Freshwater life in the time of COVID-19
Life has been strange for all of us over this last couple of months. From all of us at the Freshwater Blog, we wish you and your loved ones all the best during these difficult times.
Given that lots of us have limited opportunities to visit, enjoy and learn about rivers and lakes right now, we thought this week’s blog would collate some of the digital ways we can immerse ourselves in freshwater life, at least for the time being.
Happy exploring, please do feel free to drop us a line on twitter @freshwaterblog with your favourites and suggestions.
Educational resources
The UK Rivers Trust have produced a suite of online educational tools, including virtual field trips and GIS training. As in the video above, visitors can take a virtual trip along the River Eden in Cumbria, undertaking their own field investigations and reports.
Tomorrow (9th May) is World Migratory Bird Day, and this site has lots of ideas for how you can join their ‘virtual festival’, including ‘Plover Watch 2020‘ on the banks of the Great Lakes.
This talk by Line Gordon, director of the Stockholm Resilience Centre, discusses water as “the bloodstream of the biosphere”. The talk was published as part of a Massive Open Online Course (MOOC), which can still be completed for free.
Other free freshwater MOOCs include the University of Geneva’s ‘International Water Law’ course, and International Waters’ ‘Governance for Transboundary Freshwater Security’ course.
Here’s some articles we’ve found useful on understanding the role of freshwater research during COVID-19. This Science article highlights the risks to aquatic environments posed by the disinfectant chemicals used to tackle COVID-19 outbreaks. This research from scientists at the University of California discusses water treatment strategies to tackle the SARS-CoV-2 virus responsible for the COVID-19 pandemic in sewage and drinking water.
This piece on the World Economic Forum website highlights the links between water, food security and COVID-19. The International Limnology Society and IGB have called for researchers to document the effects of lockdown on freshwater ecosystems under the #HealingInlandWaters tag.
Free books and journals
Many academic publishers and journals are opening access to their publications during global COVID-19 lockdown. This Project Muse page features a list of dozens of publishers who have temporarily made their content freely accessible. The journal portal JSTOR have also opened access to some of their collections.
Live streams
Live video streams have become a valuable way for people to engage with landscapes and ecosystems during lockdown. In fact, we have the live soundscapes of a few of them playing whilst we prepare this article – very soothing!
You might want to check out an osprey nesting on the Foulshaw Moss wetland, or perhaps look and listen for bitterns at Brockholes Nature Reserve, both in NW England. Sadly it’s the wrong time of year to watch bears catching salmon on waterfalls in Katmai National Park in Alaska, but there are some incredible highlights to catch up on!
The Explore website hosts some amazing live streams of African landscapes. We love watching animals coming and going at a watering hole in Tembe Elephant Park, South Africa (at the moment there’s a warthog… but you can spot lions, leopards, black and white rhinos and buffalo, apparently).
At another watering hole in the Madikwe Game Reserve on the Marico River you might spot elephants, giraffes, lions, zebras, and cheetahs along with a host of wetland birds. Crocodiles and hippos are regularly seen on this stream of the Olifants River in South Africa, whilst this camera on a watering hole in the Sabi Sand Game Reserve has infrared technology, allowing you to watch wildlife through the night!
Videos
The Blue Heart documentary explores the issue of hydropower construction on Europe’s ‘last wild rivers’ in the diverse Balkan region. Produced in conjunction with the River Watch initiative, the film is timely, informative and beautifully shot. Along similar lines, the River Film Festival organised by flow:europe and the Living Rivers Foundation hosts numerous trailers of the innovative films they have shown in the past.
The WWF Freshwater Program has a range of videos documenting their important conservation and restoration work across the world. We especially like this clip about building snow banks for endangered freshwater seals in Finland.
The Stroud Center’s Stories from the Streams series follows scientists, educators and the public in exploring the Delaware River Watershed in the USA. The stories might be local, but the issues raised are global in scope.
We love Jack Perks’ incredible underwater photography and film-making (so much so, we’ve interviewed him in the past). Watch his documentary on every UK fish above, and explore his video archive here.
Podcasts
We love the Society for Freshwater Science’s Making Waves podcast – this episode on freshwater research in Arizona border landscapes is especially good. The Freshwater Trust’s Freshwater Talk podcast is worth tuning into, we particularly like the episode with conservationist and artist Frances B Ashforth.
In this episode of the Science History Podcast, Ian Harrison, the freshwater specialist at Conservation International’s Moore Center for Science discusses contemporary freshwater conservation. And in this episode of People Behind the Science Podcast, Prof. Steve Ormerod (well known to readers of the blog!) discusses his life and career in freshwater research. Both are essential listens!
Maps
In 1944, the cartographer Harold Fisk published a series of remarkable maps of the winding historical courses of the Mississippi River as part of an otherwise technocratic report to the US Army Corps of Engineers. Each map – which can be viewed and downloaded in hi-resolution here – is like a work of modern environmental art.
