We are often reminded of the impacts that global heating has on our land-based ecosystems and how higher temperatures will eventually cause the planet’s resources to diminish, impacting human health and the environment. But what about the 71% of the planet covered by the ocean? Rarely are we reminded of the issues that a warming climate pose to our marine ecosystems.

It is no secret that the earth’s temperature is warming, since the 1800s the average surface temperature has increased by 1⁰C, this is anticipated rise to 4⁰C by 2100, according to the 2018 IPCC report. How exactly does this impact the areas of the earth that are less explored than the moon — the ocean ?

Mass scale environmental impact

Increasing sea temperature is by far the biggest challenge the marine environment has faced since human studies began. These changes are having large-scale impacts such as the bleaching of global coral reefs — a result of increased thermal stress expelling the algae that lives within the animal and provides 90% of its energy — and the mass outward migration of important food fish such as salmon from an area, inhibiting food supply.

Changes to organism physiology and behaviour

Smaller-scale changes associated with temperature rises can impact the behavioural traits of marine organisms such as salmons’ ability to return home to spawn. There are physiological or physical changes to organisms such as the feminisation of sea turtles, whereby a sand temperature below 27°C hatches a male and above 31°C a female. This is a result of temperature-dependent sex determination, a process seen in some reptiles where the sexing of an animal occurs after fertilisation and is controlled by an external factor, sand temperature. In a warming world we are seeing up to 99% of turtles being born as female, limiting population growth for the future and removing key grazers from tropical marine food webs.

Sea turtle.

over three billion people rely on fish and seafood as their primary source of protein

As the behaviours and physiology of organisms shift to being less favourable, we see large declines in global populations which cannot always be prevented due to the conditions within the marine environment becoming less optimal year by year; a time scale in which current policy has not met.

Is there any good news?

Present day research does show some positives. We have found that some individual species’ tolerance to modern day heat increases are greater than we first thought, and many organisms and ecosystems are able to adapt to the 1⁰C temperature increase to some extent.

The importance of reducing the earth’s temperature by minimising our carbon footprint is paramount, in order to protect the stable food supply, provision of sustenance resources, support of employment and the ongoing maintenance of the planet’s largest carbon sink that are associated with the ocean.