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Macrophyte recovery in eutrophic shallow lakes requires both internal and external restoration measures

February 23, 2018
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Felbrigg Lake in Norfolk, UK – one of the shallow lake ecosystems in this study. Image: colinsd40 | Flickr Creative Commons

Shallow lakes are the most abundant freshwater ecosystems on earth, and are often characterized by abundant submerged vegetation, which can stabilize clear-water conditions and play a key role in ecosystem functioning. However, eutrophication – often caused by nutrient pollution – has caused increasingly cloudy water conditions in many shallow European lakes over the last century. In many places, such ‘turbid‘ lake waters have resulted in the loss of many submerged aquatic plant communities, which rely on light penetrating the water column to thrive.

Considerable environmental management efforts have been devoted to restoring clear-water conditions in shallow European lakes. However, the successful long-term establishment of stable and diverse aquatic plant (known by scientists as ‘macrophyte‘) communities often fails. As a result, macrophyte recovery patterns following the management of multiple stressors including nutrient pollution are yet to be fully understood.

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A German shallow lake with extensive summer cyanobacteria blooms: a typical feature of the intermediate recovery phase during nutrient load reduction. Image: Sabine Hilt

A new open-access study published in Frontiers in Plant Sciences aims to unravel recovery patterns of macrophytes in response to different lake restoration measures. Lead author Sabine Hilt – senior scientist at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin – and colleagues from Germany, The Netherlands, Denmark, Sweden and the UK collected and analysed data on water quality and submerged macrophyte communities in 49 temperate shallow lakes.

All studied lakes had deteriorated to a turbid state, and subsequently were subject to either external or internal restoration measures (or both). External restoration measures generally involve the reduction of external nutrient pollution, whereas internal measures include biomanipulation or phosphorus precipitation in an attempt to control eutrophication blooms.

“Based on a few existing case studies, we hypothesized that reduced external nutrient loading would often lead to an intermediate recovery state with clear spring and turbid summer conditions, similar to the pattern described for eutrophication” states Sabine Hilt. Data collected from 21 different lakes supported their hypothesis. In many lakes, clear spring conditions allowed a re-colonisation of macrophytes, but the continuation of strong cyanobacteria blooms, and turbid summer conditions.

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The ecological trajectories and management measures between turbid and stable clear state in shallow lakes. Infographic: Sabine Hilt and colleagues

This situation can be simulated using an adapted version of the ecosystem model PCLake. Model simulations indicate the existence of specific thresholds in nutrient loading for shifts between turbid, intermediate and clear-water conditions.

In contrast to external nutrient load reductions, lake internal restoration measures such as the manipulation of the fish stock often resulted in transient clear-water conditions both in spring and summer. This was shown using data from 28 different shallow lakes. Often, however, lakes returned to turbid conditions.

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Sago pondweed (Potamogeton pectinatus) overgrown with periphyton in the recovery period following nutrient load reduction (photo: Sabine Hilt)

Interestingly, the contrasting restoration measures resulted in different macrophyte species compositions. The intermediate recovery state following reduced nutrient loading was mainly characterised by a few pondweeds that can resist wave action (allowing survival in shallow areas), germinate early in spring, have energy-rich vegetative propagules facilitating rapid initial growth, and can complete their life cycle by early summer. In contrast, internal lake restoration measures often coincide with a rapid but transient colonisation by hornworts, waterweeds or charophytes.

The authors conclude that the composition of the macrophyte community and their seasonal abundance in shallow lakes during recovery from turbid, highly eutrophic conditions often depends on remnant macrophyte stands, the specific restoration measure applied, and additional stochastic influences on water clarity such as winter fish kills, cormorant predation on fish or introduction of invasive filter-feeding mussel populations. In turn, the prevailing macrophyte community can influence lake water quality. Their study suggests that lasting macrophyte recovery in shallow lakes can only be achieved when internal restoration measures are combined with reduced external nutrient loading.

