Dive Dry with Dr. Bill

022: Elkhorn Kelp

When you refer to "kelp," most southern Callifornians think of the giant kelp that forms our nearshore kelp beds with their canopies floating at the surface. However there are actually many different kinds of kelp, several of which are found here. Kelps are a related group of brown algae usually found in cooler waters. They tend to be more abundant during cold water periods... whether it be a year with cooler than average temperatures, or a longer term "ice age."

It is believed that some kelps spread to the southern hemisphere when the Ice Ages caused the warmer tropical zone to cool and be restricted near the equator, allowing dispersal across this much narrower zone. Kelp species here were undoubtedly more abundant then and during cool water periods like the Little Ice Age (1300-1900 AD). Early explorers and residents often refer to kelp being very abundant during the period of European exploration and early settlement of California which coincided with this period. Although feral animals certainly decimated our island, the lush vegetation often described by early visitors on land may also be due in part to the cooler, moister climate of that time.

One kelp that many island residents and visiting boaters have seen is the elk or elkhorn kelp (Pelagophycus porra). This kelp grows in deeper waters beyond the outer edges of the giant kelp forests. When it detaches from the bottom, it often rises to the surface thanks to its large float bulb (pneumatocyst) and drifts there. Here one can see the single large float with the antler-like branching blades ("leaves") coming off of it. Early Spanish sailors, who often explored without the benefit of good maps, knew land was near when they saw this kelp floating at the surface. The Spanish galleons approaching California's coast from Manilla knew to turn south when they spotted them adrift. This drifting elk kelp, and giant kelp, also may transport marine invertebrates and small fish to new locations allowing them to colonize an area or add new genetic material to existing populations there.

Elk kelp is found from Point Conception to San Benito, Baja California. Its holdfasts attach to rocks on gravel and sandy bottoms and may be tight or broad depending on the rock shape. There is a single stipe ("stem") leading from the holdfast to the float bulb where the blades are attached. Because elk kelp grows in deep water, where light for photosynthesis is more limited, it has developed incredibly large blades to gather as much light as possible. These blades may be 3+ feet across and 20-60+ feet long. Although the large float lifts them partially off the bottom, they are often found lying flat on the bottom especially if currents are present. In deep water these kelp are less affected by storms, so they do not need the massive holdfasts found on giant kelp. The lower disturbance level also allows the elk kelp to grow the huge blades necessary to gather the limited light.

Elk kelp is sometimes referred to as bull kelp. I usually use that common name with another kelp (Nereocystis luetlkeana) found only north of Point Conception. Unlike elk kelp, bull kelp does extend to the water surface when attached, and forms kelp forests with canopies. Over the past month I've spent a fair bit of time at depths of 60-100 feet to document this interesting kelp for future educational videos. I've been able to "crawl" under the massive blades and experience the elk kelp forest from a new and interesting perspective (see picture).

Elk kelp was first described scientifically based on specimens collected around Catalina Island. In fact when I first arrived here in the 1960's, scientists believed there were two species of elk kelp in our waters, Pelagophycis porra and Pelagophycus gigantea. The second "species" was considered endemic to Catalina waters, that is only found here and nowhere else. Later scientific studies determined the two were the same and the second "species" was reassigned to the more widespread elk kelp. Since the description of new plant and algal species was quite subjective before genetic techniques emerged, this splitting and merging of "species" was more common. Some scientists are quite human, possessing egos that enjoy describing new species and having them named after them!

While kelps may be a cold water species, and the focus of my scientific studies, I am a warm-blooded mammal. As you read this article, I am on board a Lindblad Expedition cruise ship in the southern Sea of Cortez near La Paz where I will spend much of the winter. As the cruise's "undersea specialist," I will actually be paid to dive the warm waters, gather underwater video footage and lecture on the marine life of this region. My next article will talk about my last trip to the Sea of Cortez in the early 70's. Happy golidays to all of you!

© 2003 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.

Image caption: Elk kelp blades flowing towards camera in strong current;
two elk kelp plants showing float bulbs, "antlers" and blades;
elk kelp float bulb and antlers against blade canopy;
drifting elk kelp holdfast

This document maintained by Dr. Bill Bushing.
Material © 2003 Star Thrower Educational Multimedia