Opening Plenary Speaker
Angus Atkinson
(Plymouth Marine Laboratory, UK)

Gelatinous zooplankton, such as ctenophores, jellyfish, and pelagic tunicates (larvaceans, salps, pyrosomes, and doliolids) are widespread in marine ecosystems and contain groups belonging to the fastest-growing metazoans on earth. Due to their unique feeding strategies and interactions with other organisms, these groups have significant impacts on carbon export, nutrient cycling, and transfer of energy in marine ecosystems. Irrespectively, gelatinous zooplankton remain understudied compared to crustacean taxa and are often disregarded in food web investigations. Gelatinous zooplankton are notoriously difficult to sample due to their soft body texture and patchy distribution, limiting our understanding of their behaviour and ecophysiology. Nonetheless, this view is slowly changing, and accumulating evidence shows that gelatinous zooplankton may be more important to trophic transfer and nutrient cycling in the ocean than previously thought. Moreover, recent modeling efforts incorporating gelatinous zooplankton suggest that their impact on ecosystem structure and function can, at times, be high. This is reinforcing the need for an improved understanding of gelatinous zooplankton and their impacts on marine food webs and carbon cycling. 

This session invites a diverse set of researchers from different career stages to present their latest findings on gelatinous zooplankton, including their physiology, biogeography, behaviour, genetics, ecology, and biogeochemistry. We especially encourage presentations focusing on the role of gelatinous zooplankton in ecosystems and how this may change in the future. Topics covering population dynamics to blooms and bio-invasions are welcome. We highlight the need for presentations that deal with long-term data in order to determine population trends and potential future impacts on trophic transfer and carbon export of all gelatinous zooplankton groups ranging from microscopic larvaceans to macroscopic salps and scyphomedusae. Presentations of field investigations in combination with experimental approaches, and modeling studies that quantify evolutionary changes in response to selective pressures are amongst the priority topics of this session. We aim to provide a forum to discuss the latest research results, exchange ideas and collaborate to advance our understanding of gelatinous zooplankton and their role in marine ecosystems now and in the future.

Zooplankton is exposed to a multitude of pollutants in marine environments, stemming from anthropogenic activities both at land and at sea. Such pollutants include microplastics and microfibres that are the predominant forms of plastic debris. Negative impacts on zooplankton from pollutants have been reported on many levels – from a molecular level to populations, threatening marine biodiversity and ecosystem functioning. However, our understanding of the effects of pollution on zooplankton considerably lags behind the continuous emergence of new contaminants, including novel plastics, tyre particles, plastic additives, pharmaceuticals, personal care products, endocrine disruptors, pesticides, and their transformation products. There is still ambiguity in the impact of pollutants on the breadth of zooplankton species and developmental stages, a paucity of evidence on how pollutants can impact upon higher levels of biological organisation (i.e. individuals, populations, communities, ecosystem structure and function) and additionally, a lack of understanding on the role of zooplankton in the fate of pollutants in marine environments. Furthermore, knowledge on the impacts of pollution in a changing climate with multiple anthropogenic stressors is limited.

Zooplankton play an important role in the transport of carbon from the surface ocean to the deep sea, also called the Biological Carbon Pump (BCP). Zooplankton contribute to the passive carbon flux by ingesting and modifying sinking particles, or by producing fast-sinking faecal pellets and carcasses. In addition, through their daily and seasonal migrations, zooplankton actively inject particulate and dissolved carbon into the ocean’s interior, away from the atmosphere. Consequently, they contribute to climate regulation and to nutrient recycling in the water column.

Changes in zooplankton community composition, physiology, and behaviour in response to environmental conditions have a significant effect on BCP efficiency. Yet, calculating carbon budgets has proven difficult due to insufficient parameterisation of water column processes, such as carbon recycling and export/sequestration. Knowledge gaps remain, including uncertainties in global zooplankton biomass estimates, physiological rates, zooplankton-mediated processes in the mesopelagic zone, and responses of the zooplankton-focused BCP to climate change.

As part of the Joint Exploration of the Twilight Zone Ocean Network (JETZON), we invite presentations on the way zooplankton shape the passive and active carbon flux. Presentations can include observational, experimental, and modelling studies on a broad range of zooplankton taxa, in particular tunicates and fish larvae, and their impact on the BCP. We especially encourage talks on the use of new technologies, e.g., gliders or floats, that can be integrated with traditional methods to close knowledge gaps in zooplankton-mediated carbon flux.

