Text and photos (c) 2013 Erkki “Eric” Siirila, copyright & all rights reserved.
Orange garibaldis, the “official” fish of California, are the first thing I see while entering the undersea kelp jungle of Santa Catalina Island outside Los Angeles. In front of me 50-60-meter long stalks of Macrocystis pyrifera rise from the depth of 20 meters to the surface. They get their buoyancy from gas filled bladders called pneumatocysts. When a diver explores the forest formed by the biggest kelp species in the world, not only the size amazes. Also the growth speed, which in the favorable conditions of southern California may reach 45-50 cm in 24 hours, seems unbelievable.
Diving in kelp forests provides unforgettable experiences.
Even though most kelp areas in California are protected, some others are being utilized for kelp harvesting. Harvesting takes place also in the kelp beds of Baja California, Mexico. Algin, the chemical extracted, is used for getting the right smoothness and thickness, when chemical, cosmetic, pharmaceutical and food processing industries make products for you.
A garibaldi in the waters of Santa Catalina.
Charles Darwin highlighted the biodiversity of Macrocystis habitats in the following words: “If in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would from the destruction of kelp.” In spite of being a statement before the ultra high diversity of the tropical rains forests was known to scientists, the comment still indicates something very basic about the importance of the kelp communities.
Gas-filled pneumatocysts give the kelp stalks buoyancy.
After the dive, together with diver colleagues we summarize our underwater experiences: the peak moments included encounters with a spiny lobster, horn shark and hawksbill turtle. From the shore I see an American blue heron searching for food on top of the floating kelp. Around the Macrocystis communities I also observe harbor seals and California sea lions. In the undersea jungles of Southern California at least 750 species of fish and invertebrates are known to live. A single kelp stalk may be the home to half a million critters.
Holdfasts anchor the kelp to the sea bottom.
The same kind of examples from the ocean´s forests are being told around the world. So it is no wonder that the environmental organization Oceana has started to defend the kelp beds, which are found close to shore in regions where the waters are cool – each continent, except the Antarctic, has thousands of kilometers of coast where kelp is an important part of undersea nature (see Kelp forest distribution map). In spite of this, internationally there is little environmental legislation protecting these undersea habitats. Of course all the underwater forests are not as mighty as those built by Macrocystis. In Europe, the kelp communities are formed by Laminaria species, which are common in Norway, to give one example. There they reach a height of two to five meters.
My dive continues with photography of sea urchins, which can be found under rocks at daytime. The urchins are the main enemy of Macrocystis. They eat and destroy Macrocystis´ holdfasts, the “roots” of the giant kelp. In the Santa Catalina waters there are only few urchins. In consequence, the kelp forest looks healthy. When I see a 60-centimeter California sheephead in the viewfinder, I feel grateful to it. The urchins are part of its diet. The fish, which regularly approaches divers and gives the impression of being intelligent, is well known to the Catalina visitors. This exceptionally big individual is easily recognizable and has gotten the name Oscar.
California sheephead is a fish species which controls the sea urchin populations.
Like Oscar also Californian divers have supported the survival of kelp by removing sea urchins from key bottom areas. The urchin numbers had grown much higher than normal. This lack of balance had mostly resulted from the hunting and overfishing of their natural enemies. In addition to urchin control, in California techniques have been developed to help young and drifting kelp attach to the sea floor. The support actions have resulted in the return of kelp to areas where Macrocystis had disappeared. For Santa Catalina, healthy kelp forests have become a major attraction which draws thousands of tourists to the island every year.
In Monterey I photograph the graceful sea otters. Here the good news is that the otter population of central and northern California, which was practically destroyed by fur hunters, has significantly grown. In 2013 an estimated 3,000 sea otters live in the region. The animal prays on sea urchins and, when abundant, keeps their numbers at an environmentally sound level.
When sea urchin populations grow in an uncontrolled manner, they can destroy Macrocystis forests.
The value of the sea otters and kelp forests off the Pacific coast of North America got a new recognition some time ago. In the October 2012 issue of Frontiers in Ecology and the Environment, Christopher C Wilmers, James A Estes, Matthew Edwards, Kristin L Laidre, and Brenda Konar presented a study which covers the Macrocystis-dominated kelp forests from Vancouver Island to the western edge of Alaska´s Aleutian Islands.
Sea otters feed on sea urchins and support the survival of kelp communities.
The main conclusions include that in areas where the otters are abundant and at their natural levels, they suppress the sea urchin populations significantly, i.e. so much that the kelp forests flourish. Every year the additional kelp is estimated to capture as much carbon dioxide from the atmosphere as the CO2 production of three to six million passenger cars in 12 months. In ideal conditions, the kelp forests’ capacity to store carbon equals that of a tropical rain forest of the same size. Thus the kelp forests (especially those dominated by Macrocystis) are an important carbon sink slowing down climate change and global warming.