Climate change problems: Altered lifestyles

Rising temperatures can also directly affect the metabolism, life cycle, and behaviour of marine species.

For many species, temperature serves as a cue for reproduction. Clearly, changes in sea temperature could affect their successful breeding. The number of male and female offspring is determined by temperature for marine turtles, as well as some fish and copepods (tiny shrimp-like animals on which many other marine animals feed). Changing climate could therefore skew sex ratios and threaten population survival.

The metabolism of fish and other cold-blooded animals is dependent on the temperature of the surrounding water. As it warms, their metabolism speeds up - they digest food more rapidly, grow more quickly, and have more energy to reproduce.

However, there may be neither enough food nor enough oxygen to support the increased energy needs for a faster metabolism. In addition, the cost of this speedy lifestyle is often a smaller body size, and many fish have fewer offspring as temperatures rise.

A warm welcome for diseases
It’s not just fish that grow faster in warmer water - so do many parasites and microbes that cause diseases in marine animals. This means there will be more parasites and microbes to infect marine animals. In addition, animals already stressed by rising temperatures may be more susceptible to infection.

Massive fish die-offs due to toxic algae and ciguatera poisoning, caused by tiny organisms called dinoflagellates, will also increase as temperatures climb - as will the risk of human illness from eating poisoned fish. An increase in ciguatera poisoning in the Indian Ocean was linked to climate-related coral bleaching in 1999.

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