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16th International Symposium on Aquatic Plants

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Session 1:
Lessons learned by Mediterranean ecosystems: aquatic plants research and conservation in freshwaters affected by climate change

Chair: Eva Papastergiadou (University of Patras, Greece), Kostas Stefanidis (Hellenic Centre for Marine Research, Greece). 

Topic: Mediterranean ecosystems (Mediterranean basin and parts of coastal California, Chile, South Africa, and South-West Australia) have a long history of human disturbances and water scarcity exacerbates pressures around water bodies (i.e., morphological changes, water abstraction, irregular water flow, pollution, eutrophication, water logging, and leisure activities). Ecosystems in warm climates are more sensitive to anthropogenic pressures, such as eutrophication and water extraction, than similar ecosystems in temperate or cold climates. Nowadays global climate change affects freshwater ecosystems worldwide, threatening the survival of sensitive species, increasing droughts, also in tropical and temperate regions, and consequently species extinction rates and freshwater ecosystem degradation. In this session, we welcome submissions addressing the factors that influence aquatic macrophytes richness, diversity, functional traits and habitat features, as well as biotic adaptations and resilience responses to hydrologic disturbances in Mediterranean freshwaters (e.g. streams, rivers, lakes, lagoons, ponds, etc), and in other regions that experienced increasing droughts because of climate change.

Session 2:
The macroecology of aquatic plants in freshwaters

Chair: Janne Alahuhta (University of Oulu, Finland), Jorge García-Girón (University of Oulu, Finland & University of León, Spain).

Topic: Studies on species distribution patterns and diversity have generated a number of macroecological hypotheses and rules across space and time. Unfortunately, the field of freshwater plant macroecology is still in its infancy and explanations for large-scale patterns and mechanisms in macrophytes are still elusive. This session is aimed to share recent advances in the macroecology of freshwater plants across different biogeographical areas, spatial scales, and ecosystems. By doing so, we hope to forge an exciting interdisciplinary discussion that will inspire collective efforts and consortiums aimed at stimulating the incipient rise of macroecology investigations on freshwater plants across broad spatial and temporal scales.

Session 3: Plant-animal interactions in aquatic plant beds (Zoogeochemistry session)

Chair: Liesbeth Bakker (Netherlands Institute of Ecology, Wageningen University and Research, The Netherlands), Jonas Schoelynck (University of Antwerp, Belgium).

Topic: Aquatic plants are food for herbivores and omnivores and thus part of the aquatic food web. However, they are as important as providers of habitat to other organisms. Therefore, aquatic plants play a crucial role in the conservation and restoration of riparian and benthic habitats. With ongoing global change, including eutrophication, exotic species proliferation and climate change, the properties of the plant beds may change as well as the plant-animal interactions that take place within the beds. Alternatively, restoration may make use of plant properties to attract animals whereas the animals in turn may consume the restored plant beds. This session welcomes contributions on the interactions between plants and animals, both trophic and non-trophic, to advance our understanding of the fundamental aspects of plant-animal interactions under water and in wetland vegetation and address emergent properties of plant-animal interactions in a restoration or global change context.

Session 4:
Genetic diversity and structure in aquatic plants (continental and coastal habitats)

Chair: : Ludwig Triest (Vrije Universiteit Brussel & Université Libre de Bruxelles, Belgium).

