How are river ecosystems affected by regulation?
Sampling on the Maudalsåna, a regulated river in Norway. Image: NIVA
Most rivers and streams experience natural variations in water flow throughout the year. Whilst climate change increases the risk of extreme floods and extreme droughts, ‘normal’ floods and droughts are part of the natural rhythm of river ecosystems.
Natural variations in water flow are important for many reasons. One is that they can ‘clean’ the river bottom. Although this can be devastating for the organisms which are ripped off by a flood, or killed by a drought, such ‘cleaning’ creates open spaces for colonisation by other organisms. Disturbance by floods and droughts is – in the long run – important for maintaining biodiversity in rivers.
However, rivers across the world are increasingly regulated to serve human needs, such as flood protection, transport, irrigation, hydropower generation and drinking water supply. In Norway, more than two-thirds of river basins are affected by regulation. This has altered natural flow dynamics. In winter, because more electricity is needed for heating, hydropower companies take more water from the reservoirs and release it into streams, generating electricity. As a result, many regulated rivers have relatively high discharges in winter. This is in contrast to unregulated rivers in Norway which normally have low discharges in winter because precipitation falls as snow and does not run off immediately.
Investigating the ecological impacts of regulation
Scientists at The Norwegian Institute for Water Research (NIVA), in collaboration with The Norwegian Institute for Nature Research (NINA) and colleagues from Germany, wanted to find out how such altered river flow dynamics affect bottom-dwelling river organisms. These organisms include insects, snails and other small spineless creatures (known as macroinvertebrates), as well as bottom-dwelling algae (known as benthic algae).
Benthic algae are the basis of many food webs in rivers. Macroinvertebrates feed on algae and detritus, and are themselves an important food source for fish. In their study, the researchers asked: what are the consequences of an altered flow regime for macroinvertebrates and benthic algae?
Macroinvertebrate and benthic algal populations are commonly used as indicators to assess the health (or ecological status) of rivers. The researchers investigated whether these indicators could also be used in regulated rivers, and how river flow interacts with other ecosystem stressors like acidification or nutrient enrichment.
“Studying the effects of river flow on stream biota is not straightforward,” says Susanne Schneider, senior research scientist at NIVA, “Each stream is special in its own way, has a slightly different flow regime, sediment, water chemistry, shading, and so on, than its neighbour. The interaction of so many factors – which all affect macroinvertebrates and benthic algae – makes it difficult to detect the effects of flow among all other factors which also are important. Properly replicated and controlled experimental designs in streams are rarely possible in practice.”
The flume experiments in Norway. Image: NIVA
Varying water flows and nutrient levels in flume experiments
The researchers used artificial steel flumes to standardise conditions in their experiments as far as possible. “Flumes have the advantage that we can study the influence of a certain factor, – such as flow increase – while all other conditions are kept constant,” Schneider explains.
Researchers manipulated water flow and nutrient (nitrogen and phosphorus) supply in the flumes over time. They found that an increased nutrient supply led to an increased biomass of benthic algae within a few days. Algae ‘feed’ on nutrients, and more food leads to better growth.
“We also found that a moderate increase in flow caused an increase in benthic algal biomass,” says Schneider. “This may seem surprising, because we all know that large floods can ‘clean’ the river bottom, ripping benthic algae from the bed and washing them away. But a moderate increase in flow can have a positive effect on algal growth. This happens when increased flows aren’t strong enough to rip off the algae, but do transport more nutrients to the algal patches, leading to increased algal growth.”
Interestingly, when nutrients and water flow both were increased at the same time in the flumes, the effect on algal biomass was smaller than the sum of both individual effects. This was because a larger patch of benthic algae – caused by more nutrients – can more easily be ripped off already by a moderate increase in flow. “What we learn from this is that a flood in a nutrient-rich river will have different consequences than a flood in a nutrient-poor river,” Schneider explains.
Comparing flumes and fieldwork
The researchers found that their results varied between different flumes and the nearby river from where they took the water for their experiments. “This was because ‘controlled’ flumes can never really be the same as ‘real’ ecosystems,” Schneider says.
In order to compare their flume experiments with real-world findings, the scientists studied 32 regulated and 32 unregulated river sites in Norway and Germany. In their river experiments, none of the monitoring indices of macroinvertebrates and benthic algae used for ecosystem status assessment were affected by the water flow regime. This suggests that these indices can be applied to regulated rivers as well as non-regulated ones.
“We did, however, see some effect of the long-term flow regime, calculated from five years of discharge data, on the species composition of macroinvertebrates,” Schneider says. “We found that a flow regime which is comparatively stable over several years – for example in a regulated river – changes the species composition of macroinvertebrates towards those which prefer slowly flowing water. We also saw that less variable flow conditions lead to a reduced proportion of grazers – those species that directly feed on benthic algae – among the macroinvertebrates.”
Thus, a more uniform flow regime may lead to a higher biomass of benthic algae, via a direct and an indirect effect. Direct, because the occurrence of lower and fewer floods will ‘clean’ less algae from the river bottom; and indirect because fewer grazers will eat less algae.
Sampling on the Atna, an unregulated river in Norway. Image: NIVA
Similar ecological impacts of natural and artificial flow regimes?