More recently, Hungarian cartographer Robert Szucs has fused his skill with GIS mapping and his artistic flair to create a series of beautiful images mapping the world’s watersheds. Each watershed is denoted by a different colour, lending a kaleidoscopic – but scientifically accurate – effect to his images.
Art and music
We’ve featured two of our favourite aquatic artists on the blog recently: Michel Roggo and Jacek Matysiak, and their work is always worth revisiting. The UK Canal & River Trust Waterfront online magazine is worth exploring for art, sound and writing, as is the Caught by the River blog.
Finally, we’ll leave you with two and a half hours of the most beautiful soundscapes. Recorded over three years, sound artist Annea Lockwood’s A Sound Map of the Danube traces the second longest European river’s course from the Black Forest in Germany to its delta into the Black Sea. The recordings comprise sounds from the banks, from above and below the water, animals, insects, and interviews with people who live by the river.
A guest blog by Daniel Hayes from the Institute of Hydrobiology and Aquatic Ecosystem Management (IHG), BOKU, Vienna.
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Imagine you are a river basin manager and have to decide on the best methods to assess the water quality of the streams and rivers in your catchment. What would you choose? Considering that in the European Union alone, there are over 300 different biological assessment methods, this is surely not an easy task!
In numerous countries across the world – especially developing countries – many people depend directly on river water for drinking, domestic purposes, crop irrigation and providing water to animals (see picture above). Even though these activities require appropriate water quality to be used safely, many river systems are under severe pressure due to human activities. Microbial fecal pollution of river water from sewage waste, for example, can often have wide-ranging negative implications for public health.
Fecal and biotic indicators of water quality
Fecal ‘indicator bacteria’, such as Escherichia coli and enterococci are commonly used to assess pollution levels in aquatic environments. Measuring the abundance of these indicator bacteria allows conclusions to be drawn regarding the public health risks associated with river water use. These assessments, however, require extensive laboratory equipment and finances, which might not be available in all situations.
One alternative to fecal indicator bacteria are biotic indicators such as benthic macroinvertebrates (aquatic insects). Biotic indicators can provide an integrative and cumulative measure of ecosystem health based on the combined responses of communities to stressors in the aquatic ecosystem. Such benthic macroinvertebrate assessment systems have been recently developed and tested in Ethiopia.
Assessing water quality indicators in Ethiopian rivers
In light of the need to compare the performance of different approaches for assessing water quality status, a team of Austrian, Ethiopian and Tanzanian researchers have recently published a new study.
They evaluated the consistency of fecal indicator bacteria for environmental health assessments of rivers by comparing them to assessments of physicochemical tests, as well as to macroinvertebrate indices. The scientists sampled five sites along a land-use pressure gradient on the Upper Awash River, the headwater section of one of the most important river basins in Ethiopia.
The results were shocking: the concentrations of two tested fecal indicator bacteria (E. coli and enterococci) exceeded the standards set by the European Union and the World Health Organization for safe recreational water. Hence, all sites were categorised as ‘poor’ for swimming and recreation.
According to the World Health Organization, this classification is associated with a >10% chance of gastroenteritis per single exposure. Hence, even though these guidelines pertain primarily to recreational activities such as swimming, it can be assumed that the low bacteriological water quality may also have adverse impacts on human health if water is used for the irrigation of fresh produce, drinking or domestic purposes.
Fecal and biotic indicators produce contrasting water quality assessments
Surprisingly, in contrast, the three tested African benthic macroinvertebrate indices (from South Africa, Tanzania, and Ethiopia) indicated a natural or good ecological status with slight ecological degradation at the upstream sites, and a moderate to poor status at the downstream sites. Hence, the macroinvertebrate indices reflected changes in land-use from natural forests in the headwaters to highly modified agricultural landscapes in the lower reaches.
“Considering the high values of fecal indicator bacteria, the use of river water may cause significant public health hazards, particularly to young, elderly or immunocompromised people,” says lead author Geda Kebede. “In light of this risk, it is important to establish appropriate management measures,” Kebede recommends.
Such measures could include immediate actions such as informing the public about the risks associated with water uses, or more long-term actions such as reducing fecal pollution sources. Livestock grazing in the Upper Awash River basin is a key driver of fecal indicator bacteria contamination in the river ecosystem. Therefore, solutions could include preventing cattle from entering the river zone, providing off-stream watering, and restoring riparian vegetation as buffer zones.
Summarising, this is the first study of its kind reporting the different results of water quality status assessments using fecal bacteria and macroinvertebrate indicators. Consequently, from the viewpoint of river basin management, it seems necessary to combine different indicator systems to analyse human pressures from a more holistic perspective.
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Are Pablo Escobar’s hippos restoring ‘lost’ ecological processes to Colombian freshwaters?
