**The Foragining Ecology of the Green Turtle in the Baja California Peninsula: Health Issues**

Rafael Riosmena-Rodriguez1, Ana Luisa Talavera-Saenz1, Gustavo Hinojosa-Arango2, Mónica Lara-Uc3 and Susan Gardner4 *1Programa de Investigación en Botánica Marina, Departamento de Biología Marina, Universidad Autónoma de Baja California Sur, La Paz Baja California Sur, 2The School for Field Studies, Puerto de Acapulco s/n, Puerto San Carlos, Baja California Sur 3Depto. de Virología, Facultad de Medicina Veterinaria y Zootecnia, UADY, Mérida, Yucatán, 4Centro de Investigaciones Biológicas del Noroeste, La Paz Baja California Sur, México* 

#### **1. Introduction**

476 Health Management – Different Approaches and Solutions

Youatt, W. (1867). *Sheep: their breeds, management, and diseases*. Orange Judd & Co., New

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. Heavy metals occur naturally in the environment (Sparling et al., 2000) as part of the biogeochemical cycles (Valiela, 2009), and it is often difficult to differentiate between natural and anthropogenic sources (Kieffer, 1991; Moreno, 2003). In marine systems, natural processes (e.g., upwelling, river runoff) can redistribute and concentrate heavy metals in the environment, occasionally reaching toxic levels (Sparling et al., 2000; Machado et al., 2002). The effects of these processes may vary over seasonal and spatial scales (Sawidis et al., 2001) and their understanding can aid in determining the sources as biomonitors (Szefer et al., 1998; Páez-Osuna et al.,2000), and ultimately their effects on wild life (Sparling et al., 2000; Talavera-Saenz et al., 2007). Also, they can be used for bioabsorption in contaminated waters (Kumar and Kaladharan, 2006). Caliceti et al. (2002) found a decrease in Zinc and Cadmium concentrations from the center of a lagoon, close to an industrial district, towards the Venice lagoon (Italy) openings to the sea, suggesting anthropogenic sources, while Villares et al. (2002) found that seasonal and spatial variation in metals was related to algal growth cycles and river runoff. Riosmena-Rodriguez et al. (2010) determined that heavy metals are related to the physiological features of each major analyzed taxon (green algae, red algae and seagrasses).

The processes controlling the concentration and distribution of metals in coastal environments and their consequences in the species health are poorly understood. It is generally assumed that diet is the main source of metals to sea turtles (Caurant et al., 1999; Anan et al., 2001), but little is known of the process of metal accumulation in these species because data on metal residues in most components of sea turtles' diet has been lacking. As

The Foragining Ecology of the Green Turtle in the Baja California Peninsula: Health Issues 479

Peninsula (Seminoff et al., 2002), juvenile and adult green turtles preferentially consume soft red algae, especially species of Gracilaria (López-Mendilaharsu et al., 2005). Studies in Baja California have demonstrated that these same species of red algae tend to have higher enrichment factors of metals than other groups of seaweeds (Sánchez-Rodríguez et al., 2001), which could account for the high accumulation of metals in foraging green turtles in this

Magdalena Bay is located on the Pacific coast of the Baja California Peninsula, Mexico between 24° 15′ N and 25° 20′ N, and 111° 30′ W and 112° 15′ W. It is a shallow lagoon protected from the Pacific by barrier islands, with high productivity resulting from seasonal marine upwelling along the coast. Diverse marine habitats within the bay include sandy bottoms and rocky margins, extensive beds of the seagrass *Zostera marina* and a diverse assemblage of macroalgae. A sea turtle refuge area known as Estero Banderitas is located within the mangrove channels in the northwest region of the Bay where green turtles reside year-round (Fig. 1). Because of the perceived importance of this area for green turtle foraging, its protection has been identified as a priority for conservation efforts (Arriaga et al., 1998; Nichols et al., 2000). Rodríguez-Meza et al. (2008) has found that the presence of heavy metals in the bay is heavily influenced by sediment type, organic material, and

carbonates and concluded that there was no evidence of human impacts.

Fig. 1. Study area in Estero Banderitas (24º 50´ - 25º 00´ N and 112º08´ W) located in Bahía

Magdalena, Baja California Sur, Mexico.

region.

