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Marine Ecology Progress Series

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MEPS 681:13-20 (2022)  -  DOI: https://doi.org/10.3354/meps13924

Compound-specific isotope analysis of amino acids reveals dependency on grazing rather than detritivory in mangrove food webs

Yota Harada1,*, Shing Yip Lee2, Rod M. Connolly1, Brian Fry3

1Coastal and Marine Research Centre, Australian Rivers Institute, School of Environment and Science, Griffith University, Gold Coast, Queensland 4222, Australia
2Simon F.S. Li Marine Science Laboratory, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, PR China
3Australian Rivers Institute, Griffith University, Nathan, Queensland 4111, Australia
*Corresponding author:

ABSTRACT: Colonisation of decaying leaves fallen from mangrove trees by bacteria and fungi is thought to play an important role at the base of food webs in most tropical estuaries. Compound-specific isotope analysis of amino acids (CSIA-AA) has enabled the previously difficult methodological task of measuring plant, bacterial and fungal energy flows to food webs. Here, we assessed the biosynthetic origins of amino acids at the base of a mangrove food web using the CSIA-AA approach. Trophic positions of the 2 most common mangrove fauna—fiddler crabs and sesarmid crabs—estimated from nitrogen isotopes in phenylalanine and glutamic acid approached 2, suggesting that these species are herbivores rather than microbivores. Consistent with this finding, carbon isotope fingerprints in AAs did not support the importance of essential AAs derived from fungi and bacteria but rather suggested the importance of those originating from plants, especially microalgae. These results suggest that (1) microbial mineralization of decaying leaves supports the production of more easily assimilated microalgae and (2) bacteria and fungi, as intermediates, also routinely incorporate plant-derived AAs into their biomass.


KEY WORDS: Food web · Stable isotope analysis · Amino acids · Carbon · Nitrogen · Mangrove


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Cite this article as: Harada Y, Lee SY, Connolly RM, Fry B (2022) Compound-specific isotope analysis of amino acids reveals dependency on grazing rather than detritivory in mangrove food webs. Mar Ecol Prog Ser 681:13-20. https://doi.org/10.3354/meps13924

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