When Pablo Escobar died in 1993, the drug kingpin left behind – amongst other things – a private zoo on his Hacienda Nápoles estate in northern Colombia. Whilst Escobar’s elephants, lions, giraffes and other animals were transported to other zoos when the estate was seized by the Colombian government after his death, four hippopotamuses were left behind.
The hippos – of which Escobar was said to be particularly fond – were deemed too dangerous and aggressive to move, and were left where they were. As the estate became neglected and overgrown, the hippo population at Hacienda Nápoles grew, gradually colonising artificial lakes and the Magdalena River.
It is now estimated that there are between 50 and 80 feral hippopotamuses living in Northern Colombia, with sightings of the animals taking place nearly 100 miles away from Hacienda Nápoles. One study suggests that by 2050, the wild Colombian hippo population could rise to between 800 to 5,000 animals.
Hippos are not a ‘native’ species in Colombia: there is no historical record of their presence here, or indeed anywhere in the Americas. The Hacienda Nápoles hippos have thus been called “the world’s largest invasive animal.”
There are ongoing debates about the ecological impacts of the hippo poplution on freshwater ecosystems around Hacienda Nápoles. Hippos are ‘ecosystem engineers’, meaning their activities modify and maintain the environments in which they live.
In Africa, this can have positive ecological impacts: hippos bring significant amounts of nutrients in freshwater habitats by depositing faeces after grazing on surrounding grasslands, often supporting aquatic biodiversity. However, too much hippo faeces can cause water bodies to become toxic and eutrophic, and the sediment they stir up can further reduce water quality.
Either way, it appears that, for now at least, the Hacienda Nápoles hippos are here to stay – not least because removing them would be such a difficult and potentially dangerous operation. However, an innovative new study suggests that despite their ‘invasive’ tag, the Colombian hippos may be restoring ecological processes which have not been present for over 11,000 years to the freshwaters they colonise.
Writing in PNAS, a research team led by Erick Lundgren, argue that introductions of large herbivores – such as the Colombian hippos – have restored ecological processes relative to those found in the Late Pleistocene (roughly 130,000-11,000 years ago) in a number of landscapes globally.
The authors argue that the hippos share numerous ecological traits with an extinct giant llama species, Hemiauchenia paradoxa, which once grazed Colombian grasslands. The hippos also share traits and habitat with a large semi-aquatic rhino-like mammal called Trigonodops lopesi.
The authors compared key ecological traits such as body size, diet, fermentation type and habitat in herbivore species which lived before the widespread Late Pleistocene megafauna extinctions, more than 11,000 years ago.
“This allowed us to compare species that are not necessarily closely related to each other, but are similar in terms of how they affect ecosystems,” Lundgren, a PhD researcher at the University of Technology Sydney (UTS) Centre for Compassionate Conservation (CfCC), said. “By doing this, we could quantify the extent to which introduced species make the world more similar or dissimilar to the pre-extinction past. Amazingly they make the world more similar,” Lundgren added.
In neither case do the Colombian hippos share all their ecological traits with their extinct counterparts. The giant llama (Hemiauchenia paradoxa) did not live in aquatic habitats, and the rhino-like mammal (Trigonodops lopesi) does not share the hippos’ digestion characteristics.
The point the study authors make, however, is that the ‘invasive’ Colombian hippos and other species across the world are restoring ecological processes to landscapes where they have been lost due to the extinction of large herbivores thousands of years ago. A process-led approach to environmental restoration has been advocated by initiatives such as the Pleistocene Park in Northern Siberia.
As is often the case in debates over the ‘nativeness’ and ‘invasiveness’ of different species, the impulse to look to historical ecosystems to set baselines for conservation and restoration can often reveal a complicated and dynamic ecological reality. Viewed through the lens of the study, the ‘invasive’ hippos could be understood as participating in an inadvertent functional ‘rewilding’ of the Colombian freshwater ecosystems.
Senior author Dr. Arian Wallach from the UTS CfCC says, “We usually think of nature as defined by the short period of time for which we have recorded history but this is already long after strong and pervasive human influences.”
“Broadening our perspective to include the more evolutionary relevant past lets us ask more nuanced questions about introduced species and how they affect the world. We need a complete rethink of non-native species, to end eradication programs, and to start celebrating and protecting these incredible wildlife,” Dr. Wallach said.
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Water temperature is an important variable in lake ecosystems across the world. Variations in water temperature influence a wide range of environmental patterns and processes, including species distributions, growth rate, phenology, food webs, and greenhouse gas emissions.
Predictions of future climate change suggest that lake temperatures are likely to warm in many places, altering ecosystem health and functioning. Understanding and modelling lake water temperatures is thus a key step for freshwater scientists working on climate change resilience and adaptation.
However, until now, there has been no global classification of water temperature into ‘lake thermal regions’ to support this work. A newly published study in Nature Communications addresses this shortfall.
Professor Stephen Maberly from the Centre for Ecology & Hydrology, UK and colleagues used satellite data to identify nine different lake thermal regions across the world. They grouped global lakes based on seasonal patterns of their surface water temperatures. The coldest thermal region includes lakes in Alaska, Canada, Siberia and China, and the warmest covers lakes in equatorial South America, Africa, India and south-east Asia.
