Peruvian Pinnipeds as Archivists of ENSO Effects

Environmental fluctuations in the eastern Pacific Ocean are reflected in the tissues of some of its most vulnerable apex predators, the Peruvian fur seal (PFS) Arctocephalus australis ssp.and the South American sea lion (SASL) Otaria byronia.These large pinnipeds live in sympatry along the Pacific coastline of South America and forage within the neritic waters over the continental shelf. The coastal waters off Peru are a region of great environmental fluctuations due to periodic, oscillating El Niño- La Niña- Southern Oscillation (ENSO) events, which result in ecosystem-wide food web changes. Pinniped vibrissae (whiskers) are continuously growing keratinous tissues and reflect the incorporation of prey from the region. Fine resolution sampling along their length provided trophic information on a weekly to monthly time scale over several years. Vibrissae were obtained from 2010-2016 from female (n=47), male (n=17) and newborn pup (n=6) fur seals and male (n=6) sea lions collected during pinniped rookery health assessments. Stable isotope ratios (δ13C and δ15N) in vibrissae infer temporal primary production and dietary variations in individuals. ENSO conditions were dictated by the sea surface temperature anomaly (SSTA) recordings from the Niño 1+2 Index region over 12 years. Fluctuations in vibrissae δ15N were correlated to varying SSTA readings (p15N (p15N signatures (p13C revealed minor fluctuations ranging from -18.13 to -13.17‰over the 12-year period, δ13C did reveal a significant depletion and enrichment oscillation during specific points in time, such as the 2014-2016 El Niño event, which ranged from -15.09 to -13.83‰(p=0.040). Stable isotope signatures varied between genders, but not by species. Female fur seal stable isotope signatures were significantly more depleted in both δ13C and δ15N than males (p13C and δ15N were inversely correlated to each other from 2014 to 2016; this was during the strongest El Nino-Southern Oscillation event on record (p=0.002). As δ13Csignatures became more enriched, δ15N signatures depleted from 2014 until 2016. This suggests that when ENSO warm phase conditions occur, the environments resources change in historic foraging grounds, possibly forcing pinnipeds to travel farther distances offshoreto forage or altering what they feed on throughout these stressful conditions.This study serves to help understand of the impact of oceanographic influences on these pinnipeds.ENSO conditions influence the trophic dynamics and resultant survival adaptations in both of these vulnerable Peruvian marine mammals

Temporal Baseline of Essential and Non-essential Elements Recorded in Baleen of Western Arctic Bowhead Whale (Balaena mysticetus)

This study established the first baseline of changing elemental concentrations in bowhead whale baleen over time (1958–1999). From previously published stable isotope data, year, season (summer or winter), and location (Beaufort or Bering/Chukchi seas) were attributed to each sample. Thirteen elements (Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, Zn) in baleen from nine subsistence-harvested bowhead whales (n = 138) were detected. Al, Cu, and Fe were the highest concentrations while Cd and V were among the lowest. Our data supports absorption as the main route of exposure to environmental elements rather than biomagnification due to bowhead whales’ low trophic position. A linear mixed-effects model confirmed most elements’ concentrations increased with time, while location and sex were insignificant explanatory factors. These temporal fluctuations were most likely a product of environmental changes due to a warming climate and human activities

Sympatric otariids increase trophic segregation in response to warming ocean conditions in Peruvian Humboldt Current System

Determining trophic habits of predator communities is essential to measure interspecific interactions and response to environmental fluctuations. South American fur seals, Arctocephalus australis (SAFS) and sea lions Otaria byronia (SASL), coexist along the coasts of Peru. Recently, ocean warming events (2014–2017) that can decrease and impoverish prey biomass have occurred in the Peruvian Humboldt Current System. In this context, our aim was to assess the effect of warming events on long-term inter- and intra-specific niche segregation. We collected whisker from SAFS (55 females and 21 males) and SASL (14 females and 22 males) in Punta San Juan, Peru. We used δ13C and δ15N values serially archived in otariid whiskers to construct a monthly time series for 2005–2019. From the same period we used sea level anomaly records to determine shifts in the predominant oceanographic conditions using a change point analysis. Ellipse areas (SIBER) estimated niche width of species-sex groups and their overlap. We detected a shift in the environmental conditions marking two distinct periods (P1: January 2005—October 2013; P2: November 2013—December 2019). Reduction in δ15N in all groups during P2 suggests impoverished baseline values with bottom-up effects, a shift towards consuming lower trophic level prey, or both. Reduced overlap between all groups in P2 lends support of a more redundant assemblage during the colder P1 to a more trophically segregated assemblage during warmer P2. SASL females show the largest variation in response to the warming scenario (P2), reducing both ellipse area and δ15N mean values. Plasticity to adapt to changing environments and feeding on a more available food source without fishing pressure can be more advantageous for female SASL, albeit temporary trophic bottom-up effects. This helps explain larger population size of SASL in Peru, in contrast to the smaller and declining SAFS population

Mickie Rae Edwards

https://nsuworks.nova.edu/cnso_alumni/1018/thumbnail.jp

Peruvian pinnipeds as archivist of ENSO effects off the coast of Peru

Environmental fluctuations in the eastern Pacific Ocean are reflected in the tissues of one of its most vulnerable apex predators, the Peruvian fur seal Arctocephalus australis. The coastal waters off Peru are a region of great environmental fluctuations due to periodic (every 2-7 years) El Niño-Southern Oscillation (ENSO) events, which result in ecosystem-wide food web changes. Pinniped body tissues reflect the incorporation of prey from the region, which can be evaluated using stable carbon and nitrogen isotope ratios (δ13C and δ15N). Continuously growing tissues, like vibrissae (whiskers), can potentially provide a large scale timeline of environmental data in an ecosystem where changes regularly occur and human instrumentation to measure such changes is sparse. Sea surface temperature (SST) anomalies along the Peruvian coastline are encompassed in the body of water known as Niño 1+2; a SST anomaly index used to categorize ENSO events. This region distinguishes itself from the more widely studied water bodies Niño 3, 3.4, and 4 by exhibiting more frequent and shorter-lived heating and cooling oscillations in SST. These oscillations appear to coincide with the δ13C and δ15N signatures recorded in the Peruvian fur seal vibrissae collected from 2010 (n=29), 2011 (n=12), 2012 (n=11) and 2015 (n=12). The δ13C and δ15N covary along the vibrissal length except for distinct points where their patterns are inversely related. These points are identified as transition periods between the region’s rapidly changing El Niño/La Niña phases. Adult female δ13C values throughout all sampled years (n=49), ranged from -18.13 to -13.19 ‰ ± 0.33 ‰. This reflects wide fluctuations in ocean production over time, which is our proxy to ENSO effects. Preliminary δ15N values range from 15.83 to 21.55 ‰ ± 0.85 ‰. These data suggest that these fur seals might be using alternative foraging survival strategies during these ENSO periods by foraging at two or more trophic levels. These may be the first biologic data of their kind to reveal how abiotic, ecosystem-wide changes influence the trophic dynamics and resultant survivability of the Peruvian fur seal

Peruvian Fur Seals as Archivists of El Niño Southern Oscillation Effects

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