Gulls cried in the distance as we walked along the shore at Natural Bridges State Beach. The air was crisp with a twinge of salt. We had passed numerous brown mounds of kelp when Sara excitedly pointed to a kelp mass strewn on the beach closer to the water’s edge. We found just what we were looking for: giant kelp, Sara’s primary study species.
Sara knelt down beside a piece and picked up one of the blades – the kelp’s leaf-like structures.
“You can see the really deep corrugations here, and the blade’s serrated edge.” She pointed to the corrugations, or grooves, carved into the kelp’s blade. She gently traced her finger along the serrated edges as I watched intently, realizing I would have missed these delicate details had I not been with Sara.
Giant kelp is widely distributed around the world, found along the coast of North and South America, Africa, Australia, and beyond. Distinct geological regions are home to giant kelp populations that look vastly different – despite being the same species.
“Some of these forms are so distinct that they used to be classified as separate species,” Sara explained. “Now they are termed ‘ecomorphs’ of the same species.” Different kelp ecomorphs, or individuals of the same species with different physical characteristics, vary in the form of their blades and the structures they use to anchor themselves to the ocean floor.
Sara Gonzalez is a graduate student in the Department of Ecology and Evolutionary Biology at the University of California, Santa Cruz. Previously, she studied biology at Cornell University. Trading upstate New York’s bitter winters for warmer weather and sandy beaches, she came to Santa Cruz to study kelp with Dr. Pete Raimondi.
Sara’s work with kelp began during a Fulbright Scholarship project in Chile. There, she collaborated with other marine researchers at the Pontificia Universidad Católica de Chile to study the influence of nutrients from fish excrement on kelp growth. I imagined her on the incredible Chilean coast studying its marine life, acquainting herself with the landscapes praised in poems by the famous Pablo Neruda.
While collaborating with Chilean academics studying kelp, Sara realized how embedded kelp is in today’s society as a natural resource. Kelp is harvested for its alginates, a polysaccharide found within the cell walls of all brown algae. When alginate combines with water, it forms a thick gum-like texture, which can be used in products ranging from cosmetics, daily-use items such as toothpaste, and foods such as ice cream.
“It was an interest that grew over time – being around kelp, and talking to people about kelp all the time. I got really excited about it,” Sara said, smiling and looking out towards the water.
Kelp is a foundation species, meaning it plays an important role in its community. It also forms an entire ecosystem: the kelp forest.
“The high productivity of the kelp forest and varied physical structure from the base to the canopy provide the foundation to support a diverse array of life, including many commercially and recreationally harvested species such as kelp bass, several species of rockfish, and the kelp itself,” Sara explained.
Organisms, ranging from invertebrates to fish to mammals, rely on kelp forests as a place to live, forage, and reproduce. Kelp forests also protect shorelines from erosion by creating drag against waves coming to shore.
Sara’s time in Chile piqued her interest in the morphological differences between Californian and Chilean kelp. This interest grew into a well-formed project as a graduate student. At Santa Cruz, she is studying the environment’s role in determining the kelp ecomorphs and its effects on the production of alginate.
However, today, we were two just two naturalists combing the beach shore.
We approached another mass of kelp, flushing a swarm of small insects as we knelt down beside it. Sara, ignoring the insects, reached down her hands to pick up a kelp mass the size of a soccer ball.
“This is the holdfast,” she explained, turning over the ball, which appeared to be a mass of root-looking structures. “It’s composed of haptera, which are these root-looking things.” She pointed out the network of twisting haptera, growing tightly together in a pattern which resembled the creases of a brain.
On our coast, giant kelp forests grow up to 50 meters from the ocean floor, eventually reaching the water’s surface.
“As it grows, the kelp forms more and more of these haptera, until you end up with this big, netted mass of them.” Sara slowly turned over the holdfast for me to see, pointing out the layers the haptera formed. Despite its resemblance to a mass of plant roots, she explained, a kelp’s holdfast doesn’t act like a root system at all. Rather, it’s used by kelp to anchor itself to substrate. She carefully placed the holdfast back near the pile of kelp blades.
Over the course of our walk along the beach, we encountered 3 different species of kelp: the giant kelp with its densely grooved blades, the chain bladder kelp with its line of bubble-like protrusions, and the feather boa kelp, which looked, not surprisingly, like a long feather boa.
However, our giant kelp specimen was by far the most physically impressive. Scientifically, giant kelp is equally astounding: it is one of the fastest-growing plants in the world, accumulating 12 to 18 inches of growth per day. Their high growth rates make kelp forests one of the most biologically productive communities – comparable to tropical rain forests.
Moving forward, Sara plans to continue her kelp studies by conducting a series of experiments. By rearing kelp in the lab and simultaneously planting them in the ocean, Sara will be able to elucidate the importance of environmental versus genetic factors in kelp morphology and alginate production.
Sara’s work in Chile also shed some light on the importance of nitrogen in fish excrement for kelp growth, and its role in reducing blade decay. These preliminary results prompted Sara to focus on the effects of ammonium on kelp – being the nitrogen product from fish excretion, after the ocean’s pH conditions react with the ammonia from the waste. Less is known about ammonium’s effects on kelp when compared to its close chemical relative, nitrate.
“In parts of California, there are times of the year when nitrate levels are reduced, so it is important to understand the potential contribution of fish-derived nitrogen, especially as oceanic conditions in the future are likely to change,” Sara explained.
We continued down the shore, eventually reaching a rockface with shallow pools carved into it. Inside the pools, anemones dotted the edges like flowers, their tentacles spread out like delicate sea petals. Around the pools, masses of washed-up giant kelp spread out like carpets on the rocks.
I thought of the kelp’s holdfast: its dense network of haptera forming a stronghold to the ocean floor as the kelp grows towards the water’s surface. Then, I thought of Sara. Her ideas seemed to grow in an analogous way, forming a dense network of enthusiasm and curiosity to anchor her as she reaches towards the answers.
We returned to the beach and meandered back towards my parked car, absorbed in our conversation as gulls flew overhead.
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