“Thanks to cutting-edge analysis using satellite images of more than 700 lakes, taken twice a month over 16 years, we produced the first global lake temperature classification scheme,” says Prof. Maberly. “By combining this with a lake model and climate change scenarios we were able to identify that northern lakes, such as those in the UK, will be particularly sensitive to climate change.”
The study is the result of a collaboration between researchers from the Universities of Dundee, Glasgow, Reading and Stirling and the Dundalk Institute of Technology.
The research team used climate change models to predict that under the most extreme climate change scenario (Representative Concentration Pathway 8.5), global lakes would be on average 4°C warmer, and 66% would be classified in a warmer thermal regime. Under low (RCP 2.6) and medium (RCP 6.0) future climate change scenarios, 12% and 27% of lakes would be shifted into warmer thermal regimes.
Under the most extreme climate change scenario, the research team predict that there will be a 79% reduction in the number of lakes in the coldest and northern-most thermal regime by 2100. In other words, warmer waters due to extreme climate change could cause the disappearance of over three-quarters of unique sub-polar lake ecosystems over the next century.
Even if climate change is less extreme than this scenario, there are still likely to be negative effects on cold-water species and ecosystems. “Cold-water fish species in particular can be stressed by warmer temperatures,” explains Prof. Maberly. “The potential negative impact on salmonids such as salmon, trout and Arctic charr, for example, is concerning because they play a central ecological role within food webs and also have great economic importance.”
Professor Andrew Tyler of the University of Stirling, who led the overall project, GloboLakes, says, “This is an example of pioneering UK-led research that has delivered the capability to monitor our inland waters at the global scale from satellite based platforms. This is not only yielding new insights into the impacts of climate change, but also the evidence base from which to better manage these ecologically sensitive environments and mitigate against the effects of change.”
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An app to classify lakes into the nine thermal regions is available in the R programming language at GitHub.
Climate change is increasing the frequency and intensity of extreme weather across the world. High winds and heavy rain during storm events can significantly affect freshwater systems. However, what is not yet fully understood is how extreme weather affects the health of lake ecosystems.
Freshwater scientists know that storms can alter physical processes in lakes such as water flows from tributaries, mixing in the water column, sediment disturbance and water temperature. At the moment though, scientists only have a limited understanding of how ecological processes – particularly those involving algae at the base of food webs – are affected by storms.
A new study from a global team of scientists warns that lakes around the world may undergo significant ecological shifts in response to extreme storms as a result of ongoing climate change. They state that there is a pressing need for research to inform adaptive conservation strategies.
“Though it is clear that storm events can affect water quality and wildlife in lake ecosystems, we need to develop a clearer understanding of where and when the impacts of these events might be most and least severe,” said co-author Dr. Stephen Thackeray from the Centre for Ecology and Hydrology, UK.
“If extreme weather events significantly change carbon, nutrient, or energy cycling in lakes, we better figure it out quickly,” said lead author Dr. Jason Stockwell, from the University of Vermont, USA, “because lakes can flip, like a lightbulb, from one healthy state to an unhealthy one – and it can be hard or impossible to flip them back again.”
Extreme weather and algae communities in lakes
The new open-access study, written by Dr. Stockwell and 38 co-authors, is published in the Global Change Biology journal. It focuses on algae – or phytoplankton – the microscopic organisms which support virtually every freshwater food web. Phytoplankton are vital in lake ecosystems as they take up carbon dioxide, make carbohydrates, and release oxygen using sunlight through photosynthesis. Phytoplankton are also a valuable food source for many aquatic animals.
So how might we better understand how phytoplankton – and by extension, wider lake ecosystems – respond to extreme storms?
The study authors reviewed and collated evidence from thousands of existing scientific studies. They found that only 31 studies have ever investigated the effects of storms on phytoplankton communities, and that their results provide no clear picture of the relationship. Similarly, there appeared to be no clear trends in how phytoplankton responses differ by storm types, in different lake ecosystem types, or at different times of year.
A framework for understanding the effects of storms on lake ecosystems
In response, the authors develop a framework for understanding the effects of storms on lake ecosystems, in an effort to encourage and guide future research. The framework shows that the impact of storm events on lakes is not simply the result of storm strength at one point in time and space. Instead, a watershed-scale approach is required to map the different relationships between storm, lake and watershed attributes.
As the paper’s conceptual framework (above) shows, the extent to which a lake ecosystem is affected by storm events depends on the characteristics of the storm, lake and watershed. These in turn influence lake conditions such as nutrient pollution and sediment movement during the storm event.
These altered lake conditions can then influence the dynamics of phytoplankton and zooplankton at the base of the food web, which can then cascade through higher trophic levels of the ecosystem, potentially altering its health and functioning.
