Aquatic biodiversity is under pressure, from rivers to coasts to the deep sea. This campaign invites citizens, scientists, and policymakers to explore the challenges, discover solutions, and support better biodiversity monitoring across Europe.
From species loss to ecosystem disruption, the health of our waters affects us all. Learn why biodiversity monitoring matters, what’s at risk, and how projects like MARCO-BOLO are helping turn biodiversity data into action.
Biodiversity is the foundation of life on Earth. It supports clean water, healthy soils, pollination, climate stability, and food security. But across Europe and the world, many species and ecosystems are in decline, and often, we don’t have the data to understand how fast things are changing or how best to respond.
Monitoring biodiversity helps us track these changes. It shows where species are disappearing, where habitats are under pressure, and where conservation efforts are needed. Without this information, it’s much harder to protect nature or make informed decisions about land use, climate action, or sustainable development.
It supports scientists in understanding ecosystems, helps policymakers make informed decisions, and empowers communities to take action. Monitoring guides how we manage fisheries, protect endangered species, restore habitats, and respond to environmental changes.
Aquatic ecosystems across Europe face a wide spectrum of pressures, from chemical runoff and habitat fragmentation to warming waters and invasive species. Below, we spotlight three critical challenges affecting freshwater, coastal, and marine biodiversity. Each example highlights emblematic species and ecosystem functions at risk, while offering actions that can reduce harm and support recovery.
These are just a few of the many threats that affect all the waters we share, revealing how human activity continues to reshape life below the surface.
Posidonia oceanica, a seagrass species endemic to the Mediterranean Sea, forms vast underwater meadows that support hundreds of species, including juvenile fish, crustaceans, and delicate grazers like nudibranchs. These meadows act as nurseries and feeding grounds, while also storing carbon in sediments for millennia.
Overfishing and lost gear are among the greatest threats to Europe’s seas. Species are being caught faster than they can recover, while “ghost nets” and traps continue killing long after being discarded. Every year, 2,000–12,000 tonnes of ghost gear enter European waters, choking coasts near fishing zones and ports.
What Aquatic Oddball Are You?
The waters we share are full of life - strange, sparkly, calm, and downright quirky. From freshwater streams to coastal meadows and the deep sea, every habitat has its oddballs. Which one matches your personality? Take the quiz and find out.
For Citizens: Across Europe, aquatic biodiversity is under threat, and often, we don’t have the full picture of what’s happening. MARCO-BOLO is helping change that by improving how we study and share information about life in our rivers, coasts, and seas.
For Professionals: To protect nature, we first need to understand it, and that starts with data. Yet biodiversity data is often scattered, stored in incompatible formats, or missing key context. These issues make it difficult to compare trends, assess threats, or take timely action.
Freshwater ecosystems face growing pressure from human-made noise and artificial light. These forms of pollution disrupt the natural rhythms of aquatic species, especially those that rely on darkness and quiet to feed, migrate and reproduce.
Species like the European pond turtle, which nests along riverbanks, are sensitive to light pollution. Artificial lighting near nesting sites can interfere with orientation, delay nesting, and increase predation risk for hatchlings, a concern raised in multiple ecological studies (Nature article 2018).
European eels, which begin their life in the ocean, depend on subtle environmental cues for long-distance migration. They are already critically endangered (Red List 2020). Noise pollution from roads, hydropower, and shipping can interfere with their sensory systems, increasing stress and reducing migration success. According to the European Environment Agency, noise pollution affects wildlife behaviours in nearly 30% of protected areas across Europe, including aquatic habitats (European Environmental Agency article 2025).
Why it matters: Freshwater biodiversity is declining at twice the rate of terrestrial biodiversity (WWF, 2022). Species like eels and turtles are essential to ecosystem balance, nutrient cycling, and predator-prey dynamics. The loss of their habitat and behaviour cues threatens entire aquatic food webs.
Protect quiet, dark spaces near rivers and lakes, especially during nesting seasons. Support efforts to limit fireworks and loud events in sensitive areas.
Shield lights, use timers, and avoid bright lighting near water bodies. Encourage local councils to adopt wildlife-friendly lighting policies.