Another finding that caught the scientists’ interest was that natural differences in flow regime had similar effects on the biota as those observed in artificially modified flow regimes. Macroinvertebrates and benthic algae responded to changed flow regimes, regardless of whether alteration was due to natural reasons, or caused by human regulation.
That climatic and natural variation in river flow affected benthic algae was something the researchers have seen before. Data collected over more than 20 years at the lake outlet Atna, and the headwater stream Li, both located in the Norwegian mountain area of Rondane, showed similar results. In this remote location, there is practically no human interference except climate change.
Swift recolonisation after extreme flow events
“In summary, we found that there are short-term effects of extreme events like floods and droughts on benthic algae and macroinvertebrates,” says Schneider. “Benthic algae generally were more affected by floods, while macroinvertebrates were more affected by droughts. Within a few weeks or months after extreme events, however, benthic algae and macroinvertebrates usually recolonise the rivers, and few long-term effects were apparent.”
“One prominent long-term effect was however that a new flow regime affected species composition of macroinvertebrates. Variability affected grazing macroinvertebrates – which in turn may lead to a higher biomass of benthic algae in rivers with stable flows,” Schneider added.
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See these publications for more information:
- Schneider, S.C. (2015): Greener rivers in a changing climate? – Effects of climate and hydrological regime on benthic algal assemblages in pristine streams. Limnologica 55: 21-32. (link)
- Schneider, S.C., Petrin, Z. (2017): Effects of flow regime on benthic algae and macroinvertebrates – A comparison between regulated and unregulated rivers. Science of the Total Environment, 579, 1059-1072. (link)
- Bækkelie, K.A. E., Schneider, S.C., Hagmann, C.H.C., Petrin, Z. (2017): Effects of flow events and nutrient addition on stream periphyton and macroinvertebrates: an experimental study using flumes. Knowl. Manag. Aquat. Ecosyst. 418, article number 47. (link)
- Schneider, S.C., Sample, J.E., Moe, S.J., Petrin, Z., Meissner, T., Hering, D. Unravelling the effect of flow regime on macroinvertebrates and benthic algae in regulated versus unregulated streams. Ecohydrology, submitted.
The study was funded by the Research Council of Norway (ECOREG) and by the EU 7th Framework Programme, Theme 6 (Environment including Climate Change) (MARS).
Meet the AQUACROSS team: Lina Röschel
Lina Röschel in Nova Scotia, Canada.
This week we’re delighted to publish the latest in our series of interviews with members of the EU AQUACROSS project. Lina Röschel works at the Ecologic Institute in Berlin as a Junior Researcher. Her work focuses on biodiversity conservation and ecosystem-based management of aquatic ecosystems.
On a side note, the MARS final conference took place in Brussels this week, and we’ll report back on discussions and outcomes in the coming weeks. You can see a collection of tweets from attendees here.
For now, over to Lina.
Freshwater Blog: What is your focus of your work in AQUACROSS, and why?
Lina Röschel: Within AQUACROSS, I am part of the team that provides policy orientation to all other working areas of the project. During the course of the project we have identified policies on the international, European and Member State level that are related to enhancing or hindering aquatic biodiversity protection, and have effectively examined the EU policy framework for coherence within this context.
Furthermore, we reviewed the synergies and barriers between these policies in order to identify how the different policies use the implementation of ecosystem-based management to enable aquatic biodiversity conservation. The next step for our team is to identify the major policies that negatively and positively affect aquatic biodiversity on the local level within AQUACROSS’ eight case studies. This will give insight on whether EU policies have successfully been implemented on the ground.
Why is your work important?
Our different levels of policy analysis help identify stress areas where the higher strategic policy level meets actual practitioners within our case studies. On the ground, things may look very different from what the EU level policies have anticipated. In order to support policy coordination and demand on the local level, it is important to identify these discrepancies.
What are the key challenges for aquatic management in Europe?
From a policy perspective, the challenge is clear – while a comprehensive set of policies is in place for achieving Europe’s objectives in terms of healthy aquatic ecosystems and biodiversity, the policy landscape has been unable to reverse negative trends as significant gaps in policy and implementation remain. In addition, discrepancies between sectoral policies and those policies in place to ensure environmental protection need to be addressed to aim for coherence across the EU policy framework and to ensure the sustainable protection of aquatic biodiversity.
In response to these findings, we have identified the need to mainstream biodiversity protection into existing policy frameworks as well as promote the application of an ecosystem-based management approach to address the current challenges associated with implementing environmental policies. Specifically, ecosystem-based management can help to incorporate a variety of policy objectives in an integrative, holistic manner.
For further reading on this topic, please see these two recent publications written by our team here and here.
Policy review on EU level: inner and outer core of policies relevant for the achievement of targets of the EU Biodiversity Strategy to 2020 (AQUACROSS, Deliverable 2.1)
Tell us about a memorable experience in your career.
In 2016, I was present for the Signing Ceremony of the Paris Agreement at the United Nations Headquarters in New York. Seeing national representatives from over one hundred countries sign the book, one after the other, filled me with hope, as it illustrated the unity with which cross-border environmental issues need to be addressed.
What inspired you to work in biodiversity conservation?
Growing up, I watched my dad working as a physicist and the idea of creating and uncovering knowledge became unfathomably exciting to me. I have wanted to do nothing else since.
