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Equatorward alongshore winds over major eastern boundary upwelling systems (EBUSs) drive intense upwelling via Ekman dynamics, surfacing nutrient-rich deep waters and promoting marine primary production and fisheries. It is generally thought, dating back to Bakun’s hypothesis, that greenhouse warming should enhance upwelling in EBUSs by intensifying upwelling-favourable winds; yet this has not been tested. Here, using an ensemble of high-resolution climate simulations with improved EBUS representation, we show that long-term upwelling changes in EBUSs differ substantially, under a high-emission scenario, from those inferred by the wind-based upwelling index. Specifically, weakened or unchanged upwelling can coincide with intensified upwelling-favourable winds. These differences are linked to long-term changes of geostrophic flows that dominate upwelling changes in the Canary and Benguela currents and strongly offset wind-driven changes in the California and Humboldt currents. Our results highlight the controlling role of geostrophic flows in upwelling trends in EBUSs under greenhouse warming, which Bakun’s hypothesis overlooked.Oceanic eastern boundary currents are regions with strong upwelling, which is expected to intensify with global warming through enhanced winds. Here the authors show that geostrophic flow dominates over wind effects on long-term upwelling changes for the major eastern boundary upwelling systems.

Polycyclic aromatic hydrocarbons (PAH) are semi-volatile, lipophilic, and harmful compounds that can persist for decades in a range of marine environments. There are several marine and soil microorganisms that possess enzymes involved in arene degradation. Here, we analyzed the structure (16S rRNA amplicons) and metabolic potential (inferred using phylogenetic placement) of the bacterial community in surface marine sediments from coastal waters off Concepción, Chile, and describe how microbial community patterns are shaped and altered by PAH contamination. Two depositional zones were identified, a “High PAH” area containing a mix of high and low molecular weight PAH of up to 10,350 ng∑PAH gdw −1 and with high organic matter content; and a “Low PAH” zone mostly characterized by low molecular weight PAH of up to 1810 ng∑PAH gdw −1 and lower levels of organic matter. We identified 53 hydrocarbonoclastic bacteria genera, with eight showing relatively high abundances at High PAH sites, although known PAH degrader clades were also present at Low PAH sites. With potential enzymes inferred in almost all samples, we suggest that breakdown of PAH is widespread in this area, likely resulting from the long history of local PAH emissions that may have promoted a stored microbial capacity for these degradation processes.

Intraspecific competition can lead to sexual segregation of diets or foraging behaviors in seabirds, and in some species the resulting niche partitioning is facilitated by sexual dimorphism. However, environmental stochasticity can mediate intraspecific competition and thus the extent of sex-based partitioning. The Peruvian booby ( Sula variegata ) is a sexually dimorphic seabird endemic to the Humboldt Current System (HCS), a highly variable environment due to El Niño Southern Oscillation. To determine the extent of sexual partitioning in this species, we quantified the foraging and trophic niches of breeding Peruvian boobies at Isla Guañape Norte, Peru in two years with different oceanographic conditions and nesting propensity. Morphometrics, GPS-tracked foraging behaviors, diets via regurgitates, and isotopic niches were compared between sexes and years where sample sizes permitted. Although females were larger and in better body condition than males, breeding Peruvian boobies in our study did not exhibit sex-specific foraging or isotopic niche partitioning and had few differences in diet. Anchoveta ( Engraulis ringens ) dominated diets in both years, reflecting Peruvian boobies’ dependence on this prey. Overall, while oceanographic conditions in 2016 were unfavorable enough to reduce nesting propensity, these effects did not qualitatively translate to foraging or dietary niche partitioning between the sexes for those individuals who opted to breed. In combination, our results suggest weak intraspecific competition during our study period, and highlight how the foraging strategies of Peruvian boobies have adapted to the variable environmental conditions found in the HCS.

