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Lookup NU author(s): Georgina Robinson,
Dr Gary Caldwell,
Professor Selina Stead
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
The treatment of organic wastes remains one of the key sustainability challenges facing the growing global aquaculture industry. Bioremediation systems based on coupled bioturbation―microbial processing offer a promising route for waste management. We present, for the first time, a combined biogeochemical-molecular analysis of the short-term performance of one such system that is designed to receive nitrogen-rich particulate aquaculture wastes. Using sea cucumbers (Holothuria scabra) as a model bioturbator we provide evidence that adjusting the waste C:N from 5:1 to 20:1 promoted a shift in nitrogen cycling pathways towards the dissimilatory nitrate reduction to ammonium (DNRA), resulting in net NH4+ efflux from the sediment. The carbon amended treatment exhibited an overall net N2 uptake whereas the control receiving only aquaculture waste exhibited net N2 production, suggesting that carbon supplementation enhanced nitrogen fixation. The higher NH4+ efflux and N2 uptake was further supported by metagenome predictions that indicate organic carbon addition stimulated DNRA over denitrification. These findings indicate that carbon addition may potentially result in greater retention of nitrogen within the system, however longer-term trials are necessary to determine whether this nitrogen retention is translated into improved sea cucumber biomass yields. Whether this truly constitutes a remediation process is open for debate as there remains the risk that any increased nitrogen retention may be temporary, with any subsequent release potentially raising the eutrophication risk. Longer and larger-scale trials are required before this approach may be validated with the complexities of the in-system nitrogen cycle being fully understood.
Author(s): Robinson G, MacTavish T, Savage C, Caldwell GS, Jones CLW, Probyn T, Eyre BD, Stead SM
Publication type: Article
Publication status: Published
Online publication date: 29/03/2018
Acceptance date: 11/01/2018
Date deposited: 29/03/2018
ISSN (print): 1726-4170
ISSN (electronic): 1726-4189
Publisher: European Geosciences Union
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