“This paper provides a compelling framework on understanding both direct and indirect effects of storms on lake ecosystems,” said co-author Dr. Lisette de Senerpont Domis from the Netherlands Institute of Ecology. “In a wind exposed delta area such as the Netherlands with a lot of shallow lakes impacted by agriculture we will likely experience some of the negative impacts of storms, such as algal blooms.”
New research collaborations and lake monitoring
The authors call for major new interdisciplinary collaborations to research storm impacts on lake ecosystems through networks such as the Global Lake Ecological Observatory Network. They outline the value of integrating watershed and lake physical models with biological models to better predict lake ecosystem responses to storms. They also highlight the importance of expanding long-term lake monitoring schemes, and using sensors that provide detailed data on ecological parameters during storm events.
“The framework we outline provides exciting opportunities for researchers from different disciplines to work as teams to identify the conditions and mechanisms by which storms are likely to have negative impacts on lake ecosystems,” said Dr. Stockwell. “We must quickly learn more—so we can better respond to the very real and pressing threat of climate change on lakes around the world. Without healthy lakes, we are sunk,” he said.
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An Emergency Recovery Plan for global freshwater biodiversity
2020 could be a pivotal year for the future of Earth’s biodiversity. In November, the world’s governments will meet at the Convention on Biological Diversity (CBD) conference to agree a new global deal to conserve and restore biodiversity.
Global freshwater biodiversity is in particular need of stronger and more effective policy and conservation action. Despite covering less than 1% of the Earth’s surface, freshwater ecosystems support around 10% of all known species, including one-third of all vertebrate species.
However, freshwater biodiversity has collapsed in recent decades. Freshwater species populations have declined by 83% globally since 1970, according to the 2018 WWF Living Planet Report, and now 27% of the freshwater species assessed for the IUCN Red List are threatened with extinction. It is estimated that freshwater habitats host more species per square kilometre than their land or oceans counterparts: yet freshwaters are suffering biodiversity declines two-to-three times faster.
WWF estimates that around 30% of global freshwater ecosystems have been lost since 1970. It’s not just plants and animals that rely on freshwaters – they’re vital for humans too, variously providing water, food, livelihoods, and flood and drought protection.
A major new scientific paper published in BioScience last week outlines an Emergency Recovery Plan for freshwater biodiversity declines, designed to influence discussions at the CBD conference in November. Developed through collaborations between scientists from WWF, International Union for Conservation of Nature (IUCN), Conservation International, Cardiff University and other institutions, the paper outlines a six-point plan to ‘bend the curve’ of global freshwater declines.
Based on contemporary scientific research and conservation strategies, the six key themes of the paper emphasise solutions for positive environmental change. They provide explicit recommendations for improving freshwater conservation and restoration in international agreements, particularly the CBD and the UN Sustainable Development Goals.
“Nowhere is the biodiversity crisis more acute than in the world’s rivers, lakes and wetlands – with over a quarter of freshwater species now heading for extinction. The Emergency Recovery Plan can halt this decades-long decline and restore life to our dying freshwater ecosystems, which underpin all of our societies and economies,” said Dave Tickner, WWF-UK Chief Freshwater Advisor and lead author on the paper.
The six themes of the Emergency Recovery Plan are: letting rivers flow more naturally, reducing pollution, protecting critical wetland habitats, ending overfishing and unsustainable sand mining in rivers and lakes, controlling invasive species, and safeguarding and restoring river connectivity through better planning of dams and hydropower.
“The causes of the global collapse in freshwater biodiversity are no secret, yet the world has consistently failed to act, turning a blind eye to the worsening crisis even though healthy freshwater ecosystems are central to our survival. The Emergency Recovery Plan provides an ambitious roadmap to safeguarding freshwater biodiversity – and all the benefits it provides to people across the world,” said co-author, Professor Steven Cooke of Carleton University in Canada.
The Emergency Recovery Plan aims to influence global environmental policy in three ways. First, it recommends maintaining existing elements of agreements that are already aligned to the Recovery Plan, such as CBD Aichi target 9 on invasive species and SDG 6 on clean water and sanitation.
Second, it recommends amending or extending existing targets or indicators so that they better align with the Recovery Plan. For example, CBD Aichi target 11 and SDG 15.1 both aim to increase the extent of conserved and restored habitat, but the geographic scale of their designations don’t always suit the wide range of freshwater habitats – from vast river catchments to tiny ponds. Improving these designations could help improve how freshwaters are managed and protected by global policy.
Third, the Recovery Plan identifies major gaps in policies where key freshwater issues are overlooked or underrepresented. For example, there is currently no recognition of alterations to water flows and levels in the CBD Aichi targets.
Cutting-edge freshwater research is increasingly untangling the multiple pressures that affect the health of aquatic ecosystems, and it is vital that this knowledge is translated into policy. To achieve this globally, the authors highlight the need for better collaborations between policy makers, governments, NGOs, researchers, managers and wider stakeholders, all driven by the common desire to halt freshwater biodiversity declines.
