Kelp 101

Fall 2009

A primer on the prime marine plant of the Pacific coast

This is an article from WaveLength Magazine, available in print in North America and globally on the web.

To download a pdf copy of the magazine click here: DOWNLOAD

By Neil Schulman

I’m sitting in a room with Jennifer Hahn, owner of Elakah Expeditions and well-known chef of all things from the sea. She has three camp stoves running and is showing us how to make chowder, pickles and chocolate pudding. We’re furiously taking notes and devouring samples. All three dishes are based on one ingredient – kelp.

Kelp is more than an ingredient in chowder and sushi, of course. It’s presence or absence dominates the ecology of nearshore waters. It tangles the paddles of kayakers and gives us places to fish and take shelter from the waves. And underwater, kelp is both a crowded Manhattan of the undersea world and a major driver of the ecology in other zones.

Top to bottom: kelp contributing to the land ecology; the underwater view of the kelp world; sea urchins – enemy of the kelp; and sea otters – enemy of the sea urchin.

When we talk about kelp, we’re really talking about two major species that grow in dense underwater forests on shallow ocean margins, where their holdfasts can attach to rocky bottoms and still reach sunlight. South of Santa Cruz, CA, kelp forests are dominated by giant kelp (Macrocystis pyrifera). Northwards, the dominant species is the bull kelp (Nereocystis luetkeana). It’s a bit slower growing but more tolerant of heavy waves.

When we float alongside the floating stipes (leaves), it’s easy to sense that a lot is happening out of sight beneath you. Kelp crabs and snails cling to the stipes, and anyone who fishes knows there’s a lot to be caught in the kelp forests. We’re peering down, like a bird circling above a forest canopy.

A forest is a good analogy, because the underwater vertical structure is similar to a complex forest – but with much more nutrition in the trees. With a holdfast instead of roots, all the nutrition is packed into the stipes and stalk (thallus). Combine the tasty kelp with upwelling currents that bring nutrients from the deep sea, and you have an ideal place for sea creatures to chow down.

If you’re a fish or an invertebrate, kelp forests are great neighborhoods for raising a family. The tangled forests of kelp grow several centimetres a day and provide shelter for everything from tiny crab larva to thirty-foot long grey whales hiding from pods of orca. The kelp provides a solid place for fish and invertebrates to attach egg masses. The dense stands slow currents and dampen wave action, which means it’s a great quiet place for young fish to hatch and grow up, or for the seagoing microscopic larvae of crabs and barnacles to avoid being swept out to sea.

So it’s not surprising that this edible, ideal housing development is pretty full. A study of just five holdfasts revealed 23,000 individual creatures from nine different invertebrate phyla; one dive survey revealed 204 species in the vertical structure of a kelp stand. The kelp is where the party is.

Kelp forests are also a major driver of the sea’s ecosystems. Fish raised in kelp beds range far and wide. Migratory species may hop from one kelp bed to the next up and down the coast. And by dampening wave action, kelp changes the nature of intertidal ecosystems. Less spray high on the rocks means fewer barnacles and fewer predatory snails. In contrast, critters like chitons and urchins that cling to the rocks and soft-bodied creatures like anemones thrive with less pounding. There’s some evidence that the density also “filters out” the free-swimming larva of some intertidal species, controlling the composition of the tidepools.

When I paddle Oregon’s open coast there’s no shelter from the waves. There are no kelp beds to rest in, and I’m constantly on the alert lest I be smashed into the rocks. In contrast, on a recent trip to Nuchatlitz Inlet, kelp beds were everywhere, offering us an “inside” route on the open coast that allowed us to get close to rocks inside the beds. One of the differences might be more offshore shallow rocks to which the kelp can attach. But another factor is something far more photogenic: the sea otter.

On our recent weeklong Nuchatlitz trip, we saw so many sea otters that we stopped pointing them out to each other by the end of the first day. They roamed around singly and hung out in big rafts of 30 to 40 cute, furry blobs. They would raft up in kelp beds where they eat urchins, crabs, sea cucumbers and clams.

The sea otter (Enhydra lutris) is a keystone predator. Their sense of cuisine sets off a ripple effect through the coastal ecosystem. And they’re absent in a lot of places, because they were hunted for fur in the 18th and 19th centuries, nearly to extinction. A few small population pockets exist off the California and Washington coasts. In British Columbia, they’re abundant where they were reintroduced in Checleset Bay in 1972, and have spread north and south along the west coast of Vancouver Island. And they keep the sea urchin population in check.

It’s hard to believe watching sea urchins in a tide pool, but they are voracious. They chew through the holdfasts of kelp, eat their way through the stem and move in herds that can devastate kelp forests at a rate of 30 feet per month (pretty fast for something with no arms or legs). Uncontrolled, they can create “urchin barrens” where they chow down any kelp plant that tries to regrow. Without otters, urchins have devoured miles of kelp forest on the Pacific Coast, along with the ecosystems they support. My otterless, largely kelpless home state of Oregon is a perfect example.

So a lot more may ride on the reintroduction of the sea otter than photogenic mammals. Famed ecologist Edward O. Wilson calls them the most important keystone species in the world. They’ve been reintroduced to parts of California and Washington, as well as B.C. But oddly enough, otters and kelp forests may be stuck in a chicken-and-egg conundrum. Attempts to reintroduce otters to Oregon have failed, and one of the reasons may be that without the kelp forests for shelter from predators and waves, the otters can’t survive.

Other big changes are coming to kelp forests near you. The first clue came in 1997 when a strong El Nino weather system in the tropical Pacific wreaked havoc with the complex interplay of ocean temperature, weather and currents. The El Nino warmed surface waters as much as 4°C and suppressed the summer northwest winds that cause upwelling of cold, nutrient-rich water along the west coast of North America. Kelp is both sensitive to warm temperature and reliant on nutrients from the deep. In 1997 one-third of Washington’s kelp coverage died off, especially the more temperature-sensitive bull kelp of the outer coast.

Unfortunately, these changes are likely to increase. Global warming is expected to warm oceans and increase the frequency and strength of El Ninos. So our kelp forests are in for a challenge.

But a lot is underway that can actually help these undersea kelp forests. The sea otters reintroduced to the west coast of Vancouver Island may continue to spread to new habitats and open up environments where kelp can thrive. Some scientists also suspect that kelp forests may sequester excess carbon dioxide by absorbing it in photosynthesis and increasing their growth rate, resulting in a growth spurt that might offset the affect of warmer water.

A lot is still unknown about kelp forests and the complex interactions of the sea. Will the reintroduction of the sea otter go as hoped, reach a dynamic equilibrium with the populations of urchins and allow kelp to regrow? Or will it take some new direction we can’t predict, after 150 years of their absence and other ecological change? How will the effects of global warming be felt? Will the more tolerant giant kelp replace bull kelp? Or will it prove too sensitive to the wave action farther north?

As I walk along the beaches of Nuchatlitz Inlet, with a raft of sea otters floating offshore, I think of something else. Another puzzle is the effect of kelp on land. The beach is strewn with kelp, from tiny holdfasts the size of my thumb to big mounds of decaying kelp, hopping with amphipods and chewed by deer. Kelp is clearly contributing nutrients to the beach and forest ecosystem in some way that we don’t know.

In the classroom, Jennifer Hahn shows us how to harvest kelp without disturbing its reproductive cycle. The next time I’m out paddling, I grab a kelp stipe and take a bite. It tastes like the sea.

Neil Schulman lives in Portland, Oregon, where he does environmental work and loves to eat seaweed salad.