Stable Isotope Analysis Enhances Our Understanding of Diamondback Terrapin (Malaclemys terrapin) Foraging Ecology

Denton, Mathew J.; Demopoulos, Amanda W.J.; Baldwin, John W.; Smith, Brian J.; Hart, Kristen M.

doi:10.1007/s12237-018-0476-6

Cited by 7 publications

(2 citation statements)

References 67 publications

(88 reference statements)

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“…Thus, the fluctuation in the ∆ 15 N feather−RBC is most likely due to variations in the diet at the time of feather formation rather than nutritional status. For other studies that similarly compare tissue delta values, see [88][89][90][91].…”

Section: Hypothesis 3: Diet/food Web Changes By Season/locationmentioning

confidence: 99%

Stable Isotope Analyses of Multiple Tissues of Great Shearwaters (Ardenna Gravis) Reveals Long-Term Dietary Stability, Short-Term Changes in Diet, and Can be Used as a Tool to Monitor Food Webs

et al. 2019

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The great shearwater (Ardenna gravis) is a common pelagic bird with a distribution that spans almost the entire Atlantic basin, which in conjunction with its relatively high abundance, makes great shearwaters an effective bio indicator. We compared δ13C and δ15N values from the feathers, red blood cells (RBCs), and plasma of great shearwaters collected in 2014 and 2015 from the waters off Massachusetts and Cape Cod. The δ13C and δ15N values of RBCs were quite constant between sampling periods and years, suggesting a generally stable food web over that time period. However, the δ13C of plasma indicates a small seasonal change in diet between July and September for both years, with plasma δ15N values suggesting a slight increase in trophic level late in summer. Comparison of the δ15N of RBCs and plasma indicates that great shearwaters experienced a diet shift during the first few weeks of summer 2014, but not in 2015. Comparisons with other studies suggest that these shearwaters feed at a lower trophic level than great shearwaters sampled in the Bay of Fundy and that there is a decrease in δ13C with increasing latitude, which could indicate a more pelagic diet in northern waters. Stable isotope analysis of the sixth primary feathers provided evidence that these feathers are molted in the Northern Hemisphere and that the diet of great shearwaters shortly after arrival was different in 2014 and 2015. This study demonstrates that within species comparisons of tissue isotopic signatures over time and comparisons of isotopic signatures of tissues with different turnover rates, can detect changes in diet and be used as a tool to monitor for changes in marine food webs over time and space. The relevant signals remain informative even in the absence of species-specific data on tissue-diet discrimination factors, tissue turnover rates, or knowledge of dietary components and their stable isotopic signatures, suggesting dietary changes indicative of a corresponding change in the food web.

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Section: Hypothesis 3: Diet/food Web Changes By Season/locationmentioning

confidence: 99%

Stable Isotope Analyses of Multiple Tissues of Great Shearwaters (Ardenna Gravis) Reveals Long-Term Dietary Stability, Short-Term Changes in Diet, and Can be Used as a Tool to Monitor Food Webs

et al. 2019

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“…The overlap of SEAC represented a comparison of the isotopic niche width and niche overlap (Denton et al 2018;Hill et al 2015) of the two gastropods. A function called "bayesianOverlap" represents three values which are calculated areas of the first ellipses, second ellipses and the overlap between the two areas (Pastore 2018).…”

Section: 24) Data Analysesmentioning

confidence: 99%

Feeding dynamics of invasive (Tarebia granifera) and native (Melanoides tuberculata) freshwater gastropods.

