Although this partnership takes place in Australia, I was drawn to it because it is such a great example of the relationship between wildlife and habitat. Tiger sharks prey on a variety of marine life and even mammals such as the dugongs (sea cows), and dugongs main food source is seagrass.
A MARINE ECOSYSTEM
In 2011, a heatwave killed off most of the seagrass beds in Shark Bay, Australia. Because it is a temperate species, the dominant native seagrass Wire Weed (Amphibolis antarctica) was hit hardest. In its place, however, is a fast growing more tropical native species of seagrass called Fine Sea Grass (Halodule uninervis).
The great thing about seagrass is that this ecosystem holds carbon, specifically “blue carbon” which “is the carbon captured by the world’s ocean and coastal ecosytems.” Blue carbon can store up to “twice as much carbon as the world’s temperate and tropical forests.” Losing seagrass beds, frees the stored blue carbon from the soil which, of course, reduces its mitigation of climate change. (National Science Foundation).
HOME FOR DUGONGS AND TIGER SHARKS
Scientists at Florida International University (FIU) have been following the growth of this seagrass habitat for 15 years because it is home for dugongs, which means it is also the home for tiger sharks — one of the shark species which is threatened with extinction.
Although seagrass beds are feeding grounds and nurseries for a variety of marine life, if dugonogs do not eat enough, they will not breed normally. So because dugongs are such heavy grazers of seagrass, keeping them away from the beds is paramount to their regrowth.
FIU researchers have found, however, that the tiger sharks patrolling Shark Bay looking for prey cause the grazers to stay away, which allows the seagrass beds in these areas to recover better than in the areas the sharks do not frequent.
IMPORTANCE OF TOP PREDATORS TO ECOSYSTEM HEALTH
This long-term research is being conducted “to assess how climate disturbances and the reduction of shark populations…change oceans.” (National Science Foundation)
It seems to me this study is confirming the importance of top predators in restoring and maintaining a healthy ecosystem, much like the importance of wolves in North America.
To learn more about seagrasses, go to the Smithosonian’s Ocean Find Your Blue website.
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