δ13C Y δ15N EN VIBRISAS DE LOBO MARINO DE CALIFORNIA (Zalophus californianus) COMO INDICADOR DE LA VARIACIÓN TRÓFICA ESTACIONAL EN BAHÍA MAGDALENA Y BAHÍA DE LA PAZ, BCS, MÉXICO

Abstract

ABSTRACT We explored the vibrissae of the California sea lion (Zalophus californianus) as a tissue that records the isotopic variation associated with changes in food and environmental conditions. The main aim of this work was to analyze the patterns of variation δ13C and δ15 to along the sea lion vibrissae and to compare with changes in sea surface temperature (SST) and satellite-derived chlorophyll pigment concentrations (CHL), interannual variability are examined for (CHL) and Upwelling Index (UI), in two breeding areas; Magdalena Bay (BM) and La Paz Bay (BLP). We selected a total of 13 vibrissae collected between 2008 and 2009, six females and four males of BM, and three females of BLP in 2001 and 2006. Each vibrissae was cut into about 60 pieces, depending on the length of the vibrissae; a total of 680 fragments were analyzed isotopically in a mass spectrometer of continuous flow. Comparison between females of the two sites gives a statistically significant differences by Kruskal-Wallis test (δ13C; H=223.645, g.l.=8, p<0.05 and δ15; H=250.947, g.l.=8, p<0.05), where the median values for BLP was higher in both isotopes. It could reflect higher values from the base of the food web (MOP). Seasonal variations (the sum of the average, plus the sum of both the annual and the semiannual components) were analyzed of both isotopes by Fourier analysis to identify the frequency of each component of seasonality. Additionally, we found a positive relationship in 8 vibrissae analyzed between the number of seasonal fluctuations and the length of the vibrissae; finding a significant correlation (r= 0.97, p <0.001), from which is possible to calculate a growth rate 0.16 mm / day, comparable to that found in other sea lions. Based on data from SST and CHL from 2002 to 2010 for surrounding areas the study sites, we performed the seasonal patterns in the isotopic vibrissae profiles. The correlation between the environmental and the isotopic variability was possible using the δ15N in 8 selected vibrissae. Results showed an average time lag of 3.52 months for BM and 6 months for BLP between the time of increased productivity and the time reflected this increase in the animal tissue.