Inherent Variation in Stable Isotope Values and Discrimination Factors in Two Life Stages of Green Turtles

2012 ◽  
Vol 85 (5) ◽  
pp. 431-441 ◽  
Author(s):  
Hannah B. Vander Zanden ◽  
Karen A. Bjorndal ◽  
Walter Mustin ◽  
José Miguel Ponciano ◽  
Alan B. Bolten
Keyword(s):  
Stable Isotope ◽  
Life Stages ◽  
Green Turtles ◽  
Discrimination Factors

Demography and foraging ecology of Chelonia mydas on tropical shallow reefs in Bahia, Brazil

2015 ◽  
Vol 96 (6) ◽  
pp. 1295-1304 ◽  
Author(s):  
Adriana Jardim ◽  
Milagros López-Mendilaharsu ◽  
Francisco Barros
Keyword(s):  
Red Algae ◽  
Foraging Ecology ◽  
Activity Patterns ◽  
Somatic Growth ◽  
Growth Dynamics ◽  
Chelonia Mydas ◽  
Annual Growth Rate ◽  
Life Stages ◽  
Green Turtles ◽  
Spatial Use

Long-term tagging studies, particularly those that target life stages away from nesting beaches can provide important insights in key life history traits, which are essential for the effective management of endangered species. The coast of Bahia hosts important green turtle foraging areas, but information on demography, spatial use and foraging ecology in this region is lacking. Here, we (1) examined the size-class structure of green turtles in Bahia, (2) compared the size distribution from Bahia to other foraging aggregations in Brazil, and (3) studied the somatic growth dynamics. Additionally, we investigated the (4) diet, (5) habitat use and (6) activity patterns of green turtles along shallow reefs in Bahia. From 2009 to 2013, 322 green turtles were captured and 44 were recaptured between 7 and 1218 days after initial tagging. Curved carapace length varied from 32.9 to 122.5 cm. Mean annual growth rate was 3.03 ± 1.18 cm year−1. The diet of the turtles was mainly composed of red algae of the family Gelidiaceae, Gelidiellaceae and Cystocloniaceae. There was a positive relationship between the abundance of red algae and the number of turtle sightings, with a significant increase in foraging activity during late afternoon. This study highlights the importance of this area as a mixed foraging aggregation of juvenile and adult green turtles, and reveals that foraging grounds for this species in Brazil exhibit southern immature-dominated assemblages and northern mixed aggregations. Areas with high aggregation of green turtles comprising individuals from different life stages must be targeted for conservation management.

Food source determines stable isotope discrimination factors ΔN and ΔC in tadpoles

2020 ◽  
Vol 41 (4) ◽  
pp. 501-507
Author(s):  
Julian Glos ◽  
Katharina Ruthsatz ◽  
Dominik Schröder ◽  
Jana C. Riemann
Keyword(s):  
Stable Isotope ◽  
Food Source ◽  
Trophic Ecology ◽  
Rana Temporaria ◽  
Isotope Ratios ◽  
Bufo Bufo ◽  
Discrimination Factor ◽  
Fractionation Factor ◽  
Interspecific Differences ◽  
Discrimination Factors

Abstract Analyses of stable isotope ratios are widely applied in studies on a large variety of aspects in trophic ecology. Most studies rely on a precise estimation of the relevant discrimination factor Δ (also called the fractionation factor), that reflects the fractionation or differences in isotope ratios of a certain element (mainly nitrogen N and carbon C) between an animal’s diet and its tissue and is used to identify one step in the food web. We experimentally determined ΔN and ΔC of two species of widespread amphibians in Europe, Rana temporaria and Bufo bufo, and tested for the effect of food source (cyanobacteria Spirulina vs. zooplanktonic Daphnia) on Δ and for interspecific differences. Our study shows high variation in Δ in relation to the food source, but low interspecific differences. Tadpoles that were fed with Spirulina did have considerably lower ΔN than tadpoles fed with Daphnia in both species, and lower ΔC only in R. temporaria. The range of Δ obtained here can be a useful baseline for future trophic studies on tadpoles of Rana and Bufo. The strong diet-dependency of Δ, however, argues strongly against the use of a fixed discrimination factor in future isotope studies.

Comparisons of stable isotope composition among tissues of green turtles

2020 ◽  
Vol 34 (16) ◽  
Author(s):  
Mathew A. Vanderklift ◽  
Richard D. Pillans ◽  
Natalie A. Robson ◽  
Grzegorz Skrzypek ◽  
Jessica L. Stubbs ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotope Composition ◽  
Stable Isotope Composition ◽  
Green Turtles
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