Marine biodiversity loss, fishing, and climate change

The ocean's mesopelagic of 'twilight' zone (~200m to 1000m) is one of the largest habitats on this plant, and home to an abundant and diverse fauna. The species inhabiting this zone posses a multitude of behavioural, physiological, and structural adaptations that allow them to thrive in this cold, dark, and relatively food-poor environment. Twilight zone organisms influence the cycling of nutrients and long-term storage of carbon in the ocean and are a conduit for energy flow between depth zones, functions that will be affected by climate warming and exploitation by humans. Professor Steinberg will discuss important ways in which biodiversity and abundance affects the structure of mesopelagic food ways in which biodiversity and abundance affects the structure of mesopelagic food webs and carbon cycling using examples from contrasting ecosystems in the North Atlantic, North Pacific, and Southern Ocean. Examples will illustrate how species vertical zonation and diel migration affects the export of organic matter, and how some species paly an outsized role in carbon export or other ecosystem functions. The importance of ocean time series observations and new technologies for detecting change in mesopelagic biodiversity and function will be stressed and knowledge gaps will be identified for future research.

Professor Deborah Steinberg

Virginia institute of Marine Science, USA

Professor Deborah Steinberg

Virginia institute of Marine Science, USA

Deborah Steinberg is a Professor of Marine Science at the Virginia Institute of Marine Science (VMS), William & Mary. She is a biological oceanographer with research interests that include the role of zooplankton in cycling of carbon and nutrients, the food web of the ocean twilight zone, and the effects of climate change on zooplankton community structure. She has conducted field research across the world's oceans and is currently co-lead of the Palmer Antarctica Long-Term Ecological Research program and a principal investigator for the Bermuda Atlantic Time-series Study. Steinberg earned her doctorate from the University of California, Santa Cruz. Before coming to VIMS in 2001, Steinberg was a research scientist at the Bermuda Institute of Ocean Sciences. She has served in numerous leadership positions in the broader oceanographic community including as chair of the University National Oceanographic Laboratory System that advises the US academic research fleet. Her honours include the Sverdrup Lecture Award from the American Geophysical Union for outstanding contributions to and promotion of cooperation in oceanographic research, and the State Council of Higher Education for Virginia Outstanding Faculty Award. Professor Steinberg has served as major adviser for 20 doctoral and master's students and teaches courses on Biological Oceanography and Scientific Communication Skills.

The sinking of detrital organic matter is the main contribution of living ocean ecosystems to climate regulation. The modelling of this “biological pump” in contemporary Earth System Models commonly assume that the dominant component is dead photosynthetic bacteria because they have the fastest life cycle. However, due to their small size dead bacteria sink slowly and are remineralised before reaching the sea floor. It has recently become clear that higher organisms, multicellular zooplankton and fish, are also important contributors to the biological carbon pump. Even though their rate of production of sinking faecal pellets is slow, the pellets are large and sink rapidly into the ocean interior, where the carbon is sequestered over long time. Here, Professor Andersen will use simple metabolic arguments to demonstrate how organisms of different sizes and trophic levels contribute to the biological carbon pump. The talk will augment the theoretical arguments with simulations of detailed models of unicellular plankton, multicellular zooplankton, cephalopods, and fish. The presentation will argue that understanding the biological carbon pump requires that we describe the entire ecosystem, from bacteria to whales, to quantify the contributions of each organism group in the ecosystem, and how they interact. Such full ecosystem models are required to understand how the climate regulating ability of the ocean’s ecosystem will change under future climates, and how it is affected by human interventions.

Professor Ken H Andersen

Technical University of Denmark, Denmark

Professor Ken H Andersen

Technical University of Denmark, Denmark

Ken H Andersen has a background is in theoretical physics: non-linear systems, pattern formation, and turbulence. In the last 20 years he has worked with marine science: fisheries ecology, plankton ecology, and general theoretical ecology.

