Tiger sharks help scientists discover the world’s largest seagrass ecosystem

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“This is the last !” shouted a voice above the lapping of the ocean waves against the hull of the boat. He was referring to the biologging camera tag – one of seven – attached to the massive tiger shark (Galeocerdo cuvier) which was being prepared for release. Sweat beaded on the scientists’ brows as they clapped their hands, exhausted from both hard work and the Bahamian sun. Swaying gently in the turquoise waters above the Great Bahama Bank, the boat tilted to the side as everyone leaned in to unhook the shark and watch it swim through the blue.

Little did they know she would help lead the team to one of the greatest marine discoveries in the world.

While examining footage of these camera-equipped tiger sharks across the Bahamas, Dr. Austin Gallagher, founder of the nonprofit ocean research organization Beneath the Waves (BTW), learned that these sharks spend a lot of time in seagrass habitats. Common in tropical and subtropical waters around the world, tiger sharks tend to be the largest species of shark patrolling this region of the Caribbean. With 16 main islands, the Bahamas is home to colorful corals and a host of marine plants and animals.

One of these plants is the humble herbarium. These grasslands are a vital part of the marine ecosystem due to their level of productivity and the way they provide food, habitat and nursery grounds for many species of vertebrates and invertebrates. It is only in recent years that these areas have been highlighted for their importance, particularly when it comes to combating climate change due to their ability to capture large amounts of carbon through photosynthesis and to store them safely in their root systems deep within the seabed. “Seagrasses continuously trap and store massive amounts of carbon in sediments, contributing about 17% of the total organic carbon buried in marine sediments each year,” explain the authors of the new paper. “The rapid losses of seagrass in previous decades have reduced the sequestration capacity of seagrass ecosystems, while releasing large amounts of carbon into the atmosphere. Therefore, the conservation of seagrass ecosystems is of critical global importance for managing greenhouse gas emissions while safeguarding the many endangered species and seafood resources supported by seagrass habitat.

Australia holds the title for the most species of seagrass in the world – with more than half of the 60 species reported – and Western Australia has claimed the title for the largest seagrass…until until today.

Those tiger sharks that Gallagher and his team tagged? They led scientists to the monumental discovery of 92,000 km2 (35,521 square miles) of these beds with every beat of a tail. This makes it one of our planet’s most important global climate assets – the largest seagrass ecosystem in the world! The team could hardly believe what they had stumbled upon, as seagrass beds remained poorly mapped in many regions, such that the current uncertainty surrounding estimates of the global extent of seagrass beds is multiplied by 10. “This lack of knowledge is one of the main reasons why seagrass ecosystems remain underrepresented in marine protected areas, and therefore, highlighting a clear goal for the UN Decade of Ocean Science. “, say the authors.

There’s no denying that the ocean is critical to mitigating the effects of global warming, says Gallagher: “What this discovery shows us is that ocean exploration and research is essential for a healthy future. The untapped potential of the ocean is limitless. Moreover, this discovery highlights the role science can play in building resilient communities. And we knew that with a discovery of this magnitude, we had to call on the best storytellers in the world: SeaLegacy. BTW has now partnered with the organization’s co-founders (Cristina Mittermeier, Paul Nicklen and Andy Mann) on a multi-year journey to explore and document these vital wild ecosystems, and the important links between conservation seagrass habitats and safeguarding our own future on this planet.

The ocean and our planet are interconnected species of plants and animals that work together to create environmental balance. Tiger sharks and seagrasses are two very important species that will help us better understand and respond to climate change.

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