ONLY A FEW ORGANISMS EAT THE LIVING LEAVES DIRECTLY: MANATEES, GREEN SEA TURTLES, SEA URCHINS (above) AND HERBIVOROUS PARROTFISHES
Sea grasses are the only true flowering plants (angiosperms) found in the sea. They can withstand complete and continuous submersion and produce flowers (left) and seeds underwater.
MORE THAN 30,000 ORGANISMS PER SQUARE METER HAVE BEEN RECORDED IN A SEAGRASS BED. SOME USE SEAGRASS BEDS FOR THEIR ENTIRE LIFE, OTHERS USE IT AS A NURSERY, BREEDING GROUND, OR JUVENILE HABITAT, AND SOME MAKE DAILY MIGRATIONS BETWEEN GRASS BEDS AND THE REEF (Tomtate grunts, above).
They often form vast meadows (left), but seagrasses can also be sparse and widely distributed (right)
Seagrasses usually occur in sand/mud, but one Indo-Pacific genera (Thalassodendron, right) also grows on rocks
SEAGRASSES ARE EXTREMELY VALUABLE:
PROVIDE CANOPY COVER THAT SHELTERS SMALL INVERTEBRATES AND JUVENILE FISH
MANY SPECIES GROW DIRECTLY ON THE LIVING AND DEAD LEAVES
WHEN THE LEAVES DIE, THEY DECAY AND PROVIDE FOOD FOR ORGANISMS (DETRITIVORES) THAT THRIVE ON ROTTING MATERIAL (DETRITUS)
CREATE A NUTRIENT-RICH ENVIRONMENT: THEY TAKE UP NUTRIENTS FROM THE SEDIMENT AND RELEASE THEM INTO THE WATER THROUGH THEIR LEAVES, ACTING AS A NUTRIENT PUMP.
IMPROVE WATER QUALITY BY ABSORBING NUTRIENTS AND ATTRACTING PARTICLES TO THEIR BLADES.
THEIR ROOT AND RHIZOME NETWORKS STABILIZE THE SEDIMENT AND PREVENT NUTRIENTS AND SEDIMENTS FROM RUNNING OUT TO THE REEF
THEY ARE EXTREMELY PRODUCTIVE, RIVALING THAT OF INTENSELY CULTIVATED TROPICAL AGRICULTURAL SYSTEMS.
PRODUCE LOTS OF OXYGEN. ONE SQUARE METER OF SEAGRASS GENERATES 10 LITERS OF OXYGEN EVERY DAY
PROTECT COASTLINES BY SCATTERING WAVE ENERGY
CAPTURE AND STORE A HUGE AMOUNT OF CARBON FROM THE ATMOSPHERE—EVEN MORE THAN THE WORLD'S FORESTS PER HECTARE.
Roots connect under the sediment via a complex rhizome system that traps and stabilizes sediment
GRASSES INVADED THE SEA 100 MILLION YEARS AGO. They are found from the tropics to the arctic, being absent only from Antarctica. There are four different families with 12 genera and 50 species; most are found in the tropics
Seagrass beds are home to thousands of species: fish, such as stingrays and barracuda (above), octopus, squid, cuttlefish, snails, crabs (below), shrimp, urchins, anemones, polychaetes, bivalves and even corals (bottom)
The Caribbean supports four genera, flat-bladed Thalassia (turtle grass), round-blade Syringodium, intertidal fine blade Halodule and deeper water Halophila (left to right)