He has synthesised the scattered ideas about body size-based modelling into a coherent framework and applied it to plankton ecology, fisheries ecology, and food-web modelling. A recent key discovery is how the macroecological patterns of morphology and strategies of organisms – from bacteria to whales – are determined by the limitations set by body size, by physics and chemistry, and by evolution. This insight transforms our understanding of the diversity of life away from empirical patterns of species towards the limitations set by fundamental laws of physics.

The size- and trait-based approach to fish population and community dynamics has revolutionised population models of fish. The framework provides the theoretical basis and practical implementation to deal with modern challenges to fisheries management: data-poor stock assessments, fisheries induced evolution, and ecosystem-based impact assessments of fisheries, as well as evolutionary ecology. The framework is unique in ecological theory by being built on just three central assumptions yet having a wide practical applicability.

The fossil record offers critical insights into how biodiversity, biogeography, and ecosystem function respond to climate change over geological timescales. Planktonic foraminifera, with their exceptional fossil preservation, global distribution, and ecological diversity, provide a uniquely powerful system for examining these long-term dynamics in the open ocean. Their record captures changes in species richness, ecological traits, and community composition across major climate perturbations, allowing for an assessment of how environmental stress reshapes both ecosystem structure and spatial patterns of biodiversity.

This contribution synthesises data on shifts in foraminiferal biogeography alongside evidence for ecological and functional turnover. It explores how these spatial dynamics relate to broader environmental drivers such as ocean temperature, productivity, and stratification, and considers the extent to which biogeographic and functional responses vary during periods of rapid climate change.

Understanding these relationships in the deep past provides a valuable baseline for assessing the resilience of modern marine ecosystems. The fossil record of planktonic foraminifera demonstrates that rapid environmental change does not always equate to functional collapse and highlights the conditions under which ecosystem processes persist or reorganise in response to environmental stress. These insights are essential for informing biodiversity and ecosystem service frameworks in the context of ongoing and future climate change.

Dr Tracy Aze

University of Plymouth, UK

Dr Tracy Aze

University of Plymouth, UK

Dr Tracy Aze is a marine palaeoecologist whose research focuses on the evolutionary and ecological dynamics of planktonic foraminifera. These single-celled marine organisms have an extraordinary fossil record that captures their biodiversity and biogeography over millions of years, offering an unparalleled insight into how marine ecosystems respond to environmental change on geological timescales.

Tracy’s work integrates direct sampling of the fossil record, phylogenetic methods, and geochemical data to investigate the drivers of species longevity, extinction, and resilience in the open ocean. By combining macroevolutionary theory with high-resolution fossil data, she aims to understand how ecological traits and environmental factors shape patterns of survival and loss across deep time.

She is Chair of the Neogene and Quaternary Planktonic Foraminifera Working Group and actively contributes to international efforts to improve taxonomic standards and training in the micropalaeontological community. She is also committed to fostering a supportive research culture and mentoring the next generation of scientists in palaeontology and evolutionary biology.

Tracy brings a long-term perspective to contemporary questions about biodiversity change, highlighting the value of the fossil record in understanding the resilience and vulnerability of marine ecosystems under climate stress. Her research offers essential context for interpreting current biodiversity trajectories and contributes to broader discussions about the role of past events in shaping future outcomes.

This study investigates global phytoplankton dynamics using a novel ocean ecosystem model that incorporates adaptive evolution of key traits (nutrient uptake, temperature optima, and solar radiation optima). Contrary to the prevailing theory that rising temperatures directly increase phytoplankton diversity, the simulations reveal that global phytoplankton diversity is primarily driven by primary productivity and vertical mixing, not temperature (LeGand et al submitted). Diversity is lowest in nutrient-poor subtropical gyres and permanently mixed Southern Ocean waters, while hotspots occur at the convergence of cold and warm western boundary currents. Furthermore, the study assessed the efficiency of adaptive evolution in these populations. Findings suggest that phytoplankton adapt well to spatio-temporal temperature shifts, but not to changes in nutrient conditions or solar irradiance. This maladaptation, particularly to solar irradiance, significantly hinders global primary production and redistributes its spatial patterns, with local variations up to 20% (Sauterey et al submitted). These results emphasise that omitting phytoplankton (mal)adaptation from current ocean ecosystem models compromises their accuracy in predicting both present-day phytoplankton ecology and future ocean primary production under climate change scenarios.

