The rays of the morning sun pierce the shallows, casting golden light through the gently swaying seagrass. Algae, clinging to the rocks below, ripple like silk in the rhythm of the tide. Fish swim through this underwater meadow with effortless grace, while tiny crustaceans dance between the algae growing on rocks. It feels like drifting through a dream, otherworldly, slow, and spellbinding.
When a wave passes over my head, I catch a fleeting glimpse of the red sky above, only to be pulled back into the glowing world below. The water is alive with texture and motion, with every leaf and blade a stage for nature’s quiet ballet. It’s one of those places I return to again and again throughout the seasons, watching the seagrass grow, drift, decay, and regrow, the algae shifting in color and form like a living kaleidoscope. Here, time stretches and disappears. But these magical underwater meadows are more than just beautiful; they are vital ecosystems, rich in biodiversity and essential to life on Earth.
Seagrass
I wasn’t always fascinated by seagrass and seaweed. As a small child, I remember wading into the sea and recoiling whenever strands of broken marine plants brushed against my skin. I’d scrunch up my face and try to shake them off. That instinctive reaction, one I’ve seen in many others over the years.
While filming Maydayterranean, I spoke with scientists from across the region, and their stories revealed a troubling pattern: people ripping out seagrass because they believed it was harmful, or carelessly dropping anchors that tore entire meadows from the seabed. What I learned is that much of this destruction stems from misunderstanding. Most people simply don’t know what these underwater plants are, or how vital they are to the health of our oceans.
We need laws to protect seagrass meadows, enforcement, and we need people to care. To understand why these delicate plants matter and to support efforts to restore and protect them. Because once you know what lies beneath the surface, you can’t help but want to protect it. I am not a politician, nor a scientist, I am a storyteller, so I will share with you my fascination with marine plants, and hopefully fascinate you too.
Beneath the surface, in the gentle sway of these fascinating underwater meadows, life gathers in astonishing numbers.
In just a single hectare of seagrass, as many as 80,000 fishflicker through the blades, while millions of tiny invertebrates crawl, dart, and hover between the roots. Among them, seahorses cling with their curled tails, fragile and rare, yet perfectly at home in this hidden forest.
These meadows are more than just a shelter; they are nurseries. Here, countless young fish begin their lives, safe from predators in the tangled green. I have spent hundreds of hours underwater in the Mediterranean Sea, where the greatest abundance of fish I find is around the wonderful greens of the sea.
But the value of seagrass stretches far beyond what we can see. These plants are powerful climate allies, pulling carbon dioxide from the water and locking it away in their roots and surrounding sediment. They do this 35 times more efficiently than tropical rainforests, even though they blanket just 0.2% of the ocean floor. Their roots hold the seabed in place, preventing erosion, especially during storms. And like living filters, they strip excess nitrogen from the water, cleansing it of the pollutants that cause dangerous algal blooms. Where seagrass meadows thrive, the water is clearer, the coastlines are stronger, and the surrounding life flourishes.
Algae
Algae, both microscopic and massive, occur in nearly every shape imaginable: stars, cones, spirals, pyramids, and even cells with wing-like extensions. From unicellular phytoplankton floating in the ocean to the towering kelp forests stretching more than 50 meters high, algae display an astounding diversity in both form and function.
They’re endlessly fascinating. One might resemble a bright green caterpillar, another a white half-cone shaped like a tiny seashell. Beside it, a brown algae stretches upward, as if holding a bundle of twigs in its arms. Some curl like soft, squishy ribbons, while others rise tall and sturdy, like underwater giants.
They reproduce through a fascinating mix of asexual cloning and sexual reproduction, sometimes sacrificing their own bodies in the act. Geography often plays a strange role in their life cycles, with some species reproducing sexually in some regions and only asexually in others.
From ice sheets to desert crusts, from mountaintops to volcanic springs, algae are among the most widespread organisms on Earth. They carpet ponds, cling to trees, thrive in birdbaths, and live symbiotically in lichens and coral reefs. In oceans, phytoplankton and macroalgae form the base of marine food chains and serve as indicators of environmental health.
Species like the green alga Pediastrum boryanum are used to monitor nutrient levels in freshwater, while brown seaweeds such as Ascophyllum nodosum or Himanthalia elongata show clear preferences for wave exposure, making them useful markers for ecosystem shifts.
For millennia, algae have fed humanity. Today, they offer even more: biofuels, pharmaceuticals, cosmetics, food supplements, and key compounds used in everything from toothpaste to ice cream.
A Planet-Shaping Legacy
The role of seagrass and algae in the Earth’s biogeochemical cycles, particularly in carbon and nitrogen regulations, is increasingly critical in the context of climate change. But the pressures are mounting. Ocean acidification, driven by excess carbon dioxide dissolving into seawater, alters the chemical balance and weakens the calcium carbonate skeletons of many calcifying algae, like the green Halimeda and the coralline red Crusticorallina muricata. In some areas, their growth has already diminished by half. That’s why it is so important to learn about these wonderful plants, to help protect them, through helping plant new plants, working on laws that will protect them, or other ways to safeguard them
Beneath the waves, among the gentle sway of marine plants, lies a story that stretches back billions of years, a story of resilience, adaptation, and silent transformation.
They shaped our planet long before we walked on it. Now, in the face of accelerating environmental change, our future may depend on how well we protect theirs.
Article and photos by Sabine M. Probst Saavedra