, a keystone species at the top of the ocean food chain that help manage population size and maintain the health of ocean flora. However, sharks have been on the decline in recent years due to overfishing - and now, warmer waters and ocean acidification will have major detrimental effects on remaining shark populations. The ocean's rise in temperature and carbon dioxide content have led to hungrier sharks through increased energy requirement. However, these conditions have also reduced the sharks' metabolic efficiency and removed their ability to locate food through smelling. Under such conditions, some sharks didn't even try to search for food. These effects have led to smaller sharks - in physical size and in population size. The loss of sharks would lead to perhaps the collapse of ocean life as it is known, as this keystone species is gradually thinning out and is becoming no longer able to assert dominance over smaller species.
http://www.sciencedaily.com/releases/2015/11/151112055246.htm
http://www.sciencedaily.com/releases/2015/11/151112055246.htm