More Algae

Giant kelp ( Macrocystis pyrifera ) is large, brown algae that grows in dense forests along coasts around the world. Long stalks anchor each plant to the seafloor, and they grow meters high like...
The sargassum fish ( Histrio histrio ) is a member of the frogfish family (Antennariidae) and typically lives in open waters near floating sargassum seaweed, which offers camouflage. Although capable...
Unlike the green, leafy algae we're used to seeing on the seafloor, coralline algae has a hard crust—which you can see here at the molecular level in a photo from a scanning electron microscope. Each...
Corals, sponges, and algae are the major components of most coral reef communities. To the untrained eye, they are sometimes difficult to tell apart. More about coral reef ecosystems can be found in...
What are corals? Corals themselves are animals. But tropical reef-building corals have tiny plant-like organisms living in their tissue. The corals couldn’t survive without these microscopic algae–...
Broad-leaf seagrass ( Posidonia australis ) with algae epiphytes grows at Corner Inlet Marine National Park in Australia . The marine park protects large areas of seagrass habitat from fishing—but it...
Macroscopic Algae ( Acetabularia crenulata ). More about mangrove ecosystems can be found in the Mangroves section .
Around 100 million years ago, grass from land adapted to live and reproduce while submerged in seawater—the modern-day seagrasses. This sea invasion by land plants happened four separate times,...
The open ocean is surprisingly barren to the naked eye. Every now and again you will encounter a school of fish and their attendant predators, but most of the life that you find is gathered around...
Regardless of what continent you live on, the waters that surround it are home to marine invaders. The ocean is teeming with plants and animals willing and able to move beyond their native habitats...
Stare at a tide pool and you will often see a crust of pink coating the bottom. No, this is not bubblegum from some careless teenager’s shoe: it’s a stony kind of seaweed that, like other seaweeds,...
Convict surgeonfish ( Acanthurus triostegus ) are the roaming sheep of the reef but, instead of noshing on grass, they feed on algae. Their grazing helps to balance the growth of algae and coral on...
A strain of this green seaweed, native to the Indian and Pacific Oceans, escaped public and private aquariums in California, Japan, Australia, and Monaco. It has spread widely in the Mediterranean,...
Algae, like all organisms, normally grow in balance with their ecosystems, limited by the amount of nutrients in the water. But sometimes, certain species of algae reproduce so rapidly that they...
Algae has overtaken this coral reef off heavily populated Kiritimati, or Christmas Island. Few fish swim in the murky waters. The causes include pollution, overfishing, and increased water...
A diet of algae and seagrasses gives this turtle ( Chelonia mydas ) greenish colored fat—and its name. Weighing as much as 500 pounds, the threatened green sea turtle lives its life at sea, with only...
Munch, munch. The queen parrotfish ( Scarus vetula ) scrapes algae from Caribbean coral reefs with its parrot-like beak. While feeding, hard stone and coral inevitably get mixed into its lunch, which...
“Sea grapes” may sound like something Poseidon would snack on, and not a killer algae. Yet Caulerpa racemosa var. cylindracea poses a serious threat to marine life. Spread by the bilge water of boats...
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