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‘A beautiful underwater world awash with light’: Michel Roggo’s Freshwater Project

July 18, 2019
Rotomairewhenua (Blue Lake), high up in New Zealand’s Southern Alps, is sacred to the Māori. The lake has the clearest freshwater ever reported. Image: © Michel Roggo /

Freshwater ecosystems are often key parts of our everyday landscapes: whether ponds, lakes, rivers, wetlands and canals that we might cross and pass by regularly. However, glimpsing the life that goes on below the surface of freshwaters can often be challenging, even to the most regular visitors.

Some creative artists have used film to shed a light on underwater lives, whilst others have used sound to ‘eavesdrop’ on their aural worlds. Since 2010, Swiss artist Michel Roggo has been using photography to explore and document global freshwater habitats through his Freshwater Project. Roggo’s work has taken him to more than 40 freshwater ecosystems across the world, each containing unique and unusual biodiversity and geology.

Speaking to The Freshwater Blog about the project in 2014, Roggo said: “We know what coral reefs look like, but what about the creeks, streams, lakes and ponds on our doorstep? I’m always looking for new and interesting scenes with the most dramatic light. A marsh pond, beneath the ice in a mountain stream, among algae – these habitats are hardly ever seen but they are incredibly beautiful.”

During the cold winter months, West Indian manatees escape the ocean seeking out the warmth of Florida’s freshwater headstreams. Image: © Michel Roggo /

For Roggo, shooting photographs in freshwater habitats offers two key opportunities. First, as sub-surface freshwater life is remarkably overlooked by most creative practitioners, Roggo’s explorations in The Freshwater Project offer new perspectives on spectacular and unusual underwater landscapes. For Roggo this is the process of “searching for this magic moment under the surface, with the perfect light and composition.” Roggo’s photographs are largely taken with remote-controlled submerged cameras, and he rarely dons diving gear in his explorations.

The project is also intended to have positive conservation impacts. Roggo has partnered with the IUCN Freshwater Programme to provide images which celebrate the unseen beauty and diversity of global freshwater systems, and highlight the pressures they face.

“As one of the few professional photographers specialising in underwater images of freshwater landscapes and species we strongly support Michel’s work,” said Dr. Will Darwall, Head of the IUCN Freshwater Biodiversity Unit. “We see the need for raising public awareness of the beauty of underwater freshwater habitats and species through images such as these as a most important contribution to IUCN’s own work towards valuing and conserving nature.”

A Florida red-bellied turtle at home in the massive stream of freshwater in Florida’s underground, which reaches the surface through numerous sources. Image: © Michel Roggo /

A new exhibition at the Zoological Museum at the University of Zurich in Roggo’s home country of Switzerland brings together over 900 of his photographs, documenting what the curators call ‘a beautiful underwater world awash with light’. The photographs in ‘AQUA’ – created in collaboration with local guides, including members of indigenous peoples, biologists, dive guides, skippers and pilots – document global locations including Lake Baikal, the Sense river, and the Iguazú Falls.

The Zurich exhibition is organised into five themes, where freshwaters are variously: dynamic habitats; challenging ecosystems which foster unique biodiversity; water sources in glaciers and ice caps; water sources in groundwaters; and geological agents of erosion and transport. The result is a diverse and beautiful collection of animals, plants, ice, rock and water sources across the world.

Icebergs calved off Sermeq Kujalleq glacier in Greenland float out into sea. Image: © Michel Roggo /

Roggo’s exploration of the glaciers and polar ice caps – where around two-thirds of the world’s freshwater is stored – led him to the ends of the earth, from the Ross Ice Shelf in Antarctica to the glaciers of Greenland.

“Michel Roggo has put together an impressive record of the most important freshwater habitats on Earth,” said Isabel Klusman, Head of the Zoological Museum. “This is a key step in raising awareness for these fragile and often endangered domains.” The AQUA exhibition opens on 23rd July, and is accompanied by a new book featuring a selection of 360 photographs from the Freshwater Project.