What are your plans and ambitions for your future work?
In the future I want to continue working within the field of biodiversity conservation, specifically within the marine realm. Furthermore, I think it is important to strive towards making scientific knowledge accessible to everyone.
The projects that I’m involved in aim for their results to have significant impact for general society and local businesses in addition to policy makers, so in the future I would like to focus more on successfully transferring knowledge beyond the standard of publishing results in academic journals and deliverables. This blog is a great example of achieving just that!
Read more interviews from the Meet the AQUACROSS team feature here.
‘Modest’ fine sediment and phosphate pollution in English rivers causes mortality of up to 80% of mayfly eggs
Blue-winged Olive. Image: Francisco Welter-Schultes | Wikipedia Creative Commons
Increased levels of fine suspended sediment and phosphate in aquatic ecosystems can have significant negative impacts on the survival of mayfly eggs, according to a new study. Relatively modest levels of pollution can kill up to 80% of eggs, with potentially devastating effects on mayfly populations and wider aquatic food webs.
Writing in the journal Environmental Pollution, a team of researchers led by Nick Everall of the Aquascience Consultancy carried out experiments on the blue-winged olive, a species of mayfly found across Europe, whose populations have fallen in recent decades.
Fine sediments and phosphate pollution from agricultural run-off and untreated sewage have been identified as key causes of this decline. However, until now, research has focused largely on the response of adult and larval mayfly to such multiple stressors.
Supported by the Salmon and Trout Conservation UK, the research team collected eggs of the blue-winged olive to be incubated in laboratory aquariums under different concentrations of fine suspended sediments and phosphate.
In the wild, blue-winged olive eggs are laid on the beds of fast-flowing streams and rivers, and have to survive over winter for up to eight months before hatching into nymphs. As a result, it is important to understand how stressors affect this crucial early stage in the insect’s life cycle. The researchers found that fine sediments cover mayfly eggs, starving them of oxygen and encouraging fungus growth, whilst phosphate can inhibit egg development.
When low levels of fine sediment were added to experiments with raised phosphate levels, the mortality of mayfly eggs increased significantly. However, when phosphate was added to experiments with increased amounts of fine sediment, mortality was not significantly increased.
This finding suggests that fine sediment has a greater impact on mayfly egg mortality than phosphate. As a multiple stressor relationship, it suggests that the run-off of fine sediments into aquatic ecosystems already stressed by phosphate pollution could have significant negative consequences for mayfly populations.
Mayfly egg mortality increases as suspended sediment concentrations rise at a constant level of phosphate concentration. Image: Journal Authors.
Significantly, relatively modest levels of each stressor had damaging effects on mayfly egg survival. The concentrations of fine sediment and phosphate used in this experiment were largely below the Water Framework Directive defined thresholds for river management in England. At levels close to the upper limits for management – 25mg per litre of fine sediment and 0.07 mg per litre of phosphate – the mortality rate of mayfly eggs in the experiment was 80%.
Whilst the experimental conditions don’t fully represent the fluctuating nature of pollutant concentrations found in most rivers, the research team argue that their findings show that the annual mean suspended sediment guideline standard of 25 mg per litre for the UK is not sufficient to conserve mayfly populations.
More broadly, they suggest that increased attention needs to be paid to managing fine sediment into rivers across Europe, particularly as many rivers across the continent have raised phosphate levels. The implementation of effective mitigation strategies for reducing erosion and run-off of fine sediments from agricultural land surrounding rivers is clearly needed.
MARS final conference: Managing multiple stress for multiple benefits in aquatic ecosystems
Museum of Natural Sciences, Brussels. Image: IRSNB – Thierry Hubin
Over the last four years, the MARS project has investigated the impacts and interactions of multiple stressors in European aquatic ecosystems. Funded under the EU FP7 programme, research within MARS has addressed uncertainties over how to detect, conceptualise and manage multiple stressors in surface waters. MARS was designed to support the implementation and review of the EU Water Framework.
This month MARS will host a conference ‘Managing multiple stress for multiple benefits in aquatic ecosystems’ in Brussels, Belgium to communicate the key results and recommendations from the project. Taking place over two days on 16-17 January, the conference will be have two themes – science, and management/policy.
Conference events on Tuesday 16th will focus on scientific findings, and feature sessions which summarise and review the main MARS outcomes within the context of aquatic multi-stressor research.
On Wednesday, 17th, discussions will turn to the management and policy implications of MARS research. Conference sessions will introduce MARS products for managers and policy makers (such as factsheets, guidance and tools) and discuss effective river basin management and policy under multi-stress conditions.
Hosted by the Museum of Natural Sciences in Brussels, the conference is likely to be of interest to aquatic scientists, water managers and administrators, as well as policy-makers and executives. Conference registration is free.
A conference agenda with full details of speakers and sessions is available as a PDF here.
Top 17 posts of 2017
Water outflows from Fewston Reservoir, UK. Image: James Whitesmith | Flickr Creative Commons
As the end of the year approaches, we’ve looked back over 2017 to collect 17 of our most popular posts on freshwater science, policy and conservation.
It’s been the most successful year yet for the Freshwater Blog, with record numbers of visitors. Thanks, as always, for reading. You can keep up to date with our posts, and add your voice to the debate, through our Twitter, Facebook and LinkedIn pages.
