The kelp soaks up carbon, via photosynthesis, and grows. After about seven months, the mature blades get too heavy for their biodegradable buoys, and sink.
Nereocystis leutkeana, commonly known as bull kelp, is the ‘sea vegetable’ around these parts that many of us are familiar with. This is the long brown kelp with the hollow stipe, or root, that anchors the plant to the seafloor. The stipe also allows the fronds or leaves to float just below the water’s surface to gather sunlight. At peak season, bull kelp can pack on four inches of growth every day and reach lengths of 30 feet! As an annual kelp, spores generate new plants every year. This is the kelp that local Juneau food business Barnacle Foods makes their wonderful pickles with!
BTW, cut a nice 5-7 foot length, cut the end ball that hold the fronds in half, and voila, you’ve got yourself a ocean trumpet! Some of these horns can grab four or five different notes! Note: if you harvest a chunk for a horn, you’re required to dry the fronds at home and slice the stipe for pickles!