Cichlids in Lake Malawi, home to more species of fish than any other lake in the world. Image: © Michel Roggo /
On Canada’s Pacific coast, every four years millions of sockeye salmon journey up Fraser River to Adams River to spawn and die. Image: © Michel Roggo /
The river Sense in the foothills of the Alps is the last Swiss river without a power plant on its course. Image: © Michel Roggo /

AQUA exhibition
Michel Roggo’s Freshwater Project

New MEASURES for the conservation of migratory fish in the Danube

July 11, 2019
A juvenile Beluga sturgeon – or sterlet – bred to restock the Danube River as part of the MEASURES project. Image: Daniel Trauner | MEASURES

The Danube River is one of Europe’s most diverse and important freshwater systems. Sturgeons are flagship animals in the Danube catchment: iconic migratory species, which have existed since the time of dinosaurs, and are symbolic of the Danube’s historical heritage and ecological wealth.

However, the ability of sturgeon populations to migrate through the Danube catchment to spawn and feed has been restricted by human activities such as habitat destruction, dam construction and overfishing. According to the IUCN, 85% of global sturgeon species are threatened with extinction, making them the most endangered species group in the world.

MEASURES is a major new project which aims to manage and restore ecological corridors in the Danube River basin in an effort to boost populations of the six sturgeon species. Funded by the EU as part of the Danube Transnational Programme, MEASURES aims to improve habitat quality and connectivity along the Danube, not only to benefit sturgeon species, but also other migratory fish and the wider aquatic biodiversity in the basin, too.


Cross-border collaboration for sturgeon conservation in Europe

The start of the MEASURES project follows the signing of the Pan-European Sturgeon Action Plan in November last year. The Action Plan covers eight European sturgeon species, seven of which are listed as critically endangered on the IUCN Red List of Threatened Species. It provides the first ever fish-specific action plan implemented as an EU Directive.

MEASURES is a collaboration between twelve partners across the Danube region, led by the University of Natural Resources and Life Sciences (BOKU) in Vienna, Austria. The participation of a wide range of stakeholders in the project – national authorities, international organisations, academic and research institutions, and NGOs – offers MEASURES significant potential in developing conservation and restoration strategies throughout the Danube basin.

Co-operation across national borders is crucial in providing effective conservation schemes for migratory fish such as the sturgeon. Sturgeons have long lifespans (some species can live for 150 years), and most species migrate vast distances across diverse habitats at different stages of their lives. This potentially makes them ‘umbrella’ species for the conservation of other species, who may also benefit from habitat restoration and re-connection designed for sturgeon populations.

A juvenile Beluga sturgeon ready for release in the Danube River. Image: Thomas Friedrich | MEASURES

MEASURES for sturgeon conservation: three strategies

There are three key aspects to the MEASURES project. Over the next three years, project researchers will identify and map migratory fish habitats along the Danube basin. This will allow for a harmonised and improved strategy to re-connect migratory fish habitats.

Such ‘ecological corridors’ will be re-established and brought into policy and management plans in the Danube basin. Finally, a strategy to secure the dramatically declined Danube sturgeon species will be developed, including the design of appropriate broodstock facilities and conservation stocking approaches basin-wide.

Research, mapping, dialogue and outreach

An accessible online information system containing maps of species habitats and distributions, alongside articles, reports and multimedia will be created within the project, led by the Institute of Biology, at the Romanian Academy, Bucharest. A series of workshops designed to improve national and transnational dialogue and co-operation among researchers and different stakeholders across the Danube basin will be facilitated over the project life-span.

Migratory fish habitats will be mapped along the Danube basin (activity led by the Danube Delta National Institute for Research and Development), using historical data and contemporary maps, which will be ‘field tested’ through on-site ecological measurements and fishing activities. This work will produce a migratory fish ‘Habitat Mapping Manual’ which provides information on the identification, habitat, distribution, historical trends and contemporary threats to migratory species.

Newly released sterlets. Image: Thomas Friedrich | MEASURES

Genetic conservation and re-stocking

Genetic conservation is a key issue in MEASURES, and breeding and restocking programmes will be led by the National Agricultural Research and Innovation Centre, Research Institute for Fisheries in Hungary, who will produce a ‘Genetic Conservation Manual’ detailing the process. Restockings of two key species have already taken place in April 2019, with 3000 juvenile sterlets released in Hungary, and 1000 Russian sturgeons released in Romania.

