Changes in the nekton community structure of the Northern Humboldt Current System under ENSO scenarios

Population Ecology
vendredi 20 déc. 03:55 PM (15 minutes)
Salle AB
The Northern Humboldt Current System (NHCS) is a highly productive upwelling system, which covers the northern-central area of Peru. NHCS is the area where the El Niño Southern Oscillation (ENSO) phases, and climate variability in general, are most noticeable. The ENSO warm phase, or El Niño, reduces dramatically the coastal upwelling due to a stronger stratification of the water column. Conversely, the cold phase, or La Niña, strengthens the coastal upwelling, therefore expanding the area of cold coastal waters. These fluctuations trigger changes in the biological productivity of the ocean as well as in species behaviour across different trophic levels (feeding, reproduction, growth, etc.). The main goal of our study is to describe the broad-scale changes in the spatial structure and composition of the nekton community under three ENSO phases: El Niño, La Niña and Neutral. The El Niño scenario produces the highest values of alpha diversity and species richness, whereas La Niña yields the lowest values. The spatial structure of the community predominantly shows four areal groups (with mostly pelagic, oceanic, northern-warmer, and southern-colder species), which vary in terms of areal extension and species richness across the three scenarios. A redundancy analysis (RDA) of community composition as a function of environmental variables describes the relationships between important characteristics (temperature and salinity) of the water masses present in NHCS and the species composition. Climate change models predict an increase of the frequency of El Niño events; therefore, variations in nekton community should be taken into consideration to weaken the impacts on the fishery community.

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