Global Warming and Marine Life

You’re no doubt familiar with the projected impacts of global warming on Earth’s environments. It’s important to also know that there are also significant changes in store for marine ecosystems and their inhabitants. Consider the following:

  • Increased surface temperatures are liable to cause ocean acidification, which will impact dramatically on marine life. The sea absorbs carbon dioxide from the atmosphere, and this bonds with seawater to generate carbonic acid. Increased atmospheric carbon dioxide will increase and accelerate the chemical outcomes of this process, changing the chemical nature of the underwater environment. Effects include certain ions that many sea creatures require for building shells and skeletons becoming unavailable.
  • Higher water temperatures cause corals to expel the algae that give them their colour and help create their protective outer skeletons. The departure of the algae results in what is known as coral bleaching. This leaves the colonies of animals (called polyps) that inhabit them vulnerable, and the coral may then die.
  • Rising temperatures, both on the surface and in the water, can affect the life cycles and behaviours of marine animals, many of which rely on temperature as a cue for reproduction. There are also more complex factors in the mix – for example, the offspring sex ratios of some species (such as marine turtles) are temperature dependent. The outcomes of changed temperatures for marine populations are difficult to predict.

Spotlight: What is a marine ‘dead zone’?

Sound scary? Rightly so. Dead zones are regions of the marine landscape that are no longer inhabitable by plant and animal life due to a lack of oxygen. Hundreds of these zones are known to exist.

Although the precise causes of the dead zones is not clear, global warming is suspected to be contributor, amplifying the effects of reduced oxygen on marine life. At the same time, it is speculated that bacteria populations developing in these zones will contribute to global warming through their nitrous oxide emissions.

The emergence of dead zones is a timely reminder of the limits of our understanding when it comes to the complex array of interactions that contribute to a healthy (or unhealthy) marine environment. That encompasses our own actions in relation to it.