Kelp History: Fossil Records

A kelp forest compared to a terrestrial forest.

California kelp fossils first appeared in the Miocene Period, from about 23.3 to 10.5 million years ago when the California Channel Islands began to rise and take shape. Kelp has always played the role of a drifting nursery for invertebrate colonization.

Kelp Canopy

Kelp beds off the Channel Islands, specifically Santa Catalina, San Clemente, Santa Cruz and Santa Rosa, began declining from 1911 to an all-time low in the mid-1950s (Hodder and Mel, 1978). Aerial photographs from the early 1900s were compared to modern satellite imagery. Studies found similar trends in other areas during the same period. Changes in kelp cover over geologic and historic time suggest the role of kelp may have been more significant in the past.

Kelp Raft or “Biological Island”

Drift kelp may be partially responsible for the colonization of marine habitats on the southern California Channel Islands from local mainland populations. Kelp rafts, with living marine invertebrates attached, can transport large numbers of mature individuals, enhancing the role of drift kelp in ensuring reproductive and ecological establishment.

Elkhorn Forest

Beached Elkhorn Kelp

When kelp drifts ashore, many juvenile and adult marine species die with it. Humans play a crucial role in its destiny.

Stipe or stem may contain enlarged air bladders called pneumatocysts to form flotation blades. These may number up to 100. Other stipe cells become reproductive.

Blades or the leaf-like extensions are deciduous (annual). During the time when blades drop, the algae must survive on stored food till new blades form in the spring. Some species produce blades that are up to 130 feet long, but not bulky.

Float – Air bladder or pneumatocyst.

Holdfast

Holdfast – in dark, poorly aerated water a root-like mass of tissue functions to anchor the stipe in suitable substrate like gravel.

Most brown algae have a sexual alternation of generations between two different multi-cellular stages. The differences in life cycle define a number of orders, some with a dominant diploid phase, and some with isomorphic phases, that is, they are quite similar in appearance to each other.

The largest kelps are diploid, and release flagellated swimming sperm into the water to find egg cells. It has been shown that chemical signals called pheromones aid the sperm in their quest in at least some phaeophytes.

Southern California Bight: Home of the Elkhorn Kelp

Welcome to the home of Elkhorn Kelp. The Southern California Bight is a region that includes coastal southern California, the Channel Islands and the local portion of the Pacific Ocean. This region is referred to as a bight because the characteristic north-south trending coastline found off much of western North America experiences a significant curvature or indentation (trough) along the coast of southern California. The small portion of the Pacific Ocean that occupies this region, from Point Conception in the north to just past San Diego in the south, is characterized by complex current circulation patterns, and is the temporary or permanent home to a wide variety of marine organisms. Impacting this dynamic, important coastal marine ecosystem are the millions of people who reside in the Los Angeles and San Diego regions.

Last revised 15-Aug-13