Climatic anomaly affects the immune competence of California sea lions

<div><p>The past decades have been characterized by a growing number of climatic anomalies. As these anomalies tend to occur suddenly and unexpectedly, it is often difficult to procure empirical evidence of their effects on natural populations. We analysed how the recent sea surface temperature (SST) anomaly in the northeastern Pacific Ocean affects body condition, nutritional status, and immune competence of California sea lion pups. We found that pup body condition and blood glucose levels of the pups were lower during high SST events, although other biomarkers of malnutrition remained unchanged, suggesting that pups were experiencing early stages of starvation. Glucose-dependent immune responses were affected by the SST anomaly; specifically, pups born during high SST events had lower serum concentrations of IgG and IgA, and were unable to respond to an immune challenge. This means that not only were pups that were born during the SST anomaly less able to synthesize protective antibodies; they were also limited in their ability to respond rapidly to nonspecific immune challenges. Our study provides empirical evidence that atypical climatic conditions can limit energetic reserves and compromise physiological responses that are essential for the survival of a marine top predator.</p></div

Sea surface temperature anomaly (°C) in the northeastern Pacific Ocean.

<p>Panels show the average of values recorded April 1^st to July 31^st for (<b>A</b>) 2012, (<b>B</b>) 2013, (<b>C</b>) 2014, and (<b>D</b>) 2015. The location of the San Benito Archipelago is indicated within the square. Images provided by the NOAA/ESRL Physical Sciences Division, Boulder Colorado from their Web site at <a href="http://www.esrl.noaa.gov/psd/" target="_blank">http://www.esrl.noaa.gov/psd/</a>. The plots were created by using data collected by the NCEP/NCAR Reanalysis Project [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179359#pone.0179359.ref033" target="_blank">33</a>].</p

White blood cell counts of California sea lion, <i>Zalophus californianus</i>, pups that differed between those born during normal (2012) and atypical (2014 and 2015) sea surface temperature conditions.

<p>A) Basophils, B) Band neutrophils, C) Hypersegmented neutrophils.</p

Skin-fold thickness in response to PHA challenge.

<p>Response to PHA in California sea lion, <i>Zalophus californianus</i>, pups born during normal (2012) and atypical (2015) sea surface temperature conditions.</p

Serum antibody levels of California sea lion, <i>Zalophus californianus</i>, pups born under normal (2012) and atypical (2014 and 2015) sea surface temperature conditions.

<p>A) IgG, B) IgA, C) IgM.</p