“It would be easy to interpret this work as a further message of freshwater doom but it is in fact the opposite. It is a forward-looking plan, with specific areas of action, for how to address the 21st century challenges that our freshwater ecosystems face. It presents an opportunity for us to change the trajectory of biodiversity decline in turn supporting the health of the planet and the livelihoods of people,” said co-author, Ian Harrison, from the Moore Center for Science.
“We have the last opportunity to create a world with rivers and lakes that once again teem with wildlife, and with wetlands that are healthy enough to sustain our communities and cities, but only if we stop treating them like sewers and wastelands,” said Tickner. “This decade will be critical for freshwater biodiversity: countries must seize the chance to keep our life support systems running by ensuring freshwater conservation and restoration are central to a New Deal for Nature and People.”
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David Tickner, Jeffrey J Opperman, Robin Abell, Mike Acreman, Angela H Arthington, Stuart E Bunn, Steven J Cooke, James Dalton, Will Darwall, Gavin Edwards, Ian Harrison, Kathy Hughes, Tim Jones, David Leclère, Abigail J Lynch, Philip Leonard, Michael E McClain, Dean Muruven, Julian D Olden, Steve J Ormerod, James Robinson, Rebecca E Tharme, Michele Thieme, Klement Tockner, Mark Wright, Lucy Young, (2020) “Bending the Curve of Global Freshwater Biodiversity Loss: An Emergency Recovery Plan”, BioScience, https://doi.org/10.1093/biosci/biaa002
Insect populations on German stream have declined by 81% since 1960s due to climate change
Insect populations are in big trouble. A number of recent scientific studies have documented insect declines across the world, prompting a 2019 meta-analysis of the evidence by Dr. Francisco Sánchez-Bayo and Dr. Kris Wyckhuys to conclude that “almost half of [insect] species are rapidly declining and a third are being threatened with extinction.”
Aquatic insects – which number more than 55,000 species – are important in many freshwater food webs, with species found everywhere from tiny puddles to large rivers and lakes. However, like their terrestrial counterparts, aquatic insect populations are in decline, largely due to the effects of intensive agriculture, water pollution and, increasingly, climate change.
However, researchers have often found it hard to disentangle the effects of climate change on insect populations from those of other stressors. In this context, a new study uses a unique long-term dataset from a German stream located in a nature reserve to isolate the effects of a changing climate on the stream’s insect communities since the 1960s.
Their findings are startling. Writing in Conservation Biology, the research team state that insect abundance on the Breitenbach stream declined by 81.6% between 1969 and 2010. Over this period, water temperature in the stream increased by 1.88°C, and there was a general shift towards low water flows in increasingly dry years. Their study suggests that climate change has already significantly impacted freshwater ecosystems, even in protected areas where agricultural and urban stressors are minimal.
Lead author Dr. Viktor Baranov explains, “Our analysis is based on a unique long term dataset collected by the scientists at the Schlitz river station on the Breitenbach stream from early 1960 – though our particular dataset only starts in 1969 – until 2010. This dataset is uniquely detailed and based on the weekly collection of the aquatic insects from the large, greenhouse like emergence-traps installed over the stream and parts of the riparian zone.
“The Breitenbach is a tiny stream: 6.3km in length, with a catchment area of 8.3 km². It flows to the Fulda river, with entirety of the catchment sitting in the Breitenbach valley nature conservancy area. The site was therefore sheltered from direct anthropogenic impacts such as agricultural development and industrial pollution during the period of observation. Therefore, the dataset offered us a disentangled view of the climate change impacts on this freshwater ecosystem.”
The study is the result of a collaboration at the Department of River Ecology and Conservation, Senckenberg Research Institute and Natural History Museum Frankfurt, Germany between Dr. Baranov, Dr. Jonas Jourdan, Dr. Francesca Pilotto and Dr. Peter Haase, alongside Prof. Rüdiger Wagner from the University of Kassel, Germany.
Dr. Baranov outlines the importance of studying insects as a means of understanding wider environmental change, “Aquatic insects are providers of crucial ecosystem services such as river water purification, fertilisation of flood plains, and food sources for many other animals. They are therefore generally an ‘engine’ of lowland and riverine ecosystems. We can thus learn a lot about the state and health of the environment by observing changes in insect diversity and numbers.
“Environmental changes have led to the decrease of the aquatic insects by 81.6% in the Breitenbach stream. But we also observed an increase in richness (+8.5%), Shannon diversity (+22.7%), evenness (+22.4%) and inter-annual turnover (+34%). Moreover, the community’s trophic structure and phenology has changed: the duration of emergence increased by 15.2 days while the peak of emergence moved 13.4 days earlier.
Additionally, the trophic structure of the community has altered drastically: grazer, scraper and gatherer–collector species have decreased significantly in their relative abundance, while passive filter feeders and predators have increased. Increased temperatures and increasingly dry years appear to be the chief drivers of change in the insect community.”
