Ecosystem function indicators, such as mean trophic level, are increasingly applied in conservation management. Banning fishing activities within MPAs enhances the robustness of food-web dynamics and thus increases trophic resilience. Our study provides a multiple variability index for δ¹☼ in organisms along a food chain, and verifies that tissue-specific ¹☼ analysis is essential to identify diet and species and thus is a valuable tool for research on tropical seabird ecology.ĭesignating and managing marine protected areas (MPAs) can mitigate many ocean threats. A Suess effect, caused by fossil fuel combustion and the emission of carbon with fewer ¹☼ isotopes, was observed in the bird and fish tissue from ancient to modern time. The δ¹☼ discrimination factors also differed significantly among the various tissues between tropical seabirds and their prey. δ¹☼ is tissue-specific in both seabirds and flying fish due to the variance in turn-over among the tissues and differences in the type and content of amino acids across a diverse range of tissues. We analyzed ¹☼ characteristics in samples of bird bones, feathers, eggshell carbonate and membrane from modern specimens of red-footed booby (Sula sula) as well as fish muscle, scales, and bones from its predominant food source, flying fish (Exocoetus volitans), and muscle from its secondary food source squid (Loligo chinensis), as well as in ancient sub-fossil samples of seabird and flying fish at the Xisha Islands, South China Sea. Therefore, gastropod conchiolin opercula should not be used for short-term dietary analyses in some gastropod species, but they may rather reflect the integrated long-term dietary trend. mammilla conchiolin opercula were similar to those for the foot tissues, whereas there was a larger δ¹☼ depletion in conchiolin opercula with respect to the foot tissues of C. mammilla, although the reason for this is unclear. In all the gastropod specimens analyzed, we observed a large (at least 10‰) δ¹☼ depletion in shell organics with respect to the foot tissues of C. However, the mean δ¹☼ values for the shell organics from the specimens collected in 1995 showed no significant differences between C. mammilla shells, which was a similar trend to the relationship for δ¹☼ values observed in their foot tissues. fluctuata shell organics collected in 2006 were approximately 3.6‰ higher than those for P. fluctuata foot tissues from specimens collected in 1995 were similar to those from specimens collected in 2006. mammilla may derive carbon from epiphytes and phytoplankton via their bivalve prey. fluctuata were autotrophs, such as macrobenthic marine plants and algae, whereas P. The data from the foot tissue samples confirmed that the food sources for C. We determined the stable carbon and nitrogen isotope compositions of foot tissue, conchiolin opercula, and the shell organic matrix from the marine gastropods Cernina fluctuata (Ampullinidae) and Polinices mammilla (Naticidae) collected in March 2006 from a lower tidal flat on Cuyo Island, the Philippines, together with the seagrass Enhalus acoroides and the macroalga Padina australis. novacula between the studied locations, while no differences were found for Delta(15)N, indicating that non-geographical differences should be considered in the application of scales instead of muscle for (15)N, while for (13)C differences in the geographical isotopic offset should be considered. Spatial differences were found in the Delta(13)C of X. Mean delta(13)C and delta(15)N values between species showed significant differences (paired t-test, p < 0.01) between muscle and scale with an enrichment for delta(13)C and a depletion for delta(15)N.
The isotopic offset (Delta(13)C and Delta(15)N) between muscle and scales was significantly different among species (analysis of variance (ANOVA), p 0.05). A positive correlation was found between muscle and scales in Argyrosomus regius and Xyrichtys novacula, while Dentex dentex showed no correlation due to the small length range of this species. In the present work we have compared the delta(13)C and delta(15)N isotopic signals of muscle and scales of three different fish species in order to test fish-scale sampling as a non-lethal technique in fish trophodynamics. An increase in the number of isotopic ratio studies and the vulnerability of some species have led to increased use of non-lethal methodologies for conservation purposes. Diet information of organisms was traditionally acquired by the use of lethal techniques (gut content or muscle delta(13)C and delta(15)N isotopic ratios).
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