Kelp Forests and Beaches Show Similar Patterns of Change Across California

A new study reveals the hidden connection between the kelp forests of the Santa Barbara Channel and its sandy beaches, and how this relationship can help conserve coastal ecosystems.

Kelp: A Vital Source of Food and Shelter

(Photo : Mario Tama/Getty Images)

Kelp is a type of seaweed that grows in dense underwater forests along rocky coasts. It is a foundational species, meaning that it provides food and shelter for many other marine organisms, such as fish, crabs, sea urchins, and sea otters.

But kelp is not only important for the underwater world. It also plays a crucial role in nourishing the beach food web, as fronds from these seaweeds break away and are transported to the shore by waves and currents.

This process, known as kelp wrack, is not just a random occurrence, but an essential mechanism that sustains life along these shores.

A team of scientists, led by UC Davis and UC Santa Barbara, conducted a four-year study to investigate how kelp wrack affects the beach ecosystem.

They collected and analyzed samples of kelp, sand, and water from 11 beaches along the Santa Barbara Channel, and measured the abundance and diversity of organisms that live on or near the beach, such as shorebirds, insects, crabs, and worms.

They found that kelp wrack provides a rich source of organic matter and nutrients for the beach community, and that the amount and composition of kelp wrack varies depending on the season, the weather, and the location.

They also discovered that kelp wrack influences the physical properties of the beach, such as the temperature, moisture, and oxygen levels of the sand.

Also Read: Kelp Forest Replanting by 2040 Shows Crucial to Save from Decline, Brink of Extinction 

The Kelp-Beach Connection: A Hidden Treasure

The researchers were surprised by the extent and complexity of the kelp-beach connection, which they described as "the unseen harmony" between these two ecosystems.

They found that kelp wrack supports a diverse and productive food web that includes not only the organisms that directly consume or decompose the kelp, but also those that feed on them, such as shorebirds and fish.

They also found that kelp wrack acts as a natural fertilizer, enriching the sand with nitrogen and phosphorus, which are essential for plant growth.

This in turn benefits the vegetation that stabilizes the beach and provides habitat for wildlife.

Moreover, kelp wrack helps moderate the temperature and moisture of the sand, creating a more favorable environment for the organisms that live in it.

The researchers estimated that kelp wrack contributes about 16% of the total organic carbon and 25% of the total nitrogen to the beach ecosystem, making it a significant source of energy and nutrients.

They also calculated that kelp wrack supports about 40% of the total biomass and 35% of the total species richness of the beach community.

Implications for Conservation and Management

The findings of the study, published in the Proceedings of the National Academy of Sciences, have significant implications for conservation and management of coastal ecosystems.

The researchers suggest that kelp forests and beaches should be considered as interconnected habitats, rather than isolated ones, and that strategies should be developed to protect both of them as a whole.

For example, by restoring and maintaining healthy kelp forests, the benefits can cascade to the beaches, enhancing biodiversity and ecosystem resilience.

Conversely, by preventing or reducing human impacts on the beaches, such as pollution, erosion, and development, the quality and quantity of kelp wrack can be preserved, supporting the kelp forest food web.

The researchers also emphasize the importance of public education and awareness about the value and function of kelp wrack, as many people may perceive it as a nuisance or a waste.

They hope that their study can help people appreciate the beauty and complexity of the kelp-beach connection and inspire them to care for these coastal ecosystems.

Related article: Scientists Are Growing Kelp in the Lab To Save California's Kelp Forests From Urchin Invasion