Global mapping and evolution of persistent fronts in Large Marine Ecosystems over the past 40 years.

Ocean fronts, characterized by narrow zones with sharp changes in water properties, are vital hotspots for ecosystem services and key regulators of regional and global climates. Global change is reshaping the distribution of material and energy in the ocean; however, it remains unclear how fronts have varied in the last few decades. Here, we present a global, fine-scale digital atlas of persistent fronts around Large Marine Ecosystems and demonstrate significant global increases in both their occurrence and intensity. In subtropical regions (around boundary currents and upwelling systems) and polar regions, persistent frontal occurrence and intensity are rapidly increasing, while in tropical regions, they remain stable or slightly decrease. These enhancements may be respectively related to changes in boundary currents, upwelling, and sea ice retreat. This spatially heterogeneous trend holds important implications for the redistribution of front-related ecosystem services and air-sea interactions but has not been captured by representative high-resolution climate projections models or observation-assimilated ocean models.

Early Transport Patterns and Influencing Factors of Different Stocks of Uroteuthis edulis in the East China Sea.

Uroteuthis edulis (U. edulis) is an important economic loliginid resource in the East China Sea (ECS). Its flexible life history traits enable the population to quickly adapt to changes in habitat. Understanding the early transport process helps us to grasp the habitat requirements of populations at key life history stages. In this study, particle tracing was used to simulate the early transport trajectories (within 120 days). The gradient forest method (GFM) and generalized additive mixed models (GAMMs) were used to analyze the key environmental variables that affect the early transport trajectories and the impact of environmental factors on the transport process, respectively. The results showed that spring stock tracers were transported to the northeast of the release area (Pengjiayu water) and the Pacific side of Japan. Summer stock tracers were transported to the north and northeast of the release area (Zhoushan island). Current velocity, salinity, and temperature were key environmental variables that affected the trace element ratios of spring stock at early life history stages. Mixed-layer depth (MLD), velocity, and chlorophyll a concentration (Chla) were key environmental variables for summer stock. Zonal velocity was positively correlated with the trace element ratio for spring and summer stock (0.14-0.16 m/s), while the meridional velocity showed an opposite correlation. The physical driving mechanisms of the Kuroshio warm current (or the Taiwan warm current) and the Yangtze River determine the paralarva retention location during early transportation. The differences in the dominant factors of the water environment in the retention area may affect the paralarva physiological functions and food availability. This study provides a scientific basis for a comprehensive understanding of the migration characteristics of U. edulis with different stocks.

Mesoscale eddies exert inverse latitudinal effects on global industrial squid fisheries.

Squid species, as a burgeoning global food source, has garnered significant concerns due to expanding fisheries and little regulation. Elucidating the dynamics of squid fisheries and their biophysical coupling mechanisms is crucial for predicting spatiotemporal variations in squid fisheries and their sustainable management. Mesoscale eddies are discrete rotating oceanographic features that dominate local environmental variations and have been shown to modulate top predators. However, given controls of both predators and environmental factors, it remains unknown how eddies impact mid-trophic level species such as squids. Using satellite-based global squid fishery datasets, we showed an inverse latitudinal pattern of eddy-induced squid fisheries, where fishing activities are aggregated in (repelled from) cyclonic (anticyclonic) eddy cores in tropical waters and anticyclonic (cyclonic) eddy cores in temperate waters, and this pattern can be significantly enhanced with increasing eddy amplitude. Regarding solely the satellite-based global squid fisheries, eddy-induced environmental variations may generate a trade-off between food intake and energy expenditure, causing these oceanic squids to prefer cool cyclonic eddies in hot but food-limited waters, and warm anticyclonic eddies in nutritious but heat-limited waters. Given that eddy activity is projected to continuously enhance under global warming, our finding of eddy-driven bottom-up control for squid fisheries highlights an increasingly important hotspot for squid stock predictions and ecosystem-based ocean management in a changing climate.