The joy and sorrow of the ocean's hidden forests

Diving off the coast of Wales, I’m submerged in a tiny corner of the vast kelp forest ecosystem that thrives in cold temperate latitudes of the world's ocean. From the UK to Norway, South Africa, Japan, Australia and the Americas kelp forests are found along one-third of the world’s coastlines and are a type of blue forest. Providing habitat, oxygen, and carbon storage on a staggering scale, blue forests are the lifeblood of our ocean.

Hidden beneath cool Atlantic waters, a kelp forest off the Welsh coast. © Lou Luddington

The kelp forests of the UK coast may be modest compared to the towering jungles of giant kelp (Macrocystis pyrifera) of Australasia and the Americas or the stands of majestic sea bamboo (Ecklonia maxima) along South Africa’s coasts but they are no less vital. Like their terrestrial counterparts, these underwater forests are essential to life on Earth. Although kelp is not a tree, it plays the same crucial role in the ocean that forests do on land. It captures sunlight, absorbs carbon dioxide, and releases oxygen through photosynthesis, forming the foundation of the marine food web. Alongside seagrass meadows, mangrove swamps, salt marshes and seaweed gardens, kelp forests make up the blue forest. They are unique in their ability to capture and store vast amounts of carbon. This process, known as blue carbon sequestration, allows these ecosystems to absorb up to 10 times more carbon per hectare than terrestrial forests, locking it away in underwater sediments for hundreds of years. This makes blue forests one of the most effective natural solutions in the fight against climate change. But they do far more than sequester carbon. These vibrant ecosystems create and support an astonishing diversity of life, pump out oxygen, furnish us with food, resources and livelihoods, protect our coastlines from flooding and erosion, stabilise our climate and nourish our mental well-being. Our blue forests are the powerhouses of the ocean that we cannot do without. In the words of legendary oceanographer, deep sea explorer and field researcher:

Saltmarshes are coastal wetlands that are flooded and drained by the tides. From above, they appear as a mosaic of land and water, with winding creeks and isolated pools among the low-growing salt-tolerant vegetation of grasses, rushes and seaweeds. They are found throughout the world’s coastal areas where there is low-lying land and a temperate climate. © Lou Luddington

Seagrass is a flowering plant that grows as meadows in calm, shallow marine environments. Important as nursery areas for many commercial fish species and rich in biodiversity, they also have a huge capacity for absorbing and storing carbon. Since the late 19th century, around one third of the world's seagrass meadows have disappeared, prompting seagrass restoration and protection programmes worldwide. © Lou Luddington

Underwater garden of brown and red seaweeds on a bright sunny day. Front centre are the button holdfasts of thongweed (Himanthalia elongata). These sprout whip-like fronds from the centre that form a golden curtain, providing refuge for small fishes and crustaceans. © Lou Luddington

Along tropical and sub-tropical coasts mangroves replace salt marshes and are dominated by trees rather than low growing plants. Mangroves thrive in salty waters where the land meets the sea and are one of the most biodiverse habitats on the planet. © Danel Wentzel

My freedive in the kelp is at summer's end when the water is still balmy from a season of sunshine. The kelp look shabby, abraded and overgrown, signs of imminent change and a shift towards autumn underwater. An invisible pulse of energy sweeps the ragged fronds one way, bending and flexing the stipes, then hauls them back the other. They flutter and billow in the flow like drapes in a blustering wind, as the surge pours through and over them. Honed by these forces they are made to move like water. Supple and yielding they orientate with the flow, stretching, twisting, eddying. In heavy seas, this is where their strength lies. No oak, pine or redwood tree could survive such ferocity on land.

Beneath the canopy of northern kelp where a lush growth of understory life thrives in the shade. In autumn the ephemeral red seaweeds start to die back and the kelp look shabby and overgrown with epifauna, animals that grow on the kelp. © Lou Luddington

The annual lifecycle of furbellows (Saccorhiza polyschides) means their days are numbered. Gaunt and wave-ravaged, the fronds are etched with a meandering network of furrows, the grazing trails of blue-rayed limpets (Patella pellucida). These tiny herbivores use their many-toothed radula to bite chunks from the seaweed, speeding its demise. Grey top shells (Steromphala cineraria) another type of sea snail, dot the kelp fronds too. Instead of feasting on the kelp, they use their brush-like radula to sweep it clean of surface algae and sporelings to eat. By contrast, Northern kelp (Laminaria hyperborea), the perennial mainstay of these northeast Atlantic forests, may live for several years shedding their overgrown and ragged fronds in winter and early spring to make way for new growth. Once discarded they drift and sink or are wrecked on the shore forming a rich strandline habitat. Pulled apart by the forces of nature they are torn, mulched, dissolved, eaten, digested. Molecules that were once seaweed may become plankton, fish, seal, snail or bird, recycled into a new existence. This dynamic flow of nutrients, energy and resources fuels the ocean’s natural cycles, nourishing the next wave of life.