The MARS project, which has investigated the interactions and impacts of multiple stressors on aquatic ecosystems since 2014 (and which supports this blog), hosts its final conference in January 2018. You can find out details here.
Happy 2018!
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Caddisfly larvae tend remarkable underwater ‘gardens’ (January)
Caddisfly (Tinodes waeneri) larva. Image: Guam Insects | Creative Commons
Caddisflies are found in freshwaters across Europe, with their larvae well-known for their remarkable ability to build cases from organic materials such as vegetation, sand and silt (which can take on beautiful creative forms). In Britain alone, there are around 200 different caddisfly species, making them one of the most diverse groups of pond animals.
New research by a team of ecologists from the UK, Germany and Malaysia has shown how caddisflies are not only resourceful ‘house builders’, but also productive ‘gardeners’ of their habitats. Writing in Freshwater Biology, the researchers, led by Nicola Ings, describe how caddisflies actively encourage food growth in their local environment, through ‘weeding’ and ‘fertilisation’. (read more)
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Small birds, big effects: the little auk transforms high Arctic ecosystems (February)
Little Auk colony on the Cape York Peninsula, Greenland. Image: T Davidson
The North Water Polynya is a large area of open sea in Baffin Bay between Greenland and Canada. The area is the largest polynya – an area of sea that remains ice-free year-round, though surrounded by sea ice – in the world, and is one of the most biologically productive marine habitats in the Arctic Ocean.
Ecosystems on the Greenland coastline of the North Water Polynya are transformed – both positively and negatively – by nutrients brought back to land from the open sea by a tiny ‘ecosystem engineer’ bird, the little auk, according to a new study. (read more)
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Life in a Drop of Water: an interview with underwater photographer Liam Marsh (February)
Mayfly larvae after moult, in a drop of water. Image: Liam Marsh
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The restored Lippe River in Germany. Image: Benjamin Kupilas | REFORM
A new study by researchers based in Germany and the USA examined the responses of fish communities to the restoration of the Lippe River in Germany over a 21 year period. The Lippe has been heavily modified by human activity since the early 1800s, with a largely reinforced and straightened channel and bed, highly fragmented flows as a result of numerous weirs, and the widespread destruction of its riparian and floodplain landscapes.
The research team analysed data collected for 4 years before, and 17 years after, restoration at Klostermersch, where two stretches totaling over 3km in length were restored in 1996 and 1997. Restoration involved reconnecting the river’s floodplain with the river, removing bank fixations, widening the river from 18 to 45 metres in width, building a series of small islands, introducing full trees as deadwood, and reintroducing ‘natural’ floodplain drainage systems. In essence, the Lippe River ecosystem was encouraged to become more diverse in structure and dynamic in process. (read more)
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Common ground for multiple stressor research (March)
Delegates at the Portugal meeting. Image: Vanessa Bremerich / Markus Venohr
Last week, researchers from three EU aquatic science projects – MARS, GLOBAQUA and SOLUTIONS – met in Sesimbra, Portugal to present their findings, and to discuss opportunities for collaboration. The three projects share a common interest in the effects of multiple stressors on aquatic ecosystems, and their representatives met at a workshop to develop the potential for shared outputs such as policy briefs and water management guidance. (read more)
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The rapid evolution of Europe’s newly-discovered first cave fish (March)
The newly discovered cave loach from the Danube-Aach system. Image: Jasminca Behrmann-Godel
A diver has made an unusual discovery in an inaccessible underground cave system in Southern Germany: a population of Europe’s first documented cave fish. The pale coloured loach of the genus Barbatula is thought to have diverged from surface fish around 16,000 to 20,000 years ago, following the retreat of ice age glaciers.
“The cave fish was found surprisingly far in the north in Southern Germany,” said project leader Jasminca Behrmann-Godel of the University of Konstanz in Germany, lead author on a newly-published study in Current Biology. “This is spectacular as it was believed before that the Pleistocene glaciations had prevented fish from colonizing subterranean habitats so far north.” (read more)
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What is good ecological status and why does it matter? (April)
‘Good ecological status’ is a key term in the EU Water Framework Directive – the policy framework through which European freshwaters are managed. Member states are required to conserve and restore their rivers and lakes to good ecological status by 2027. But what does ‘good ecological status’ mean, and why does it matter?
A new film by the EU MARS project gives an engaging and accessible introduction to the concept. Produced by MARS scientists Christian Feld and Sebastian Birk at the University of Duisburg-Essen, the short film ‘Good ecological status of rivers and lakes’ emphasises the value of healthy aquatic ecosystems to human and non-human life, both now and in the future. (read more)
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Multiple pressures and the ecological status of European rivers (May)
Floodplain on the River Ouse, Yorkshire. Image: alh1 | Flickr Creative Commons
The EU Water Framework Directive is the ambitious water policy designed to reduce pressures and achieve a good ecological status for all European water bodies. However, assessing the multiple pressures acting on aquatic ecosystems, and understanding their combined impact on the ecological status of rivers and lakes is challenging, particularly at large scales. Understanding these interactions and impacts is crucial to the planning of effective water policy and management.
