Mesocosm experiments have become an essential approach for addressing grand challenges in aquatic sciences, especially those related to biodiversity, ecosystem functioning, and responses to environmental change. By closing the gap between laboratory experiments and natural systems, mesocosms are a powerful tool for testing ecological theories, investigating functional diversity, and understanding the impacts of global change. They allow researchers to explore biogeochemical processes, understand the response of communities and organisms to individual, multiple, and/or combined stressors, and inform nature-based solutions to global problems.
This session aims to highlight recent advances in mesocosm-based research. We invite contributions from limnological and oceanographic studies that apply experimental approaches to freshwater (e.g., lakes, ponds, reservoirs, rivers, streams), marine, or transitional ecosystems (e.g., estuaries, coastal lagoons, wetlands, riparian areas). Of particular interest are studies addressing (1) grand ecological challenges for aquatic ecosystems related to climate change impacts, alterations of biodiversity, land/sea use, and pollution; (2) emerging and interdisciplinary topics, such as (but not limited to) functional traits and diversity, community assembly, ecosystem stability, trophic interactions, global change impacts, and restoration or management strategies; (3) novel mesocosm designs, innovative experimental methods, and data integration across spatial or temporal scales; (4) mesocosms as a tool for testing nature-based solutions for climate and anthropogenic impacts.
This session, led by the AQUACOSM Early-Career Researcher Network, provides a space for researchers to share findings, discuss challenges, and connect with peers and senior scientists working in similar areas. By encouraging collaboration and visibility (among the AQUACOSM network and beyond), we aim to reinforce the Early Career Researcher (ECR) community in experimental aquatic science and advance the role of mesocosm-based research in addressing global environmental challenges. We encourage abstract submissions for both oral and poster presentations. Contributions from undergraduate and graduate students, postdoctoral researchers, and other early-career scientists are especially welcome.
Lead Organizer: Cihelio Alves Amorim, WasserCluster Lunz - Biologische Station GmbH (alvescihelio@gmail.com)
Co-organizers:
Maja Ilić, University of Cologne (maja.ilic@uni-koeln.de)
Anna Schmidt, University of Vermont (anna.schmidt@uvm.edu)
Gabriela Ágreda-López, IMDEA Water Research Institute (gabriela.agreda@imdea.org)
Gülce Yalcin, Leibniz Institute of Freshwater Ecology and Inland Fisheries (guelce.yalcin@igb-berlin.de)
Presentations
11:00 AM
THE WORLD’S OLDEST MAN-MADE BIOLOGICAL EXPERIMENT - ANCIENT STONE JARS AS NATURAL MESOCOSMS FOR STUDYING ECOLOGICAL STRUCTURE IN TEMPORARY AQUATIC ECOSYSTEMS (10610)
Primary Presenter: Laura Käse, Copenhagen University (kaese.laura@gmail.com)
Biological experiments are often short-lived, yet effects on communities and processes require time to emerge. Consequently, conclusions become more robust with longer durations. A striking real-world example can be found in central Laos, where thousands of large stone jars are scattered throughout the landscape. For ~2000 years, rainwater interacting with jar geology and varying tree cover has created unique and replicated aquatic ecosystems. Their clustered layout enables testing of ecological and evolutionary questions. Here, we report how these ancient mesocosms can be used to test ecosystem responses to local abiotic variation and disturbance. The jars contained between 5 to 254 liters, but the capacity of the jars was substantially larger (from about 45 to over 1,000 liters). We show that tree cover dominates every jar ecosystem’s state, with variations in tree cover density creating gradients in oxygen (O2) and nutrient concentrations among jar ecosystems. Litter contribution to aquatic ecosystems leads to higher nutrient levels and lower O2 concentration, even in systems under different long-term selection, in the oldest man-made ecosystems ever analyzed. The jar communities, obtained from environmental DNA, reveal very distinct composition in each jar shaped by abiotic conditions and a seemingly high degree of idiosyncrasy. This system provides a rare long-term perspective on how alternate wetting and drying together with terrestrial inputs influence aquatic ecosystems, providing insights into resilience, biodiversity, and ecosystem function in a changing world.
