Warhorses of the Algarve: An interview with cinematographer João Rodrigues

The penultimate sequence in the Seasonal Seas episode of Blue Planet III highlights how the lives of seahorses in the waters of the Algarve, Portugal, are turned upside down by human influence – once luscious seagrass beds now reduced to apocalyptic sandy barren scenes.

Local Portuguese cinematographer and marine biologist, João Rodrigues, explains first-hand the seemingly impossible task of filming in the Ria Formosa, and the importance of these underwater prairies.

Not just for seahorses but for us too.

I had dreamed of working as a wildlife cinematographer for the BBC ever since I had the chance to contribute, even in a small way, as a safety diver on Blue Planet II. So, when Joanna Haley, Producer for the Seasonal Seas episode, contacted me, it was a moment I will never forget.

Initially, she approached me looking for new animals and behaviors for the series. I suggested telling the story of the long-snouted seahorses in the Ria Formosa and Jo trusted me to bring their story to Blue Planet III as a cinematographer.

It became one of the most challenging, rewarding and beautiful journeys of my career.

The Ria Formosa itself stretches for around 55 kilometres along Portugal's southern coast. It is a constantly changing landscape of tidal channels, islands, mudflats, salt marshes and seagrass meadows, and one of the most important coastal ecosystems in Portugal.

My connection with the Ria and its seahorses began in 2017, when I photographed the seahorse research and conservation work being carried out at CCMAR by Dr Jorge Palma and Dr Miguel Correia.

Later, I met researcher Filipe Parreira, who was doing his PhD on seahorses. He has become a good friend and, luckily, someone crazy enough to take on the challenge of helping me film these animals for the BBC.

Over a coffee, Filipe told me that seahorses could ambush and eat hermit crabs. He also talked about their "hotels" and some of his ideas for future research, which highlighted to me that there was a much more surprising story to tell.

The long-snouted seahorse is one of the most iconic residents of the Ria Formosa.

What makes them special to me is that they are so small and seemingly delicate, yet incredibly resilient, and much more formidable than they look. They are surprisingly fierce predators and can tackle prey you would never expect a seahorse to take on. I have spent many years photographing them, and every encounter still feels special.

In 2001, the Ria Formosa was home to more than two million seahorses – the highest number of seahorses in the world. But encounters became increasingly rare, with the long-snouted seahorse population having declined by 94% in just 7 years.

It was not one single threat.

Illegal capture of seahorses appears to have placed enormous pressure on the population, while the loss of seagrass and other structures they use as holdfasts has changed the habitat they depend on.

The spread of the invasive seaweed, anchoring, illegal beam trawling and increasing human activity have added to that pressure.

Because these seahorses have small home ranges and are closely tied to particular habitats, they have very little room to escape when those habitats change.

Conditions can change dramatically between locations just a few hundred metres apart, with visibility and currents difficult to predict.

Finding a seahorse could take hours.

We avoided the summer months because of the intense tourism, boat traffic and anchoring. Outside summer, the lagoon could be quieter, but the water was colder and the weather unpredictable.

Even in dry suits, spending four hours almost completely static, eventually takes its toll. The cold gets deep into your body, and shaking hands make the tiny, delicate movements needed for macro shots much harder.

And after all that, the seahorse could simply hide or swim away!

One of our filming locations was in a deeper part of the lagoon - home to some very bold octopuses.

We nicknamed one of them Zacarias.

The seahorses would sometimes enter his territory and he would simply push them out of the way. But Zacarias was fascinated by my equipment, especially the dome, which reflected his own image.

So, every time we filmed there, I could spend half the dive trying to convince Zacarias to leave my gear alone. It was probably the first time in my career I had to negotiate with an octopus just to get a shot!

Eventually, Zacarias became part of the story - a reminder that, no matter how much you plan, wildlife often decides what the story is going to be.

Seagrass meadows can look like grass on the seabed, but they are incredibly productive habitats. They provide food, shelter and nursery grounds for a huge variety of marine life.

Studies have shown that fish density and biomass are significantly higher in vegetated habitats, with commercial fish production around twice as high. They also help stabilise the seabed, improve water quality and store carbon.

So much life depends on what looks, from above, like a simple underwater meadow.

Globally, seagrass meadows are under serious pressure. Their extent has declined significantly over the past century, driven by poor water quality, coastal development, physical disturbance and climate change.

Some meadows are recovering where pressures have been reduced, but the overall picture remains concerning. We are still losing these habitats in many parts of the world.

And that matters because when you lose a seagrass meadow, you are not simply losing plants. You are losing an entire habitat and everything that depends on it.

There are some very simple things people can do. If you are boating, avoid anchoring on seagrass whenever possible. An anchor and its chain can tear up the plants and leave scars in the seabed.

In shallow or sensitive areas, slowing down and navigating carefully can also make a big difference.

But perhaps the most important thing is simply recognising what is beneath the surface. Once we understand that a seagrass meadow is a living habitat supporting so much marine life, we are much more likely to treat it with care.