In this context, a recently published study provides an assessment of multiple human pressures and their relationships with ecological status for all European rivers. Writing in the (open-access) Nature: Scientific Reports journal, Bruna Grizzetti from the EC Joint Research Centre and colleagues estimate that only 38% of EU rivers reach ‘good’ or ‘high’ ecological status. 20% are rated as ‘bad’ or ‘poor’, whilst 42% are ‘moderate’. (read more)
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Environmental restoration prompts widespread water quality increases in China (May)
Lake Taihu on the Yangtze Delta Plain, China: one of the water bodies assessed in the new study. Image: Balázs Andor Zalányi | Flickr Creative Commons
Restoration is a key element of contemporary environmental management, as damaged or degraded ecosystems are guided towards healthier, more resilient and diverse states. As a result, there is widespread interest and attention given to restoration in scientific, management and policy circles globally, particularly about the outcomes and effectiveness of different restoration initiatives.
New insights into restoration management are emerging from China, where many aquatic ecosystems have been highly altered and degraded in recent decades. A new study published in the journal Water Research suggests that water quality in rivers and lakes across China has improved in recent years as a result of significant investment in environmental restoration and water treatment, funded by the Chinese government. (read more)
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The European eel is one of the continent’s most remarkable and wide-ranging aquatic animals. Young eels (known as elvers) are born in the Sargasso Sea in the West Atlantic Ocean, and migrate back to European watercourses. Here, they mature and grow larger over a number of years, before making the journey back to the Sargasso Sea to spawn themselves.
However, European eel populations are subject to considerable threats. Some eel populations have dropped by over 90% across the continent in recent decades, largely as the result of overfishing and habitat loss. The European eel has been designated as ‘Critically Endangered’ by the IUCN Red List of Threatened Species since 2008 as a result.
A new community-engaged animation has sought to tell the eel’s story, through the voices of children. Protect the Eels is a an animated journey into the hidden ecologies of the River Avon in south-west England, as told by the children of Victoria Park Primary School Bristol, using their drawings, ideas and voices. (read more)
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The politics of biodiversity and hydropower on ‘Europe’s last wild river’ (July)
Local residents and environmental NGOs protest against hydropower development on the Vjosa. Image: Oblak Aljaz
After 20 years of postponement, an unfinished hydropower construction on the Vjosa River in Albania was cancelled earlier this year. The Vjosa is Europe’s last ‘wild’ large river, flowing entirely unobstructed through inaccessible gorges and enormous gravel banks and islands on a course of almost 270 kilometers from the Pindus Mountains to the Adriatic Sea. However, the river system is currently the subject of a number of hydropower constructions, which potentially threaten its rich – but little researched – biodiversity. (read more)
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European public want more environmental protections according to new survey (August)
Water is a key element of EU environmental policy. Image: Symbolique 2006
Over half of the European public are in favour of more environmental protections across the continent, according to a new European Parliament survey.
53% of the 27,901 EU citizens interviewed by Kantar Public for the survey thought that existing environmental protections across Europe were ‘insufficient’. 75% of citizens thought that more policy and management interventions were necessary to protect European environments. (read more)
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Vulnerable estuary fish populations require stronger conservation management (August)
Gweek estuary, Cornwall. Image: Tony Armstrong | Flickr Creative Commons
Estuaries are transitional ecosystems where freshwater and marine waters meet, and their biodiversity overlaps. As a result of their supporting roles in trade, transport, fishing and tourism, estuaries are often also highly altered and pressurised ecosystems.
According to a new study, European estuaries are home to some of the most vulnerable and least resilient estuarine fish populations in the world. Writing in Nature Scientific Reports, Rita P. Vasconcelos and colleagues outline that European estuaries are particularly pressurised by human activities such as overfishing, habitat alteration and pollution. However, the authors of the newly published study argue that these highly-pressurised European estuaries are often lacking in sufficient protected area coverage to help conserve vulnerable fish species. (read more)
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The restoration of large woody debris rapidly increases degraded river biodiversity (September)
The River Wensum in Norfolk, England – one of the rivers used to observe the effects of large woody debris additions in this study. Image: Colinsd40 | Flickr Creative Commons
The reintroduction of large woody debris is a common tool for river restoration schemes which aim to encourage biodiversity and natural flood protection. However, environmental managers have, as yet, been hindered by a lack of scientific evidence on the ecological effects of adding trees and logs to river and stream ecosystems.
A new study by Murray Thompson from the Centre for Environment, Fisheries and Aquaculture Science and colleagues provides valuable new insights to this knowledge gap. Writing in the Journal of Applied Ecology, Thompson and colleagues report on how the presence or absence of large woody debris influences aquatic species and food webs along five rivers in England.
The research team found that populations of aquatic invertebrates and brown trout were higher in the restored and target stretches than in the control stretches. In other words, the presence of large woody debris caused rapid increases in invertebrate and brown trout abundance. (read more)
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Freshwater megafauna as conservation flagships? (October)
The arapaima, a fish native to the Amazon Basin, which can grow to over 3 metres in length. Image: Lynn Chan | Flickr Creative Commons
Freshwater megafauna such as sturgeon, river dolphins and turtles could act as valuable ‘flagships’ for freshwater conservation, according to a new open-access study published in the journal BioScience.
In the last decade or so, it has become apparent that freshwater biodiversity is both highly threatened, and is decreasing at a higher rate than its terrestrial or marine counterparts. In part, this awareness can be mapped to an influential – and highly cited – 2006 paper by David Dudgeon and colleagues.