A second round of re-stockings are planned for the autumn as part of a public event. Cutting-edge methods for detecting the presence of rare Danube sturgeon using eDNA testing in river water will be deployed together with the Joint Danube Survey organized by the ICPDR.

“Conservational restocking is one of many necessary actions to save endangered fish. In conjunction with the provision and restoration of habitat it is essential to increase the number of animals of species and populations on the very brink of extinction”, says Thomas Friedrich, an aquatic scientist from BOKU.

A new Strategy for the Danube Ecological Corridor

The activities will be brought together at the end of the MEASURES project by BOKU in a ‘Strategy for the Danube Ecological Corridor’, which will focus on habitat connectivity as a key policy and management issue. Overall, the project will significantly advance our understanding of the Danube basin, the interdependence of sturgeon species and their freshwater habitats, and the threats they face.

There is significant Europe-wide appetite for co-operation and collaboration in conserving and restoring for sturgeons. We will follow the progress of MEASURES, and related projects, over the coming months and years.


MEASURES website

Illegal trafficking of the European eel: the ‘world’s greatest wildlife crime’

July 5, 2019
Glass eels from the River Shannon estuary in Ireland. Image: European Eel Foundation

The European eel is one of the most fascinating and mysterious freshwater fish in the world. Its lifecycle takes place across vast oceans: mature eels spawn in the Sargasso Sea in the North Atlantic, and their larvae drift on ocean currents for nearly a year towards European shores. When approaching the coastline, the larvae metamorphosise into a transparent ‘glass eels’ a few centimetres long. These glass eels enter river estuaries, grow into ‘elvers’ and begin migrating upstream.

Eels can take decades to reach maturity in freshwater rivers and lakes, before migrating downstream back out into the open ocean as adults to spawn. This remarkable spawning cycle has yet to be fully documented by scientists.

European eel populations are in severe decline. According to the IUCN, the number of eels entering European catchments has declined by 90% since the 1970s. This is partly due to obstructions such as dams, weirs and hydropower plants blocking the eels’ migration routes, and the loss of spawning habitats such as wetlands across Europe.

Other factors in eel declines include changes to oceanic currents, disease and parasites and pollution (particularly of PCBs). As a result, the European eel is now classified as ‘critically endangered’ by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

Operation Elver – a major 2018 operation by EUROPOL and SEPRONA to tackle illegal eel trafficking.

Clearly, there are many pressures on European eel populations at all stages of its lifecycle. However, recent evidence shows the increasing impact of illegal fishing and trafficking as a major factor in European eel declines. Whilst the export of European eels out of the European Union has been suspended since 2010, between 300 to 350 million eels – as much as 100 tonnes of fish – are illegally trafficked from Europe to Asia each year, according to EUROPOL. This figure accounts for around one-quarter of the total number of glass eels reaching the European coastline each year.

“Trafficking of the European eel is the world’s great wildlife crime in both traded individuals and market value. It affects 25% of the total stock of European Eel and is hampering the recovery of this precious species,” said Andrew Kerr, Chairman of the Sustainable Eel Group. “It is therefore vital that we stop all smuggling because it undermines every single effort used to establish adequate protection from other human impacts.”

Suitcases full of glass eels confiscated in Spain during ‘Operation Elver’ in 2018. Image: EUROPOL

Eels are a culinary delicacy in China and Japan, but when supplies of Japanese eels declined in the 1990s, Asian eel farming shifted to using European eels. Wildlife traffickers have responded to this demand by setting up illegal trade routes transporting live glass eels caught in estuaries across Europe to Asia.

The tiny eels are often smuggled in suitcases – each containing up to 50,000 fish – and transported by road and air to Asia. Here, they are grown on in fish farms to their full size. Because of the complexity of their lifecycle, European eels cannot be commercially bred in captivity, fostering the demand for glass eels which can be harvested and transported in huge numbers.

Where a glass eel might cost a euro to buy, a fully grown eel can be sold for ten times as much. This profit margin has led to an illegal trade in European eels estimated to be worth €3 billion each year. This trade has been called ‘the world’s greatest, yet least known, wildlife crime’ by the Sustainable Eel Group.