Topic: Molecular tools became increasingly important in ecology, allowing us to understand underlying diversity patterns in aquatic plants. In aquatic populations, molecular ecology can be used to to identify species or hybrids, to understand their survival strategy that can be mixed (sexual/clonal) and their dispersal movement ecology . Habitat modifications may disrupt gene flow and alter genetic connectivity of aquatic plant populations through isolation-by-distance, as well as changing their local structure. This session aims to compile work on how genetic information of populations can be used in aquatic plant ecology to better understand their biogeographical migration history, life strategies, survival and movement ecology for practically aiding the management of aquatic plant vegetations. Focus will be on the relevance and applications, not on the molecular methods as such. This session will include presentations on:
•Species and hybrid identification (phylogenetics and barcoding)
•Large-scale patterns (phylogeography, long-distance dispersal)
•Gene flow (pollen flow and seed flow), isolation-by-distance
•Survival strategies (sexual, clonal, mixed) and fine-scaled structures
•Movement ecology, spread and dispersal patterns

Session 5:
Causes and patterns of macrophyte decline and recovery

Chair: Sabine Hilt (IGB Berlin, Germany), Andreas Hussner (Heinrich-Heine-Universität , Germany).

Topic: In many freshwater bodies, the abundance and community composition of submerged and/or floating macrophytes is of key importance for several ecosystems functions such as habitat, nutrient retention or carbon processing. Understanding the causes and patterns of changes in macrophyte communities is thus crucial for a sustainable management of these water bodies and their functions. In recent decades, a number of general concepts have been developed, such as regime shifts between alternative stable states in eutrophic shallow lakes and lowland rivers, the occurrence of crashing/recovery states or boom-bust cycles of invasive species. Yet we are still far from understanding the complex patterns and causes of spatial and temporal changes in macrophyte communities. A pelagic focus in limnological research and a lack of macrophyte data in sufficient temporal and spatial resolution have been reasons for this knowledge gap. However, recent developments in macrophyte monitoring due to legislation (e.g. EU Water Framework Directive) and new methods (remote sensing, hydroacoustics) have improved this situation and allow for new insights. In this session, we welcome fundamental and applied contributions with a mechanistic or methodological focus on causes and patterns of macrophytes decline and recovery at all spatial and temporal scales.

Key session objectives:
•Unravel patterns of shifts in macrophyte abundance and community composition
•Identify key drivers for shifts in macrophyte abundance and community composition. 

Session 6:
Friends or foes: Wanted and unwanted effects of herbicides on aquatic plants facing multiple stressors

Chair: Elisabeth Gross (Université de Lorraine, France), Gertie Arts (Wageningen University and Research & Wageningen Environmental Research, The Netherlands), Ryan Thum (Montana State University, USA). 

Topic: Herbicides may affect aquatic plant performance unintentionally or through targeted action. Their use in aquatic systems underlies dissimilar regulation in different parts of the world. In Europe, the Water Framework and Pesticide Directive provides the guideline to limit the impact of herbicides and other anthropogenic pollutants on water bodies. In the US, the Environmental Protection Agency (EPA) and relevant state authorities regulate herbicide use, but application in water bodies can be allowed as a decisive tool to control invasive alien aquatic plants. For the admission of herbicides on the market, a dossier needs to be submitted based on – mostly – short-term experiments with standard primary producer species (algae and aquatic macrophytes). What is missing in our understanding of effects of herbicides on aquatic plants, are long-term effects, e.g. carry-over effects to the next season or effects on the recovery and competitive ability of aquatic macrophytes. In addition, aquatic plants are not only threatened by herbicides but by multiple other stressors acting on them, such as climate warming, heatwaves, eutrophication, browning or salinization. A better understanding of single and multiple stressor effects on aquatic plants is key in order to understand effects at the ecosystem level. This session intends to bring together the different views and to provide a platform to outline known targeted and side effects of herbicide use in freshwater systems and to place them in a scenario of multiple simultaneous stressors acting on them.

Key session objectives:
•To bridge ecotoxicology and aquatic plant ecology
•To assess the role of herbicides and other anthropogenic pollutants in aquatic plant decline

Session 7:
Macrophytes as Nature Based Solutions in urban ecosystems (BiNatUr session)

Chair: Jan Staes (University of Antwerp, Belgium), Krzysztof Szoszkiewicz (Poznań University of Life Sciences, Poland), Krister Karttunen (Finnish Environment Institute, Finland), Jonas Schoelynck (University of Antwerp, Belgium). 

