California kelp
Off Monterey, the Edges of Earth expedition team falls in love with the vibrant, dense kelp forests of the region.
We felt the cold water slowly creep into our thick wetsuits, alerting us from the moment we got in that this was going to be the definition of a temperate dive. And despite our efforts to mentally trick ourselves into ‘warmth’, we couldn’t help but feel overwhelmed by the raw Pacific. But after another whole 45 minutes submerged in Monterey’s brisk winter waters, and our mind’s veering in the direction of hot showers, none of us were quite ready to surface yet.
We were immersed in that vibrant, dense kelp forest – one of the most spectacular sights we’ve yet to come across in our dive journeys – that made enduring this brutal chill worthwhile. After spending months diving California’s kelp back in 2021, we had our heart set on revisiting this destination for our two-year global expedition exploring the most interesting edges of earth. And despite our seemingly long first visit, we had a feeling we’d somehow only scratched the surface of these compelling Californian seascapes.
Now for those of you unfamiliar, you might be wondering what’s so intriguing about kelp. Of all the wonders of the sea, can kelp really be that compelling? To some, these underwater forests are just as (if not more so) fascinating and visually impressive as their terrestrial counterparts. Kelp, with around 30 different genera, are a type of large brown seaweed, and seaweed is considered a kind of algae. As algae, they’re distinctly different from plants despite their shared trait of converting sunlight into energy through photosynthesis.
These seaweed species both grow directly up to the ocean’s surface, creating a ‘forest-like’ canopy, and form a deeper ‘sub-canopy’ layer beneath it, much like tropical rain forests. The sub-canopy species contribute significantly to the structure of the kelp forest, providing a dynamic and diverse habitat. The structure of kelp not only consists of blades that form a canopy but also includes a holdfast – a root-like structure that anchors the kelp to the rock reef – but that’s where the similarities with a plant’s root system end. The holdfast is densely packed with small invertebrates such as brittle stars, amphipods, copepods, and tunicates. These organisms make their home in the interstitial spaces of the holdfast, even though the kelp itself may only be present for a few years. The three-dimensional structure of kelp, paired with its massive size, all makes for a diverse diving experience – one that our team has fallen in love with over the years.
Kelp forests are also known for their rapid growth. Some species, like bull kelp, are annuals, growing from tiny spores to full-sized kelp in a single season, to then reproduce and die off. Others, known as perennials, such as giant kelp, can survive for up to seven years. In fact, much like trees, some perennial kelp even develop growth ‘rings’ that indicate their age and history. Kelp’s importance however extends beyond just the sea it thrives in. When it washes ashore and begins to decay, it becomes a crucial part of the food chain for intertidal communities. Kelp can drift into deep-sea canyons, offering sustenance to otherwise energy-poor environments where photosynthetic organisms are absent.
While on expedition and over the course of two weeks, we made our way through these kelp forests in Northern, Central and Southern California and we came to realise they very much foster a complex web of interactions between all the species of their local ecosystems. Birds feed on the fishes that inhabit the canopy, while mammals such as sea lions, harbour seals, and southern sea otters hunt the fishes and invertebrates passing through the forest. The rocky reefs that support the kelp forests are home to hundreds of invertebrate species. Crabs, hermit crabs, and, in the southern parts of California, spiny lobsters, find refuge in kelp forests. Predators like sea stars and octopuses prey on snails, worms, and other invertebrates attached to the rocky reef.
However, our mission in California wasn’t solely to take in the sights of the thriving patches of kelp forests that still remain in the Golden State. Rather, we were there to document the significant loss these forests have faced since 2014. According to the University of California, Santa Cruz, satellite imagery has shown a dramatic reduction in kelp forest coverage, plummeting by over 95% in certain areas of the state. In Northern California, only isolated patches of healthy bull kelp remain. The decimated areas have been overtaken by what scientists refer to as ‘urchin barrens’, where purple sea urchins dominate rocky reefs that were once vibrant with kelp and other algae.
During our time in California, much of our focus was on one area in particular – Monterey Bay National Marine Sanctuary (MBNMS) – which encompasses areas in both Northern and Central California. Established in 1992 through the National Marine Sanctuaries Act, this federal marine protected area stretches from Marin to Cambria, covering 276 miles of shoreline and 6,094 square statute miles of ocean. Extending an average of 30 miles offshore, MBNMS reaches depths exceeding 12,743 feet. It is one of the largest marine sanctuaries in the United States and boasts one of North America’s most extensive underwater canyons as well.
With goals centred around resource protection, research, education, and public use, MBNMS offers exceptional diving, particularly in Monterey and Big Sur. To better understand the sanctuary’s underwater wonders, we met Dr. Steve I. Lonhart, a California native, veteran diver and marine ecologist whose work in kelp science started with studying a single species of snail that lives up and down the kelp 30 years ago. Today, he’s one of the leading authorities on central California kelp ecosystems, and has contributed to many of the studies and monitoring efforts in the state.
His research delves into the complex interactions between marine species and how unique environmental factors affect these dynamics. By examining the inner workings of kelp forests, Dr. Lonhart has been able to provide his agency and the public with essential, accurate data on these critical marine ecosystems – all aimed at better understanding what sits beneath California’s surface and how we are meant to best manage it.
