Peruvian Fur Seals as Archivists of El Niño Southern Oscillation Effects

Mickie R Edwards,Amy C Hirons,Susana Cárdenas-Alayza,Mya Daniels-Abdulahad,Michael J Adkesson

doi:10.3389/fmars.2021.651212

Mickie R Edwards, Amy C Hirons + Show 3 more

Open Access

https://doi.org/10.3389/fmars.2021.651212

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Abstract

Peru’s coastal waters are characterized by significant environmental fluctuation due to periodic El Niño- La Niña- Southern Oscillation (ENSO) events. This variability results in ecosystem-wide food web changes which are reflected in the tissues of the Peruvian fur seal (Arctocephalus australis). Stable isotope ratios (δ13C and δ15N) in Peruvian fur seal vibrissae (whiskers) are used to infer temporal primary production and dietary variations in individuals. Sea surface temperature anomaly (SSTA) recordings from the Niño 1+2 Index region captured corresponding ENSO conditions. Fluctuations in δ15N values were correlated to SSTA records, indicating that ENSO conditions likely impact the diet of these apex predators over time. Anomalous warm phase temperatures corresponded to decreased δ15N values, whereas cold phase anomalous conditions corresponded to increased δ15N values, potentially from upwelled, nutrient-rich water. Vibrissae δ13C values revealed general stability from 2004 to 2012, a moderate decline during 2013 (La Niña conditions) followed by a period of increased values concurrent with the 2014–2016 El Niño event. Both δ13C and δ15N values were inversely correlated to each other during the strongest El Niño Southern Oscillation event on record (2014–2016), possibly indicating a decline in production leading to an increase in food web complexity. Lower δ13C and δ15N values were exhibited in female compared to male fur seal vibrissae. Findings suggest ENSO conditions influence resource availability, possibly eliciting changes in pinniped foraging behavior as well as food web of the endangered Peruvian fur seal.

Highlights

Large-scale climatic anomalies associated with periodic, alternating El Niño- La Niña-Southern Oscillation (ENSO) conditions are recorded globally through a combination of atmospheric and oceanic teleconnections, resulting in significant, ecosystem-wide impacts (Ropelewski and Halpert, 1987; Trenberth et al, 1998; McPhaden et al, 2006; Sulca et al, 2017)
This is a substantial distance, previous ENSO years have shown documented impacts in the coastal Peruvian ecosystem based on the index, including the 1997/98 anchoveta fishery collapse which is believed to have caused a Peruvian fur seal mass mortality event documented in Punta San Juan reserve (PSJ), Peru (Arias-Schreiber and Rivas, 1998; Cárdenas-Alayza, 2012)
The δ13C and δ15N values acted as a proxy for sex-related resource and habitat use

Summary

Introduction

Large-scale climatic anomalies associated with periodic, alternating El Niño- La Niña-Southern Oscillation (ENSO) conditions are recorded globally through a combination of atmospheric and oceanic teleconnections, resulting in significant, ecosystem-wide impacts (Ropelewski and Halpert, 1987; Trenberth et al, 1998; McPhaden et al, 2006; Sulca et al, 2017). The 1997/98 El Niño affected behaviors in northern elephant seals (Mirounga angustirostris) off the coast of southern California, whose foraging trip duration and distance traveled increased to compensate for lower foraging success (Crocker et al, 2006) During this same ENSO event (1997/98), South American sea lions (Otaria byronia) off the coast of Peru were recorded foraging at deeper depths evidenced through dietary changes. This apex predators’ diet altered from predominantly anchoveta and squat lobster (Pleuroncodes monodon) to mostly demersal species; interestingly, the only time pelagic squat lobster was absent in this otariid’s diet was during the recorded El Niño event (Soto et al, 2006)

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