World Seagrass Day / Seagrass Awareness Month

An often overlooked but critically important ocean habitat is seagrass. Over the years, the month of March has become Seagrass Awareness Month in many parts of the world, and there are calls for the UN to officially recognise March 1st as the International Day for the Conservation of Seagrass Meadows, World Seagrass Day.

Seagrasses are deep-rooted plants (not seaweed) that grow in salty and brackish waters and are found in coastal regions of every continent except Antarctica. ⁣These coastal ecosystems, along with mangroves and tidal marshes, are considered blue carbon ecosystems for their capacity to take up and sequester significant quantities of coastal blue carbon from the atmosphere and ocean in both the plants themselves and the sediment below. They are now recognized for their important role in mitigating climate change.

seaweed vs seagrass

Algae or “seaweeds” (left) differ from seagrasses (right) in several ways. Algae on the seafloor have a holdfast and transport nutrients through the body by diffusion, while seagrasses are flowering vascular plants with roots and an internal transport system. (Courtesy of the Integration and Application Network (, University of Maryland Center for Environmental Science )

Blue carbon ecosystems also provide numerous benefits essential for climate change adaptation along coasts, including

  • Protection from storms and sea level rise
  • Prevention of shoreline erosion
  • Regulation of coastal water quality
  • Provision of habitat for commercially important fisheries
  • Provision of habitat for endangered marine species
  • Provision of habitat for flagship marine species, such as sea turtles and manatees
  • Food security for many coastal communities

Seagrasses are known to be one of the most vital and economically powerful ecosystems in the world. They are known as the “lungs of the sea” because one square meter of seagrass generates 10 liters of oxygen per day through photosynthesis. 

Similar to mangroves, seagrasses play a critical role in carbon and nutrient sequestration. One acre of seagrass can sequester 740 pounds of carbon per year (83g carbon per square meter per year) – that’s about the same amount emitted by a car traveling around 3,860 miles (6,212 km). Annually worldwide, that’s about 83 million metric tons of carbon and they can capture it up to 35 times faster than tropical rainforests. Seagrasses help with nutrient cycling and improving water quality by absorbing nutrients in runoff from land and releasing them into the water – an especially important function in nutrient poor regions. 

worldwide seagrass meadow location map

Seagrasses are found across the world, from the tropics to the Arctic. Shades of green indicate the number of species reported for a given area. The darker shades of green indicate more species are present. (Short, F. et al. 2007.)

Seagrass meadows serve as a filtration system for agricultural runoff and land based pollutants acting as a protective coastal barrier between the land and vulnerable ecosystems further offshore. ⁣Although seagrasses account for less than 0.2 percent of the world’s oceans, they sequester approximately 10 percent of the carbon buried in ocean sediment annually.

Despite these benefits and services, coastal blue carbon ecosystems such as seagrass meadows are some of the most threatened ecosystems on earth. It’s estimated that up to 29 percent of the global coverage of seagrass has already been lost. Major threats include degradation of water quality due to poor land use, such as deforestation and dredging, as well as nutrient runoff, climate change, and overfishing. Additionally, seagrass beds are vulnerable to disease and invasive species. ⁣

Sebadal / Seagrass from Rafa Herrero Massieu on Vimeo.

Some simple steps that you can take to help preserve seagrass ecosystems include: 

  • Don’t litter
  • Limit the amount of fertilizer and pesticides you use
  • Don’t dump anything hazardous down the drain
  • Be careful when boating by going slow and avoiding shallow areas
  • Support conservation efforts and offset your blue carbon footprint
  • Sign the global petition to the UN in support of March 1 as World Seagrass Day to increase awareness of these vital ecosystems worldwide

You can help support seagrass restoration and conservation around the world by purchasing a blue carbon sequestration offset through The Ocean Foundation Seagrass Grow project blue carbon calculator

Find out more about seagrass and ways to protect it at Project Seagrass and Seagrass Watch

sea turtle in bed of seagrass

Adult green sea turtles spend most of their time grazing in seagrass meadows. (Clifton Beard, Flickr)


  5. Global seagrass distribution and diversity: A bioregional model – F. Short, T. Carruthers, W. Dennison, and M. Waycott

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