Porner, E., K.J., Benoit-Bird, E.L., Hazen, C.M., Waluk, C.J., Robinson, J., Gómez-Gutiérrez & W.F., Gilly (2022). Decline and recovery of pelagic acoustic backscattering following El Niño events in the Gulf of California. Enrique Curchitser (Eds.), Progress in Oceanography. 205: 102823. DOI: 10.1016/j.pocean.2022.102823.
Elan Porner 1, Kelly J. Benoit-Bird 2, Elliot L. Hazen 3, Chad M. Waluk 2, Carlos J. Robinson 4, Jaime Gómez-Gutiérrez 5 y William F. Gilly 1
Climatic variability exerts enormous pressures on the structure and function of open ocean ecosystems. Althoughthe responses of primary producers and top predators to these pressures are being increasingly well-documented,little is known about how midtrophic communities respond to oceanographic and climatic variability. Weaddress this knowledge gap through a study of the effects of El Niño Southern Oscillation (ENSO) and localenvironmental conditions on acoustic proxies of the midtrophic community in the Gulf of California, Mexico. Wequantified the intensity and distribution of nighttime acoustic backscatter (120 kHz) in the upper 200 m of thewater column during 10 oceanographic cruises (2007–2017) and described its response to environmental vari-ability using generalized additive models. ENSO conditions were the strongest drivers of variability in back-scatter after accounting for seasonal increases in backscatter with sea surface temperature and chlorophyll-aconcentration. Acoustic backscatter in the central Gulf of California decreased significantly during the positivephase of ENSO. Following El Nin ~o events in 2009–10 and 2015–16, mean backscatter declined by an order ofmagnitude and remained depressed for more than two years before recovering to pre-El Nin ~o levels. Scatteringlayer density increased with total backscatter, likely an influential factor determining prey availability forpelagic predators. Our findings demonstrate large and sustained impacts of El Nin ~o on the midtrophic communityin the Gulf of California and further highlight the need to better understand the responses of midtrophic com-munities to environmental variability.
Palabras clave: Hydroacoustic; Backscattering layers; Midtrophic communities; generalized additive models; El Niño southern oscillation
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