We reconstructed a high‐resolution, alkenone‐based sea surface temperature (SST) record spanning the last ca. 150 years, from a sediment core retrieved within the main upwelling zone off Peru. A conspicuous SST decline is evidenced since the 1950s despite interdecadal SST variability. Instrumental SST data and reanalysis of ECMWF ERA 40 winds suggest that the recent coastal cooling corresponds mainly to an intensification of alongshore winds and associated increase of upwelling in spring. Consistently, both proxy and instrumental data evidence increased productivity in phase with the SST cooling. Our data expand on previous reports on recent SST cooling in other Eastern Boundary upwelling systems and support scenarios that relate coastal upwelling intensification to global warming. Yet, further investigations are needed to assess the role of different mechanisms and forcings (enhanced local winds vs. spin‐up of the South Pacific High Pressure cell). Key Points A coastal SST decline is occurring since the 1950s in Peru's main upwelling zone The cooling trend is likely driven by an enhancement of spring/summer upwelling Enhanced upwelling and warming offshore aimed to foster coastal productivity

The Chilean upwelling bays are highly productive ecosystems shaped by their interactions with the open ocean. Although significant knowledge exists regarding their hydrodynamic and ecological processes, the spatial dynamics of trophic transfer and heterotrophic resynthesis of organic matter remain insufficiently understood. To address these knowledge gaps, we conducted a compound-specific isotope analysis of amino acids (CSIAA) on suspended and sinking particulate organic matter from Mejillones and Antofagasta bays, two oceanographic environments characterized by contrasting hydrodynamic conditions and topographic orientations. In Mejillones Bay, the CSIAA trophic positions for metazoan (1.7 ± 0.5) and protozoan (2.3 ± 0.3) were significantly higher compared to those in Antofagasta Bay (metazoans: 1.3 ± 0.6; protozoans: 1.5 ± 0.3), highlighting protozoans as primary trophic vectors. MixSIAR analysis indicated that phytoplankton is a key source of particulate organic matter in both bays; however, Mejillones Bay exhibited a greater proportion of microbially degraded organic matter. Enhanced heterotrophic resynthesis in Mejillones Bay (ΣV: 1.9–2.5) was associated with lower oxygen levels, increased concentrations of NO₂ ⁻ , and heightened stratification of the water column. Additionally, depth-dependent variations in δ 15 N for phenylalanine and threonine indicated a greater solubilization of particles, which contributed to a reduction in the export of particulate organic matter (averaging 9 ± 2 mg C/m²/d). These findings underscore the critical role of the intricate interactions between the bay’s topographic features and the physical and biological processes that ultimately influence the cycling trajectories of particulate organic matter in upwelling bays.

Aim Project shifts in the habitat suitability of 505 fish and invertebrate species in the Eastern Tropical Pacific that are likely to occur by the mid-21st century under “high greenhouse gas emissions” (RCP 8.5) and “strong mitigation” (RCP 2.6) scenarios. Location The Eastern Tropical Pacific Ocean, a discrete biogeographic region from the Gulf of California to northern Peru. Methods Ensemble simulations of climate change effects on fish and invertebrate species caught by four major fisheries in the region, based on four species distribution models and three Earth system models. Results Simulation results indicated that species' habitat suitability increased or remained the same in the northern and southern margins of the Eastern Tropical Pacific but decreased by up to 14% in some fisheries along Central America. The largest declines in the average species habitat suitability index were projected for small pelagic fisheries (up to −46%), while the highest local species turnover was projected for coastal small-scale fisheries (up to 80%). Under RCP 8.5, species in the southern half and northern equatorial region of the Eastern Tropical Pacific were projected to shift south-east at a rate of approximately 30–60 km decade-1, respectively. Demersal species were projected to move into shallower, inshore waters with a shift in depth centroids estimated at a rate of around 1 to 13 m decade−1. Range shifts towards the equator reflect movements to cooler habitats that are characteristic of equatorial upwelling systems. Range shifts towards shallower, inshore waters reflect habitat compression associated with the expansion of oxygen minimum zones.

