The Together for the Med team visited the Hippocampus NGO and explored their marine conservation activities in Mar Menor: key challenges, on‑the‑ground actions and support.
Mar Menor, Europe’s largest saltwater lagoon, sits on Spain’s south-eastern coast. It is home to an emblematic population of long-snouted seahorses (Hippocampus guttulatus) and a remarkable diversity of species found within this unique Mediterranean lagoon. Decades of tourism and intensive agriculture have pushed this fragile ecosystem to the brink. The Asociación Hippocampus, a small volunteer-led NGO, has spent nearly two decades working to protect it.
As part of Together for the Med’s Support Programme for the Development of HPAs, a field visit was organised at the end of June 2026 carried out in Spain to meet the Asociación Hippocampus, one of the project holders backed by the programme.
This article looks at the challenges facing the lagoon, how Hippocampus responds to them, and what support programmes like Together for the Med can offer small conservation organisations like it.
Mar Menor’s ecosystem needs urgent protection
Mar Menor covers around 17,000 hectares of salt water (or hypersaline water). It is separated from the Mediterranean Sea by La Manga, a narrow strip of land stretching 21 to 22 kilometres. Its waters are saltier than the open sea, with temperatures swinging from 9 °C in winter to over 30 °C in summer. This unusual setting has produced a distinctive ecosystem.
Mar Menor conservation depends heavily on protecting species found only in this type of environment. The lagoon hosts an emblematic subspecies of long-snouted seahorse (Hippocampus guttulatus), the Iberian Killifish or Toothcarp (Apricaphanius iberus), the fan mussel Pinna nobilis, seagrasses like little Neptune grass (Cymodocea nodosa) and beds of dwarf eelgrass (Zoostera noltii). Additionally to these marine plants, there are several green and red algae mix within underwater prairies.
Tourism took off around the lagoon in the 1970s and 1980s, bringing hotels, marinas and a thriving local economy. Intensive irrigated agriculture, including the use of some banned phytosanitary products, has driven persistent eutrophication and a decline in water quality. The resulting environmental concerns and controversy contributed to a drop in tourist numbers in parts of the area, together with other socio-economic affections.
Agriculture remains one of the lagoon’s main sources of pressure, largely through nutrient run-off feeding eutrophication. The sector carries real economic and political weight locally, which slows coordinated action from public authorities. Even so, the ecological situation has shown signs of improvement over the past decade, with eutrophication levels declining and some animal populations, including seahorses, showing signs of recovery. In addition, during their stay around the lagoon, BlueSeeds team with Asociación Hippocampus members have met with members of the farming community who were tired to be pointed fingers at, and were willing to be part of the solution. Like most inhabitant of the area, they wish for their children to witness a recovering lagoon, blooming with life, once again.
It is against this backdrop that the Asociación Hippocampus works. Founded in 2007, the organisation has made the long-snouted seahorse its flagship species. As an umbrella species, protecting the seahorse supports scientific studies, ecological monitoring and protection measures that benefit the whole lagoon ecosystem.
How the Asociación Hippocampus protects the lagoon
Hippocampus organises its work around three main pillars: scientific monitoring, public awareness and education, and targeted environmental projects such as Plumbum.
Scientific monitoring and ecological restoration
Volunteers carry out regular underwater transects to track seahorse populations across the lagoon. The association also shares data on water quality and habitat conditions with researchers working on seahorse reintroduction, in partnership with the University of Murcia and the Spanish oceanographic Institute (IEO) at San Pedro del Pinatar.
Hippocampus also supports the RemediOS project, led by the Spanish Institute of Oceanography (IEO-CSIC). The project uses the European flat oyster, Ostrea edulis, a species once abundant in the lagoon, to explore its potential for nutrient bioextraction and ecological restoration through pilot oyster reef trials.
Education and community outreach
Transmission of knowledge sits at the heart of Hippocampus’s mission. The association runs guided underwater trails for both residents and visitors and works with around ten local schools each year. Pupils take part in sea and beach outings, learn to identify local species using a dedicated waterproof field guide, and are introduced to the threats facing the lagoon. This outreach matters because many residents have limited awareness of the biodiversity around them, often preferring swimming pools to the sea itself being surrounded by several Natura 2000 sites.
The Plumbum project: tackling lead pollution
Launched in 2017, Plumbum is Hippocampus’s flagship circular economy green initiative. Volunteer divers collect abandoned fishing lead weights from the seabed. The lead is then cleaned, sorted and transformed into new diving belt weights. According to the association, more than two tonnes of lead, representing around 25,000 individual pieces, have been removed from the marine environment since the project began (an earlier milestone recorded 585.7 kilograms collected by mid-2018, according to San Pedro del Pinatar’s town council). Beyond its direct environmental impact, Plumbum promotes circular economy practices by giving the recovered metal a second life.