Despite the multiple threats and pressures faced by freshwater ecosystems across the world, they tend to receive less conservation attention, research and investment than their terrestrial and marine equivalents. In their new paper, lead author Dr. Savrina F. Carrizo (IUCN) and Dr. Sonja Jähnig (Leibniz-Institute of Freshwater Ecology and Inland Fisheries, IGB) together with other IGB researchers and a team of international co-authors, suggest that freshwater megafauna could provide a focus for conservation action by acting as flagships for overlooked aquatic ecosystems and biodiversity. (read more)
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Sketching another world: Stephen Thackeray’s aquatic art/science drawings (November)
Daphnia and microplastics. Image: Stephen Thackeray
At the start of last month, a succession of drawings of curious organic forms began appearing on our twitter feed. Penned by CEH and MARS freshwater scientist Stephen Thackeray as part of ‘Inktober‘, the images revealed a fascinating underwater world of often-microscopic aquatic life.
Keen to find out more about his interdisciplinary talents, we spoke to Stephen about his art/science practice. (read more)
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AQUACROSS interviews address gender equality in research (November)
Image: AQUACROSS
AQUACROSS seeks to advance the application of ecosystem-based management for aquatic ecosystems in an effort to support the EU 2020 Biodiversity Strategy and other international conservation targets. The women featured in the AQUACROSS interview blog series will share their common passion for aquatic biodiversity and conservation, their motivations to advance scientific knowledge, and their stellar achievements on this path.
Ultimately, in outstanding research there are no genders. We as researchers share a passion for providing answers and transferring our science to others, with the pledge to leave behind a better world than the one we found. The featured interviews in this blog series will showcase the progress that these AQUACROSS researchers are carrying out towards this goal. (read more)
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Thanks for reading, and a very happy 2018 to you!
How do multiple stressors affect food webs in South Wales streams?
A Welsh stream. Image: Kev Lewis | Flickr Creative Commons
Human activities are altering freshwater ecosystems and biodiversity across the world at an unprecedented rate. However, predicting how freshwater species populations are affected by multiple stressors is often difficult, as a result of the complex and interactive ecological processes such as trophic links, competition and mutualism that take place across an ecosystem.
In turn, changes in species composition can have unexpected or emergent effects on ecosystem processes and dynamics. For example, changes in food availability and competition for predator species can lead to ‘trophic cascades’ throughout an ecosystem. As a result, predicting and mitigating the ecosystem-level effects of human stressors requires a detailed understanding of such ‘inter-specific’ interactions between species.
Stream ecosystems are often extremely sensitive to the impacts of human disturbance. The intensification of catchment land use – often agriculture and urbanisation – is a major driver of biodiversity loss in streams. Bottom-dwelling aquatic insects (or ‘benthic macroinvertebrates’) are often abundant in stream ecosystems, and their communities play key roles in a wide range of ecosystem processes.
However, despite increasing evidence that macroinvertebrate communities are being altered by human pressures, there has been relatively little research on the effects such alterations have on wider freshwater food webs.
Stonefly. Image: Wlodzimierz | Wikipedia Creative Commons
A new open-access study published in Molecular Ecology aims to address this shortfall. A research team led by Caitlin Pearson from the Cardiff School of Biosciences, Cardiff University used a DNA technique called ‘next generation sequencing‘ to investigate the feeding habits of two macroinvertebrates – the Caddisfly, Rhyacophila dorsalis and the Stonefly, Dinocras cephalotes – in streams affected by different intensities of livestock farming.
The study – carried out along ten upland streams in South Wales – allowed the research team to analyse how predatory macroinvertebrate diets varied along a land-use intensity gradient. As a result, it offers new insights into how human stressors affect ecological communities in streams.
Lead author of the study, Caitlin Pearson – who is now heavily involved in river conservation with the UK’s West Cumbrian Rivers Trust – summarises the key findings:
“We know that agricultural land use can affect streams and the organisms that live there, but know less of the consequences for stream food webs. In part this is because of the difficulties of resolving feeding interactions, particularly among small organisms or where predators eat soft-bodied prey that leave no remains. We tried to overcome these problem here by probing the guts of predators simultaneously for the DNA of many possible prey types using next generation sequencing.
Both of the predators we investigated were generalists, consuming overall 30 different prey taxa in proportion to their availability. This included greater use at agricultural sites of the prey that were tolerant of agricultural conditions. These are important new insights that tell us something of the mechanisms through which how land use affects stream communities, and potentially stream ecosystem functioning.”
Caddisfly. Image: Janet Graham | Flickr Creative Commons
Cardiff University Professor of Ecology and MARS researcher Steve Ormerod continues:
“Modern molecular methods – such as next generation sequencing – are adding very powerful tools to the work of freshwater ecologists. In this example, we’ve not only gained a wholly new view of the way invertebrate predators feed, but also we have a new perspective of the way in which agricultural intensification affects stream ecosystems.
Predators such as the large and beautiful stonefly Dinocras cepahalotes are being lost from these sites more likely because of physical stressors such as sedimentation rather than because their prey are depleted. This is in line with similar effects we’ve seen previously (Larsen & Ormerod 2010), and illustrates how classical and modern ecological methods can work together for river management.”