Seabirds face increasing pressure from commercial fisheries through both direct mortality and indirect competition for shared prey resources. In Chile’s Humboldt Current System, artisanal purse-seine fisheries target small pelagic fish species such as anchoveta ( Engraulis ringens ), which also comprise key components of the Humboldt penguin’s ( Spheniscus humboldti ) diet. To investigate the potential for spatio-temporal overlap between purse-seine fisheries and penguin foraging areas, we tracked breeding Humboldt penguins from Isla Choros, Coquimbo Region, northern Chile, during the autumn and spring breeding seasons of 2022 using GPS dive loggers. We quantified penguin at-sea distribution and overlap with fishing effort data obtained from purse-seine vessels operating in the Coquimbo Region. Tracking data from 22 penguins revealed a bimodal foraging pattern linked to nest location. Penguins nesting on the eastern, mainland-facing side of Isla Choros foraged exclusively in coastal waters, while western-nesting individuals foraged both offshore and inshore, likely depending on environmental conditions. Kernel Density Estimation (KDE) analysis identified two core foraging zones: one along the mainland coast near Playa de los Choros and another southwest of the island. Purse-seine fishing effort in autumn was concentrated along the coast, overlapping substantially with the coastal foraging zone of the penguins. Nearly 60% of the penguins’ coastal core foraging area overlapped with the 50% KDE of autumn purse-seine activity. In contrast, spring fishing effort was more dispersed and located farther south, with no overlap observed between spring fishing and penguin foraging areas. These findings suggest a high likelihood of indirect resource competition between Humboldt penguins and fisheries during the autumn breeding season—a critical time when penguins are energetically constrained as central place foragers. We provide the first empirical evidence of substantial seasonal overlap between Humboldt penguins and inshore purse-seine fisheries at the Humboldt Archipelago and highlight the need to integrate seabird ecology into fisheries management. To protect vulnerable seabird populations such as the Humboldt penguin, marine spatial planning should consider critical foraging habitats and breeding schedules. Future work should aim to quantify dietary overlap, assess potential sub-lethal effects of prey depletion, and monitor the impact of small-scale, untracked fisheries within key penguin foraging areas.

This study summarises six years of spatio-temporal patterns of the discarded demersal community fauna recorded by onboard scientific observer program for both artisanal and industrial crustacean fisheries between 2014 and 2019, from mesophotic to aphotic depths (96 to 650 m) along the southern Humboldt Current System (28–38°S). In this period, one cold and two warm climatic events were observed during the austral summer 2014, 2015–2016 (ENSO Godzilla), and 2016–2017 (coastal ENSO), respectively. Satellite information showed that Chlorophyll-a concentration varied seasonally and latitudinally, associated with upwelling centres, while equatorial wind stress decreased southward of 36°S. Discards were composed of 108 species, dominated by finfish and molluscs. The Chilean hake Merluccius gayi was dominant and ubiquitous (occurrence, 95% of 9104 hauls), being the most vulnerable species of the bycatch. Three assemblages were identified: assemblage 1 (~200 m deep), dominated by flounders Hippoglossina macrops and lemon crabs Platymera gaudichaudii , assemblage 2 (~260 m deep), dominated by squat lobsters Pleuroncodes monodon and Cervimunida johni and assemblage 3 (~320 m depth), dominated by grenadiers Coelorinchus aconcagua and cardinalfish Epigonus crassicaudus . These assemblages were segregated by depth, and varied by year, and geographic zone. The latter represented changes in the width of the continental shelf, increasing southward of 36°S. Alpha-diversity indexes (richness, Shannon, Simpson, and Pielou) also varied with depth and latitude, with higher diversity in deeper continental waters (>300 m), between 2018–2019. Finally, at a spatial scale of tens of kilometres, and a monthly basis, interannual variations of biodiversity occurred in the demersal community. Surface sea temperature, chlorophyll-a, or wind stress did not correlate with discarded demersal fauna diversity of the crustacean fishery operating along central Chile.

Fil: Mattoni, Camilo Ivan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina

Gooseneck barnacles of the genus Lepas are sessile crustaceans settling and growing on free-floating substrata. They can be used as indicators for floating time of objects such as plastic, algae, airplane wrecks or human corpses. Precise estimates of floating time are only possible when accurate growth rates of Lepas are known. However, many factors modulate the growth of these crustaceans, making floating time estimates difficult. In this study, we measured growth rates of L. australis and L. anatifera in the Central Humboldt Current System over two consecutive summer and winter seasons. Growth patterns were best described by a logistic growth curve. Using the asymptotic value (maximum size) for each species and each season, we selected the linear phase of growth to fit simple predictive linear models to estimate floating time. Growth rates of L. anatifera were almost twice as high in the warmer summer months compared to the winter season suggesting that growth rates are strongly associated with temperature. Consequently, seasonal or regional growth rates are required to precisely estimate floating time of objects at sea.