Freshwater macrophytes—rooted and free-floating vascular plants inhabiting lakes, rivers, wetlands, and streams—play a foundational role in ecosystem functioning. They regulate nutrient cycles, stabilize sediments, structure food webs, and support biodiversity; their ecological significance is widely acknowledged. However, linkages between the diversity, spatial distribution, and temporal dynamics of macrophyte communities and their associated ecosystem functioning remain understudied, particularly in the context of accelerating global environmental change.
With freshwater ecosystems undergoing unprecedented changes due to climate variability, eutrophication, land-use transformations, invasive species, and hydrological alterations, this proposed session addresses the urgent need to integrate macrophyte community dynamics into broader freshwater ecological research.
Understanding how macrophyte communities respond—and how those responses affect ecosystem functioning in turn—is essential. Notably, recent advances in trait-based ecology have shown how plant life forms, such as emergent and submerged species, exhibit realm-specific adaptations and distinct trait-environment relationships, leading to divergent impacts on ecosystem functions like carbon cycling and nutrient uptake.
The session will bring together limnologists, aquatic botanists, and macroecologist to explore:
Spatial and temporal dynamics of macrophyte community composition across climate and nutrient gradients Functional trait diversity of species and communities and its implications on ecosystem processes, such as denitrification, methane flux, and habitat provisioning The role of macrophytes in mediating responses to disturbances like droughts, floods, habitat degradation or invasive species Comparative studies across freshwater systems globally, with a focus on dataset harmonization and modelling frameworks
We particularly encourage submissions that address the reciprocal relationship between macrophyte communities and ecosystem functions— through field data, experiments, modelling, or synthesis—and that integrate aspects of global change in freshwater systems. Contributions linking macrophyte diversity to biogeochemical states, food web interactions, or remote sensing advances are also welcome.
Lead Organizer: Lars Iversen, McGill University (lars.iversen@mcgill.ca)
Co-organizers:
Lindsay Trottier, McGill University (lindsay.trottier@mail.mcgill.ca)
Yang Liu, McGill University (yang.liu15@mail.mcgill.ca)
Alice Dalla Vecchia, University of Parma (alice.dallavecchia@unipr.it)
Presentations
04:30 PM
ECOSYSTEM-ATMOSPHERE CO2 EXCHANGE IN SUB-ARCTIC LAKES; WHAT IS THE ROLE OF EMERGENT MACROPHYTES? (11205)
Primary Presenter: Sari Juutinen, Finnish Meteorological Institution (sari.juutinen@fmi.fi)
Northern lakes are important sources of carbon dioxide (CO2) to the atmosphere, yet global estimates of lake CO2 exchange remain uncertain. In particular, the contribution of emergent macrophyte vegetation to lakes’ greenhouse gas (GHG) exchange is poorly known. We hypothesized that in sub-arctic lakes, often poor in organic matter and nutrients, vegetated areas contribute substantially to lakes’ ecosystem-atmosphere net CO2 and GHG exchange. To test this hypothesis, we studied three lakes in the Atmosphere-Ecosystem Supersite in Pallas, Finland (68°00'N 24°09'E). The lakes had low organic carbon and nutrient concentrations but differed in catchment properties and sediment organic content. We measured ecosystem-atmosphere CO2 exchange for two years in open water and vegetated areas (Carex spp., Equisetum fluviatile and Nuphar lutea) with paired transparent and opaque chamber measurements using portable GHG analyzers. In addition, high-frequency water CO2 concentration and eddy covariance measurements were conducted in one lake. Macrophyte abundances were modeled using field and Sentinel-1 and 2-data. We observed net uptake of CO2 in the vegetated areas, ca. 100–500 g CO2 m2 y-1, which counters the effect of the CO2 emissions in the open water areas, ca. 100–200 g CO2 m2 y-1. On the other hand, macrophyte production can fuel heterotrophic respiration due to relocation of dead plant material. Accounting for the vegetated areas in lakes’ GHG exchange is essential and assuming that they behave like terrestrial wetlands is not a valid approach.