Meet the AQUACROSS team: Andrea Funk
Dr Andrea Funk on an ecological survey of the Danube River. Image: Andrea Funk
This week we continue our series of interviews with researchers from the AQUACROSS project. AQUACROSS is an EU-funded project which seeks to advance the application of ecosystem-based management for aquatic ecosystems, to help support the EU 2020 Biodiversity Strategy and other international conservation targets.
Dr Andrea Funk is an expert in wetland ecology, with a special focus on biodiversity, and the restoration and conservation of river-floodplain systems. Her current research focuses on meta-community dynamics in floodplain networks, and species-distribution modelling with an emphasis on floodplain restoration.
We spoke to Andrea to find out more about her work, inspirations and aspirations in freshwater ecology.
What is your focus of your work in AQUACROSS, and why?
My work focuses on the coordination and implementation of the AQUACROSS assessment framework for the Danube basin. More specifically, my focus is on the river-floodplain system along the navigable stretch of the Danube River where we explore trade-offs and synergies of biodiversity targets (especially related to protected areas), ecosystem services (like recreation or tourism) and multiple human activities (like navigation or energy production) related to hydro-morphological alterations based on statistical models.
Riparian silver birch woodland on the Danube floodplain. Image: Andrea Funk
Why is your work important?
Floodplains are key elements for biodiversity protection. They are biodiversity hotspots, they provide a multitude of ecosystem functions and services, but, in turn are also hotspots of multiple human activities. Contributing to our understanding of these highly complex systems provides a basis for a strategic and more integrated management approach, as well as restoration planning.
What are the key challenges for freshwater management in Europe?
Biodiversity is declining rapidly, this is particularly acute for freshwater systems. Freshwaters host rich communities of life including many sensitive and endemic species. In turn, freshwater ecosystems are threatened due to multiple human activities which are also conflicting with multiple ecosystem services and ecosystem functions those systems provide. A main challenge is to balance all these different interests toward a sustainable protection of biodiversity.
Sunset over the Danube. Image: Andrea Funk
Tell us about a memorable experience in your career.
I’m used to having those memorable experiences quite frequently – scientific life is always full of surprises.
What inspired you to become a scientist?
I was always fascinated by water, mud (or call it aquatic sediments) and the life in it.
What are your plans and ambitions for your future scientific work?
With my modelling focus I hope that I can further contribute to the understanding of complex systems and therefore the conservation and restoration of biodiversity hotspots.
Brass, Three Down: multiple pressures on Arctic Charr populations in Lake Windermere
Lake Windermere is the largest natural lake in England. Plummeting to a depth of around 64 metres, its waters support one of Britain’s largest populations of Arctic charr. Charr are cold-water fish, most commonly found in sub-Arctic regions, and their presence in Windermere is often described as a ‘relic’ of the last ice age, as sea-run populations were trapped in the lake when glaciers retreated from the area around 12,000 years ago.
Arctic charr populations in Windermere live on the southern edge of the species’ habitat niche. As a result, they are the least resilient of the salmonid species to warming lake waters due to climate change. There are two distinct populations of charr in Windermere, which live in the deep basins to the north and south of the lake, separated by a shallower ridge.
Populations of charr in both basins have declined in the last 20 years, largely as a result of warmer lake waters which hold less oxygen, eutrophication from agricultural and waste water pollution, and the introduction of invasive species such as roach, which compete with charr for zooplankton prey.
A new film – available to watch in full above – called Brass, Three Down casts a poetic and meditative eye over the place of Arctic charr in the communities local to Windermere, and the multiple pressures their populations face. The film follows a local fishermen, who fishes for charr using traditional techniques (the types of lures used give the film its name), a potter who makes the ceramic pots used traditionally to preserve the fish, and a local chef using charr in his Michelin starred restaurant.
Produced by Henry Iddon and Richard Berry, Brass, Three Down also features Dr Ian Winfield from the Centre for Hydrology and Ecology, who are carrying out long-term ecological studies on charr populations in the lake, to inform conservation and restoration strategies.
Multiple stressor effects on fish assemblages in the Austrian Alps
The Drava River at Villach, Austria. Image: Andrey | Flickr Creative Commons
The rivers and stream ecosystems of the mountainous European Alps are under increasing stress as a result of human activities. So-called ’hydromorphological’ alterations – those which change the hydrological regime (or flow) and morphological character (or shape) – are particularly common on Alpine rivers and streams.
Such hydromorphological pressures are often caused by the construction of hydropower plants – which harness the power of fast-flowing streams to generate renewable energy – and flood protection measures along river and stream channels. In addition to alterations to water flows and aquatic habitat, hydromorphological pressures (or stressors) can cause alterations to habitat connectivity for migratory species and – indirectly – to water quality.
Scientists are increasingly documenting the numerous negative ecological impacts of these stressors in Alpine rivers and streams – particularly on fish populations. However, knowledge of stressor impacts remains incomplete, particularly when multiple stressors act in combination.
In this context, a new study investigates the ecological impacts of multiple stressor combinations on fish populations in two river basins in the Austrian Alps – the Drava and the Mura. The open-access study, published in Science of the Total Environment, was supported by the MARS and AQUACROSS projects.