Anthropogenic activities have altered the biodiversity and geographic ranges of zooplankton as well as many of the pelagic habitats they occupy. These changes have impacts on ecosystem function and their food webs, thus, knowledge on zooplankton species diversity, distributions, ecology and evolution will continue to be essential for understanding and predicting the complex changes in marine ecosystems. Molecular, optical, and acoustic methods have been rapidly improved in the last decades to explore and monitor different aspects of zooplankton. Each of these methods, however, has different strengths and weaknesses and can independently only detect certain aspects of the impact from environmental change on zooplankton communities. The combination and integration of diverse methods provides the opportunity of a new perspective on the biodiversity, biogeography, ecology, and evolution of zooplankton. Integrated approaches offer unprecedented insights into the intricate dynamics of zooplankton communities, their ecological interactions, and evolutionary trajectories. This symposium invites contributions that validate, calibrate, and optimize methodologies as well as research on zooplankton diversity, ecology, and evolution, showcasing how integrated approaches provide a deeper understanding of these organisms within the context of global change.

Zooplankton play a key role in carbon and nutritional transfer from primary producers to fish and in biogeochemical cycling. Essential to resolving these roles is data on zooplankton diets. A variety of methodologies are available for dietary analyses, each with their own set of advantages and disadvantages. Biochemical analyses (fatty acids and stable isotopes) of zooplankton tissues provide integrated information on prey types assimilated (e.g., primary producer types, detritus, trophic group) and can also be used to assign trophic level. Traditional microscopic gut content analysis can quantity and identify taxonomic prey individual, however, it is feasible only for large individuals and biased toward hard-bodied dietary items. DNA metabarcoding of zooplankton gut contents is a highly promising technique that can provide species-specific dietary information, including frequently-overlooked gelatinous and soft-bodied microzooplankton prey. Despite their potential, DNA gut sequence data can be difficult to interpret due to primer biases, contamination with host material, the prevalence of parasitic sequences, and gene copy number. Questions remain as to the comparability of data generated using different analytical approaches, how data from different analysis types can be combined to enhance food web interpretation, and the wider applications of these approaches to support food web model parameterization. In this session, we welcome submissions for zooplankton dietary studies utilizing all available methods, emphasizing novel approaches, including molecular techniques, compound specific isotopes, integration of multiple approaches, modelling and wider ecological applications of zooplankton dietary information.

Zooplankton are sensitive indicators of change in aquatic ecosystems, and their abundance and composition are vulnerable to the rapidly changing conditions observed in many marine and freshwater systems worldwide. As major primary consumers and predators, zooplankton play a significant role in the transfer of energy and material across aquatic food webs, and changes in their abundance and composition can impact ecosystem structure and function. Changes can be characterized and tracked from a variety of different perspectives, including species relative abundance and trait composition, diversity metrics and other indices, phenology shifts, etc. This session will focus on using time series to identify and understand zooplankton population and community changes, relationships to environmental and ecological changes, and potential effects on higher trophic levels. This theme session welcomes contributions using a broad variety of approaches related to the development, integration and application of methods for pelagic habitat assessment, with particular focus on the following topics: 1) Empirical analyses of time series and the development of indicators and indices to track changes in the ecosystem; 2) Assessment of the pelagic habitat status using indicators of the plankton community or its components; 3) Numerical and statistical modeling studies, genetic methods and other new methodologies for the assessment of the ecosystem status; 4) Incorporation or discrimination of climate-driven and anthropogenic responses for the assessment of ecosystem state.

Marine microzooplankton (<200 µm) are important grazers in the microbial food web, as well as a source of food for the mesozooplankton. There is a high level of morphological and functional diversity in the microzooplankton including ciliates, flagellates, radiolarian, foraminifera, and small metazoans, with a range of strategies for energy production. Microzooplankton play a critical role in biogeochemical cycling in marine systems, and environmental stressors such as ocean warming and acidification may have enormous influence on these fast-growing protists.