04:45 PM
Managed hydrochory: A novel process-based restoration approach for submerged macrophytes in regulated rivers (10888)
Primary Presenter: Colin Burke, Australian Rivers Institute - Griffith University (colin.burke@griffithuni.edu.au)
Hydrochory, the dispersal of propagules by water, is a critical process for recovery and resilience of freshwater macrophytes. Dams and other instream barriers fragment river networks, alter flow, and reduce opportunities for propagule movement and settlement, limiting recolonisation and connectivity. Downstream of a large dam in the mid-Brisbane River, south-east Australia, severe flooding has caused extensive scouring and substantial loss of submerged macrophytes that the threatened Australian lungfish relies on for spawning, juvenile refuge, and food resources. The dam inhibits natural hydrochory of macrophyte propagules, therefore active restoration is required to reestablish macrophytes downstream of the dam. We trialled the world’s first process-based restoration of submerged macrophytes through managed hydrochory, manually releasing vegetative propagules of two native species, Vallisneria nana and Myriophyllum verrucosum, just below the dam. Three releases (~50 kg wet weight per release) occurred over three months across a 1.5 km river reach. Wooden stakes were installed and monitored to evaluate propagule retention and establishment relative to local hydrology. Stakes increased retention, with most propagules trapped within the first 300 m, although some travelled the full reach. Establishment of both species was greater in shallow, fast flowing areas. Our approach shows early success and demonstrates that managed hydrochory can provide an effective, low-cost method for restoring submerged macrophyte habitat in regulated rivers following major scouring events.
05:00 PM
MODELLING AQUATIC BRYOPHYTES AND OTHER MACROPHYTES IN DETERIORATING RIVERS (11718)
Primary Presenter: Krister Karttunen, Finnish Environment Institute (krister.karttunen@syke.fi)
Bryophytes are an integral and important part of aquatic vegetation and biodiversity especially in river rapids and riffles. We modelled aquatic macrophyte data, some 50 bryophyte and 150 tracheophyte taxa, in 295 river sites with standardized sampling to estimate ecological quality. Using RIVPACS type approach we recognized 11 distinct plant communities in natural or near natural state. Size and soil of catchment area and latitude could be used to characterize natural macrophyte communities in pools and riffles. Based on reference communities we estimated ecological quality of impacted sites utilizing two indices: taxonomic completeness (O/E-taxa) and percent model affinity (PMA). Bryophytes in rapids alone can be used in ecological classification of rivers, though most reliable results are achieved by studying all aquatic plants in both riffles and pools. To assess changes in biodiversity we further modelled how species frequencies change due to environmental loading and disturbance, with a larger data of 780 sites and 124 bryophyte taxa. We paid special attention to more common proper aquatics with high confidence interval in the model. Of these, four species have clearly lower frequency even in sites of good ecological status than in reference sites whereas three were more frequent. Sites in high ecological status naturally did not differ from refence sites. This indicates that the target of the European environmental policy, good ecological status of all water bodies, is not good enough to maintain aquatic biodiversity
05:15 PM
A Trait-Based Framework for Aquatic Plants Life Forms: The Emergent–Floating–Submerged (EFS) Continuum (10804)
Primary Presenter: Yang Liu, McGill University (yang.liu15@mail.mcgill.ca)
1. Freshwater plants exhibit diverse life-form strategies that allow them to persist across environments ranging from temporary flooded wetlands to deep lakes. Existing frameworks for freshwater plants, such as emergent, floating, and submerged life-forms, rely on the categorical classifications of species into fixed groups. Although they are widely used to describe ecological and evolutionary patterns in plant communities, these categorical schemes remain inconsistent across studies, fail to capture mixed or plastic morphologies within species and do not provide a quantitative link between fluctuating freshwater environments and plant morphology and function. 2. Here we introduce a continuous trait-based framework—the Emergent–Floating–Submerged (EFS) continuum—to describe aquatic plants based on the proportional expression of three key leaf type dimensions. Using a dataset spanning 1,640 species worldwide, we show that the EFS continuum captures morphological variability that can be used to understand ecological and evolutionary plant adaptations. 3. We found that continuous EFS traits outperform classical categorical definitions in predicting trait–environment relationships, revealing life-form dependent community responses to water transparency, alkalinity, and nutrient enrichment in community assembly models. We also show that the EFS framework can be used to map the evolutionary transitions among aquatic life forms. Emergent leaf strategies represent the ancestral condition within aquatic lineages and the principal source of transitions to alternative life forms, particularly submerged strategies. Floating strategies were comparatively rare and exhibited few inferred transitions. Together, these findings demonstrate that life-form identity is more accurately represented as a continuous and evolutionarily dynamic spectrum rather than as fixed categories. 4. Synthesis: By integrating inter and intraspecific leaf variation within a unified quantitative framework, the EFS continuum provides a scalable foundation for predicting functional change and ecosystem responses in freshwater systems under global environmental change.