11:00 AM
REDUCED METHANE EMISSIONS FROM POND MESOCOSMS USING A NOVEL AERATION TECHNOLOGY (10846)
Primary Presenter: Sam Poon, Toronto Metropolitan University (s1poon@torontomu.ca)
Methane is the 3rd most abundant greenhouse gas in the atmosphere, contributing 28 times the impact of CO2 emissions on a per mass basis, therefore an ideal target gas to remove from the atmosphere. This study explores a tool to reduce methane emissions from aquatic systems. EM Fluids (EMF) has developed a solar-powered device that enhances gas mass transfer rates (e.g., like oxygen) across the air-water interface by ~2x with minimal energy input. The EMF device is hypothesized to increase methanotrophic activity, while decreasing methanogenic activity through increased oxygenation in the water column. Further, by increasing gas mass transfer, the treatment may aid in gas transport from ebullition into the water column, making it more readily available to methanotrophs. In lab water columns, methane mass transfer rates from bubbles into the water column significantly increased using the EMF device. In field-based pond mescosms, net methane emissions, net methane oxidation, and gas-mass transfer during ebullition were observed over the summer months; preliminary analyses found net methane emissions were reduced and net methane oxidation was increased under EMF treatment. The study provides insight into future applications of EMF technology in large freshwater bodies to reduce methane and overall greenhouse gas emissions.
11:00 AM
Are laboratory-based stable isotope dosing experiments representative of field-based experiment outcomes when exploring the role of dissolved organic matter in freshwater ecosystems? (11422)
Primary Presenter: Sydney Enns, University of Bristol (sydneyenns@gmail.com)
Within the EU, an estimated 1 billion tonnes of livestock-derived organic matter are produced annually. These products frequently enter streams via urination or defecation of livestock directly into streams or by leaching of manures and fertilisers through soil. Our recent research has shown that DOM can be highly bioavailable as a nutrient resource for freshwater biota. Investigating this uptake relative to inorganic nutrient uptake using stable isotope dosing in mesocosms is a novel approach developed by our group and applied in the field. Such experiments are often considered optimal as they run under natural ambient stream conditions, but they can be costly, requiring large amounts of staff time to set up and run. An alternative approach is to perform experiments in a controlled, laboratory setting which can minimize staff time needed to set up field-based equipment, while also allowing for tight control over key limiting factors such as temperature and light during the experiments. A common criticism is that such laboratory experiments do not represent natural conditions. Here, we report the results obtained from 2 stable isotope dosing experiments in replicate mesocosms conducted in both the field and laboratory in an attempt to investigate if laboratory-based experiments can produce findings comparable to those generated under field ambient conditions. Preliminary results suggest that similar patterns are observed in bulk 15N and 13C uptake in both biofilms and bryophytes in laboratory and field-based experiments, though absolute rates of uptake vary between the two approaches. Further work is currently underway to examine these patterns and determine how accurate laboratory mesocosm experiments are at simulating field-based experiments.
11:00 AM
PHYTOPLANKTON CONTROLS ON NUTRIENT INFLUXES: EVIDENCE FROM FRESHWATER MESOCOSM SYSTEMS (11824)
Primary Presenter: Eva Hendrickson, Rubenstein Ecosystem Science Laboratory (eva.hendrickson@uvm.edu)
Interactions between nutrient availability and phytoplankton growth play a foundational role in shaping lake ecosystem function. However, climate change has disrupted the rate and timing of nutrient delivery to lakes via extreme storm events, drought, changing ice cover, and altered mixing regimes. Increased and variable nutrient loading can stimulate changes in phytoplankton biomass, community composition, and functional diversity. To investigate the impact of changing nutrient delivery timing on phytoplankton functional diversity and biomass, we deployed 16 pelagic (closed-bottom) mesocosms on Lake Champlain, Vermont, USA. We tested three nutrient addition treatment groups and a control over a 14 day period: all nutrients at once (pulse), daily additions (press) and sporadic (random pulse). Besides the control group, all treatments were increased by the same nutrient concentration by the end of the 14 days (84 µg NH4-N/L and NO3-N/L and 31 µg PO4/L), manipulating only the rate of delivery. The treatments were meant to simulate natural occurrences of nutrient pulses into lakes such as agricultural run-off, mild or extreme rain events, intermittent mixing, and snow melt. Preliminary results indicate variability in phytoplankton response between treatments, with ongoing analyses examining differences in metabolic carbon flux. These results provide insight into phytoplankton traits that are conserved across disturbance events and will facilitate prediction of community composition and functional diversity of phytoplankton communities with intensifying climate change.