Topic: Aquatic ecosystems are increasingly being used and created as sinks and sources for water. In urban environments, there is a need to store and infiltrate increasing amounts of water, generated by runoff on degraded and sealed soils. There are risks and opportunities when using or creating Urban Aquatic Ecosystems. Opportunities, when we can design urban water parks that can fullfill this sink/source function while also generating many other ecosystem services, such as habitat for biodiversity, climate regulation, air quality regulation, health effects, etc… A well-designed Aquatic NbS should also be home to macrophytes as they are essential to the aesthetic quality of the site, water purification and biodiversity. How do we need to design and manage such aquatic NbS to maintain these ecosystem services over time? Especially when these systems are be exposed to extremes in terms of water level fluctuations (floods and droughts) and associated water quality issues. A smart design and management is needed because there is especially a risk when we are using and exposing existing high biodiversity ecosystems to such extremes. Currently, there is not much knowledge about the role of macrophytes in Urban Aquatic Ecosystems. What can we learn from the species composition and ecological succession over time? Are macrophytes (and other species) sentinels of ecosystem health? What should we do with exotic/invasive species? Should native species be actively introduced? What can we learn from cases where an ecological design has been applied? What are lessons learned?

Session 8: Macrophyte monitoring (Biomonitoring based on macrophytes/Environmental monitoring based on macrophytes)

Krzysztof Szoszkiewicz (Poznań University of Life Sciences, Poland).

By monitoring the diversity and abundance of macrophytes, we can obtain valuable information about the ecological condition of the water body. Aquatic plants are sensitive to environmental changes, mainly related to nutrient enrichment, sedimentation, and hydrological as well as morphological alterations. In the context, aquatic plants, can be used to assess the water quality and the ecological health of aquatic ecosystems. Moreover aquatic plants are efficiently used to detect the level various stressors in rivers and lakes. We encourage presenters to share their latest research findings, as well as innovative methodologies, techniques, and tools that can advance the field of aquatic plant ecology and biomonitoring. This session will include presentations on:
•Water quality biomonitoring systems using aquatic plants
•EU Water Framework Directive in rivers and lakes – experiences, recent changes
•Plant-based monitoring in aquatic ecosystem management and conservation
•Biotic and abiotic stressors that can be efficiently detected by macrophytes
•Ecotoxicology and aquatic plant toxicity testing
•Novel techniques for aquatic plant-based monitoring
•Ecosystem functioning and services of aquatic plants

Session 9: Management of macrophytes

Chair: Deborah Hofstra
(National Institute of Water and Atmospheric Research, New Zealand), Iris Stiers (Vrije Universiteit Brussel, Belgium).

Topic: Aquatic plants play a substantial role in the functioning of aquatic ecosystems, but some macrophytes, mostly alien species, are invasive and have significant ecological and economic impacts. Alien invasive species are considered second only to habitat loss as the drivers of biodiversity decline in freshwaters globally. Their impacts are additional to other stressors on the aquatic environment, often operating independently from them and escalating over time in the absence of management. The selection of an appropriate management option that will decrease negative effects of invasive macrophytes is largely dependent on the species (its ecology and impacts), the invasion pathways and size of the invaded area, and the outcome sought. The outcomes sought by management agencies may be driven by legislative requirements, the need to protect biodiversity, rare or threatened species habitat, and are increasingly related to the risks as perceived and accepted by the public. To successfully manage the threats and mitigate the impacts of invasive aquatic weeds, science is challenged to develop tools and approaches that can be implemented within a complex range of aquatic environments (including a changing climate), and that will provide predictable outcomes within appropriate timeframes and at scale. This session welcomes papers on all aspects of macrophyte management, from invasion ecology, to pathway and vector interception of invasive species, and the restoration of desirable species. We also welcome papers on on public perception or communication and outreach.

Session 10:
Other topics.


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