Advocate for quiet zones along rivers and reduced noise from roads and infrastructure near freshwater habitats.
Visit AquaPlan, Plan-B Project below, and other EU-funded initiatives to see how data and conservation work connect.
Posidonia oceanica, a seagrass species endemic to the Mediterranean Sea, forms vast underwater meadows that support hundreds of species, including juvenile fish, crustaceans, and delicate grazers like nudibranchs. These meadows act as nurseries and feeding grounds, while also storing carbon in sediments for millennia
Seagrass meadows are declining globally, with rates accelerating from 0.9% per year before 1940 to 7% per year since 1990 (Waycott et al., PNAS 2009). In the Mediterranean, P. oceanica is particularly vulnerable to coastal development, pollution from land, and underwater construction that stirs up sand and mud, which can bury, suffocate and damage the seagrass. Marine litter, especially plastics, also accumulates in shallow zones and can smother seagrass beds, reducing light and oxygen availability (Porcino et al., Sustainability 2023), harming the species that depend on them. With fewer sheltered habitats, vulnerable species like nudibranchs, which rely on seagrass habitats for shelter and prey, disappear. As the seagrass meadows vanish, biodiversity suffers, fish stocks decline, and water quality worsens.
Why it matters: Seagrass ecosystems store “blue carbon”, prevent shoreline erosion, and support coastal fisheries. P. oceanica meadows can sequester carbon at rates comparable to or exceeding tropical forests, and their loss puts both biodiversity and climate resilience at risk.
Take part in local efforts like #EUBeachCleanup or support groups such as Waste Free Oceans. Cleanups stop litter from reaching fragile marine habitats and harming wildlife.
Volunteer or donate to organisations that replant and protect native seagrass. Healthy seagrass beds provide food, shelter, and carbon storage for countless marine species.
Advocate for green infrastructure like rain gardens or permeable pavements. These measures limit pollution and nutrients entering coastal waters, improving water quality.
Speak up during local development projects to ensure seagrass beds and other sensitive ecosystems are protected. Your voice can influence decisions that shape coastal resilience.
Overfishing and lost fishing gear are major threats to marine biodiversity across European waters. Many species are caught faster than they can recover, while lost nets, ropes, and traps (known as ghost gear) continue to trap and kill marine life long after being discarded. According to the European Environment Agency, between 2,000 and 12,000 tonnes of ghost gear enter Europe’s seas every year, with coasts seeing high concentrations near fishing zones and ports.
Basking sharks, protected under European law, are especially vulnerable. Their surface-feeding behaviour and migratory routes bring them into contact with drifting fishing gear, leading to injuries, strandings, and deaths. These sharks are globally endangered due to centuries of exploitation and remain at risk in European waters (Rudd et al., Scientific Reports 2011). Octopuses, particularly in Mediterranean and Atlantic trap fisheries, are often caught in lost and illegally set pots and creels. This creates a cycle of accidental capture that affects both biodiversity and artisanal fishers (Bonanomi et al., Scientific Data 2022).
Deep-sea habitats are slow to recover and highly vulnerable. Ghost gear that sinks can crush sensitive coral gardens, entangle deep-sea sponges, and smother life on the seafloor (WWF 2020). The damage is often invisible but persistent, disrupting ecosystems that have developed over centuries.
Why it matters: Marine species like octopuses and sharks play important roles in keeping ocean ecosystems healthy. The decline in their numbers affects how nutrients move through the food web and how habitats stay balanced. When these species disappear, entire ecosystems can become less stable and less able to recover from change. Responsible fishing and gear management are essential to protect these species and the ecosystems they support.
Participate in or back initiatives that retrieve lost fishing gear. Programs led by fishers and NGOs help remove hazardous debris from marine habitats and protect wildlife.
Use tools like the Good Fish Guide or FishChoice Calculator to check how seafood is caught and whether it is sustainable. Making informed choices helps protect marine ecosystems.
Ask about responsibly sourced seafood. Choosing certified or local sustainable options reduces pressure on overfished species and supports environmentally friendly practices.
Discover and support EU-funded initiatives like NETTAG+, LIFE OASIS, and the WWF Mediterranean Ghost Gear Project, which work to reduce marine pollution and protect biodiversity.
