How is climate change affecting marine ecosystems?

Sep 4

When we’re talking about a marine ecosystem, we mean a collection of living organisms, such as fish, coral, and algae, and their environment in oceans, seas, and coastal areas. These ecosystems include coral reefs, mangroves, seagrass beds, and the open ocean, all interacting to support life and maintain ecological balance.

Marine ecosystems are biodiversity hotspots, home to countless species. They play a crucial role in producing oxygen (phytoplankton in the ocean generate about half of the world's oxygen) and regulating the climate by absorbing carbon dioxide and excess heat. In fact, the ocean is one of our best allies for climate solutions.

But unfortunately, marine and ocean habitats are not immune to the effects of climate change. So let's take a closer look at how they’re impacted, focusing on the three areas which are often called climate change’s ‘deadly trio’:

Rising temperatures

Greenhouse gas emissions release heat into the atmosphere, and the ocean absorbs a considerable amount of it. Estimates say, to date, that the ocean has absorbed around 90% of the heat generated by human-made rising emissions.

This increased temperature has a range of impacts on marine ecosystems, including mass coral bleaching, which happens when reefs lose their life-sustaining microscopic algae under stress. This destroys vital habitats for diverse marine life. In general, increased temperatures negatively affect the health, growth, and photosynthesis of many crucial habitats, and species are being forced to migrate to cooler waters to survive.

Ocean acidification

Ocean acidification is the process where the ocean becomes more acidic due to the absorption of excess carbon dioxide from the atmosphere. When CO2 dissolves in seawater, it reacts to form carbonic acid, which lowers the ocean's pH, making it more acidic. There has been an increase of 30% in acidity when compared to the pre-industrial age.

Acidification reduces the availability of calcium carbonate, which is essential for marine organisms like corals, shellfish, and plankton to build their shells and skeletons. Impacts on these species can cascade through the entire marine food chain, impacting services such as fisheries. This starts from the impact on plankton, which form the base of the ocean's food chain, highlighting the need to focus on entire ecosystems – not just the damage you can more easily see, such as coral reefs.

Deoxygenation

In addition to the problems associated with increased temperatures and more acidic waters, marine ecosystems have to deal with ocean deoxygenation. Again, due to warmer water temperatures as well as increased oxygen consumption by various organisms adapting to challenging conditions, there are more reduced-oxygen environments in our oceans. This further stresses marine life. In fact, extreme marine heat waves can outright kill native species and open up habitats to be taken over by other non-indigenous species.

The conditions in our marine environments are becoming increasingly difficult for species to thrive, with numerous threats to their habitats and survival. Biodiversity is at risk as ecosystems become less resilient, and this vulnerability is a direct result of climate change.

What can be done to protect marine ecosystems?

Facing the reality of climate change can be frightening and emotional, so we’ve decided to finish up by focusing on how our seas and oceans can (and already are) being protected.

Expanding marine protected areas (MPAs): These are designated zones designed to protect and conserve marine life, habitats, and ecosystems by enforced rules – predominantly around restricted human activity. This allows the area to recover and helps to restore biodiversity, while keeping the marine ecosystem protected from further environmental stressors. These MPAs are particularly important for habitats such as coral reefs, mangroves and seagrass beds.
Reducing greenhouse gas emissions: Ecosystems can adapt, but they need to be given a chance – and a limit of global warming to a maximum of between 1.5°C to 2°C is key to allowing our ecosystems (marine and otherwise) to become more resilient. Transitioning to renewable energy, improving energy efficiency, and reducing fossil fuel use are all ways to slow ocean warming and acidification.

In conclusion, climate change poses significant threats to marine ecosystems, impacting their ability to sustain life, regulate the climate, and support biodiversity. However, there is hope. By expanding marine protected areas, reducing greenhouse gas emissions, and taking collective action to protect these vital ecosystems, we can give our oceans a fighting chance to recover and thrive. After all, the health of our planet depends on the health of our oceans.

About the author:

Sarah Hooper is dedicated to educating and raising awareness about the importance of marine ecosystems and their protection. She is a strong advocate for policies that regulate pollution, safeguard biodiversity, and promote sustainable ocean use. While she encourages individuals to make changes such as reducing plastic waste and supporting sustainable fishing practices, Sarah emphasizes that lasting impact comes when companies and governments take meaningful action.