• Taxonomy, systematics and biogeography of microzooplanton
• Biodiversity of microzooplankton and their role in estuarine, coastal and oceanic systems
• Advances in understanding microzooplankton influence on biogeochemical cycling
• Microzooplankton in a changing ocean of warming, acidification and deoxygenation
• New methods for studying the ecological role of the microzooplankton

Zooplankton serve as critical links in aquatic food webs and influence biogeochemical cycling. Because of this key trophic role, their spatial and temporal distribution, abundance, and behavior are used as indicators of ecosystem structure and function. Traditional net sampling of zooplankton, along with data processing, is labor intensive and requires significant taxonomic expertise. While imaging has a long history of application in zooplankton ecology, recent developments in in-situ optical imaging technologies and artificial intelligence/machine learning (AI/ML) are poised to revolutionize zooplankton ecology. New imaging systems are becoming more energy efficient and versatile, allowing for deployments on various observation platforms such as AUVs, Argo floats, and moorings. The rapid rise of AI/ML and significant advances in computing have led to an increased taxonomic resolution and specificity in zooplankton image processing. Furthermore, in situ observation of zooplankton allows distribution and abundance to be combined with information on organism traits, such as lipid reserves, egg clutch size, and body size, and datasets can be integrated with complementary high-resolution data streams, such as acoustics and eDNA, to reveal drivers of zooplankton population changes. In addition to this tremendous potential, technological developments also bring significant new challenges, such as ensuring quality control of massive image datasets, data storage and sharing, intercalibration of instruments, developing processing and classification algorithms, and extending observations through time by comparing with traditional sampling. We welcome contributions on all aspects of zooplankton imaging, including imaging system development, AI/ML data processing, comparisons to traditional net sampling, as well as efforts to integrate imaging with other high-resolution observational technologies. Presentations focusing on new emerging technologies should extend beyond the purely technical and aim to provide insights into ecological and biogeochemical processes. We aim to foster discussion on the advantages, shortcomings, and future needs that must be considered in order to apply imaging technology to zooplankton ecology.

S9/S12 Merged Description
Sustainability of fisheries requires a better understanding of stock dynamics and resilience to climate and anthropogenic forcing. Zooplankton play a key role integrating variations at the base of the food web and transferring them toward higher level consumers including fishes. Thereby, zooplankton production and its variability in response to global change are highly relevant to fisheries production and ecosystem functioning. Understanding the impact of zooplankton production on fisheries recruitment is a crucial step needed to forecast stock response and resilience to environmental variability. Ultimately, the foundation of marine food webs, and subsequent trophic transfers, are essential for supporting higher trophic levels such as larval and adult fishes. The realized and predicted impacts of climate change on global fisheries are of high interest to the international community, and thus research aimed at understanding how climate change impacts different levels of the marine food web (e.g., microbial community, crustaceans, gelatinous grazers and predators, larval fishes) is of high importance. Advancement on these topics will enhance efficient incorporation of zooplankton production and trophic interactions into the ecosystem-based management of marine resources. This session will share and review the new information for understanding functional and structural roles of zooplankton production on fisheries trophodynamics and production. In particular, we encourage presentations and discussions using experimental, observational and modeling approaches linking zooplankton productivity to growth and survival of forage fish larvae and juveniles in their nursery grounds. We hope this session will bring out key questions about how zooplankton production and trophic web variability may impact fisheries recruitment and productivity and stimulate debate and foster international collaborations.

Zooplankton, mainly krill and copepods, play great roles in polar ocean ecosystems. They serve as trophic links that transfer carbon and energy from microalgae to higher trophic levels. Meanwhile, they also contribute in determining the efficiency of the biological carbon pump of polar oceans via passive sinking of moults, carcasses, feacal pellets and via activities such as grazing, diel vertical migration and respiration. The polar ocean is undergoing rapid climate change (e.g. warming, changes in extent of sea ice) with contrasting rates and directions among different sectors of Arctic Ocean and Southern Ocean. These changes have had and would have profound impacts on the distribution, phenology, community of zooplankton and their role played in structure, function and service of polar ocean ecosystems. In this session we welcome submissions on all polar zooplankton related topics, including but not limited to comparison of key species or functional groups and the maintenance of biodiversity and ecological processes (e.g. trophodynamics, biogeochemical cycle) in the regional and circumpolar scale of both Arctic Ocean and Southern Ocean, examining the short-term or time-series response and resilience of zooplankton to climate and environmental change using traditional and new methods, discussing new monitoring technology (mooring, molecular approaches) which can be used in future polar zooplankton research. We encourage bipolar comparisons of zooplankton communities with respect to e.g., ecosystem functions and services, biodiversity, vulnerability/resilience to change.

