Mediterranean Algae, a Spanish company tackles nutrient pollution in ports and coastal waters. Its system uses algae to clean seawater. It also provides reliable real-time data on water quality. This helps ports meet EU requirements and reduce their environmental impact.

With the support of BlueInvest, the company received advice and gained visibility to scale up.

A problem beneath the surface

Across Europe, wastewater rich in nutrients flows into the sea. This is an issue, as too much nitrogen lowers oxygen levels and harms marine ecosystems and biodiversity.,

A well-known example is Spain’s Mar Menor, where nutrient pollution caused a severe ecological collapse.

For founder Yago Sierras, the COVID-19 lockdowns marked a turning point. Living in Alicante, he saw coastal waters recover quickly when human activity slowed. This showed that ecosystems can bounce back under the right conditions.

Inspired by this, he co-founded Mediterranean Algae in 2021.

A simple natural solution

Drawing on their background in marine sciences, the team uses macroalgae as a natural way to remove excess nutrients from seawater. Installed directly in ports, the system lets seaweed absorb nitrogen and phosphorus as the water flows through.

At the same time, sensors continuously measure water quality, tracking how conditions improve. A central platform processes this data and gives operators a clear, real-time view of environmental performance.

By combining treatment and monitoring in one system, Mediterranean Algae offers ports a practical way to clean water while documenting results.

The system is flexible and scalable, designed to fit different port sizes. And there’s a bonus: the seaweed doesn’t just clean - it grows into biomass that can be turned into high-value products, from plant-based food additives to sustainable active cosmetic ingredients. 

Tested in real conditions

The company installed its first full system at the Port of Alicante. It treated around 22 million litres of water and reduced nitrogen and phosphorus levels by 60 to 75%.

Scaling across Europe

Today, Mediterranean Algae works with over 30 clients across the Mediterranean and Atlantic coasts, with new projects rolling out in Valencia, Barcelona, and the Balearic Islands. 

In the longer term, the company aims to build a network of systems that improve water quality while generating environmental data at scale. As Yago explains, this creates “a new layer of climate infrastructure for coastal environments.”

Growing with BlueInvest

Mediterranean Algae joined BlueInvest in 2022, pitching at BlueInvest Day as a pre-seed startup. For the team, pitching alongside different companies from the EU blue economy was also a learning opportunity, helping them better understand the steps needed to scale.

In 2023, the company joined the BlueInvest Readiness Assistance programme, where it received targeted support on strategy, fundraising, and market positioning.

“BlueInvest gave us visibility and credibility with international investors and helped us position ourselves as a serious player in European climate and ocean innovation,” says Yago. 

This journey came full circle at BlueInvest Day 2026. The company returned as a mature scale-up and received both the People’s Choice Award and the Ocean Bioresources Award, shared with Decameal.

About BlueInvest

BlueInvest is the EU's innovation and investment platform for the blue economy, offering business coaching, fundraising support, and networking opportunities for ocean technology companies.

Interested individuals can register with the BlueInvest Community to explore programme features and opportunities or contact lu-blueinvest@pwc.lu. 

More information

Website: Mediterranean Algae

Social media: Mediterranean Algae on Linkedin