Community Coastal Column: What is Kelp?

Ivy Munnerlyn, Coastal Programs Coordinator

Here in the Coastal Programs department of the NEC, we have fallen head over heels for all things KELP. You’ll probably see many more Coastal Columns focusing on kelp research, recovery, and cultural significance in the coming months. But before we dive into any of that, I want to offer a brief primer on the biology of seaweeds and how they function as organisms. 

 The first thing you need to know about seaweed is that it’s a multicellular alga, not a plant. In fact, it has more in common with the microscopic creatures we call “plankton” than the land plants we see around us. Seaweeds can be divided into three categories: brown algae, red algae, and green algae. You know brown algae as kelp, and have probably come across red algae like dulse at the grocery store. Both of these groups are incredibly ancient, and represent some of the first multicellular life forms on earth. Green algae like sea lettuce evolved more recently, and thrive in shallow waters with lots of sun.

Anatomy of kelp: The long leaf-like structures called “blades” are attached to a stem-like “stipe.” Some blades also have a pneumatocyst. These structures are  lled with CO2, and help keep the kelp a oat and growing towards the sunlight. They also make a great popping sound when stepped on.

One important similarity that seaweed shares with land plants is the ability to photosynthesize. In fact, studies estimate that roughly 30 percent of the oxygen we breathe is produced by oceanic algae. And just like our redwoods, kelp can sequester huge amounts of carbon. Along with marshes and mangroves, kelp forests are emerging as a critical source of blue carbon sequestration. The kelp forests of the Northcoast are dominated by bull kelp (Nereocystis luetkeana), which can reach heights of more than 100 feet. Kelp is also the fastest growing “plant” in the world, expanding by up to 4 feet a day. 

An organism this large soon runs into logistical problems – how can it transport nutrients through such a huge body? How can it stay afloat in turbulent waters? Kelp has evolved some ingenious solutions to these problems. To transport nutrients, kelp uses a system similar to the xylem and phloem tubes that plants use to move water and sugars. Instead of sugars, nutrients are transported through the kelp in the form of an alcohol called “mannitol.” This substance is produced by a wide variety of life forms, and is used by humans for medical treatment, and as a sweetener in gum and candies. 

 As you can see in the diagram below, there are a number of other, similar features shared by kelp and land plants. The long leaf-like structures called “blades” are attached to a stem-like “stipe.” Some blades also have a pneumatocyst. These structures are filled with CO2, and help keep the kelp afloat and growing towards the sunlight. They also make a great popping sound when stepped on. 

The kelp forests of Southern and Central California have been studied for decades, but much of the kelp dynamics of the north coast remain a mystery. Sizeable kelp beds exist in Trinidad Bay and College Cove, as well as Point Saint George in Del Norte County. In future Coastal Columns, we will take a look at the state of kelp forests in California and how they compare with the situation on the north coast. If you have knowledge or observations to share about kelp and seaweed, you can reach me at ivynecmail@gmail.com

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