Often missed and unnoticed by many people are vast meadows of seagrasses growing in our oceans. Seagrasses are believed to have first appeared about 100 million years ago and evolved from terrestrial plants that adapted to life in marine environments. They grow only in salty or brackish water and are rooted into the sediment of the ocean floor. And they offer powerful biodiversity and ecosystem benefits — along with huge carbon sequestration capabilities.
Seagrass 101
There are 72 known different species of seagrasses, with the largest concentration of seagrasses in the world found in the Indo-Pacific region, in an area known as the Coral Triangle area. Though this region boasts the highest diversity of seagrass species and the greatest area of seagrass cover, seagrasses can be found on coastlines across the world the largest of which can be found in the Bahamas and is almost 100,000 square meters wide.
A Biodiversity Powerhouse
Seagrass meadows, a component of Blue Carbon, are one of the most productive ecosystems on Earth, providing a habitat for a wide variety of marine organisms: Various fish species, waterfowl, dugongs, and manatees, as well as Green Sea Turtles, are among the main species that rely on seagrasses and their sensitive ecosystems for food.
They are particularly significant for fish and crustaceans, acting as nurseries for many species. Biodiversity within these meadows is very high, and they play a critical role in marine food chains.
A Tremendous Carbon Sink
Seagrass meadow, as a powerhouse of biodiversity, makes them excellent carbon sinks. Research shows that they are much more effective than terrestrial forests in their ability to store carbon in the long term, primarily in the sediment and can store up to 35 times more carbon per hectare than tropical rainforests. This makes them a crucial part of global efforts to mitigate climate change. Along with their rich biodiversity, doubly so.
Seagrasses are Under Threat (of course they are)
Seagrass meadows are under serious threat worldwide, primarily due to water pollution, coastal development, and the effects of climate change which include ocean acidification and rising water temperatures. The UK alone has lost almost 90% of its seagrass meadows, and globally loss is at an all-time high due to human related and climate related actions.
If we are to protect and restore these hugely beneficial ecosystems then conservation efforts are needed more urgently than ever.
There are many actions we cant take to start to build seagrass meadow resilience. Here are some of them:
- Education and awareness raising,
- Increase the scope of our Marine Protected Areas.
- Improve water catchment management to decrease polluted water runoff.
- Ensure there are sustainably managed fishing/ human practices.
- Cut back on use of poisons and fertilizers and agricultural and livestock farming near the ocean.
- Blue Carbon Credit programs that ensure long life protection and income for communities such as those mentioned here.
Even More Ecosystem Services
Seagrasses also play a crucial role in maintaining water quality by filtering nutrients and pollutants from the water and helping avoid deathly algal blooms. They play an important role in erosion control through stabilizing sediment and help to prevent coastal erosion through their root systems and produce a significant amount of oxygen, contributing to the overall oxygen budget of the world’s oceans.
Their high productivity also helps to balance the overall carbon-oxygen equilibrium. If this were not enough, they also provide substantial economic benefits to humans that include commercial fishing and tourism. Additionally, they are involved in nutrient cycling, sediment stabilization, and carbon sequestration – ecosystem services that would be extremely costly for humans to replicate artificially. Their loss would have severe economic as well as environmental impacts. As with mangroves, these are already naturally occurring Nature-based Solutions that with the right support can benefit us enormously.
Finally, An Interesting Fact About Seagrasses
Seagrasses, being true flowering plants, have a unique reproductive process compared to other marine organisms: They can reproduce both sexually and asexually.
Sexual Reproduction
Seagrasses produce both flowers and seeds. Some are hermaphroditic (meaning each plant has both male and female reproductive organs), although there are some species with separate male and female plants, they are able to release pollen grains into the water, which are carried by currents to fertilize the flowers. Once fertilized, the flowers develop into fruits, which float in the water and eventually settle onto the seafloor. There, the seeds germinate and grow into new plants.
Asexual Reproduction
Many seagrasses also reproduce vegetatively, which involves parts of the plant breaking off and growing into a new plant, or the expansion of the plant’s underground root system, called rhizomes. A new plant grows from nodes on the rhizome, which can lead to extensive, interconnected meadows of seagrass that may all be genetically identical, essentially forming a single, large organism.