11:00 AM
USING A MESOCOSM EXPERIMENT TO TEST HOW AMBIENT PH INFLUENCES PHOSPHORUS SENSITIVITY OF CALCAREOUS PERIPHYTON MATS (11174)
Primary Presenter: Kelsey Solomon, Florida International University (ksolomon@fiu.edu)
Limestone-based freshwater ecosystems, such as the Everglades in South Florida, are dominated by CaCO3-rich periphyton mats that are sensitive to phosphorus (P) enrichment. Previous research shows pH also strongly influences diatom assemblages and is indistinguishable from P as a primary driver, highlighting the need for experiments to disentangle pH effects from P. Using a 10-day ex situ mesocosm experiment, we tested how ambient pH influences the P sensitivity of calcareous periphyton mats from Everglades National Park (EVER) and Big Cypress National Preserve (BICY). We applied low (6.0) and high (8.0) pH across a P gradient (0–1000 µg P/L) and assessed periphyton attributes and algal assemblage composition using a randomized block design. Low pH and higher P were associated with increased algal content (pH: β = 0.43, p = 0.03; P: β = 0.08, p = 0.04), mat total P (pH: β = 0.80; p < 0.001; P: β = 0.24; p < 0.001), and gross primary production on some days (Day 2 pH: β = 2.16, p = 0.002; Day 8 P: β = 0.42, p = 0.01) compared to the high pH and lower P treatments. The pH x P interaction was not significant, and neither pH, P, nor their interaction affected mat organic content or algal assemblage composition. EVER mats and assemblages responded more strongly to low pH and P than BICY mats, likely due to lower mineral content. These findings suggest low-pH environments may stimulate algal production and demonstrate the value of a mesocosm approach for testing stressor interactions that may be difficult to assess in observational studies or large-scale field experiments.
11:00 AM
USING MESOCOSMS FOR MITIGATION STUDIES - FROM WASTE TO RESOURCE: RECYCLING OLIVE OIL WASTEWATER FOR SUSTAINABLE AGRICULTURE (10919)
Primary Presenter: Jens Nejstgaard, IGB - Leibniz-Institute of Freshwater Ecology and Inland Fisheries (jens.nejstgaard@igb-berlin.de)
The environmental impact of olive mill wastewater (OMWW) is a major concern in the Mediterranean and other regions where olive oil production is a key economic activity. OMWW has a high organic load, high phenolic content, and low biodegradability, which can cause toxicity to aquatic life and disrupt freshwater ecosystems when discharged untreated, especially in areas experiencing water shortages. To address these concerns, the EU PRIMA CYCLOLIVE project (https://www.cyclolive.eu) explores sustainable strategies for recycling olive oil byproducts through both technological innovation and ecological assessment. One critical aim is to develop affordable, nature-based local solutions, such as constructed wetlands, to effectively treat both OMWW and solid waste in a cyclic, sustainable way. Here, we present the first results from mesocosm experiments designed to simulate OMWW discharge scenarios under standardized conditions and quantify the effects of both untreated and treated OMWW on aquatic ecosystems. The experiments serves to: 1) observe short-term responses of planktonic communities and water quality to OMWW inputs, allowing for a better understanding of its ecological effects under controlled, but near-real conditions, and 2) most importantly to investigate what mitigation potential establishing constructed wetlands could have to both decrease the detrimental effects of olive oil byproducts the aquatic environment, while also using the treated wastewater in intelligent low-cost irrigation systems, to mitigate the water shortages and support the farming communities.
11:00 AM
THE IMPACT OF SALINIZATION AND WARMING ON SHALLOW LAKES THROUGH COLLABORATIVE RESEARCH BY EARLY-CAREER SCIENTISTS USING MESOCOSM STUDIES (10045)
Primary Presenter: Cihelio Amorim, Federal Rural University of Pernambuco, WasserCluster Lunz and Middle East Technical University (alvescihelio@gmail.com)
Climate change and salinization are important threats to freshwater ecosystems, especially shallow lakes. To investigate the interactive effects of climate and salinity, we conducted three parallel mesocosm experiments in cold semiarid and warm Mediterranean Türkiye. Salinity was manipulated as a gradient (0-50 g/L) or as factorial treatments (4 and 40 g/L), combined with temperature treatments (ambient, heatwave, constant warming). In the first, an eight-month-long experiment with 16 different salinities (0-50 g/L), we found a unimodal response of key variables. Total nitrogen, phosphorus, chlorophyll a, alkalinity, and suspended solids increased with salinity. Water clarity peaked at 17 g/L, whereas it was lower at both low and high salinities in both climates. In the second experiment, lasting 8 weeks, we tested the impact of salinity (4 and 40 g/L) and a 2-week heatwave (+6 °C) across two climates. Higher salinity and a warmer climate enhanced phytoplankton biomass. The heatwave had negligible effects on key variables. The third experiment highlighted the stronger influence of higher temperature (+4.5 °C) on oxygen concentration, pH, and alkalinity, particularly in warmer climates and at salinity 40 g/L. All of these were made possible through the collaboration of more than 40 volunteers, interns, MSc and PhD students, supported by METU and TÜBİTAK, as well as 19 researchers supported by the EU-H2020 AQUACOSM-plus project. In conclusion, salinization is a critical stressor in shallow lakes, with its effects modulated by climate and temperature.
SS082P Mesocosm-Based Approaches for Tackling Grand Challenges in Aquatic Ecosystems
Description
Time: 11:00 AM
Date: 14/5/2026
Room: 517C