**5. Conclusions**

492 Health Management – Different Approaches and Solutions

than in the stomach content. Similar relationships have been observed in green turtles from Japan (Anan et al., 2001). However, contrary to the findings of Maffucci et al., (2005), Zinc concentrations in the livers and kidneys of green turtles in our study were not significantly different from their stomach contents. The distribution of metals among organs is influenced by both duration and concentration of exposure. Liver is a major site of short-term Cadmium storage, whereas during long-term exposure, Cadmium is redistributed from the liver to the kidney where it is absorbed and concentrated (Thomas et al., 1994; Linder and Grillitsch, 2000; Rie et al., 2001). Therefore a significantly greater concentration of Cadmium in green turtle kidney than liver is often observed (Storelli and Marcotrigiano, 2003; Maffucci et al., 2005; Gardner et al., 2006) and likely results from years of accumulation in this long-lived species. While kidney Cadmium concentration may serve as a good indicator for assessments of sea turtle health, liver more closely reflects the concentration of this metal in the food and so analyses of liver may provide a better indication of recent environmental exposure. Accordingly, Cadmium concentrations in the livers analyzed in the present study were not different from the food in the sea turtles' stomachs. Concentrations of Fe and Zinc in liver were also similar to the stomach contents. Whereas, Plumb, Nickel and Manganese concentrations in liver were similar to kidney, but were lower than in the stomach contents, which may indicate metabolic processing of these metals. Alternatively, Copper concentration was higher in liver than in the turtles' food and appeared to be preferentially

**4.3 Metals in sea turtle stomach contents and marine plants from the bay** 

Two principle components, PC(1) and PC(2), explained 68%of the total variance in the data.When plotted relative to PC(1) and PC(2), the plant samples collected in the bay formed a grouping at the left side of the plot while the green turtle tissue samples and the plants from the stomach contents plotted higher on PC(1) (Fig. 4A). Examination of the loadings plot for each of the metals confirmed that samples scoring high on PC1 had signatures dominated by Cadmium and Zinc (stomach contents and kidney) or Cu (liver) (Fig. 4B). This agrees with the observation that the plants in the stomach contents contained greater percent contributions of Cadmium and Zinc than the samples collected in the bay, while Pb and Mn contributed more to the metal profiles in the bay samples as shown in Fig. 2; a tendency that was consistent in all five plant species. The metal profiles in the sea turtle tissues more closely resembled the plants in the stomach contents than the same species of plants collected within Estero Banderitas. The fact that the concentrations of Cadmium, Fe and Zinc in green turtle liver were the same as the stomach contents but different from the plants collected in the bay suggests that sea turtles collected inside of Magdalena Bay use foraging resources outside of the Estero Banderitas region. Further support of this conclusion is provided by the fact that three algal species (*N. baileyi*, *P. capillacea* and *U. lactuca*) in the stomach contents were not found in Estero Banderitas. Franzellitti et al. (2004) proposed that tissue metal profiles can be used as "environmentally acquired markers" to determine sea turtle feeding areas. Similarly, principle component analyses have been applied previously to determine sources of metals in aquatic environments (Ruiz-Fernández et al., 2001). Comparison of the metal signature profiles in plants from the bay and the sea turtle stomach contents indicate that the plant species contained inside the sea turtle stomachs originated from a location outside of Estero Banderitas, in an area where Cadmium and Zinc concentrations dominate the metal profiles in the environment. Surface water metal concentrations have been strongly correlated with upwelling events and natural

accumulated in liver over kidney.

Conservation of threatened species, such as the green turtle (*Chelonia mydas*), is closely related to habitat quality. In particular there are issues related to heavy metals, the presence of epibionts, parasites and fibropapiloms who might play a crucial role in the species survivorship. The process of metal bioaccumulation in marine food chains is poorly understood because very little data is available on metal concentration at different trophic levels and their temporal or spatial variation and its influence in turtle health. The Baja California Peninsula, Mexico serves an important role for feeding and developing sea turtles. High concentrations of metals detected in food items (seaweeds and seagrasses) and in green turtles (*Chelonia mydas*) from Magdalena Bay prompted an investigation into the sources of metals in the region in relation to the health issues of the animals. We compared metal concentrations in sea turtle tissues in relation to plant species found in their stomach contents, and with the same species of plants collected inside a sea turtle refuge area known as Estero Banderitas and determine the health state of turtles based on our long term monitoring efforts. Our results showed that Iron, Copper, and Manganese were the most significant metals found in seagrasses, red, and green algae. We found significant more variation in temporal heavy metal concentrations in relation to the maximum abundance in

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the samples and spatial variation in relation to the studied taxa suggesting that herbivores' have a differential intake of the metals. Also, our results suggest that heavy metals might be incorporated regularly in the diet of many herbivorous animals with severe consequences to their health. Differences in the metal concentrations between marine plant species in relation to animal tissue were minimal. Principal components analysis of the percent contribution of individual metals to the overall metal signature of each plant or tissue sample generated three principal components that explained 80.7% of the total variance in the data. The plant samples collected within Estero Banderitas formed a separate grouping from the green turtle tissue samples and the plants from the stomach contents. The plants in the stomach contents contained greater percent contributions of Cadmium and Zinc than the plants collected inside the bay, while Plumb and Manganese contributed more to the metal profiles in the bay samples. The metal profiles in the sea turtle tissues more closely resembled the stomach contents than the same species of plants collected within Estero Banderitas, and suggest that sea turtles collected inside Magdalena Bay use foraging resources outside of the Estero Banderitas region. Green turtle from Estero Banderitas seems to be healthy at this stage in comparison with nesting areas in the Pacific and Atlantic of Mexico our data on fibropapilomas and epibionts strongly support this idea. Our data supports the suggestion that metal profiles can be used as "environmentally acquired markers" to improve our understanding of the extent of sea turtle foraging areas. Management strategies for these species should consider monitoring the levels of metals.

#### **6. Acknowledgements**

Funding for this project was provided by a grant to SC Gardner from the Consejo Nacional de Ciencia y Tecnología (Conacyt, SEP-2004-CO1-45749) and the Centro de Investigaciones Biológicas del Noroeste, S.C. (CIBNOR). The authors express their appreciation to Dr. Wallace J. Nichols, Rodrigo Rangel and the Grupo Tortuguero for their assistance in this project. We also appreciate the expertise of Dr. Samuel Chávez Rosales and Griselda Peña Armenta for their help with the quantitative analyses. This research was conducted in accordance with Mexican laws and regulations, under permits provided by the Secretaria de Medio Ambiente y Recursos Naturales (SGPA/DGVS/002-2895).

#### **7. References**


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