Bull Kelp    Nereocystis luetkeana



One of the largest of the brown seaweed group called kelp, Bull kelp can grow to lengths of around 100 feet, however the plant in the photograph is a young one only three feet long.  Very fast growing, it matures in one season growing some seven inches a day.  It consists of a single long trunk or stipe which is attached to the bottom using a mesh of finger-like projections called a holdfast that adheres to rocks. The stipe widens along it's length ending in a floating, hollow bulb that holds the plant upright in the water column.  From the bulb sprouts two sets of blades or fronds each of which can contain up to 50 individual fronds.  The fronds are long (around 12 feet) and narrow (less than 8 inches). The plant seldom is found alone, usually occurring in large dense kelp beds and ranging from Alaska to central California in the nearshore subtidal zone.


The surface of the fronds and stipe are used by a variety of animals and plants as shelter.  Kelp crabs can be found along the stipe feeding on various small attached plants as well as the kelp itself.  Various species of perch and other fish prowl the understory.  It is also eaten by sea urchins (relatives of sea stars) who nibble on the holdfast and stipe like marine beavers.


This group of seaweeds has a complex life history. Bull kelp, unlike other kelp, produce patches on the blades which are composed of mobil reproductive cells called zoospores with half the chromosomes of a regular cell. These patches sink to the immediate area of the parent releasing the zoospores.  The zoospores germinate into separate male and female microscopic plants.  Sperm then swim from the male plant to the egg of the female plant and fertilizes it.  The resulting young plant with a full set of chromosomes grows into the large Bull kelp.


Bull kelp has been used by humans as food.  The sliced stipe is made into pickles or salsa and the blades can be dried and eaten like potato chips or added to soups or other dishes.