“The river ecosystems of the European Alps are highly under stress through various human activities which are affecting the physico-chemical conditions of running waters and are strongly influencing and impacting their morphological character, hydrological regime and as a consequence, inhabiting aquatic biota and the overall ecological integrity,” explains lead author Rafaela Schinegger, a researcher at the Institute of Hydrobiology and Aquatic Ecosystem Management at the University of Natural Resources and Life Sciences, Vienna (BOKU).
“This is particularly true for many rivers and streams in the European Alps, which constitute the ‘water towers’ of Europe, providing numerous aquatic ecosystem services to their inhabitants and the areas beyond”.
“By analysing an extensive dataset from the 2nd River Basin Management Plan of the EU WFD implementation in Austria, we found a general trend of decreasing ecological integrity with increasing number of stressors and maximum stressor in two Alpine river basins of Southern Austria – the Drava and Mura rivers. Fish metrics based on age structure, fish region index and biological status responded best to single stressors and/or their combinations”, says Schinegger.
A small hydroelectric dam in the Austrian Alps. Such projects can cause multiple stressors on the river ecosystem. Image: Michael Thomas | Flickr Creative Commons
The research team identified seven different stressor categories of single stress or multiple stressor combinations, with up to four stressors acting together at a single site. Just under two-thirds (62%) of stressor-affected ecosystems were impacted by multiple stressor combinations.
Over two-thirds (69%) of the 2590 water bodies investigated across the Drava and Mura basins were impacted by significant human stressors. Connectivity disruptions were the most common stressor found in the basins (1213 water bodies: 47% total), followed by morphological alterations (578 water bodies: 22%), and water abstraction (413 water bodies: 16%).
This analysis provides invaluable information for water managers in the Austrian Alps seeking to prioritise their efforts to mitigate the effects of multiple stressors in rivers and streams. It shows that increases in stressor occurrence reduces overall ecosystem integrity, and that fish assemblages may be negatively affected by such multiple stressor combinations. In terms of biological response, fish metrics based on age structure, fish region index and biological status responded most to single stressors and/or their combinations.
“The knowledge gained in this work provides a basis for advanced investigations in Alpine river basins and beyond, supports WFD implementation and helps prioritizing further actions towards multi-stressor restoration and management.”
One significant finding made by the study is that 37% of headwaters in Austria’s river basins are still in a very good or good ecological state. The authors argue that there is a pressing need for environmental policy and management to protect these headwater reaches from human pressures, particularly from hydropower construction.
Meet the AQUACROSS team: Fiona Culhane
Dr. Fiona Culhane
Last week, Manuel Lago introduced the EU-funded AQUACROSS project in a blog post which called for a greater focus on gender equality in environmental science and policy-making.
This week, we begin the first of a series of interviews with AQUACROSS researchers by speaking to Dr Fiona Culhane from the University of Liverpool in England. Fiona introduces us to her research, and her motivations for studying aquatic environments.
Freshwater Blog: What is your focus of your work in AQUACROSS, and why?
Fiona Culhane: The focus of my work in AQUACROSS is on the links between people and aquatic ecosystems, from an ecologist’s perspective. Through AQUACROSS, I am exploring how human activities and the impacts these have on aquatic ecosystems will ultimately affect our own well-being and the socio-economic system, via the ecosystem. Though my main focus is on marine environments, I am interested in looking at these effects at a large-scale, across the aquatic realms, and developing methods that can work in data poor situations.
Cattle and donkeys grazing the edge of Lough Erne, Northern Ireland. Image: Fiona Culhane
Why is your work important?
In order to manage ecosystems sustainably, we need to understand the links in the system and the consequences of our own actions. If we put this in terms of our own well-being and the socio-economic system, we may better be able to highlight the trade-offs that occur with resource use so that we can make more informed decisions about how to protect the environment for future generations.
What are the key challenges for marine management in Europe?
Marine environments are large, highly connected ecosystems, where knowledge is often patchy or disparate. The challenge for management is to make decisions that take account of the connectivity and to do this with limited information.
Marine ecosystem services are varied, and interlinked with those in freshwater and estuarine environments. Image composite: Fiona Culhane
Tell us about a memorable experience in your career.
When I started my first post-doc job at the University of Liverpool, I joined the team working on the ODEMM project. After years working alone on my PhD it was a big change. The group was highly collaborative and I realised how productive, inspiring and motivating it can be to work like that. It was a turning point for me because I recognised that was how I would like to continue working as a scientist in the future.
What inspired you to become an ecologist?
I have always loved nature and cared about the environment, most probably influenced by my mother as she is always pointing out different species of plants and animals to me. I was excited to get to secondary school, to finally be able to study science, which became one of my favourite subjects. As time went on, I saw that being a scientist could be a way to make a difference to the world. A job where I could travel and work outdoors was also really appealing to me.
Looking out across the Firth of Clyde in Western Scotland. Image: Fiona Culhane
What are your plans and ambitions for your future scientific work?
As my career has progressed, I have seen that being an ecologist is not only about making a difference to the environment and biodiversity but also to people’s lives. I am very interested in the connection between the state of the ecosystem and the health and wellbeing of people. I am interested in developing methods that can work in data poor situations, such in the developing world, where the knowledge base is poor, but where people are most affected by changes to their ecosystems.
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