Algae and Coral Reefs

A creeping green presence spreads across a vibrant coral reef, engulfing the colors in a sea of green. The green menace is algae, living plants that are the base of the food chain for all life in the ocean environment. Coral reefs and algae are usually able to strike a balance; however, changing ocean conditions threaten to destabilize this relationship. Like an overbearing friend, algae can grow out of control and take over the coral reef, threatening the seafood industry and even human wellbeing. What is causing algae, a critical food source for many fish and an essential element of the ecosystem, to dominate coral reefs?


The endangered hawksbill sea turtle on a healthy coral reef

Nutrient pollution can tip the scales in favor of algae and cause the plants to overcome the reefs. Nutrients, while also important for the environment, can be harmful in large amounts. In a feeding frenzy, the algae consume excess nutrients, such as nitrogen, and continue to grow until they completely cover the coral reef. This situation is more likely to happen to coral reefs that are close to developed areas, like the corals in Florida, since nutrient pollution from agriculture and urban environments can make its way into these waterways.


A black tipped reef shark on a healthy coral reef

Algae-covered coral reefs are a problem because the excess of algae makes these reefs less biodiverse, meaning there aren’t as many types of fish and other wildlife. These reefs are also more susceptible to pathogens, making them less resistant to disease than healthy reefs. This means less available seafood to feed the 1 billion people worldwide that depend on food from coral reefs and to support multi-billion dollar fishing industries. Furthermore, the increase in nitrogen, phosphorous, and other nutrients in waterways, also known as eutrophication, is harmful to human health. The spikes in algal growth caused by eutrophication can lead to harmful algal blooms, which can cause human illness.


A startled octopus, morphing from camouflage to red. The surrounding reef has very little live coral.

Nutrient pollution that ends up in the sea travels down rivers and waterways stemming from communities like the ones near you. This also means that nutrient pollution can be reduced at the source. Communities are rallying to reduce nutrient pollution, from stream cleanups to volunteering to monitor water. You can help reduce nutrient pollution around your home by:

  • not dumping paint, oil, debris, or other household chemicals into street gutters or storm drains;
  • limiting fertilizer use, which can lead to the buildup of nitrogen and phosphorous in the ocean;
  • and using phosphate-free cleaners, detergents, and soaps to avoid contributing to nutrient pollution.
    • Check out this Safer Choice search engine from EPA to make environmentally friendly shopping easier!


One comment

  1. Matt Salas · December 1

    Hey nice article! I write about similar outdoor stuff along with other things that I like to write about, you should check out some of my stuff! also, I subscribed to your blog!


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