The grazing trails of blue-rayed limpets (Patella pellucida) scrawled over the fronds of furbellows. © Lou Luddington

Blue-rayed limpets (Patella pellucida) nestled on a frond of northern kelp. As the summer comes to an end and sea conditions get more lively they will migrate down the stipe to overwinter in the holdfast. © Lou Luddington

Gleaming in a beam of sunlight a grey topshell (Steromphala cineraria) sits among a furry colony of hydroids growing on the kelp. As important herbivorous grazers of UK seaweed gardens and kelp forests, they help to keep these ecosystems in balance. © Lou Luddington

Seaweeds washed up on the shore become part of a shifting line of decomposing organic matter and debris left along the high water mark. This strandline creates a rich habitat for invertebrates such as sandhoppers, flies and beetles which in turn become food for foraging shore birds. © Lou Luddington

Compared to the bustle of spring, it’s quiet in the autumn forest; I miss the hoards of gently pulsating sea jellies that cloud the water all summer long and lament the absence of spider crabs that have migrated back to deeper water. Territorial by nature ballan wrasse (Labrus bergylta) remain in residence, patrolling their patch among the kelp. I spot a chunky male, coloured amber to match the scene and greet him with a broad smile that lets a trickle of cold water into my dive mask. He looms closer eyeing me, then slips behind a curtain of tangled fronds. I wonder how the fish feels in my presence; studies have shown fishes to be sentient beings, capable of feeling joy, curiosity and fear (Balcombe, 2016). Acutely aware of their surroundings they are social, cunning and crafty, endearing traits they share with us.

Blue jellyfish (Cyanea lamarkii) cruising through a kelp forest in high summer. Jellyfish bloom throughout the summer months in the northern hemisphere feasting on the rich plankton soup. Their long, stringy tentacles are packed full of venemous stinging cells that entangle and subdue their prey. The deadly beauties of summer seas. © Aleksander Nordahl

Perching on its kelp throne this spider crab (Maja squinado) enjoys a lofty lunch spot, as it snips at seaweeds with its long pincers. These large crabs make annual migrations in their thousands to Wales' shallow coastal waters where they gather in the summer months to mate and moult. © Lou Luddington

All ballan wrasse (Labrus bergylta) begin life as female. After a few years some will change sex and become male. Male fish then establish and defend territories within the kelp forest, building nests from seaweed pushed into rock crevices for the females to lay their eggs. © Lou Luddington

These fleeting precious moments underwater lodge in my mind and hit heart-centre. They make me appreciate the importance of these cold water forests as rich habitats for fishes like the wrasse, and countless other species. Each kelp supports a community of life—mussels, crabs, starfish, and anemones all finding refuge among the fronds, stipe or holdfast. In a study of animals associated with a single northern kelp holdfast, scientists found 90 different species and 10,000 individuals living among its branches (Teagle et al., 2018). Yet, for all its vibrancy and vitality, this ecosystem is fragile and under threat.

The urge to breathe prompts me to release my grip on the kelp and I begin to rise. Relishing the sensation of weightless surrender I enjoy the slow ride back to the air, accelerating as I near the surface, then bobbing to an abrupt halt. Breathing at the bright interface between air and water I’m reminded how the blue forests of the world helped create the air that we breathe. Crafted from carbon dioxide, water and sea minerals, all the blue foresters are bound by their mastery of light. Everything they are has evolved to link the capture of light to the flourishing growth and a life-giving byproduct, oxygen.

Blue forest ecosystems are essential to maintaining the balance of the ocean. Their role in coastal protection, carbon storage, and biodiversity is vital but they face significant threats worldwide. Mangroves buffer shorelines and store large amounts of carbon but are being deforested for agriculture, aquaculture, and urban expansion, while also suffering from rising sea levels and temperature changes due to climate change (Duke et al., 2007, McLeod et al., 2011). Seagrass meadows, which provide nursery habitats for marine species and help stabilise sediments, are degraded by pollution, sedimentation, and physical destruction from coastal activities like dredging and anchoring and are particularly vulnerable to water quality and temperature shifts (Waycott et al., 2009, Kennedy et al., 2010).

Salt marshes, essential for flood protection and water filtration, are under pressure from coastal development, pollution, and altered tidal flows, with rising sea levels threatening to submerge them if they cannot keep pace (Barbier et al., 2011). Kelp forests and seaweed gardens support rich marine biodiversity and provide coastal protection. Both are under threat from warming ocean temperatures, pollution, trawling and overfishing of commercial species such as Atlantic cod (Gadus morhua), which are critical to controlling ravenous sea urchins that can overgraze kelp creating underwater deserts (Tegner and Dayton, 2000).

NIVA scientists survey a recently trawled kelp forest in northern Norway. Seaweed has been mechanically harvested in Norway since the 1970s and currently around 120-180,000 tonnes of northern kelp (Laminaria hyperborea) is harvested each year. © Aleksander Nordahl

Filamentous turf algae overgrowing kelp in Norway. © Aleksander Nordahl

School teacher Karoline Kvalø from Lofoten Underwater Club trains her freediving while smashing sea urchins with a hammer outside Henningsvær, Norway. In collaboration with Tarevokterne, an NGO dedicated to kelp restoration, urchin removal allows the kelp forests to regrow in areas grazed barren by the urchins. ©Aleksander Nordahl

These ecosystems are all interconnected in their role in maintaining healthy coastal environments. Left intact and unexploited, their service as dynamic, thriving ecosystems is unequivocal. Around the world, scientists and conservationists are working to protect and restore these vital ecosystems, providing hope that we may reverse some of the ocean’s human-induced loss.

The blue forest is a mighty collective, a union of ocean-bound primary producers that are the light-harvesting foundations of our planet without which all life would falter. To know this, to learn it or to remind oneself is an act of mindful pursuit and a first step towards caring for the ocean. In her poem “Messenger” Mary Oliver writes, “My work is loving the world… Let me keep my mind on what matters, which is my work, which is mostly standing still and learning to be astonished.”

At Reflections our work is loving the ocean and sharing what we see, so that others may learn to stand still and be astonished or outraged or conflicted. What happens next is up to you.

Join us as we discover the blue forest ecosystems, glide among their fronds, stems and branches, delve into the rich stories they hold, explore the lives and characters they’ve captivated, learn of their woes and perils, delights and superpowers, consider the science and art, deep connection and disconnection, use and misuse, loss and restoration and reflect on what the future holds for our human relationship with the blue forest.