Dr Pedro Cermeno

Consejo Superior de Investigaciones Científicas, Spain

Dr Pedro Cermeno

Consejo Superior de Investigaciones Científicas, Spain

Pedro Cermeno holds a PhD in Biological Sciences (2006) and has a track record of highly competitive postdoctoral fellowships, including the Fulbright Program and the Marie Curie International Fellowship Program. He is currently research scientist at the Institute of Marine Sciences in Barcelona, Spain. His international research experience spans leading institutions such as Rutgers University, MIT, and Columbia University's Lamont Doherty Earth Observatory. He has coordinated eight competitive national and international research grants and has published over 60 scientific papers, including contributions to Nature, Science, and PNAS. Pedro's core research interests are dedicated to understanding marine life's evolutionary and ecological dynamics, specifically how biodiversity emerges, recovers from mass extinctions, and responds to the Anthropocene crisis. A significant focus of his work is on improving predictions of ocean plankton distributions and their role in biogeochemical fluxes under future climate change scenarios. Beyond fundamental research, Pedro actively explores the commercial expansion of sustainable microalgal feedstocks and is committed to translating scientific knowledge into societal solutions for ecosystem protection and a more habitable planet.

The impacts of climate change on marine ecosystems and the cascading feedbacks on the carbon cycle and climate have been highlighted as a “known-unknown” in the past four Assessment reports of the IPCC. The quantification of ecosystem-led carbon-climate feedbacks requires a realistic representation of marine ecosystem structure and functioning in global ocean carbon cycle models. Here, Professor Le Quéré will present an effort to introduce functional diversity in the PlankTOM global ocean biogeochemistry model based on the representation Plankton Functional Types (PFTs), grouping organisms according to their influence on carbon fluxes. PlankTOM uniquely represents explicitly heterotrophic bacteria/archaea, six types of phytoplankton, and five types of zooplankton. The model parameters are set following three optimisation logic using available observations, producing three branches based on the same model structure and physical environment but with different outcomes. Results show how the differences in ecosystem outcomes transfer through to differences in carbon dynamics, including primary and secondary production, and carbon export to the ocean interior. We then use emergent properties of the model to evaluate proximity to observed ecosystem dynamics. We further demonstrate that the addition of a viral component exerts an important influence on recycling and export. The presentation will argue that a new generation of Ocean Systems Models (OSM) is needed to build the tools necessary to address marine issues including ecosystem-led carbon-climate feedbacks, risks of ecosystem shifts and tipping points, ocean productivity and food resources, and the effectiveness of proposed active marine carbon dioxide removals.

Professor Corinne Le Quéré CBE FRS

University of East Anglia, UK

Professor Corinne Le Quéré CBE FRS

University of East Anglia, UK

Corinne Le Quéré is Royal Society Research Professor of Climate Change Science at the University of East Anglia (UEA), UK. She conducts research on the interactions between climate change and the carbon cycle, including those mediated by marine ecosystems. She spearheads the development of marine carbon-cycle models that include the representation of marine ecosystems regrouped by Plankton Functional Types (PFTs). She instigated and led for 13 years the annual update of the global carbon budget within the Global Carbon Project, and was author of three assessments reports by the Intergovernmental Panel on Climate Change, and is former Director of the Tyndall Centre for Climate Change Research. She is member of the UK Climate Change Committee and was the founding Chair of France's High Council on climate, two independent committees that advise their respective Governments on how to respond to climate change.