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The Galapagos Islands are among the most important nesting areas for the green sea turtle, Chelonia mydas, in the eastern Pacific Ocean. In addition, the coastal waters of this oceanic archipelago host many important feeding areas for this species, although little is known about green turtle feeding ecology at these sites. The goal of this study was to identify and quantify the most important items in the diet of the green turtle at the foraging grounds of Bahia Elizabeth, Caleta Derek and Punta Nuñez. Our analysis was based on 65 oesophageal samples from turtles captured in 2006 and 2007. We compared spatial and seasonal composition of diet using non-metric multidimensional scaling analysis (MDS) and analysis of similarity (ANOSIM). Green turtle diet was composed mainly of the algae species Ulva lactuca, Polysiphonia sp., Hypnea sp. and Dictyota sp., and the red mangrove Rhizophora mangle. Turtles also consumed animal matter, mainly cnidarians, albeit to a lesser extent. Content of turtle diets was different among feeding grounds and seasons. The ANOSIM showed that diet composition can differ between foraging grounds using presence/absence of diet items. Even though U. lactuca was the most abundant algae consumed in both seasons, changes in species richness of algae were found between both sampling events, with diet during the warm season more varied than the cold season (χ2 = 16.84, df = 6; P < 0.05).

Human impact and global warming are driving major modifications to the world's ecosystems, the coastal zone being one of the most damaged. Seagrass meadows constitute coastal communities that have experienced great losses worldwide. The dominant seagrass in the meadows of the Pacific coast of North America is Zostera marina. There is evidence that Z. marina has been replaced in some places by the opportunistic seagrass Ruppia maritima with important implications for the trophic connections of local ecosystems. In México, there are few reports on the distribution and loss of seagrass meadows. Here, we report on the importance that R. maritima has gained in three wetlands of northwest México, replacing Z. marina and modifying local trophic networks. We made extensive samplings on Z. marina and R. maritima meadows, recording shoot density and marking their spatial distribution with GPS. We included information on the presence of R. maritima at other wetlands of northwest México from historical reviews and current sampling. R. maritima was recorded in 29 localities, 3 of which are new records. Their shoot density and spatial coverage were highest in late fall and decreased in late spring, while Z. marina meadows increased after the reduction of R. maritima meadows. R. maritima now constitutes a primary food source for green turtles in the sampled wetlands, something unprecedented a few years ago. Improvement of wetland management plans is needed to stop environmental degradation, R. maritima invasion, and the loss of ecosystem functions.

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