Hilt S, Alirangues Nuñez MM, Bakker ES, Blindow I, Davidson TA, Gillefalk M, Hansson L-A, Janse JH, Janssen ABG, Jeppesen E, Kabus T, Kelly A, Köhler J, Lauridsen TL, Mooij WM, Noordhuis R, Phillips G, Rücker J, Schuster H-H, Søndergaard M, Teurlincx S, van de Weyer K, van Donk E, Waterstraat A, Willby N and Sayer CD (2018) Response of Submerged Macrophyte Communities to External and Internal Restoration Measures in North Temperate Shallow Lakes. Front. Plant Sci. 9:194. doi: 10.3389/fpls.2018.00194

The Beauty in the Bog

February 14, 2018
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Peat can be cut or mined from peatlands for use as fuel, for growing plants, insulation, packaging and beauty treatments. But the bare peat left behind doesn’t support much life. Credit: nz_willowherb, Flickr, CC-BY-NC 2.0

A guest post by Dr Claire Wordley from Conservation Evidence.

Soggy, centuries-dead plants may not sound like they should be a global conservation priority. But peatlands – soils where water saturation prevents organic matter from fully decaying – store 500 billion metric tons of carbon worldwide. That’s more per metre than rainforests, and the equivalent of half of the carbon that is currently in the atmosphere. Peatlands also contain a wide variety of animals and plants, some of which only live in these wet habitats. Bitterns and bearded tits, ruffs and phalaropes, even tigers and orangutans, all call peatlands home.

Healthy peatland vegetation is fundamental to capturing carbon, housing biodiversity and regulating water cycles. This week, an online resource collecting the evidence for what works (and what doesn’t) to conserve and restore peatland vegetation has been published. This is the first chapter of the ‘wetland synopsis’, a three year project to gather the global evidence for the effects of interventions to conserve plant communities in all types of wetlands, run by researchers at Tour du Valat in France in collaboration with Conservation Evidence at the University of Cambridge in the UK.

Across the world, peat has been dug up to add to compost in garden centres, dried out to allow the planting of timber or crops, or even mined as a fuel to burn. As the peatlands are exploited, wonderful and fragile ecosystems are lost. The Dutch landscapes of polders and windmills? Built to keep water out of drained peatland. East Anglia’s arable desert? Once wet fenland on peat soils. Oil palm plantations in Indonesia? Planted after the lush peat swamp forests were cut and burned. But this is not the end of the story; people are working hard to conserve peatland vegetation, and even restore it to some places where it has been lost.

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A healthy peatland can contain a mix of mosses, shrubs, trees and open water. Boardwalks allow people to explore and enjoy the bog without damaging the plants. Credit: Tania & Artur, Flickr, CC-BY-NC-ND 2.0

The ‘peatland synopsis’ collects together and summarises the evidence for 120 different ‘interventions’, actions that conservationists might take to conserve or restore vegetation on wet peat soils: areas like bogs, fens and peat swamp forests. The authors, led by Nigel Taylor, gathered scientific papers from over 220 journals, plus unpublished reports by NGOs and governments. Experts then scored the evidence for each intervention, to estimate the benefits of that intervention, any harms arising from it, plus the certainty in the evidence. The results are available for free on the Conservation Evidence website, and those related to restoration can also be found on the Restoration Evidence website, a new site devoted to collecting the evidence for the restoration of habitats globally.

So what can be done to stop the draining of the swamps, and to restore those that have been drained? The gathered evidence can show us the best strategies. ‘Rewetting’ peat, for example by blocking drainage ditches, was the intervention with the most evidence by far. It led to the recovery of bog and fen vegetation in many studies. Removing trees (usually plantation forests) along with rewetting, also tended to increase typical high-latitude peatland vegetation such as Sphagnum moss, cottongrass and sedges, although the precise effects depended on the site. Spreading mosses and other plants over bogs and fens often led to the establishment of typical bog and fen species, although again the success rates varied.

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There are large areas of peat swamp in the tropics. It is important to monitor the effects of any conservation interventions, and report the results so others can learn what works and what doesn’t. Credit: CIFOR, Flickr, CC-BY-NC-ND 2.0

Some interventions, however, appeared not to work very reliably. Planting ‘nurse plants’ for peatland vegetation didn’t seem to help (in either tropical or boreal studies). Creating mounds or hollows in the peat surface before planting vegetation didn’t affect Sphagnum cover in Canadian studies, although one study in peat swamp in Thailand reported that planting trees into mounds of peat led to thicker stems. Adding root-associated fungi to plants before planting didn’t work for most of the 15 Indonesian species in which it was studied; however, in one study, some fungal treatments did slightly increase the growth and survival of one species.

