Climatic anomaly affects the immune competence of California sea lions

Abstract

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.

Immune-mediated hookworm clearance and survival of a marine mammal decrease with warmer ocean temperatures

“…Therefore, it is not surprising that the average blood glucose levels and growth rate of pups were highly correlated in our study, suggesting that glucose could be a good marker of the energy balance in a pup, and an important factor to consider in the health assessment of wild pinnipeds given the connection between energy balance and immune system. For instance, recent studies have shown that Californian sea lion pups with better body condition and higher glucose levels have higher total IgG ( Banuet-Martínez et al, 2017 ). In humans and laboratory animals, glucose metabolism is one of the most important factors driving T-cell activity and production of antigen-specific IgG ( Mohammed et al, 2012 ; Palmer et al, 2015 ).…”

“…Regardless, the mechanisms that drive decreased survival during years with low ocean productivity have not been intensely explored beyond assuming that this results from direct mortality because of starvation. However, in some otariid populations, in years with abnormal SST, the immune competence of pups decreases ( Banuet-Martínez et al, 2017 ), suggesting that environmental variables can affect the health of marine mammals by impairing their immune function. If these immunological changes impact offspring survival, there could be additional negative consequences between a warmer ocean, health, and survival of marine vertebrates.…”

The life history strategy of a fur seal hookworm in relation to pathogenicity and host health status

“…RBC and HG were measured as previously described ( Seguel et al, 2016 ), and anemia defined as HG concentrations below 10 g/dL and/or RBC bellow 3 × 10 3 /μL, according to published reference values for pups in this population ( Seguel et al, 2016 ). Additionally, we recorded the scaled body mass (total length/weight) (BM) ( Banuet-Martinez et al, 2017 ), total serum protein concentration (TP) and white blood cell counts (WBC) as general measurements of the pups' health. These indicators were measured in each capture following previously described methods ( Seguel et al, 2016 ), and the average for each pup was used for statistical analyses.…”

Climate variability and life history impact stress, thyroid, and immune markers in California sea lions (Zalophus californianus) during El Niño conditions

“…When forced to increase foraging effort, nursing adult female sea lions have difficulty in allocating resources towards pup development (Ono et al , 1987). Additionally, body condition and glucose-dependent immune markers, IgG and IgA (Palmer et al , 2015), were reduced in dependent CSL pups born during anomalous conditions of high SST in 2015 (Banuet-Martínez et al , 2017), and also showed abnormalities to erythrocytes, which can further impact nutrient uptake (Flores-Morán et al , 2017). This extended period presented a unique opportunity to investigate the effects of sustained stressors on CSL facing abnormally high energetic demands.…”