Eel is a delicacy in Chinese and Japanese cuisine. Image: Little MiMi | Pixabay Creative Commons

A press conference held last week in London announced that increasing law enforcement efforts to curb illegal eel trafficking have seized 15 million eels and made 153 arrests across the EU since last year. This figure represents a 50% rise in arrests compared to the year before. Convened at the Sustainable Eel Group’s 10 Year Anniversary Event, the press conference featured representatives from EUROPOL, the UK National Wildlife Crime Unit and Spain’s Nature Protection Service (SEPRONA), who are collaborating on the issue across Europe.

“This is our flagship operation in terms of environmental crime. All the arrests mentioned are in Europe with the majority from Spain, France and Portugal. The main actions have been taken from SEPRONA, they have led the way in Europe along with the Portuguese and French authorities,” said Jose Antonio Alfaro Moreno from EUROPOL.

“The people arrested in Europe are poachers, mules and members from other criminal networks. We have focused not just looking at trafficking glass eels as a single issue, but the wider criminal networks,” Moreno continued. “Year after year, more countries are joining our actions. For example, this year we are carrying out more work in Croatia, Czech Republic, Germany, Switzerland and Macedonia. For the next season, we want to follow the line of the inquiry into eel meat production in Asia and DNA traces. With this, we expect more countries to get involved with high ambition for action. The criminal groups learn and develop their methods, so EUROPOL need to stay one step ahead.”

An elver migrates across a Danish beach towards freshwater. Glass eels grow into elvers upon reaching European coastlines. Image: Willfried Wende | Pixabay Creative Commons

A 2016 study used DNA barcoding to prove that glass eels seized at Hong Kong International Airport were sourced in Europe, providing the first genetic evidence of the illegal eel trade between Europe and Asia. Advances in such technologies have the potential to support enforcement and prosecution, as well as facilitate international co-operation between European and Asian countries on the issue, the study – led by Florian Stein from the Technische Universität Braunschweig, Germany – suggests.

Earlier this year, researchers announced a new DNA testing method to identify illegally trafficked European eels, which has already led to the arrest and prosecution of smugglers in Hong Kong. The test – which is quick and costs around $1 dollar to administer – can identify a species from a meat sample, living specimen or even from environmental DNA in the water used to transport live eels. “This test works for anything with DNA,” said marine scientist Demian Chapman, one of the developers of the testing method. “The endgame for us is that this technology will be at every border checkpoint in the world.”

For now, European eel populations remain critically endangered across the continent, as these fascinating and mysterious fish are impacted by multiple pressures. The hope is that attempts to curb illegal smuggling of glass eels will complement wider conservation efforts to re-connect migration routes and restore habitats for eel populations.


European eel information on the IUCN Red List website

Sustainable Eel Group website

Lakes in the long term

June 27, 2019
Lake monitoring Windermere
Lake monitoring on Windermere in the Lake District, UK. Image: Stephen Thackeray

A guest blog by Dr. Stephen Thackeray, a lake ecologist at the Centre for Ecology & Hydrology.


A cold wind bites and stiffens fingers that deftly prepare the probe for its descent. Moments later the instrument slips through the surface and glides from well-lit to ever-darker waters, where it will gather important data on the living conditions experienced by the hidden life of the lake. This is a world unseen. A world of constant change, where warmth, light, nourishment and danger vary hugely in time and space. It is also a place of super-abundant life.

This event is the latest episode in a multi-decade scientific endeavour that has tracked the changing fortunes of some of England’s most iconic lakes in Cumbria; a landscape now endowed with UNESCO World Heritage Status. Data from this ongoing year-round research, initiated by the Freshwater Biological Association in the 1940s and continued by the Centre for Ecology & Hydrology since 1989, tells a story of long-term change in the physical, chemical and biological conditions of the lakes. In Windermere, it is a story of decades of nutrient enrichment caused by sewage inputs and agricultural run-off and, increasingly, a story of climate change.