There are many things we can do to help peatlands, as researchers, conservationists and individuals. Researchers can test more interventions that might be used to conserve and restore peatland plants – for over half the interventions studied, no evidence was found, and very few studies were found from tropical peatlands. These all represent important knowledge gaps. Conservationists can use the available evidence to make the best possible decisions about what to do with their peatland, and, where possible, test the interventions that they are undertaking and publish the results. Individuals can avoid buying compost containing peat (look for peat-free logos) and avoid palm oil, or buy certified sustainable palm oil products instead. And we can all learn to appreciate swamps, bogs and fens; if you live near a peatland nature reserve then visit, and marvel at the beauty in the bog.

Conservation Evidence website.

Messages from MARS

February 6, 2018
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MARS leader Daniel Hering addresses the final project conference in Brussels. Image: Jörg Strackbein

The EU FP7 MARS Project“Managing multiple stress for multiple benefits in aquatic ecosystems”celebrated its final conference in Brussels last month. On the 16 and 17 January 2018, around 150 water scientists, managers and policy-makers convened in the time-honoured halls of the Museum of Natural Sciences, Brussels.

The event concluded four years of in-depth research by MARS scientists on multi-stressor effects on European surface and ground waters, highlighting the implications for Water Framework Directive (WFD) related management.

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Ana Cristina Cardoso speaking to the MARS conference. Image: Jörg Strackbein.

Among the array of fascinating results generated by the MARS project, four key messages were reported at the conference.

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Message 1: Mitigating pressure-effects on aquatic ecosystems requires an understanding of multi-stressor impacts.

WFD water management is designed using the Driver-Pressure-State-Impact-Response concept. Significant pressures on aquatic ecosystems are identified first. These pressures are assumed to have impacts on ecological status of a river, lake or groundwater. Mitigation actions are then selected on the basis of these pressures (known as the “pressure-response shortcut”).

This approach may not fully account for the complex interactions and impacts of multiple stressors. As a result, MARS advocates aquatic science research that investigates the direct causes of deteriorated ecological status. Such an approach would allow for more informed management decisions targeting the actual, multi-stressor reasons for ecosystems not reaching good status.

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Multi-stressor/impact relationships lie at the heart of informed river basin management. The WFD monitoring programmes generate valuable data sources for such analysis. EQR = Ecological Quality Ratio; ESS = Ecosystem Services.

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Message 2: Environmental ‘noise’ can obscure evidence from multi-stressor/impact relationships in river basins. Experiments can help unravel multi-stressor interactions and impacts.

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Multi-stressor evidence at the river basin scale (most relevant for water management) is more obscure compared to the evidence gained at experimental scale (under controlled conditions) or European scale (with many and long stressor gradients).

Water managers deal with water bodies in the ‘real world’. Here, multi-stressor effects on aquatic biology often interfere with other (natural) factors like weather conditions or river flow dynamics.

Distinguishing multi-stressor effects from such complex environments is a bit like trying to identify a musical tune played in a noisy room. Nevertheless, water managers need to understand the multi-stressor combinations acting in their basin to devise appropriate mitigation measures.

Multi-stressor experiments (like those conducted by MARS in the Austrian Alps) help uncover the ‘noise-free’ pathways of multi-stressors interactions and impacts, and thus offer valuable insights for informed management decisions.

 

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Message 3: Multi-stressor interactions are common in rivers and lakes across Europe and need to be considered in River Basin Management. Interactions are highly context-specific, requiring targeted, localised research to inform management.

fig 3About one-third of the 156 MARS case studies studies analysed showed significant interaction effects (in paired-stressor/impact relationships). The strength of interaction effects at river basin scale is as large as at experimental scale.

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Message 4: River Basin Management in Europe will benefit from (more) data-driven analyses, modelling and interpretations which are tailor-made for the river basin to be managed.

WFD monitoring data from surface and ground waters across Europe is increasingly available, allowing researchers new opportunities to analyse multi-stressor/impact relationships. This evidence can feed into basin-specific prognostic or diagnostic models that enhance our understanding of aquatic systems, and help facilitate their effective management. Practitioners from applied aquatic science and water management can work together as interdisciplinary ‘water body doctors’.