Naidoo

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Tarebia granifera has invaded several South African estuaries, outnumbering native gastropods such as Melanoides tuberculata. Comparative feeding dynamics can aid in estimating and understanding invasion impacts. This study aimed to explore the feeding dynamics of these gastropods with the use of two different approaches. Stable Isotope Analyses (SIAs) were used to investigate the dietary preferences and niche overlaps in the St Lucia Estuary, while Functional Response Experiments measured the relationship between the consumption rate of a food resource and its availability. These experiments were run both with and without the presence of heterospecific chemical cues (secondary metabolites secreted by either species) to determine whether chemical cues influence the functional responses of T. granifera and M. tuberculata. Mixed species experiments were also conducted to observe individual behaviour (active, inactive and feeding) over time and measure resource consumption when both species are placed together under high and low food availability. The SIA showed that both gastropods exhibited generalist diets, however, due to niche partitioning, there was no significant difference in their dietary niche overlap. In the FR experiments, both species exhibited Type II FRs and had similar feeding rates. However, in the presence of heterospecific chemical cues, M. tuberculata exhibited a higher feeding rate at high food availabilities, whereas T. granifera showed efficient feeding dynamics under limited food resources. In the mixed species experiments, T. granifera spent more time feeding under low food availability while M. tuberculata spent more time feeding under high food availability. This study showed that in certain conditions (e.g. high resource availability) the alien species did not always have a feeding advantage. A multiple method approach is recommended when assessing ecological impacts of invasive species. iv ACKNOWLEDGEMENTS First and foremost, I would like to express my sincere gratitude to my supervisor Dr Nicola K.Carrasco and co-supervisor Dr Nelson A.F. Miranda, for giving me this opportunity. I would like to thank my supervisors for always having faith in me and for always providing me with invaluable guidance throughout my project. It was a great privilege to work and study under two proficient supervisors. I would like to extend my gratitude to Professor André Vosloo, for his valuable input towards my project.A special thank you to Caroline Fox from Ezemvelo KZN Wildlife for logistical support and for providing us with the helpful information in the field. Dr Grant Hall of the Stable Isotope Laboratory at the Mammal Research Institute (University of Pretoria) is also acknowledged for processing and analysing the stable isotope samples.A sincere thank you to Jamila Janna for providing valuable data for this study. I would also like to thank my research colleagues, Merusha Govender, Merrisa Naidoo, Njabulo Mdluli, Natleen Govender and Mandy Jones, for their assistance and continuous support in the fi...

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Isotopic niche of New Jersey terrapins suggests intraspecific resource partitioning, and little variability following a major hurricane

Denton

Hart

Wnek³

et al. 2023

Hydrobiologia

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Diamondback terrapins (Malaclemys terrapin) are sexually dimorphic generalist turtles that inhabit salt marshes and estuaries along the Atlantic and Gulf coasts of the United States. On October 29th, 2012, Hurricane Sandy made landfall in New Jersey, USA, directly impacting terrapin populations inhabiting central and southern Barnegat Bay. To examine potential food web mediated impacts to the terrapin population and their foraging dynamics we examined carbon and nitrogen stable isotope values collected from terrapin tissues (2011, 2015, 2019) and resource taxa (2015, 2019) within Barnegat Bay. Isotopic analysis revealed that mature females had lower carbon and higher nitrogen values than immature females and males with almost no isotopic niche overlap, whereas males and immature females had statistically similar values with overlapping niches. Terrapins and resources collected from island habitats contained higher carbon and nitrogen values than those from mainland habitats, with little overlap in niche between habitats. There were no significant temporal variations detected in either carbon or nitrogen values from terrapins between years, or within each habitat pre- and post-Hurricane Sandy. These findings suggest long-term terrapin foraging dynamics have remained relatively stable, signifying resilience to disturbance events within the study site.

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Stable Isotope Analysis Enhances Our Understanding of Diamondback Terrapin (Malaclemys terrapin) Foraging Ecology

Cited by 7 publications

References 67 publications

Stable Isotope Analyses of Multiple Tissues of Great Shearwaters (Ardenna Gravis) Reveals Long-Term Dietary Stability, Short-Term Changes in Diet, and Can be Used as a Tool to Monitor Food Webs

Stable Isotope Analyses of Multiple Tissues of Great Shearwaters (Ardenna Gravis) Reveals Long-Term Dietary Stability, Short-Term Changes in Diet, and Can be Used as a Tool to Monitor Food Webs

Feeding dynamics of invasive (Tarebia granifera) and native (Melanoides tuberculata) freshwater gastropods.

Isotopic niche of New Jersey terrapins suggests intraspecific resource partitioning, and little variability following a major hurricane

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