THRESHOLDS: Disentangling the effects of climate-driven processes on North Sea herring recruitment through physiological thresholds

• Applicant: Professorin Marta Moyano, Ph.D.
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions ; Animal Physiology and Biochemistry ; Oceanography
• Term: from 2017 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 386574018

The most profound, mechanistic understanding of how bottom-up (climate-driven, physical-driven) processes impact animals can be gained by exploring the physiological basis of responses in vital rates (survival, growth, reproduction) to changes in the mean and variance of multiple, key drivers. Climate-driven changes in fish appear driven by a number of (potentially interacting) processes affecting the survival of early life stages. Disentangling these processes requires an amalgam of laboratory, field and modelling experiments. This project (THRESHOLDS) uses three separate but integrated approaches to provide a step change in our mechanistic understanding of how climate variability impacts on the structure and function of lower trophic levels of marine systems (focusing on ichthyoplankton and various size-classes of zooplankton). THRESHOLDS examines the first two months of life of Atlantic herring (Clupea harengus) in the North Sea, the period when the year class is established. First, laboratory experiments will explore the impact of prey type and size on larval physiology under contrasting thermal environments, and calibrate nutritional condition proxies to be applied to field-caught larvae. Second, field sampling will first document the in situ plankton (proto-, micro-, and mesozooplankton) and larval herring dynamics during the fall- and wintertime in the North Sea. This plankton dataset will be extended with previous data to create a unique 7 yr-time series of North Sea herring larvae and its prey (15-2000 µm). And finally, key factors controlling larval growth within the time series will be identified using Generalized Additive Mixed Models and simulations with an physiological Individual-based model. THRESHOLDS advances the state-of-the-art using a holistic approach to address i) climate-driven impacts on recruitment of a key ecosystem player, ii) the under-studied protozooplankton-ichthyoplankton link, iii) optimal foraging in marine fish larvae, and iv) the calibration and use of physiological proxies on field-caught fish larvae. Furthermore, North Sea herring larvae are an ideal case study to examine climate-driven plankton dynamics because i) one of the longest, spatially-explicit time series of early life stages of any marine fish has been collected, ii) successful pre-work has developed the physiological techniques and collected field samples to be used in this study, iii) a physiological-based IBM with a proven track record exists, and iv) a very strong network of international collaborators exists who will offer in-kind contributions of ship-time, historical samples and, along with the project PI, provide an unsurpassed knowledge base of the ecology of the target species.

• DFG Programme: Research Grants