MARS is helping create the conditions for such work by offering:

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Sebastian Birk (right) in conversation with Angel Borja at a ‘World Cafe’ session. Image: Jörg Strackbein

Summing up, MARS researcher Sebastian Birk is hopeful about the impacts the project can continue to have, “This final conference of the MARS project inspired the renewal of our Hippocratic oath ‘first not to harm’ but to be beneficial to our water resources. We feel confident that our project built bridges towards closing the gap between science and practice when it comes to more effective water management under multiple stress.”

View a full photo gallery from the conference here.

Find out more about MARS here.

Meet the AQUACROSS team: Asya Marhubi

February 2, 2018
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Asya Marhubi at Grutas de Tolantondo, México.

This week we continue our series of interviews with researchers from the EU AQUACROSS project by talking to Asya Marhubi. Asya works for IMDEA Water in Madrid, Spain on research support for the AQUACROSS project. She has an interdisciplinary background encompassing International Development Studies, Spanish and Latin American Studies and Corporate Social Responsibility.

We spoke to Asya to find out more about her work.

Freshwater Blog: What is the focus of your work in AQUACROSS, and why?

Given my academic background on international development my focus has traditionally been on socioeconomic development, however the fate of the two are inextricably linked with that of the environment, and concerns regarding climate change and environmental conservation have been ubiquitous throughout my education and professional career.

For this reason, within AQUACROSS, my work has been centred on the socioeconomic system, focusing on policy orientation under WP2, supporting the development and update of the AQUACROSS Assessment Framework under WP3, and contributing to work being performed on drivers of change under WP4.

Why is your work important?

It contributes towards deepening our understanding of the links between ecological and socioeconomic systems, and of the wellbeing benefits that are provided by a healthy ecosystem. I believe that through strengthening the understanding of the links between the two systems is crucial in order for us to move closer to holistic approaches to environmental management that give appropriate weight to the value of goods and services provided to us by the environment.

What are the key challenges for aquatic management in Europe?

From my perspective, one of the key challenges of water management in Europe is the negotiation of trade-offs between different water uses and users (including the environment), especially under the context of climate change adaptation and increasing water scarcity.

This context also brings into the foreground the rising need to decouple water use and economic growth in order to ensure that the global quest for socioeconomic development does not come at a disproportionate cost to the environment, and to the legacy left for future generations.

Tell us about a memorable experience in your career.

In addition to my work at IMDEA Water, over the past year I have had the opportunity to manage social media and other dissemination activities for the Foro de la Economía del Agua (Water Economics Forum).

Through this initiative I have had the opportunity to hear from numerous Nobel Prize Laureates and international experts of world renown on a wide array of topics related to water resource and service management, such as George Akerlof, Gro Harlem Brundtland, Mohan Munasinghe, Michael Hanenmann…to name just a few.

What inspired you to take your career path?

My interest in global issues stems from my childhood; growing up as an Omani citizen to British and Zanzibari parents, I saw first-hand the stark differences between my family’s life in Oman, and those of my relatives living in Zanzibar, and England. After beginning my undergraduate degree in International Development, and Spanish & Latin American Studies in 2006, I have come to appreciate that the disparity within my own family is a result of a large, and intricate set of systems.

Through my academic, personal and professional experiences, I have sought to gain a deeper understanding of these systems that shape our lives. I believe that their complexity requires us to adopt a holistic and collaborative approach, in order to change the nature of these systems for the better.

What are your plans and ambitions for your future work?

International development is an inherently interdisciplinary field, and fundamentally, this has given me the opportunity to study and work alongside people from diverse academic and cultural backgrounds. Given the complexity of the today’s global issues, and their ever-evolving nature, especially in the digital and globalised age, I believe that this is an essential skill.

And while I do not know exactly where my career will take me, it is my hope to contribute to bridging the gap between natural and social sciences, and to championing the adoption of holistic and interdisciplinary perspectives and approaches to the challenges we face.

AQUACROSS project website.

How are river ecosystems affected by regulation?

January 26, 2018
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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.”

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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.

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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

January 18, 2018
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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.

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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

January 12, 2018
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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.

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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.

Everall NC et al (2017) Sensitivity of the early life stages of a mayfly to fine sediment and orthophosphate levels, Environmental Pollution, Online: In Press.

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