Coastal oceans account for just 7% of the global sea surface, yet they are among the most productive and biodiverse ecosystems on the planet. These regions support vital ecosystem services and natural resources but are increasingly threatened by pollution, habitat loss, overfishing, and climate change. Coastal ecosystems are particularly vulnerable because they are already heavily impacted by human-induced stresses. Yet, predicting how intensifying anthropogenic stressors will affect coastal ecosystems, especially in temperate regions, remains a hard problem – one that requires high-resolution, long-term biological and environmental data to solve. Plankton, the microscopic organisms that underpin the marine food web, play a central role in the functioning of coastal systems (Chapter 1). Plant-like cells called phytoplankton produce about half of
Earth’s oxygen and fuel marine food webs, while the tiny animals called zooplankton connect these primary producers to higher trophic levels. Despite their ecological importance, our understanding of how planktonic metabolism and function respond to environmental variability remains limited. The southern Bight of the North Sea offers a natural laboratory to study these dynamics, combining strong seasonality, high riverine nutrient inputs, and oceanographic variability. This PhD thesis contributes to addressing this gap by developing and applying a metatranscriptomic monitoring framework to study the spatiotemporal dynamics of microeukaryotic plankton in the southern North Sea. By combining monthly and diel sampling campaigns with a systems biology approach, this research provides new insights into how taxonomic composition and metabolic activity of plankton communities are shaped by environmental drivers. |
