Experimental determination of stable carbon and nitrogen isotope fractionation between mangrove leaves and crabs

Cm Herbon,I Nordhaus

doi:10.3354/meps10421

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 490:91-105 (2013) - DOI: https://doi.org/10.3354/meps10421 Experimental determination of stable carbon and nitrogen isotope fractionation between mangrove leaves and crabs Carolin M. Herbon, Inga Nordhaus* Leibniz Center for Tropical Marine Ecology (ZMT), Fahrenheitstraße 6, 28359 Bremen, Germany *Corresponding author. Email: inga.nordhaus@zmt-bremen.de ABSTRACT: The analysis of benthic food webs in mangrove forests is complicated by the lack of experimental investigations of consumer-diet discrimination factors (Δ15N and Δ13C) for most mangrove invertebrates. This study aimed to determine the fractionation of δ13C and δ15N between mangrove leaves and Episesarma singaporense and E. versicolor (Sesarmidae) for 90 d in Java, Indonesia. The consumption rates of both species and stable isotope fractionation of leaves from 5 plant species (Acanthus ilicifolius, Aegiceras corniculatum, Avicennia alba, Derris trifoliata, Rhizophora apiculata) were compared. Δ15N between R. apiculata leaves and muscle tissue was 5.0‰ for E. singaporense and 5.4‰ for E. versicolor after 50 d. δ15N of muscle tissue increased significantly after 50 d, most likely due to the internal recycling of nitrogen. δ13C did not change during the experiment, and Δ13C was 5.1‰ for E. singaporense and 4.1‰ for E. versicolor after 90 d. Leaves of D. trifoliata and R. apiculata were preferentially consumed, indicating their higher nutritive value. We concluded that (1) the discrimination values for mangrove crabs feeding on a leaf diet are much higher than previously assumed, which can most likely be explained by the selective assimilation of isotopic heavy carbon compounds and by metabolic cycling of non-essential amino acids; (2) the frequently used average discrimination factors are inappropriate for the study of benthic food webs in mangrove forests with a high biomass of leaf-eating crabs; and (3) E. singaporense and E. versicolor can meet their nitrogen demand by assimilating nitrogen from R. apiculata leaves and by using internal reserves for at least 50 d. KEY WORDS: Fractionation · Discrimination factor · Stable isotopes · Nitrogen · Carbon · Consumption rate · Food preference · Mangrove Full text in pdf format PreviousNextCite this article as: Herbon CM, Nordhaus I (2013) Experimental determination of stable carbon and nitrogen isotope fractionation between mangrove leaves and crabs. Mar Ecol Prog Ser 490:91-105. https://doi.org/10.3354/meps10421 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 490. Online publication date: September 17, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Highlights

Food webs of mangrove forests have been investigated by stable carbon and nitrogen isotope analyses in various countries (e.g. Rodelli et al 1984, Bouillon et al 2004, Mazumder & Saintilan 2009)
This study aimed to determine the fractionation of δ13C and δ15N between mangrove leaves and Episesarma singaporense and E. versicolor (Sesarmidae) for 90 d in Java, Indonesia
We concluded that (1) the discrimination values for mangrove crabs feeding on a leaf diet are much higher than previously assumed, which can most likely be explained by the selective assimilation of isotopic heavy carbon compounds and by metabolic cycling of non-essential amino acids; (2) the frequently used average discrimination factors are inappropriate for the study of benthic food webs in mangrove forests with a high biomass of leaf-eating crabs; and (3) E. singaporense and E. versicolor can meet their nitrogen demand by assimilating nitrogen from R. apiculata leaves and by using internal reserves for at least 50 d

Summary

Introduction

Food webs of mangrove forests have been investigated by stable carbon and nitrogen isotope analyses in various countries (e.g. Rodelli et al 1984, Bouillon et al 2004, Mazumder & Saintilan 2009). Studies have shown high variability for the consumer-diet discrimination factors Δ13C and Δ15N with regard to specific tissues, taxonomic classes, habitat, diet isotopic ratios, protein quality of the diet, life-history level and other factors (e.g. Caut et al 2009, Robbins et al 2010, Boecklen et al 2011, Florin et al 2011). This indicates the importance of a careful choice of discrimination factors in food web studies. Isotope discrimination factors have been examined for a range of invertebrate species, mainly insects (see Caut et al 2009 and references therein), studies for brachyuran crabs are rare

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