Novel zooplankton sampling techniques are beginning to increase space-time coverage by zooplankton population censuses, causing a shift in research attention toward collecting and processing zooplankton "big data". Use of autonomous platforms, remote sensing, bioinformatics and computer science is proliferating to both improve estimates of zooplankton population sizes and assess morphological traits more rapidly and at larger spatio-temporal scale. Key areas of research development include performance testing, validation, and use case studies and implementation of monitoring programs.  This session invites presentations on the applications of new technology and techniques that advance our ability to measure the distribution, abundance and taxonomic composition of free swimming zooplankton in the ocean. Presentations are invited on use of autonomous ocean vehicles, acoustics, eDNA, satellites, imaging, machine learning, big data, bioinformatics or any other related topic.  Comparative studies that address the pros and cons of different technologies are encouraged.  The scope of presentations should address how these approaches are advancing our ability to census free-swimming zooplankton in situ. 

Diapausing calanoid copepods (especially in the genus Calanus and Neocalanus) are supremely adapted to the seasonality of polar and subpolar ocean habitats. They play a key role in the functioning of marine ecosystems, including biogeochemical cycling and trophic dynamics. Lipid storage is necessary for survival of diapausing copepods and also supports higher trophic levels in higher-latitude food webs. This session invites contributions from modeling, observational and experimental studies about this functional group. Subjects may include but are not limited to: 1) trends in abundance and body size, 2) how environmental factors influence population dynamics, 3) the role of predation in determining copepod dynamics, distribution, phenology and life history, 4) developmental, physiological and genetic mechanisms underlying the diapause and life history strategies; 5) patterns and consequences of phenological variability and biogeographic boundary shifts, 6) theoretical, statistical and dynamic modeling analyses and future projections of diapausing copepod abundance and 7) impact of change in abundance of diapausing copepods on higher trophic levels.

Southern Ocean ecosystem dynamics play a critical role in global processes and are thus crucial to implementing regional and global climate change mitigation and adaptation efforts. However, research challenges in understanding these ecosystems remain, including quantification of ecosystem variability, coordination of sampling and modelling methods, and robust projections of future ecosystem change at multiple scales - all of which are needed to support conservation and sustainable management decisions. This joint session, coordinated by the Integrated Marine Biosphere Research (IMBeR) regional programme, Integrating Climate and Ecosystem Dynamics in the Southern Ocean (ICED), and the Scientific Committee on Antarctic Research Krill Expert Group (SKEG), aims to address these research challenges, focusing on Antarctic krill-centered systems in the Southern Ocean. This session will build on the strong modelling research network already developed between these initiatives over the past few years, bringing together new and innovative approaches in Southern Ocean research to develop ecosystem models that represent species dynamics across various spatial, temporal, and organizational scales in support of sustainable governance. The scope of the session will include i. Modelling Southern Ocean ecosystems and species in present and future environments: ii. Empirical ecological studies investigating zooplankton from individuals to populations; iii. Projections of ecosystem change; iv. Policy implications and decision-making, and v. Integrated understanding of natural and human systems interactions. Additionally, efforts that promote collaboration across scientific disciplines and generate links between scientists and fishery managers for the purpose of improving management are highly encouraged.

This session is supported by established researchers from ICED and SKEG and run by early careers researchers with an impetus to involve the next generation of early career researchers and support community-driven input. Our main objective is to develop concrete actions and mobilize research efforts to support the 5th International Polar Year and the United National Decade of Ocean Science Collaborative Centre for the Southern Ocean Region (DCC-SOR). Finally, we strongly encourage interested participants to also explore the related session, “Recent Advances in Global Euphausiid Ecology.”

