Kelp Forest


by Holly Hill
former Point Lobos park aide

Macrocystis -  Giant Kelp by Marc ShargelIt is an irresistible lure - the sea and its inhabitants. And, it would be difficult if not impossible for any naturalist to resist an inquiry into one of the most diverse, complex, and unique ecosystems on earth. This ecosystem is the great kelp forest.

But what most of us refer to as "kelp" is actually one form of algae - brown algae, Phaephyta, which seemingly dominates cool (50 degree F 10 degree C) waters off the North American Pacific coast. Several species occur here, but it is the giant kelp, Macrocystis, and bull kelp, Nereocystis, that most of us encounter in nearshore waters as SCUBA divers, waders, boaters and kayakers.

As for those who choose not to venture beyond the water's edge, encounters with kelp are seasonally common when winter storms or heavy seas deposit mounds of entangled kelp "high and drying" along our beaches (much to the dismay of those living downwind of the decomposing tonage!).

These masses, known as "drift," are something of a tribute and clue to the incredible growth rate (reportedly up to 18 to 24 inches a day) and success of these marine forest species.

Nereocystis - Bull Kelp by Marc ShargelLife for Macrocystis (and similarly for Nereocystis) begins as a spore released by the floatless reproductive blades - sporophylls - found near the holdfast (all Nereocystis blades are sporophylls) and these spores find substrate and develop into microscopic male and female plants. The male releases sperm and the female does release a single egg or several eggs. Nonetheless, unions of the two do occur, and from these the kelp plant with which we are familiar develops.

Growth begins at the holdfast where fronds, consisting of a stipe with numerous blades that are supported and pulled upward by the carbon monoxide-filled floats, lengthen as they seek the surface. This lengthening separates the new leaves which continue to grow and eventually form the kelp canopy. Old fronds that have died eventually become drift. The drift, in turn, is partially broken down to become a valuable food source for grazers such as abalone and sea urchins, while the larger masses of drift become buffered areas protecting juvenile fishes and other inhabitants from severe wave action and predation. And even beached drift continues to function in much the same way, providing food and protection for terrestrial organisms.

To say the kelp forest is complex and unique is clearly an understatement. Perhaps as we learn more, new words and terminologies will be coined to allow us to express the profound nature of the marine kelp forest.