05:30 PM
EUPHORIA: CONTINENTAL-SCALE PHENOLOGY OF FRESHWATER MACROPHYTES AND LINKS TO ECOSYSTEM FUNCTIONING (10042)
Primary Presenter: Benjamin Misteli, Wassercluster Lunz (benjamin.misteli@wcl.ac.at)
Phenology, the timing of seasonal life-cycle events, is a key but overlooked dimension of freshwater macrophyte ecology. Shifts in the onset, peak, and duration of growth stages can alter primary production, nutrient uptake, habitat provisioning, and species interactions, yet broad-scale assessments of macrophyte phenology are almost absent. Here we present the EUPHORIA (European Plant Phenology Research in Aquatic Systems) project, a continent-wide, collaborative network that quantified phenological traits of common native and non-native macrophytes across European lakes, rivers, and wetlands. From April to October 2025, more than 100 early-career researchers applied standardized protocols to track key events (growth, flowering , peak biomass, senescence) and linked them with climatic conditions, water depth and water quality (including nutrient availability) along latitudinal and climatic gradients. We will present first results on the spatial variation in phenological traits and on correlations between traits, temperature and light conditions across sites. These findings will contribute to a better understanding of freshwater plant responses to environmental change and improve predictions of macrophyte dynamics under future climate scenarios. By providing a continental scale assessment, EUPHORIA offers valuable insights for conservation and management strategies in European freshwater ecosystems.
05:45 PM
INTEGRATED MODELLING OF CLADOPHORA, DREISSENIDS, PHOSPHORUS, AND PHYTOPLANKTON IN THE NEARSHORE OF LAKE ONTARIO (11168)
Primary Presenter: Yasasi Fernando, University of Toronto (yasasi.fernando@mail.utoronto.ca)
Cladophora glomerata has re-emerged as a dominant benthic macrophyte in the nearshores of the lower Great Lakes, leading to extensive fouling of local beaches with decaying organic material. These blooms are influenced by several factors, including nutrient loading, light availability, and the presence of dreissenid mussels, thus requiring a more granular approach to modelling its growth and impacts. We present a novel process-based model that couples dissolved and particulate phosphorus with three interacting biotic compartments – phytoplankton, dreissenid mussels, and Cladophora. While these submodels have been studied individually, the evaluation of the range of dynamics they can collectively produce has been limited. Our analysis presents the findings from a comprehensive sensitivity analysis that identifies key drivers and ecological thresholds that control macrophyte biomass, nutrient retention, and the balance between benthic and pelagic production. Our study clearly identifies and addresses several knowledge gaps and outstanding questions to improve our understanding of the nearshore system. We discuss how these results can guide monitoring design and data collection, and identify management levers for reducing nuisance blooms, ultimately contributing to the effective management of macrophyte proliferation in the nearshores of Lake Ontario.
SS036B Macrophyte Communities and Ecosystem Functioning in a Changing Freshwater World
Description
Time: 4:30 PM
Date: 13/5/2026
Room: 524C