The warm El Niño episodes are generally accepted to be harmful to the development of cold-water anchovy populations, but favourable for abundant populations of sardine, adapted to warmer waters. IRD researchers and their Peruvian partners (1) have been studying fluctuations in pelagic fish populations in the world’s richest oceanic ecosystems for fish, the Peru-Humboldt Current system, off Peru. They showed that the traditional explanation does not always hold true. During the 1997-98 El Niño event, one of the strongest of the XXth century, anchovy in fact adapted and reproduced by taking advantage of refuge habitat ‘loopholes’ located very close to the coast. The existence of these areas, with specifically different climatic conditions, appear to have favoured the survival of these populations in spite of generally unfavourable climatic conditions.
Near the coasts of Peru and Chile, the Humboldt Current ecosystem is the world’s most productive fishing zone. This cold-current zone, with frequent coastal upwellings ( 2 ), occupies less than 1 % of the world’s ocean surface and provides 15 to 20 % of global maritime catches. Unlike other large regions of upwelling, this ecosystem proves to be more exposed to variations in climate. Its geographical location brings it under the direct influence of disturbances generated by the El Niño-La Niña events which arise every 3 to 7 years. Other climatic cycles, called El Viejo-La Vieja by reference to the first two, also bear influence, but on a longer time-scale with a period of about 50 years. Large-scale alternation of abundance of sardine and anchovy populations corresponds to these warm (El Viejo) and cold (La Vieja) climatic regimes. At smaller scale, the El Niño events would induce massive die-offs in anchovy, adapted to cold, nutrient-rich coastal waters, whereas the populations of sardine (and of other species like jack mackerel or mackerel), which live in the warmer waters, would experience an upsurge in numbers during or just after these episodes.
A recent study conducted by IRD researchers and their Peruvian partners ( 1) in this part of the Pacific, has called this traditional theory into question. Indeed, as there is no single type El Niño event, each one different in intensity, length and environmental consequences, pelagic fish would not have one single adaptive response to these events. In order to analyse these adaptive strategies and explain the fluctuations observed in sardine and anchovy populations, the scientists chose an overall approach. This took into account a whole range of available data: climatic, biological and ecological, at different time-scales (3 ). They put forward a hypothesis, based on the variations in habitat size for each species, to interpret the alternate fluctuations of anchovy and sardine populations at decadal scales, not only on inter-annual periods.
Hélène Deval | EurekAlert!
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Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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