The krill and plankton that form the foundation of the marine ecosystem are also being affected by the increasing acidification of the ocean. More CO2 being absorbed by the ocean means that some of these species will be unable to form and maintain their protective calcium carbonate shells, threatening key species further up the food chain. Studies show that plankton populations could decrease by as much as 40% by 2050. Coral reefs and polar regions are on the frontline of the acidification crisis, with North Pacific salmon, mackerel, herring, cod and baleen whales among the species under the most immediate threat.

Warmer seas will also affect the distribution of whales. If their prey moves as a result of climate change, they will likely follow. Mass movement of species to different habitats will result in increased competition for diminishing amounts of prey.

Toxic chemicals banned decades ago could kill off more than half of the worlds killer whale population in 30-50 years, scientists believe. PCBs (polychlorinated biphenyls) are man-made organic compounds once used in electrical equipment, flame retardants and paints until they were found to be so dangerous to human health that they were banned in the US in the 1970s and Europe in 1987. Resistant to heat, chemicals and natural degradation, the same things that made PCBs so attractive also makes them hard to destroy, and so they remain in the ecosystem decades later. Some were improperly stored or disposed of, or even directly discharged into soils, rivers, wetlands and the ocean.Entering the food chain, they have worked their way up to concentrate in top predators, causing cancers, altering behaviour, damaging immune systems and harming reproduction. European killer whale populations, along with dolphins and porpoises, are the most contaminated in the world, and some of the most heavily exposed populations are not expected to survive the next few decades.

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Priceless poo: the global cooling effect of whales - chinadialogue ocean