Global climate change and other anthropogenic pressures have major impacts on the structure, biodiversity and functioning in aquatic ecosystems. Climate change pressures include transitional environmental change, increased variability and extreme events and long-term disturbance. It is still unclear how these pressures affect ecosystem responses, including their resilience and recovery. Large-scale mesocosm or enclosure experiments provide realistic settings by including higher system complexity in terms of species interactions at various trophic levels. Thus, mesocosm experiments are a powerful tool to obtain a mechanistic understanding of how various global change and other anthropogenic pressures affect ecosystem responses. Moreover, mesocosms offer the unique ability to test possible measures to mitigate or counteract anthropogenic pressures through environmental engineering and nature-based solutions. We welcome presentations on empirical studies where scientific questions about various aspects of aquatic ecosystem functioning have been tested using mesocosms or similar ecosystem level experimentations. We particularly invite scientists that study effects of increasing variability and extreme events on resilience and recovery of biodiversity and ecosystem structure and functioning or regime shifts that change ecosystem structure and functions in response to global climate and environmental change. We strongly encourage early career scientists who have participated in the AQUACOSM or AQUACOSM-plus (www.aquacosm.eu) Transnational Access (TA) programs to present their results from the mesocosm experiments. This session also aims to serve as a meeting point for all persons interested in ecosystems scale experimentation on a global scale (see mesocosm.org).
Lead Organizer: Stella Berger, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) (stella.berger@igb-berlin.de)
Co-organizers:
Jens Nejstgaard, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) (jens.nejstgaard@igb-berlin.de)
Tatiana M Tsagaraki, University of Bergen, Department of Biological Sciences (tatiana.tsagaraki@uib.no)
Meryem Beklioğlu, Middle East Technical University (meryem@metu.edu.tr)
Behzad Mostajir, Marine Biodiversity, Exploitation and Conservation (MARBEC), University of Montpellier-CNRS-Ifremer-IRD (behzad.mostajir@umontpellier.fr)
Presentations
03:00 PM
IMPACTS OF PLANKTIVORY AND HYPOLIMNETIC HYPOXIA ON ZOOPLANKTON DAILY MIGRATION BEHAVIOR IN AN EXPERIMENTAL POND SYSTEM (6210)
Primary Presenter: Anna Schmidt, University of Vermont (anna.schmidt@uvm.edu)
Zooplankton perform daily migrations between surface pelagic waters, where they feed at night, and deeper waters (diel vertical migration, DVM) or littoral areas (diel horizontal migration, DHM), where they hide from visual predators during the day. We hypothesized that 1) in systems with hypoxic hypolimnia, DVM decreases and is replaced by higher DHM, and that 2) DVM and DHM are more extensive in lakes with higher fish predation pressure. Through the AQUACOSM Transnational Access program, we sampled zooplankton in 16 experimental ponds (30 m x 15 m x 3 m) at the National Experimental Platform in Aquatic Ecology (PLANAQUA) at the CEREEP-Ecotron ÎledeFrance facility in France. The ponds were manipulated with fish and nutrient treatments (2 levels each) in a 2 x 2 factorial design. We sampled zooplankton in the epilimnion, hypolimnion, and littoral zone of each pond near noon and midnight to characterize migrations. We found that crustacean DVM decreased and DHM was not impacted by lower hypolimnetic dissolved oxygen, partially supporting our first hypothesis. Our second hypothesis was not supported - as planktivore abundance increased, crustacean DVM decreased and DHM was not impacted. Some rotifer genera exhibited weak migration patterns. We discuss trophic and behavioral cascades among crustaceans, rotifers, and Chaoborus in response to gradients of fish planktivory and oxygen. These findings contribute to the body of knowledge regarding impacts of global changes and other pressures on zooplankton community dynamics and aquatic ecosystem function.
03:15 PM
Multi-stressor effects of salinity and heatwaves on zooplankton grazing in a synchronized mesocosm experiment (6332)
Primary Presenter: Sarah Hasnain, Middle East Technical University (sarah.s.hasnain@gmail.com)
Salinization due to rising temperatures and reduced hydrological inputs, and increased heatwave frequencies present an emerging threat to shallow lakes ecosystem structures and functions. Individually, both stressors reduce the richness and diversity of zooplankton species and functional traits and favour smaller bodied taxa in these ecosystems. However, the combined effect of these stressors on zooplankton grazing remains poorly understood. We conducted grazing trials with zooplankton communities from coordinated mesocosm experiments exposed to salinity (low: 4g Cl L-1 and high: 40g Cl L-1), and heatwaves (absent and present) in two different eco-regions (Central Anatolian Steppe and Mediterranean). Grazing experiments were performed two weeks period prior to, during, and after the application of the heatwave treatment in the mesocosms. Preliminary results show no differences in grazing rates between high and low salinity mesocosms prior to heatwave application, with heatwaves only reducing grazing rates at low salinity. These results suggest that salinity mediates the effect of heatwaves on zooplankton grazing in shallow lakes.
03:30 PM
Investigation of the effects of climate change induced disturbances to zooplankton community stability with a multidimensional approach (4665)
Primary Presenter: Dilvin YILDIZ, Middle East Technical University (dilvinim@gmail.com)
Global warming is rising at an unprecedented rate; increasing temperature and changing precipitation patterns affect the functioning of lake ecosystems. Yet, little is known about the interactive effects of temperature rising and increasing DOC entrance with flush floods on zooplankton community stability when these stressors occur simultaneously. An in-situ mesocosm experiment was conducted to examine the impacts of warming and DOC increase on zooplankton community stability. Zooplankton communities were exposed to heating (ambient+ 4 C°, no DOC), DOC pulse (ambient, 8 mg C L-1), and a combination of them as mixed treatment (ambient+ 4 C° & 8 mg C L-1) compared to control (ambient + no DOC). We hypothesized that stressors would affect zooplankton community stability, zooplankton community (a) would show no “resistance” to disturbance of both individual stressors, (b) would be “resilient” to “recover” shortly within experimental time, and (c) the combined effect of DOC and temperature increase would be greater than individual effects of the both stressors. Our study builds a foundation for under-standing the effects of global warming and increasing humic substances on zooplankton community stability. It highlights that concomitant impacts of more than one stressor should be considered important in predicting the response of the communities besides their individual effects.