Support through Together for the Med
As a small, largely volunteer-run structure, Hippocampus has been accompanied in 2026 through Together for the Med’s technical and financial support programme for small Mediterranean conservation organisations.
This accompaniment has focused on understanding the association’s operational and institutional context, identifying its main support needs, and exploring ways to strengthen its long-term structure, including administrative capacity and wider networking with other Mediterranean organisations.
What the mission revealed: observations and challenges
During our field visits in Mar Menor, the Hippocampus team shared with us a set of concrete, measurable results.
- A network of 60 to 70 volunteers, most from the Murcia region, supports the association’s activities.
- The Plumbum project has removed over two tonnes of lead fishing weights from the lagoon since 2017.
- Around ten local schools take part in Hippocampus’s educational programme each year.
- Hippocampus has uploaded biodiversity data to GBIF data base, for global monitoring, and it is permanent contribution to open science worldwide.
- Seahorse populations and broader biodiversity indicators have shown signs of recovery over the past decade, alongside falling eutrophication levels. However, these gains remain fragile, and the long-snouted seahorse population is still following a declining curb over recent decades, particularly following eutrophication crises in 2016 and 2019 (Vivas et al., 2023).
The association’s entire board, including administrative and financial roles, is unpaid. Its president has described how a small core of volunteers carries most coordination and technical work, while broader participation remains occasional. Long-term challenges include renewing the volunteer base and securing enough funding to support at least part-time paid roles in administration and finance to continue offering citizen science actions and community education.
Hippocampus has been relying mostly on donations from local businesses and in-kind support such as donated equipment since its creation. The association is now working to obtain a public-interest status, a process that is underway and soon completed. Achieving this recognition would open the door to donations from larger national companies which could benefit from tax deduction in exchange of these donations, giving the association a more sustainable, long-term funding base.
Governance adds another layer of complexity. Environmental and agricultural policy in the whole country fall under separate levels of administrations, which can slow coordinated decision-making. Relations between Hippocampus and regional authorities have always been constructive, with regular exchanges on the lagoon’s ecological data. It remains difficult, however, to assess how far scientific recommendations directly shape political decisions and management procedures and outcomes.
Conclusion
Mar Menor illustrates both the fragility of Mediterranean coastal ecosystems and the resilience of the communities working to protect them. The Asociación Hippocampus, through scientific monitoring, education and projects like Plumbum, has built up nearly two decades of credibility and local trust, even while facing real structural constraints tied to its volunteer-based model.
Strengthening organisations like Hippocampus, through technical support, networking and improved funding access, is key to helping them sustain their impact over time.
Questions you might have
What is the Asociación Hippocampus?
The Asociación Hippocampus is a volunteer-led NGO founded in 2007 in San Pedro del Pinatar, dedicated to protecting Mar Menor lagoon, with a particular focus on the long-snouted seahorse (Hippocampus guttulatus).
Why is the seahorse important to Mar Menor’s ecosystem?
The long-snouted seahorse acts as an umbrella species. Efforts to protect it, such as monitoring and habitat restoration, generate benefits for the whole lagoon ecosystem, since its habitat requirements overlap with those of many other species and habitats.
What pressures are threatening Mar Menor?
The lagoon faces pressure from intensive agriculture and nutrient run-off, decades of tourism development, and eutrophication. Research has also examined a possible link between residential proximity to the lagoon and childhood lung cancer incidence in the Region of Murcia (Ojeda-Sanchez et al., 2024), a finding that contributed to public concern in the area, near the old mines and quarries at La Union hills.
What is the Plumbum project?
Plumbum is a volunteer-run initiative launched by Hippocampus in 2017 to collect and recycle lead fishing weights abandoned on the lagoon’s seabed, and coastal Mediterranean seafloor reducing pollution while promoting circular economy practices.
Is Mar Menor’s ecological situation improving?
Recent years have brought some encouraging signs, with eutrophication levels declining and certain populations, including seahorses, showing signs of recovery. Longer-term data still show a marked historical decline in seahorse numbers (Vivas et al., 2023). The recent recovery therefore remains fragile and needs continued monitoring. Despite the official European, national, regional, and local ongoing efforts, the whole lagoon required true legal enforcement, maintain and improve water and ecosystem qualities according to the rights of nature that the lagoon already has.