For the Love Of Nature, Art and Bad Humor
A Comic Gallery of Creative Expression in the Pursuit of Knowledge
Eastern Oyster
Crassostrea virginica
Drifting along the current in the quiet, shallow waters
of the Atlantic Ocean and Gulf of Mexico, you can find a miraculous speck.
The speck is one of millions found where
fresh water meets salt. Those brackish and
saltwater bays, estuaries, creeks and intertidal zones
are where a speck can grow up to be a hero.
But first it has to survive.
The speck is a teeny-tiny oyster egg. It only takes six hours for that fertilized egg to transform into a slightly larger speck – a free-swimming, planktonic oyster larva.
Along with millions of other planktonic specks,
oyster larvae are at the mercy of a vast water column
and many predators. But they do have some good things going for them. Oysters are protandric hermaphrodites - they start as male and later change to female, and a single oyster can produce baby oysters on its own.
Usually, though, they have help: other oysters producing millions of eggs to make up for the losses, since most
larvae get washed into unfavorable habitat or eaten
before reaching adulthood. Oysters can live for up to
twenty years, but most don’t survive past six.
The larvae that do survive spend the next two to three weeks developing a shell, slowly resembling mini oysters
as they float in the current.
When it’s time to settle down, they search with a
newly developed foot for something hard to attach to -
mangrove roots, sea walls, docks, other oyster shells, or artificial reefs built by Marine Discovery Center volunteers.
Oysters glue themselves in place with a
cement-like substance and stay there for the rest of
their lives. Once attached, their name changes:
the miraculous speck is now a spat.
A living reef forms when spats fuse together with
other live oysters and oyster shells. Reefs make
excellent habitat - not just for oysters, but for a host of other marine life. They provide shelter, nursery grounds, food and biodiversity for fish, bigger fish, mussels, barnacles, anemones, crabs, turtles, birds and your uncle, you know, the one with the fishing boat.
Oysters can clean large amounts of water in a short amount of time just by eating and breathing. They pump water in
and over their gills to breathe oxygen and trap bits of algae,
organic particles, and phytoplankton to eat.
That filter-feeding helps reduce excess algae, sediment, nitrates, ammonia, phosphates, detritus, bacteria, and other pollutants, leaving the water much cleaner.
An adult oyster can filter 50 gallons of water each day.
Oysters have economic value too. Throughout human history, they have been used as currency, road and
building material, and water-treatment solutions to
help remove pollutants.
They're also a major part of the global seafood industry - farmed and wild-harvested oysters are a popular delicacy rich in protein, vitamins, and minerals. Out of more than 200 oyster species worldwide, only five are still commercially harvested, including the Eastern Oyster.
The pearl industry loves them too. Pearls come in a
range of sizes, shapes and colors, and are the only gem formed inside a living creature.
Oysters have three-chambered hearts, colorless blood, and no brain. Having two shells makes them bivalves.
They can close their shells tightly and survive out of the water during low tide for up to two weeks. Sometimes noise makes them close up too. When they shut tight to hide from the outside world, we should really call them bye bye-valves.
Oysters have been around for 15 million years. But in more recent times, we’ve lost 80% of the world's oysters
to pollution, dredging, disease, overharvesting,
changing ocean conditions, freshwater discharges,
erosion from development, and wetland loss.
They're making a comeback, though, thanks to
programs like Shuck and Share, which collects discarded oyster shells from restaurants and uses them to build
and restore oyster reefs. Protected sanctuaries are
essential too, giving oyster populations a chance to
recover and spread past those boundaries.
Oysters are amazing. They provide shelter, habitat and food for countless species. They improve water quality.
They contribute economic value. They protect shorelines.
All this makes them a keystone species - their ecosystem depends on them, and so do we, whether we know it or not.
Oysters are the true heroes of the marine world.
It's astounding that something starting life as a speck
and growing only a few inches long could play such an
outsized role in the health of our oceans.
Let's all hope that oysters continue their global comeback - even bigger than Cher's - and may they keep saving the bay as heroes for another 15 million years and beyond.
This comic was a final project for the Florida Master Naturalist Program - Coastal Systems. Hosted by the Marine Discovery Center.
