Ioannis Kalaitzakis

In most bird species, breeding individuals behave as central-place foragers during reproduction, commuting regularly between the breeding site and foraging areas to find food for both self-maintenance and offspring rearing. Such movements are constrained by the need to find enough resources around the breeding site in a short time and may be modulated by several factors, including resource availability, weather, and breeding phase. By GPS-tracking 20 individuals across > 1400 foraging excursions, we characterised the foraging behaviour of Mediterranean gulls Ichthyaetus melanocephalus breeding in a coastal area, where they can forage in both terrestrial and marine habitats. Moreover, we investigated whether intrinsic factors and weather conditions affected the choice of performing foraging excursions targeting marine habitats. Females foraged closer to nesting sites than males during egg incubation compared to chick-rearing, whereas the range of male foraging excursions was unaffected by breeding stage. Overall, foraging excursions involved mostly farmland areas (43% of locations), inland waters (23%) and open sea (16%). Use of marine habitats increased from egg incubation to chick-rearing and was more frequent in males than females. Marine habitats were exploited mainly under favourable weather conditions, with small waves and moderate wind speed. Mediterranean gulls thus showed individually flexible foraging behaviour, expanding their trophic niche by increasingly relying on marine habitats late in the breeding season and possibly enhancing the provisioning of highly nutritious food to their offspring.

Seabirds are exposed to numerous threats throughout their life‐cycles, including land‐based threats during their breeding season such as invasive species, diseases, or light pollution. Here we assess the timing, scope, and severity of land‐based threats to populations of highly mobile petrels, albatrosses, storm‐petrels, and alcids in the Atlantic Ocean, to guide priorities for their conservation across their mostly island‐breeding areas. By combining our own field expertise of these species with a literature review, we built a dataset characterizing 18 threats for 49 species across 38 Large Marine Ecosystems. We analyze this dataset by highlighting the most impactful threats and the most impacted regions. Addressing invasive alien species on Tristan da Cunha & Gough and on the islands of the Canary Current are the interventions with the greatest potential to stimulate seabird population recovery across the Atlantic Ocean. Our results highlight priorities for targeted management actions that can support seabird conservation.

Seagrass meadows are natural carbon sinks, yet the effect of ocean acidification on their carbon burial capacity remains poorly understood. Here we investigated natural carbon dioxide vents in Ischia, Italy to assess how seawater pH influences carbon burial in an area dominated by the seagrass Posidonia oceanica . Organic carbon burial rates (mean ± standard error) between 1954 – 2021 were low under ambient conditions (1.5 ± 0.5 g m ^-2 yr ^-1 ) but increased sharply under acidified conditions (7 ± 1 g m ^-2 yr ^-1 ), reaching sevenfold higher values under extreme acidification (10 ± 3 g m ^-2 yr ^-1 ). Stable isotopes suggest that these patterns reflect changes in the relative contribution of seagrass, macroalgae, and epiphytes to buried carbon. These findings reveal that ocean acidification can substantially alter coastal carbon cycling, potentially through shifts in community composition, with important implications for understanding past and future feedbacks between seagrass ecosystems and the marine carbon cycle.