The lake supports a bewilderingly complex web of life. Microscopic plants and animals, organisms that challenge our perceptions of what distinguishes these groups, along with larger invertebrates and fish coexist there. Competitors, predators, prey, cannibals, parasites. Environmental change affects them all.

Mesocyclops: a plankton species used to understand long-term changes in Lake District lakes. Image: Stephen Thackeray

Our long-term records allow us to trace these effects. Our lake monitoring has shown increases in algal growth in response to rising phosphorus concentrations, including increases in the prevalence of blue-green algae. Sediments accumulated in the darkest recesses of the lake interior provide us with an even longer-term view of these changes. Deposited ‘mud’, although opaque and turbid, provides a window into the distant past. Such records have clearly shown how changing wastewater treatment has affected the algae of the lake.

Though the fossil record suggests that blue-green algae have existed for billions of years, excessive growth can affect water taste and odour, raise treatment costs, and result in unsightly scums. Research at this iconic lake prompted sewage treatment improvements in the early 1990s, in order to address these issues.

Closterium plankton
Closterium plankton. Image: Stephen Thackeray

Over the same time period that the lake has been enriched with nutrients, it has also warmed. Even winter temperatures have been rising. With warming has come a shift in the underwater seasons, with spring plankton blooms shifting earlier in the year, as well as spawning times for perch. However, perch spawning times have not kept pace with changes in the seasonal timing of plankton food resources, meaning that larval perch may emerge out of sync with their main food resource.

This change in nature’s calendar might already be affecting the survival of the young fish. The fortunes of other fish species have been changing too. Over the same long time scales we have seen that catches of the cold-water Arctic charr, a fish similar to trout and salmon, have greatly declined, while numbers of warm-water roach and bream have increased.

Water flea
Bosmina, or ‘water flea’. Image: Stephen Thackeray

We have these exceptional records, objectively documenting ecological change more accurately than the shifting baselines of generational memories, thanks to the ongoing efforts and dedication of skilled field researchers. The Cumbrian lakes are sentinels, helping us understand the consequences of climate change, and other emerging environmental issues.

However, their relevance is not restricted only to northern England. Just as the species within these lakes are interconnected, so too are researchers across the world. Data and ideas flow through this network, as energy flows through a food web, creating opportunities to collaborate, learn, and build a global picture of how life beneath the water surface is changing.

As such, records from the Cumbrian Lakes are increasingly being used in large-scale scientific investigations into pressing environmental issues that will have global implications. Continuation of this vital work is more important than ever.


Dr. Stephen Thackeray’s research webpage.

Europe’s largest dam removal project underway on the Sélune River in France

June 20, 2019
Drilling the first hole in the 36-metre high Vezins Dam on the Sélune River
Drilling the first hole in the 36-metre high Vezins Dam on the Sélune River. Image: Roberto Epple-ERN | WWF

Europe’s largest dam removal project so far took a significant step forward last week as the first breach was made in the 36-metre high Vezins Dam in Normandy, France. The dam, located on the Sélune River, was been scheduled for dismantling in 2017, along with another 15-metre high dam, La Roche-Qui-Boit.

The removal of the dams is designed to reconnect migration routes for fish such as the Atlantic Salmon and European Eel, and to improve water quality in the river and re-naturalise flows of sediment through the Sélune catchment. The story here is indicative of global trends: a recent study suggests that only around one-third of global rivers are free-flowing – with dam construction a key factor in fragmenting and regulating water flows.

The La Roche-Qui-Boit and Vezins dams were built on the Sélune in 1914 and 1927 respectively. Before their construction, migratory fish could move throughout the river’s catchment between their spawning grounds in tributaries and headwaters and their feeding grounds out at sea. The dams provided an impassable obstacle for salmon, limiting their spawning grounds to a small area below the dams. Removal of the dams will open up 90km of the Sélune River to migratory fish, which is estimated to increase juvenile salmon habitat three-fold, and increase adult salmon numbers returning to the river by more than 1400.