Decades of intensive study at the Schlitz river station generated the rich datasets which allowed the researchers to analyse the environmental effects of climate change in the stream over time.
Dr. Baranov emphasises the importance of such ongoing long-term studies, stating, “Our findings would have been missed in shorter datasets, as most of the observed effects span decades. This study illustrates the value of the long term datasets in the study of the climate change effects on the freshwater communities, and the complex – and often non-linear – nature of community responses to the global climate crisis.”
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9th European Pond Conservation Network Conference announced
A note from Dr. Richard Walton:
We are thrilled to announce the 9th European Pond Conservation Network Conference which will be held at University College London over 18-22 May, 2020.
Responding to the considerable need to conserve European ponds, the conference will combine pond biology, hydrology and landscape ecology with pond conservation practice. We welcome and encourage both scientists and conservation practitioners to attend and present their observations.
Please visit the conference website for further information, registration details and to submit an abstract. The deadline for abstracts is 28th February 2020 and the Early Bird deadline for registration is 20th March.
We hope to see you at the meeting – a four-day celebration of ponds and pond people!
Kind regards,
Could listening to the underwater sounds made by freshwater life help us better document and protect aquatic ecosystems? A new special issue of the Freshwater Biology provides intriguing evidence to suggest that it could.
Acoustic monitoring has emerged as a key tool for ecologists and conservationists in recent years. Bioacoustics (the study of sounds produced by or affecting living things) and ecoacoustics (the study of environmental sounds relating to ecosystem processes) continue to grow in popularity as approaches to ecological monitoring.
These approaches centre on the idea of passive acoustic monitoring, or PAM, where researchers place autonomous acoustic sensors (aka microphones) in study sites to capture sound recordings of the environment over time.
The recordings – whether transcribed by human researchers listening back, or by computer algorithms – can then be used to calculate biodiversity metrics such as species abundance, behaviour and phenology. Technological advances increasingly make PAM an affordable, long-term and non-invasive ecological sampling approach for researchers: a ‘listening ear’ on a changing world.
However, the use of such acoustic monitoring techniques has yet to be fully explored or adopted in freshwater systems. The new special issue, edited by Dr Simon Linke, Dr Camille Desjonqueres and Dr Toby Gifford, outlines the opportunities acoustic monitoring offers to freshwater researchers and conservationists, in an effort to raise awareness of its potential.
“Monitoring freshwater ecosystems is time consuming and costly. Using acoustics enables us to observe what is going on 24/7,” says Dr Desjonqueres. “We took over the editorial desk of Freshwater Biology for an issue,” Dr Linke continues. “We invited the biggest names in the field to help us tackle some of the key steps towards operationalising acoustics in the freshwater realm.”
The special issue contains nine studies that investigate underwater acoustics (including the work by Ben Gottesman and colleagues which we covered last year), and three studies on water birds and frogs. Tracing a lineage of describing underwater sound back to Aristotle, the editors identify six key challenges for the widespread uptake of freshwater ecoacoustic monitoring.
1. Characterising sounds and linking them to organisms and ecosystem processes
Four main groups of freshwater organisms are known to produce sounds: amphibians, crustaceans, fish and insects. However, it is rare that researchers can visually identify the source of different sounds in underwater environments. Lowering a hydrophone beneath the water’s surface can be a surprising and disconcerting experience: the listener becomes immersed in the invisible soundworlds created by aquatic life. How might such soundscapes be translated into useful ecological metrics?
The editors highlight the need for more comprehensive catalogues of the sounds of freshwater life, which could offer researchers ‘reference recordings’ to compare to their own studies. In this issue, two studies develop such ‘soundtype references’ in Costa Rica and Northern Australia.
2. Improving automatic sound detection and analysis techniques
In addition to better identifying and cataloguing freshwater sounds, the editors highlight the need to improve how recordings are processed and analysed. Autonomous sound recorders have the potential to generate a lot of data, particularly if multiple recorders are used over an extended period.
Manual transcription of these recordings – whether through listening, or the use of visual spectrograms – is thus time-consuming. As such, automatic sound recognition technologies – which can identify organisms based on their sonic signatures – are needed.
In this special issue, two papers develop the basis of what editor Dr Gifford calls a “Shazam for fish” by documenting the calls of different species of piranhas in Peru, and the spawning calls of ‘love-sick’ burbot in northern Canada. Another study develops an automated detection algorithm for the underwater vocalisations of the spadefoot toad, whilst another uses a deep learning algorithm to acoustically detect the highly-endangered white-bellied heron in Bhutan.
3. Archiving and sharing freshwater acoustic data
As researchers make advances in identifying aquatic life through sound, it is important that their data is archived and shared amongst the global scientific community, the editors state. They write that, “While the Cornell Lab of Ornithology’s Macaulay Library contains some fish sounds (982, which represents 0.25% of all calls), these are mainly marine and from the 60s and 70s.”
