The plants in the tanks are artificial: It is easier to maintain fish if there aren’t plants to worry about also. Two of the artificial plants represent readily recognized species of ecological importance.
Rhizophora mangle is a member of the same plant family as guavas and eucalyptus. It grows in areas of shallow brackish water in estuaries, the places where rivers empty into the ocean. Individual plants have stilt roots stretching from their branches into the water and mud, and mangrove thickets are often impenetrable.
Red mangroves are distinct from the many other mangrove species not only by their stilt roots, but also by their seeds, which germinate and form a root while still attached to the parent plant. These seedlings float, root-down, when they fall off, and can disperse widely before the root grows long enough to reach the mud.
Mangroves play an important role in tropical estuaries. They trap sediments, helping to build new land that is eventually occupied by other species. Without the mangroves, much of this sediment would carry further out to sea, and clear-water communities such as coral reefs would not be able to grow.
Macrocystis pyrifera is a brown seaweed, more closely related to diatoms and water molds than to green land plants. It is one of the most important seaweeds of the California coast, forming “kelp forests” offshore that are habitat to many other marine organisms.
Each kelp plant is composed of a holdfast, stipe, and blades. The stipe, like a stem or trunk, transports nutrients from the blades above to the holdfast below. Gas-filled bladders at the base of each blade, called pneumatocysts, help keep the kelp upright and oriented towards the surface.
The blade is like a leaf. It extends horizontally in the water to get sunlight for photosynthesis. At the same time it filters the sunlight to the deeper regions of the kelp forest.
Instead of roots, kelp has a root-like anchor called a holdfast, which fastens the kelp to the rocky bottom. The holdfast does not absorb nutrients.
One stipe, with pneumatocysts and blades, makes up a single frond. There are usually several fronds of different ages growing from a single holdfast.