Understanding how population structure and connectivity emerge in organisms with complex life cycles remains a central challenge in marine ecology, particularly in pelagic systems where dispersal potential is often high. In this study, how life-stage–specific processes shape population structure in the scyphozoan jellyfish Aurelia aurita across a fjord system was investigated. Field observations of benthic polyps and pelagic m...

Tracing population structure and dispersal of planktonic organisms is a challenging yet crucial task, as it helps identify how populations are connected across regions, detect isolated or vulnerable populations and anticipate how human-driven changes in ocean may alter these dynamics. Here, we used the top predator Cyanea capillata , a bloom-forming jellyfish, as a target organism since its population structure, dispersal and...

Aim This study sets out to understand the variability in larval traits of dispersive life stages of a famous invader, the European shore crab Carcinus maenas , in its native distribution range. Location North East Atlantic coast from the Norwegian Arctic to the southern European distribution limit of C. maenas in Southern Spain. Taxon European shore crab Carcinus maenas (Crustacea, Decapoda). Methods We quantified latitudinal...

The role of small prey (< 200 µm) in larval marine fish nutrition is largely understudied. Here, we explore the contribution of protozooplankton (PZP 20–200 µm) to larval fish diets, compared to metazoan microzooplankton (MZP 55–200 µm). More specifically, we tested whether the contribution of PZP increased during the low productivity season and decreased as larvae grow. We used North Sea autumn spawning herring ( Clupea haren...

Biological invasions of jellyfish may critically affect ecosystems and ecosystem services, yet their complex life cycle makes tracking their origins and dispersal vectors a challenging task. Here we combine citizen science observations, oceanographic modeling, and population genetics to track swarms of the invasive nomad jellyfish, Rhopilema nomadica , across the Eastern Mediterranean Sea. Jellyfish observations were recorded...

During the era of biodiversity loss, a complete species census and understanding where the different species occur is of high priority. Even though this knowledge has increased tremendously, mainly with expanded use of integrated taxonomic identification, there are groups where our knowledge is very limited, both in terms of diversity and distribution. Ctenophores are such a group. Due to a lack of identification literature, d...

Causes and consequences of jellyfish bloom formation are subject to controversial discussions worldwide. While medusae have been studied to a broader extent, the knowledge on polyp stages of scyphozoans is limited thus hampering reliable prediction of jellyfish bloom formation. This study describes the occurrence, abundance, habitat characteristics and interactions of scyphozoan Aurelia sp. polyp colonies with other fouling or...

Aquatic ecologists face challenges in identifying the general rules of the functioning of ecosystems. A common framework, including freshwater, marine, benthic, and pelagic ecologists, is needed to bridge communication gaps and foster knowledge sharing. This framework should transcend local specificities and taxonomy in order to provide a common ground and shareable tools to address common scientific challenges. Here, we advoc...

The oceans’ uptake of anthropogenic carbon dioxide (CO 2 ) decreases seawater pH and alters the inorganic carbon speciation – summarized in the term ocean acidification (OA). Already today, coastal regions experience episodic pH events during which surface layer pH drops below values projected for the surface ocean at the end of the century. Future OA is expected to further enhance the intensity of these coastal extreme pH eve...

To improve our mechanistic understanding and predictive capacities with respect to climate change effects on the spring phytoplankton bloom in temperate marine systems, we used a process‐driven dynamical model to disentangle the impact of potentially relevant factors which are often correlated in the field. The model was based on comprehensive indoor mesocosm experiments run at four temperature and three light regimes. It was...

We investigated whether nutrient limitations of primary producers act upward through food webs only in terms of density effects or if there is a second pathway for nutrient limitation signals channelled upward to higher trophic levels. We used tritrophic food chains to assess the effects of nutrient‐limited phytoplankters (the cryptophyte Rhodomonas salina ) on herbivorous zooplankters (the calanoid copepod Acartia tonsa ) and...