Dr. Lonhart explained that the decline of the kelp forests was not a gradual process but actually an abrupt collapse following an unprecedented ocean warming event along the US West Coast back in 2013, which scientists generally referred to as ‘the blob’. This marine heatwave catalysed the collapse of the kelp forests, and was met with a series of other factors that contributed to their decline. Research conducted by multiple stakeholders, including Dr. Lonhart, his MBNMS colleague Chad King, and other researchers across multiple universities and agencies, highlighted that kelp forests north of San Francisco had, in the past, demonstrated resilience to extreme warming events. Kelp for decades had managed to survive past marine heatwaves and El Niño events.
The kelp forest community was further compromised by the loss of the sunflower sea star, an important predator. Recent research in Washington indicates small stars can consume high numbers of newly recruited purple urchins, whereas adult stars eat only one purple urchin per day. It further says that the sea star wasting disease, decimated sea star populations, and may have contributed to the rapid transformation of reefs, transitioning them from kelp dominated to urchin dominated. There are teams around Monterey committed to exploring ways to cultivate sea stars and introduce them back into the kelp forests in hopes it will diminish the kelp’s predation. However, Dr. Lonhart and other scientists are unsure this will be effective.
Another significant predator of urchins is the southern sea otter, with a population in the sanctuary that’s remained steady at around 2,000 for the last few years. It’s theorised that these otters could play a vital role in restoring balance within the kelp forests, aiding the natural cycles of these marine ecosystems. However, these approaches and their effectiveness remain subjects of debate within the scientific community and are all still under trial, review and speculation. Southern sea otters focus on urchins worth eating, and the urchins in a barren tend to be empty and therefore not worth consuming. So, while the otters may not convert a barren back into a kelp forest, the otters do help reduce urchins within the remaining segments of healthy ones, which gives scientists like Lonhart hope for the future.
There are many unknowns surrounding the intricate relationship between kelp, purple urchins, sunflower sea stars, and many other marine organisms and species. And this is exactly what drives the type of research and monitoring work being done within MBNMS. Rather than purely emphasising conservation goals, the team’s research aims to illuminate the ever-evolving nature of the world’s oceans and hopes to focus more so on uncovering answers to that which we simply do not know. By examining ecological processes and the interactions between various organisms, Dr. Lonhart, King and their colleagues, provide critical insights into the forces shaping marine environments today.
As we walked the Breakwater docks, overlooking one of the more famed dive sites in Monterey as heavy storms started to roll in, Dr. Lonhart went on to explain the sanctuary’s mission in more detail: “Today our efforts are motivated by the irregular distribution of kelp in certain areas, raising both scientific and policy-related questions that I’d love to find answers to. This rigorous scientific inquiry is essential for understanding and potentially mitigating the challenges faced by the kelp here.”
The research and monitoring teams are trying to accumulate the most up-to-date and relevant information so that informed decisions can be made about these underwater forests in decline. The importance of this research lies in its potential to drive the right kind of conservation and community action – as this is a high priority in Monterey. For example, teams of citizen scientists have, historically, taken matters into their own hands. While diving, they come with hammers in hand to eliminate purple sea urchins themselves. According to the dive community, this method is an effective way to control the urchin population. However, the actual data on the effectiveness of this culling method is actively being evaluated.
“Hammering-to-kill” purple sea urchins has been a long-standing practice among divers to, in their minds, protect the kelp forests by eliminating the problem. However, as of April 2024, this method was no longer allowed in the sanctuary zone. This cessation offers scientists a valuable opportunity to assess how the kelp forest’s health will be impacted by ceasing the process. Dr. Lonhart and his colleagues plan to identify new kelp beds and compare them with existing ones, focusing on the surrounding urchin activity. The insights gained will help inform governmental policies and community action to mitigate any negative human impacts on these vital marine ecosystems.
“We aim for our efforts to be strategic and impactful, ensuring that every action taken provides the most value. It’s not about futilely pushing water with our hands, only to see it flow back. Instead, we focus on making meaningful progress in the right areas and in the right direction,” Dr. Lonhart said to further his point that the work he is doing uses science to inform action.
The sanctuary is an extensive area encompassing a variety of habitats beyond just the kelp forests. It includes deep-sea environments, underwater volcanoes, and giant submarine canyons. Yet groundbreaking research doesn’t require venturing into the most exotic reaches of the ocean or even venturing that far from shore. There is so much left unknown about the ecosystems sitting right at our front door. Despite studying these environments for over three decades, Dr. Lonhart is constantly discovering something new – new species, new information, and new facts that will help shape the future of California’s coastline.
While we don’t have all the answers about kelp forests, it’s clear they bring a unique diversity and three-dimensional component that’s unmatched by other marine environments. It’s truly majestic to move through a kelp forest with sunlight filtering down from all directions, creating an enchanting underwater experience unlike anything else in the world. Despite the bone-chilling temperatures of the temperate waters, the allure of these forests leaves underwater explorers wanting nothing more than added time among the stripes.
After diving many of the farthest reaches of our globe, it’s safe to say that California’s kelp forests are some of the most captivating places on earth for those who love a cooler plunge – a place that so many are dedicated to see thrive for future generations. Our team couldn’t help but feel an overwhelming sense of gratitude towards those working to maintain Monterey Bay National Marine Sanctuary, protecting some of the most stunning and crucial facets of the ocean – and all so close to a place we call home.
Main photograph taken by Chad Kings/NOAA.
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