The Vezins Dam on the Sélune River
The Vezins Dam on the Sélune River, which is being dismantled after nearly a century of operation. Image: Iwan Hoving | WWF

Large reservoirs of slow-moving water have formed behind the dam walls, where river sediments are prevented from moving downstream towards the river estuary at Mont St Michel. This has two linked ecological problems. First, the build-up of sediments and reduction in water flow can lead to algae blooms and reductions in water quality. Second, the dams disconnect natural sediment flows throughout the river catchment, altering how material and nutrients flow through the river system. In effect, dams don’t only fragment water flows along a river system, but also disconnect its ecosystems and their natural processes.

“The removal of the Vezins Dam signals a revolution in Europe’s attitude to its rivers: instead of building new dams, countries are rebuilding healthy rivers and bringing back biodiversity,” said Roberto Epple, president of European Rivers Network. “Nature can recover remarkably quickly when dams are removed and I look forward to watching salmon swimming past Mont St Michel and spawning in the headwaters of the Sélune for the first time since my grandparents were young.” Epple continued.

Mont St Michel at the estuary of the Sélune River
Mont St Michel at the estuary of the Sélune River. Image: morosphinx | Flickr Creative Commons

The Vezins and La Roche-Qui-Boit dams were both built around a century ago, and campaigners argue that they are now inefficient and obsolete, and that their environmental impact outweighs their ability to produce renewable energy. “There are tens of thousands of old, obsolete dams in Europe that can and should be removed,” said Arjan Berkhuysen, managing director of the World Fish Migration Foundation. “We are hopeful that by removing not only big dams like this but also by removing small barriers through local efforts we can restore these important life sources.”

A 2018 BBC Radio 4 programme interviewed some of the river restoration practitioners involved in the Sélune River project, outlining that the first phase of the project was to empty the lake above the Vezins dam, and stabilise its sediments. This process has now been completed, allowing for last week’s first breach of the dam wall itself. The smaller La Roche-Qui-Boit dam is due to be demolished in 2021.

The empty reservoir above the Vezins Dam following drainage
The empty reservoir above the Vezins Dam following drainage. Image: Roberto Epple-ERN | WWF

The dismantling of the dams on the Sélune River will provide a valuable case-study for environmental scientists and policy makers seeking to understand how river ecosystems respond to dam removal. The scientific project responsible for the dam removal has a 16 year ‘lifespan’ to monitor the river’s ecosystems for years to come. Similar large-scale projects, such as the removal of the 64-metre high Glines Canyon Dam on the Elwha River in Washington State, USA have resulted in increasing migratory fish populations, and the creation of new habitats due to naturalised sediment flows, both along the river and out into its estuary.

The Sélune River dam removal project has been opposed by some members of the local community, partly because of the recreation and tourism value of the lakes created above the dam walls. A recent analysis of the evolution of the Sélune project suggests that such discord stems from the difficulties of creating meaningful dialogue and ‘shared visions’ for the landscape in decision-making processes.

As the shifting-baseline theory suggests, what people might imagine as a defining feature of a place – such as a dam lake – can often be a relatively recent alteration to the landscape. What dam removal asks us to do – ecologically, politically, and aesthetically – is to imagine river landscapes unconstrained by human actions, and instead with resurgent ability to plot their own course. This, of course, is not always an easy process to get everyone on board with.

The Sélune project is taking place at the same time as major hydropower construction projects threaten the health and status of free-flowing rivers in Eastern Europe, and across the world. Clearly, despite this hopeful project there is significant work to be done in balancing the need for renewable energy with the critical need to conserve and restore freshwater biodiversity. We will follow these projects closely in the coming months.


The Sélune River Restoration Programme

Microplastics colonised by toxic plankton in brackish ecosystems

June 6, 2019
Microplastics under the microscope. Image: Chesapeake Bay Program | Flickr Creative Commons

Microplastic pollution is an increasingly widespread issue in both freshwater and marine ecosystems across the world. It is estimated that more than 8.3 billion tonnes of plastic has been created since the 1950s, with more than half of this figure produced in the last 13 years. Plastic pollution is an issue which spans terrestrial, freshwater and marine ecosystems: it is estimated that a fifth of the plastic entering the world’s oceans is transported by rivers.

Plastic fragments smaller than 5mm are known as microplastics. Research suggests that because of their potential uptake and transmission through food webs, microplastics prompt a significant, but poorly understood, threat to aquatic life.