03:45 PM
EFFECTS OF CONSECUTIVE HEAT WAVES ON MICROBES IN THE MEDITERRANEAN SEA: A MULTI-OMIC STUDY TO DETEC CHANGES IN MICROBIAL COMMUNITIES BASED ON IN SITU MESOCOSMS (5476)
Primary Presenter: Maria Alvarez-Sanchez, Universidad de Alicante (maria.alvarez@ua.es)
Marine microbes have an important role on biogeochemical cycles, since they manage the recycling and remineralization of many essential nutrients. Due to climate change and global warming, an increase in frequency of heat waves has been observed in the Mediterranean Sea area, which could have an important impact on the resilience and structure of the marine microbial communities. Here, we have addressed the effect of these heat waves on the marine microbes during 20 days in situ mesocosm that was conducted as part of the EuropeanAquacosm-plus-TA project at the CNRS-MEDIMER infrastructure (Sète, France). A scenario of an occurrence of two consecutive heat-waves up to 5°C above natural temperature was tested. Triplicate 1700L mesocosms were heated each 5 days followed by 5 days without heating. Triplicate other mesocosms acted as controls without heating.To assess diversity and abundance changes in bacterial communities, the 16S rRNA analysis, microscopy and flow cytometry analyses were carried out. To analyze the functional changes in microbial communities, metagenomic analyses were performed as well as metabolic activity assays using BONCAT tagging. This method allows tracking metabolically active cells after the incorporation of a non-canonical aminoacid followed by fluorescent labelling of these proteins by CLICK chemistry. In this work, we will show the results from these multi-omic analyses and we will try to highlight the effect of global warming on the microbial communities in the Mediterranean Sea; one of the most sensitive oceanic “biosensor” within global warming.
04:00 PM
DIFFERENCES IN THE RESILIENCE OF SPECIES IN A BENTHIC COMMUNITY FACING OCEAN WARMING (6405)
Primary Presenter: Léa Joly, GEOMAR (jolyleasn@gmail.com)
Warming is a major threat for organisms and has sharp consequences on benthic intertidal invertebrates due to their reduced mobility. Although they are exposed to daily temperature variations in temperate ecosystems, the effects of springtime warming on their functional traits are not well documented. The present study assessed the resilience of three marine invertebrates of the Wadden Sea to warming. Metabolic and phenological responses of <em>Mytilus edulis</em>, <em>Macoma balthica</em> and <em>Peringia</em> sp. were investigated under natural and warming scenarios in a mesocosms experiment. Benthic substrate and associated species were collected in the Wadden Sea and maintained in tanks in Sylt from March to June 2022. Three temperature treatments were applied: Ambient (i.e. field temperature), and elevated 1.5 and 3 degrees above ambient values. Respiration rates were measured to represent species’ metabolism while the physiological adjustments for the fitness were characterised by growth and body condition index. <em>Mytilus</em> and <em>Peringia</em> appeared to be highly resilient to warming, with a brief acclimation phase. They displayed an increased growth in warmer treatments without consequences for the condition. Conversely, <em>Macoma</em>’s growth was not stimulated by warming and individuals’ condition was negatively affected. These differences in species’ responses are expected to modify the structure of the coastal Wadden Sea ecosystem in the future, possibly increasing the vulnerability to additional stressors such as the introduction of invasive species.
04:15 PM
Spring phytoplankton bloom collapse and composition shift induced by predators under simulated warming in in situ mesocosm in the coastal Mediterranean (5090)
Primary Presenter: Thomas Trombetta, University of Amsterdam (t.trombetta@uva.nl)
To better understand the potential responses of phytoplankton blooms to global warming, an in situ mesocosm experiment was carried out in the coastal Mediterranean (Thau Lagoon, south France) in April 2018. Four treatments were applied: 1) natural planktonic community with ambient water temperature (C); 2) natural planktonic community at +3 °C elevated temperature (T); 3) exclusion of larger zooplankton (> 200 µm) with ambient water temperature (MicroZ); and 4) exclusion of larger zooplankton at +3 °C elevated temperature (TMicroZ). Warming strongly depressed the phytoplankton bloom amplitude as the chlorophyll a concentrations was two times lower in the T treatment, most likely due to the increase of the top-down control by zooplankton. This was supported when the larger zooplankton fraction was removed (MicroZ vs TMicroZ), as in this weakened top-down control conditions, the phytoplankton biomass increased under warming. Warming also modified phytoplankton composition by enhancing smaller green flagellates and dinoflagellates at the expense of diatoms and prymnesiophytes. Finally, warming modified phytoplankton successions, promoting an early bloom of picophytoplankton, mainly small green flagellates, and a late bloom of diatoms. Our findings suggest potentially weaker spring blooms, dominated by smaller phytoplankton and dinoflagellates in the future in coastal waters and point at the role of the top-down pressure intensification on its changes, with potential consequences for coastal food web dynamics and trophic transfer efficiencies under future ocean conditions.
SS046D Mesocosm Based Experimental Studies to Address Challenges Emerging From Global Change on Stability of Aquatic Ecosystems
Description
Time: 3:00 PM
Date: 6/6/2023
Room: Auditorium Illes Balears