Initiatives such as the Freshwater Information Platform are driving forward open-access sharing of datasets, and perhaps there is scope to develop their sound libraries in the future.
4. Understanding acoustic patterns across landscapes
The way that ecosystems and biodiversity vary across landscapes is called spatial heterogeneity by ecologists. Traditional ecological surveys account for spatial heterogeneity in their design, often by replicating study methods in different areas of a landscape.
The editors suggest that ecoacoustic methods have yet to adopt similar approaches. They suggest that this is due to the volume of data generated by ecoacoustic methods and the demands it places on computer analysis systems. In this issue, one paper uses a regular spaced set of hydrophones to show that acoustic activity of aquatic insects (Hempitera sp.) is higher in open water than vegetated areas.
5. Understanding acoustic patterns over time
Ecoacoustic methods offer researchers the potential to monitor ecosystems over long timescales, offering an insight into the diurnal and seasonal patterns of life that occur in them.
Two studies in the issue (here and here) highlight nightly aquatic insect activity patterns. The editors suggest that studies which seek to identify aquatic animals by their calls should focus on such times of day when activity is highest.
6. Making links between sound and ecological health
The end goal of all ecological assessments is to understand the ecological health and condition of a landscape. Whilst there are limits to the scope of this in freshwater environments (e.g. only 20% of fish are soniferous), the editors highlight three useful approaches.
First, changes in aquatic sound can indicate changes to the wider ecological community. Second, ecoacoustics can help us understand the effects of noise on aquatic ecosystems. Third, ecoacoustics could help the automatic detection of invasive species – such as the round goby – reaching an ecosystem.
Clearly, ecoacoustic techniques offer new opportunities for freshwater scientists and conservationists seeking to understand and protect aquatic ecosystems, and the wide-ranging and innovative studies in this special issue highlight their rich potential.
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Microplastic pollution could inhibit stream ecosystem functioning
Could plastic pollution affect how a stream ecosystem functions? According to a newly published study, the answer is yes.
Plastic pollution is rapidly growing in visibility as one of the key environmental concerns of this ‘Anthropocene’ age. Researchers around the world are increasingly focusing their efforts on understanding the effects that plastics – and particularly microplastics – might have on aquatic ecosystems.
As yet, however, this work has been largely focused on seas and oceans. Whilst there is a growing body of research on the effects of plastic pollution on freshwater ecosystems, there are still many unanswered questions.
The new study, led by Naiara López-Rojo, shows that microplastic pollution may cause significant effects on how stream ecosystems function. The research team used microcosm experiments (essentially glass jars filled with stream water) to study how different concentrations of microplastic pollution affected the growth of caddisflies, and the rates at which they decomposed leaf litter.
Leaf litter decomposition is a vital component of many stream ecosystems. Leaf litter – the leaves that fall into a stream from surrounding vegetation – is a key energy source for many invertebrates at the heart of stream food webs. Its decomposition – accelerated by invertebrates such as caddisflies – helps release carbon and nutrients to the wider ecosystem.
Recent studies show that microplastics are being found even in remote sites, carried on atmospheric currents. How might their presence affect stream ecosystems?
López-Rojo, from the University of the Basque Country, Spain, and colleagues, exposed caddisflies and leaf litter to different concentrations of microplastics in water. They found that microplastics were rapidly ingested into the bodies of the caddisflies – most likely through the ingestion of particles attached to leaf litter – and then excreted.
This finding is consistent with recent studies, such as that by Fred Windsor and colleagues in rivers in South Wales, UK, which show evidence of microplastic uptake by invertebrates.
López-Rojo and colleagues found that higher concentrations of microplastics caused increased caddisfly mortality – which increased 9-fold at the highest concentration. However, they found that altering microplastic concentrations did not significantly affect caddisfly growth.
The researchers observed that increasing the concentration of microplastics in the microcosms caused leaf litter decomposition rates by the caddisflies to decline.
The study, published in the journal Environmental Pollution, is short in length and based on a relatively small sample size (32 microcosms, observed over a number of weeks). So why are its findings significant?
First, it provides more evidence to show that microplastics can be rapidly ingested into the bodies of freshwater organisms, and thus potentially accumulate and move through the food web into larger animals. Second, it suggests that the functioning of stream ecosystems – in this case through the key process of leaf litter decomposition – could be inhibited by the presence of high concentrations of microplastics.
The authors highlight the need for better monitoring of microplastic pollution in stream ecosystems to understand the extent of the pressures it might exert. In particular, they suggest that more research is needed to understand how microplastic pollution might affect ecosystems already influenced by multiple contaminants and stressors.
What is clear is that microplastic pollution is a growing issue for freshwater conservation and policy. López-Rojo and colleagues’ study is likely to be only the latest advance in the ongoing scientific effort to document and unravel its effects on freshwater ecosystems.
The Freshwater Blog 