A new study adds to this growing knowledge base, suggesting that microplastics are readily colonised by aquatic microorganisms, which could lead to the growth of toxin-producing plankton species.

Researchers from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) and the Leibniz Institute for Baltic Sea Research, Warnemünde (IOW) incubated polyethylene and polystyrene microplastics with natural microfauna at different stations in northern Germany: the Baltic Sea at Heiligendamm, the lower River Warnow and a wastewater treatment plant.

River Warnow at Rostock
The lower River Warnow at Rostock, close to one of the sampling sites in the study. Image: wolfro54 | Flickr Creative Commons

Their results, published in the Frontiers in Microbiology journal, show how microplastics act as valuable micro-habitats for microorganism colonisation, with over 500 different species observed from the 15-day experiment. The researchers suggest that a plastic item weighing one gram, floating in the sea, can support more living organisms than a thousand litres of surrounding seawater.

“Microplastics may represent a significant habitat and transport medium for microorganisms. Our experiments showed that microorganisms, such as Pfiesteria piscicida, enrich on plastic items, where they exhibit much higher densities than in the surrounding water or on driftwood,” said Dr. Maria Therese Kettner from IGB.

The dinoflagellate Pfiesteria piscicida highlighted by Dr. Kettner was the most common coloniser of microplastics in the study. It was observed at densities around fifty times as high as in the surrounding water, and around two to three times as high as on comparable wood particles.

Pfiesteria piscicida is a potentially toxic plankton species – its Latin name means ‘fish killer’ – which presents a significant threat to human and animal life at high concentrations. In addition, the dinoflagellate Heterocapsa – known for toxic ‘red tide’ blooms which can cause mass mortality of bivalves – was observed as another microplastic coloniser. In short, the study suggests that microplastic pollution may act as a catalyst for toxic plankton blooms.

Pfiesteria piscicida plankton
Pfiesteria piscicida – the toxic ‘fish killer’ plankton. Image: Alchetron Creative Commons

IGB researcher Prof. Hans-Peter Grossart, who led the study, highlighted another key finding: “Unlike natural substances such as wood or colonies of algae, microplastic particles decay extremely slowly, and may therefore transport the organisms they host over long distances.” In other words, microplastics may provide a durable dispersal medium for harmful microorganisms, which could potentially be carried over long distances by rivers and ocean currents.

“However, communities on microplastic particles often change when they ‘travel’ and adapt to their new environment,” said marine microbiologist Dr. Matthias Labrenz. “Therefore, these aspects need further investigation,” suggested the IOW researcher. Research and policy on ‘invasive’ aquatic species often focuses on transport mechanisms such as shipping: this study suggests that microplastics may act as a vector for introducing potentially harmful microorganisms into new environments.

The researchers raises a third issue, suggesting that colonised microplastics have the potential to change carbon, nutrient and energy dynamics in aquatic environments. Recent research suggests that cyanobacteria which have colonised microplastics exhibit increased photosynthetic activity. Dr. Kettner and colleagues suggest that since numerous algae species were detected in this study, an increase in photosynthetic activity in areas of microplastic pollution could be expected.

The research team highlight that colonised microplastic particles add to the overall load of organic aggregates in marine environments. Some of these particles are likely to be transported vertically between the sea surface and floor by ocean currents. As a result, the researchers suggest that microplastic colonisation observed in the study has the potential to affect the oceanic carbon pump and vertical fluxes of nutrients in marine environments.


Marie Therese Kettner; Sonja Oberbeckmann; Matthias Labrenz; Hans-Peter Grossart, (2019) “The eukaryotic life on microplastics in brackish ecosystems” Frontiers in Microbiology, 10 art. 538 (open-access)

Europe’s aquatic ‘life support system’: good ecological condition correlates with ecosystem service provision

May 23, 2019
Floodplains and wetlands are vital habitats for providing natural water purification and flood protection. Image: Quoc Viet | Creative Commons

European aquatic ecosystems can better provide vital services – such as water purification and flood protection – to humans when they are in good ecological condition, according to a new study. These findings highlight the need to protect and restore European waters, not only for the non-human lives they support, but also for the health and well-being of human communities.