**2.1 Study area** 

**2. Materials and methods** 

adults, green turtles forage largely on marine algae and seagrasses with variation in the diet due to the relative availability of food types over geographic and temporal scales (Garnett et al., 1985; Brand-Gardner et al., 1999; Seminoff et al., 2002). In 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 (de la Lanza et al. 1989; Talavera-Saenz et al. 2007) or their temporal (Abdallah et al., 2006; Rodriguez-Castañeda et al., 2006) or spatial variation (Kalesh and Nair, 2006) and their effects on the photosynthetic process (Catriona et al. 2002). High concentrations of heavy metals have been found in sea turtles from many regions of the world (Storelli and Marcotrigiano, 2003). Although metal concentrations vary greatly by region and tissue type, green turtles (*Chelonia mydas*) have been found to have exceptionally high kidney cadmium concentrations. Elevated Cadmium levels have been measured in green turtles from around the world including Japan (Sakai et al., 2000; Anan et al., 2001), China (Lam et al., 2004), Europe (Caurant et al., 1999), Australia (Gordon et al., 1998) and the Arabian Sea (Bicho et al., 2006). Gordon et al. (1998) found that Cadmium concentrations in green turtles from Australia were up to three times higher than the levels reported in commercial seafood products. The presence of epibionts, parasites (internal and external) might occasionally cause the death of some marine turtles and being predecessors of fibropapiloms (Aguirre y Lutz, 2004; Work, 2000, Work *et al*., 2005). The presence of fibropapiloms in Hawaiian waters was related with the presence of hirudineans (Díaz, *et al.,* 1992). This kind of infections are might be related with their foraging habitat and its conservation condition, their health condition to escape predators and, for the females, the fecundity reduction (Gámez et al., 2006; Alfaro, et al., 2006; Badillo, 2007).

The Baja California Peninsula serves an important role as foraging grounds for five of the world's seven sea turtle species (Gardner and Nichols, 2001). Although much of the peninsula is considered pristine, exploitation of mineral deposits has occurred since the 19th Century and concentrations of Cadmium, Zinc, Copper and Plumb in sediment and marine fauna have been observed above those in more industrialized regions (Gutiérrez-Galindo et al., 1999; Shumilin et al., 2000). In the mid 1970's, Martin and Broenkow (1975) reported that concentrations of Cadmium along the coast of the Baja California Peninsula were remarkably elevated as compared to other regions of the eastern Pacific. Sources of heavy metals in Baja California have been generally attributed to natural factors related to upwelling and the biogeochemistry of the region, however, the potential contribution from anthropogenic sources (e.g. mining and urbanization) cannot be entirely dismissed (Martin and Broenkow, 1975; Sañudo-Wihelmy and Flegal, 1996; Méndez-Rodríguez et al., 1998; Gutiérrez- Galindo et al., 1999; Shumilin et al., 2001). Rodríguez-Meza et al. (2008) developed an extensive evaluation of the heavy metals in sediments and seaweeds along ten sites in the bay. They suggested that the high levels of some heavy metals are related to terrigenous input from the arroyos and biogenic origin by the upwelling. In order to better understand the sources of heavy metals to marine species, more information is needed on metal concentrations in primary producers that make up the base of the food chain. However, few (Riosmena-Rodriguez et al., 2010) papers have approached the study of natural levels of heavy metals in seaweed communities and their temporal and spatial variation. Previous studies in Magdalena Bay, Mexico (Méndez et al., 2002; Gardner et al., 2006) have found high concentrations of metals in marine vertebrates, despite the lack of obvious anthropogenic sources. For example, Cadmium, Zinc, and Iron concentrations in the herbivorous green turtle, *Chelonia mydas*, were the highest ever reported in sea turtles globally (Gardner et al., 2006). In Magdalena Bay, like other regions of the Baja California Peninsula (Seminoff et al., 2002), juvenile and adult green turtles preferentially consume soft red algae, especially species of Gracilaria (López-Mendilaharsu et al., 2005). Studies in Baja California have demonstrated that these same species of red algae tend to have higher enrichment factors of metals than other groups of seaweeds (Sánchez-Rodríguez et al., 2001), which could account for the high accumulation of metals in foraging green turtles in this region.
