Fossil Holdfast Shows Kelp Forest That Supports Varied Ecosystem Exist Before Modern Marine Mammals [Study]

(Photo: Wikimedia Commons/Peter Southwood)
Fossil Holdfast Shows Kelp Forest That Supports Varied Ecosystem Exist Before Modern Marine Mammals [Study]

The underwater kelp forests on the Pacific Coast have been around for millions of years. They even predated modern marine mammals.

Fossil Holdfast Shed Light About Kelp Forest

A new study demonstrates that kelp thrived off the Northwest Coast over 32 million years ago, predating the emergence of the contemporary species of bivalves, birds, sea urchins, and marine animals that now live in the forests.

Given their much older age, these coastal kelp forests-which are now home to a diverse array of animals, including seals, otters, sea lions, and numerous fish, birds, and crustaceans-likely served as a primary food source for the long-extinct desmostylian mammal. The grazer, which resembled a hippopotamus, is believed to have ancestors similar to modern sea cows, manatees, and terrestrial elephants.

"People initially said, 'We don't think the kelps were there before 14 million years ago because the organisms associated with the modern kelp forest were not there yet,'" said paleobotanist Cindy Looy, professor of integrative biology at the University of California, Berkeley.

"Now, we show the kelps were there, it's just that all the organisms that you expect to be associated with them were not. Which is not that strange, because you first need the foundation for the whole system before everything else can show up."

The proof comes from recently found fossils of the holdfast, the component of the kelp that resembles roots and anchors it to rocks or seabed animals anchored to rocks. The blades, which usually float in the water because of air bladders, are supported by the stipe or stem attached to the holdfast.

These fossilized holdfasts, which can still hold on to clams and encase barnacles and snails, were discovered by Looy's colleague Steffen Kiel and were dated to 32.1 million years ago, amid the Cenozoic Era, which spans from 66 million years ago to the present. The University of California Museum of Paleontology (UCMP) has the earliest known fossilized kelp, which is thought to have been dated 14 million years ago. It has a blade resembling modern bull kelp and one air bladder. The underwater forest kelps are much older than previously thought.

What Is a Kelp Forest?

Kelp forests are undersea ecosystems generated in shallow water by the dense development of numerous species known as kelp. Kelps are enormous brown algae despite their striking resemblance to plants. Under perfect conditions, kelp can grow 18 inches (45 cm) daily, and certain species can reach 150 feet (45 m) underwater! Because of their amazing development, kelp forests can spread swiftly to locations where they were previously nonexistent.

In cold, nutrient-rich seas, kelp grows well. Because kelp adheres to the seafloor, eventually rises to the ocean's surface, and relies on sunshine to generate food and energy, kelp forests are always coastal and require shallow, reasonably clear water. Kelp forests do not overlap with mangrove forests, warm-water seagrass beds, or coral reefs since kelps generally reside farther away from the tropics.

More types and more diverse organisms can be found in kelp forests than in virtually any other oceanic habitat. The thick blades serve as a protective shelter for many creatures' young against predators and even strong storms.

Many mammals and birds, including seals, sea lions, whales, sea otters, gulls, terns, white egrets, great blue herons, cormorants, and shore birds, depend on kelp forests for food and protection.