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Marine Ecology Progress Series

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MEPS 712:87-99 (2023)  -  DOI:

Role of crab holobionts in benthic N cycling in mangroves with different trophic status

Mindaugas Zilius1,*, Marco Bartoli1,2,3, Stefano Bonaglia1,4, Ulisse Cardini1,3, Vitor G. Chiozzini5, Ugo Marzocchi1,6, Paula C. Moraes5, Anastasija Zaiko1,7,8, Elisabete S. Braga5

1Marine Research Institute, Klaipeda University, 92295 Klaipeda, Lithuania
2Department of Chemistry, Life science and Environmental Sustainability, Parma University, 43124 Parma, Italy
3Department of Integrative Marine Ecology (EMI), Stazione Zoologica Anton Dohrn-National Institute of Marine Biology, Ecology and Biotechnology, Genoa Marine Centre, Villa del Principe, 16126 Genoa, Italy
4Department of Marine Sciences, University of Gothenburg, 40530 Gothenburg, Sweden
5Oceanographic Institute, University of São Paulo, 05508-120 São Paulo, Brazil
6Center for Water Technology (WATEC), Department of Biology, Aarhus University, 8000 Aarhus, Denmark
7Cawthron Institute, 98 Halifax Street East, 7010 Nelson, New Zealand
8Sequench Ltd, 1/131 Hardy Street, 7010 Nelson, New Zealand
*Corresponding author:

ABSTRACT: Microbial dinitrogen (N2) fixation and intense bioturbation by macrofauna can contribute to reduce nitrogen (N) limitation in mangrove systems. In particular, crabs are important ecosystem engineers that rework sediments, redistribute organic matter, accelerate nutrient cycling and shape microbial communities in mangrove sediments. Hosting functionally diverse microbial communities, crabs form a discrete ecological unit (a holobiont). In this study, we report rates of respiration, inorganic N fluxes, net N2 fixation, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) measured in the fiddler crab Leptuca thayeri and sesarmid crab Armases rubripes holobionts, which are dominant in oligotrophic and eutrophic mangrove systems of southeast Brazil, respectively. We measured lower biomass-specific rates of respiration and ammonium (NH4+) production for the larger L. thayeri compared to A. rubripes, with very different molar ratios of O2 respiration to NH4+ production (152:1 vs. 20:1, respectively). This suggests a size-metabolism relationship, different food quality or different coupling of N excretion and assimilation by the crab holobionts in the 2 systems. Both crab holobionts contributed to net denitrification and DNRA, with faster N cycling in A. rubripes in the eutrophic system. Net N2 fixation was also detected, with nearly 4-fold higher rates in A. rubripes compared to L. thayeri. Overall, our results illustrate active and complex N cycling associated with the 2 dominant crab holobionts and highlight their potential and overlooked role as important conduits of fixed N, which may double N2 fixation rates in the mangrove’s rhizosphere.

KEY WORDS: Fiddler crab · Sesarmid crab · Holobionts · Mangroves · Nitrogen cycle · N2 fixation

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Cite this article as: Zilius M, Bartoli M, Bonaglia S, Cardini U and others (2023) Role of crab holobionts in benthic N cycling in mangroves with different trophic status. Mar Ecol Prog Ser 712:87-99.

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