California's Ancient Kelp Forest

Nov 10, 2009

(PhysOrg.com) -- The kelp forests off southern California are considered to be some of the most diverse and productive ecosystems on the planet, yet a new study indicates that today's kelp beds are less extensive and lush than those in the recent past.

The kelp forest tripled in size from the peak of glaciation 20,000 years ago to about 7,500 years ago, then shrank by up to 70 percent to present day levels, according to the study by Rick Grosberg, professor in the Department of Evolution and Ecology and the Center for Population Biology at UC Davis, with Michael Graham of the Moss Landing Marine Laboratory and Brian Kinlan at UC Santa Barbara.

Kelp forests around offshore islands peaked around 13,500 years ago as rising sea levels created new habitat and then declined to present day levels. The kelp along the mainland coast peaked around 5,000 years later.

This transition from an extensive island-based kelp system to a mainland-dominated system coincided with conspicuous events in the of the maritime people in the region, suggesting that climate-driven shifts in kelp ecosystems impacted human populations that used those resources.

Understanding the past history of a population is crucial to understanding its genetics in the present, Grosberg said.

"Kelp is interesting because it disperses only over short distances," Grosberg said. "Populations can become genetically isolated from one another even if they are quite close together."

"We wanted to know how connected the coastal kelp populations were since the last glacial maximum," he said.

On land, scientists can reconstruct the history of a forest or grassland from fossilized pollen or leaves. But kelp do not make pollen, and marine sediments do not preserve a good record of the plants.

The researchers used depth charts of the southern California coastline and information from sediment cores on past nutrient availability to reconstruct potential kelp habitat as sea levels changed over the last 20,000 years.

"We could reconstruct changes in kelp cover at a scale of 500 years and determine how fragmented or connected the populations were," Grosberg said.

People have lived off the produce of kelp forests when resources on land dwindled, and those changes are recorded in shell middens and other traces. That archaeological record can now be compared with the ecological history to get a more complete picture of California's coast.

"Now we know what was happening with kelp, what was happening with the ecology on land, and what the people were doing," Grosberg said.

The study was published online Oct. 21 in the journal Proceedings of the Royal Society B.

Provided by UC Davis (news : web)

Explore further: 14 detained trying to prevent Faroe Island dolphin hunt

add to favorites email to friend print save as pdf

Related Stories

Plans in the works for huge manmade reef

Jan 01, 2007

Thinning kelp beds off Southern California are expected to flourish again after completion of one of the country's biggest artificial kelp reefs.

Researchers discover forests of endangered tropical kelp

Sep 26, 2007

A research team led by San Jose State University and the University of California, Santa Barbara has discovered forests of a species of kelp previously thought endangered or extinct in deep waters near the Galapagos Islands. ...

Fast-growing kelp invades San Francisco Bay

Jul 10, 2009

(AP) -- A fast-growing kelp from the Far East has spread along the California coast from Los Angeles to San Francisco Bay, worrying marine scientists and outpacing eradication efforts.

Decline in Alaskan sea otters affects bald eagles' diet

Oct 03, 2008

Sea otters are known as a keystone species, filling such an important niche in ocean communities that without them, entire ecosystems can collapse. Scientists are finding, however, that sea otters can have even farther-reaching ...

Is that sea otter stealing your lunch -- or making it?

Feb 16, 2008

Hunted to near extinction, sea otters are making a steady comeback along the Pacific coast. Their reintroduction, however, is expected to reduce the numbers of several key species of commercially valuable shellfish dramatically, ...

Recommended for you

No-take marine reserves a no-win for seahorses

14 hours ago

A UTS study on how seahorses are faring in no-take marine protected areas (MPAs) in NSW has revealed that where finishing is prohibited, seahorses aren't doing as well.

Dolphin hunting season kicks off in Japan

19 hours ago

The controversial six-month dolphin hunting season began on Monday in the infamous town of Taiji, but bad weather would delay any killing, a local official told AFP.

User comments : 0