Seagrass

Sixty-five percent of U.S. estuaries and coastal water bodies are moderately to severely degraded by excessive nutrient inputs, which lead to algal blooms and low-oxygen (hypoxic) waters that can kill fish and seagrass and reduce essential fish habitats.

That's been devastating for fish that spend their juvenile days among the seagrass. Where the invasive crabs have moved in, the total weight of fish is down tenfold.

To celebrate the June 5 World Environment Day, diplomats from more than a dozen foreign embassies and international organizations Monday joined the U.S. State Department to plant underwater seagrass in the Potomac River, a tributary of the Chesapeake Bay.

The green crab has few predators, aggressively hunts and eats its prey, destroys seagrass, and outcompetes local species for food and habitat.

They are not seen again until they arrive as larger juveniles in shallow coastal waters, where they dine on seagrass and algae.

There has been some investigation into the potential of seaweeds as a carbon store, and although more is needed, one study says that seaweed habitats are believed to be the most productive of all coastal vegetated ecosystems, and suggested that the world’s seaweed sequesters as much carbon as all the planet’s seagrass meadows, saltmarshes and mangroves combined.