Bruna Grizzetti and colleagues mapped European aquatic ecosystem services in relation to ecological conditions in rivers, lakes, groundwaters, coastal and transitional waters, floodplains, riparian areas and wetlands across the continent.

They found that there was a strong correlation between the delivery of regulating and cultural ecosystem services and good ecological condition. In other words, when aquatic ecosystems have abundant biodiversity, sufficient habitat and non-harmful chemical conditions, they are generally better at providing water purification, erosion retention, flood protection and coastal protection services. In addition, the authors suggest that recreation services – such as tourism – are generally increased in ecosystems with good ecological condition.

On the other hand, Grizzetti and colleagues found that provisioning services were correlated with poor ecological conditions. This is because their measure of provisioning services is based on water abstraction – an extractive process which is likely to negatively alter habitat and water availability in an ecosystem.

The relationship between ecosystem condition and ecosystem service delivery. Image: Grizzetti et al, 2019

What are ecosystem services?

Ecosystem services are the many and varied benefits that ecosystems provide to humans. They are grouped in four categories: supporting services (e.g. nutrient cycling), provisioning services (e.g. food production), regulating services (e.g. water purification), and cultural services (e.g. recreation opportunities).

The logic behind the ecosystem services concept is that if the wide-ranging benefits humans derive from the environment can be quantified and communicated, then the argument for conserving and restoring ecosystems will be strengthened.

The ecosystem services and environments considered in the study, highlighted in grey. Image: Grizzetti et al, 2019

Grizzetti and colleagues mapped six aquatic ecosystem services in their study: water provisioning, water purification (through nutrient retention), flood protection (by floodplains), natural coastal protection, and recreation value. For each service, measures of natural capacity (i.e. the potential of the ecosystem to provide the service), flow (i.e. the actual use of the service), sustainability (i.e. flow compared to capacity), efficiency and human benefits were calculated and mapped.

What is ecological condition?

The researchers calculated ecological condition across Europe using monitoring data for ecological status taken by Member States under the Water Framework Directive.

Ecological status is a measure of the abundance and composition of different organisms in a food web and the habitat and chemical conditions of an aquatic environment, and represents an integrative measure of the condition of the water body. Data on ecological status in 79,630 water bodies across the EU was used to map ecological condition in this study.

Mapping water provisioning (top row) and water purification (bottom row) services across Europe. Image: Grizzetti et al, 2019 (full-size image)
Mapping erosion prevention (top row) and flood protection (bottom row) services across Europe. Image: Grizzetti et al, 2019 (full-size image)

Good ecological condition promotes ecosystem service provision

The research team, supported by the Joint Research Centre of the European Commission and the EU FP7 projects MARS and GLOBAQUA, recently published their findings in an open-access paper in the journal Science of the Total Environment.

They suggest that their findings support calls to protect and restore aquatic ecosystems through the EU Water Framework Directive and Biodiversity Strategy, the United Nations Sustainable Development Goals (SDG 6 – Clean Water and Sanitation and SDG15 – Life on Land), and the Convention on Biological Diversity.

Study co-author Olga Vigiak said: “We mapped freshwater ecosystem services in Europe and put them in relation with the ecosystem condition. Regulating and cultural services (like water purification, erosion prevention, flood and coastal protection, and recreation) were correlated with good ecosystem status.

Conversely, provisioning services (i.e. water abstractions for domestic and economic activities) put pressure on aquatic ecosystems. The study supports the need to protect and restore aquatic ecosystems to ensure the delivery of vital ecosystem services in the future.”

A key takeaway point from this study is the extent to which daily human lives rely on healthy functioning natural environments. In an increasingly urbanised world, this connection is not always perceivable, but what Grizzetti and colleagues’ study shows is that aquatic ecosystems in Europe form a giant ‘life support system’ for both human and non-human communities. It is in all of our best interests to protect and restore them.


Grizzetti, B. et al (2019), Relationship between ecological condition and ecosystem services in European rivers, lakes and coastal waters, Science of The Total Environment, Volume 671, 25 June 2019, Pages 452-465

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