Euphausiids (krill) are a critical component of global zooplankton communities. They play a key role in pelagic food webs as consumers of lower trophic-level organisms and as prey to numerous top predators, including commercially important fishes, marine mammals, and seabirds. Euphausiids also contribute to the biogeochemistry of the global oceans through the cycling of elements including carbon, nitrogen and phosphorous. Furthermore, they can act as a major conduit for carbon export and sequestration to the deep ocean. Although euphausiids share traits that make them extremely successful, recent studies have shown clear impacts of climate change and other anthropogenic stressors (including warming, ocean acidification, deoxygenation, and pollution) on euphausiids, globally. In this session, we invite researchers to present their recent work advancing our understanding of euphausiids in any of the world’s oceans. This work can focus on, but not necessarily be limited to, (1) universal traits of euphausiids that contribute to their success (e.g., swarming, reproductive strategy, continuous molting, DVM), (2) niche separation and overlap between euphausiid species, (3) biogeographic patterns and environmental drivers thereof, (4) parasites and pathogens, (5) evidence of climate change impacts, (6) impacts of anthropogenic stressors, (7) trophic ecology and food web dynamics, (8) role in biogeochemical cycles and carbon sequestration, and (9) advances in technology for studying euphausiids (from molecular to remote and autonomous sensing). While we also invite research on Antarctic krill, we note that there is a session on “The role of zooplankton (including Antarctic krill) in Southern Ocean ecosystems in a changing world: integrating across scales, disciplines, and methods”. Thus, we encourage interested participants to explore both sessions.

Numerical models are crucial tools used to overcome some of the inherent limitations of field and laboratory experiments, disentangle the roles of various ecosystem drivers, test hypotheses and improve our understanding of marine ecosystems under a changing climate. Despite significant improvements in their representation over recent years – such as more functional groups, feeding strategies, or behaviours – zooplankton are still poorly represented in most numerical models. They are often limited to being used as a closure term for phytoplankton (top-down) or as a background resource grouped with primary production for fish (bottom-up control). Ultimately, this misrepresentation reduces our confidence in model projections of pelagic community structure, carbon flow from the surface to the ocean’s interior and energy flow from plankton to higher trophic predators under modern and future climate conditions. To change this paradigm quickly will require genuine and increased interactions between observational, experimental, theoretical, and modelling disciplines.

The session invites contributions from everyone interested in improving the representation of zooplankton in models at all scales of space, time and complexity – including (but not limited to) field biologists, physiologists, ecologists, theoreticians, statisticians and modellers. Topics may include model parameterisation; approaches that aim to better represent the diversity of zooplankton traits and functions; case-studies or overviews of specifics model types (IBMs, biogeochemical, size-spectrum, ecosystem, empirical, mechanistic); models focussed on individual functional groups (e.g. gelatinous zooplankton, copepods); studies that highlight the importance of zooplankton in operational and/or stakeholder-oriented forecasting frameworks used for policy advice (e.g., climate scenarios, fisheries, habitat suitability, Marine Protected Areas, Digital Twin of the Ocean). We also welcome studies that emphasise the use of new types of observations (e.g., metagenomics, acoustics, imaging), identify data gaps and data meta-analysis efforts needed for improving model design, model-data comparison, and data assimilation.

Microplastics at the sea-surface make news headlines around the world, and many of us have heard of the North Pacific Garbage Patch. Those that live near the coast are being regularly reminded to control or manage the release of plastics into the marine environment, while the ambitious plans to mop them up gets some in a froth. But few studies have been, and are being, conducted that examine the assemblages of organisms that co-exist with the rubbish at the sea-surface. These organisms, the neuston, comprise a mix of interphase specialists such as Janthina, Halobates, and pontellid copepods, as well as facultative members that move up into this stressful layer of the ocean at night time to feed. A wide variety of nekton also use this space as a nursery ground for their eggs and larvae. This session will focus on the biology and ecology of neuston assemblages around the world, the links between assemblages and environmental drivers and on new insights into their interactions with the Anthropocene.

This session is envisioned to accommodate papers that contribute to the overall scope of the Symposium, but which do not fit within a specific Theme session listed above. We encourage all studies, especially those dealing with new horizons in zooplankton productivity, ecology or life history, as well as studies explicitly focusing on adaptation to climate change pressures, effects of extreme events or ecosystem indicators in order to better understand the challenges facing our marine ecosystems in the future. Oral and poster contributions are welcome. This session will be co-convened by Early Career Ocean Professionals, supported by the organizing committees.