Beschreibung: Large-scale environmental patterns in the Humboldt Current System (HCS) show major changes during strong El Niño episodes, leading to the mass mortality of dominant species in coastal ecosystems. Here we explore how these changes affect the life-history traits of the surf clam Mesodesma donacium. Growth and mortality rates under normal temperature and salinity were compared to those under anomalous (El Niño) higher temperature and reduced salinity. Moreover, the reproductive spatial–temporal patterns along the distribution range were studied, and their relationship to large-scale environmental variability was assessed. M. donacium is highly sensitive to temperature changes, supporting the hypothesis of temperature as the key factor leading to mass mortality events of this clam in northern populations. In contrast, this species, particularly juveniles, was remarkably tolerant to low salinity, which may be related to submarine groundwater discharge in Hornitos, northern Chile. The enhanced osmotic tolerance by juveniles may represent an adaptation of early life stages allowing settlement in vacant areas at outlets of estuarine areas. The strong seasonality in freshwater input and in upwelling strength seems to be linked to the spatial and temporal patterns in the reproductive cycle. Owing to its origin and thermal sensitivity, the expansion and dominance of M. donacium from the Pliocene/Pleistocene transition until the present seem closely linked to the establishment and development of the cold HCS. Therefore, the recurrence of warming events (particularly El Niño since at least the Holocene) has submitted this cold-water species to a continuous local extinction–recolonization process.

Beschreibung: Record temperatures across most of the world in 2023 also affected water resources and water-related hazards. Heatwaves contributed to deepening and new droughts in South America and Canada. There were many extreme rainfall events, including several cyclones. The global water cycle in 2023 was influenced by a change in circulation and ocean water temperatures in the Pacific Ocean from La Niña to El Niño conditions but against a backdrop of overall increasing sea surface temperatures due to global warming. The higher temperatures increase the strength and rainfall intensity associated with storm systems such as tropical cyclones. There were a relatively large number of such events in 2023, and the human and economic toll was large. The year started with continuing heavy rain and flooding in the Philippines and the western USA. In February, cyclonic storm systems hit Madagascar, Malawi and Mozambique in southeast Africa, while heavy rain caused floods and landslides in southeastern Brazil. In April, southeast Asia was hit by a large-scale heatwave, followed by cyclone Mocha in Myanmar. The first half of the year also saw extremely dry conditions in northern Argentina and nearby regions and in southwestern Europe. In May, record dry conditions in northern Italy were abruptly ended by heavy rainfall and flooding. An extremely wet season in South Korea, India and Pakistan brought landslides and flooding between June and August, while in Canada, very dry and hot conditions caused a record wildfire activity. From July onwards, very dry and recurrent hot conditions across South America led to a rapidly developing drought in the Amazon basin that intensified during the second half of the year. In September, a Mediterranean cyclone or ‘medicane’ brought heavy rainfall to Greece and caused reservoir dams to fail in Libya, killing thousands. In November, several years of deepening drought in Somalia were interrupted by heavy rainfall and flooding, while nearby South Sudan largely remains in drought. The final weeks of 2023 brought severe storm systems with heavy rains and flooding to the northeast coast of Australia. At the start of 2024, the greatest risk of developing or intensifying drought appears to be in Central and South America (except southern Brazil and Uruguay), southern Africa and western Australia. Regions unlikely to develop drought for at least several months include the Sahel region and the Horn of Africa, northern Europe, India, China and southeast Asia, and southern Brazil and Uruguay.