Profiling bacterial communities associated with sediment-based aquaculture bioremediation systems under contrasting redox regimes

Abstract

Deposit-feeding invertebrates are proposed bioremediators in microbial-driven sediment-based aquaculture effluent treatment systems. We elucidate the role of the sediment reduction-oxidation (redox) regime in structuring benthic bacterial communities, having direct implications for bioremediation potential and deposit-feeder nutrition. The sea cucumber Holothuria scabra was cultured on sediments under contrasting redox regimes; fully oxygenated (oxic) and redox stratified (oxic-anoxic). Taxonomically, metabolically and functionally distinct bacterial communities developed between the redox treatments with the oxic treatment supporting the greater diversity; redox regime and dissolved oxygen levels were the main environmental drivers. Oxic sediments were colonised by nitrifying bacteria with the potential to remediate nitrogenous wastes. Percolation of oxygenated water prevented the proliferation of anaerobic sulphate-reducing bacteria, which were prevalent in the oxic-anoxic sediments. At the predictive functional level, bacteria within the oxic treatment were enriched with genes associated with xenobiotics metabolism. Oxic sediments showed the greater bioremediation potential; however, the oxic-anoxic sediments supported a greater sea cucumber biomass. Overall, the results indicate that bacterial communities present in fully oxic sediments may enhance the metabolic capacity and bioremediation potential of deposit-feeder microbial systems. This study highlights the benefits of incorporating deposit-feeding invertebrates into effluent treatment systems, particularly when the sediment is oxygenated.

Macrophyte detritus as nursery diets for juvenile sea cucumber Stichopus cf. horrens

“…Furthermore, bacterial production during detrital breakdown may have contributed variably to the nutrition of juveniles between treatments through the constant release of bioavailable compounds. Studies have demonstrated that systems with oxic‐anoxic sediment conditions produced Holothuria scabra sea cucumbers with significantly higher biomass compared to animals grown in oxic treatments (Robinson et al, ; Robinson, Caldwell, Jones, Slater, & Stead, ). These studies concluded that the anaerobic condition in redox‐stratified sediments was more suitable for holothurian culture because it produced considerable amounts of extracellular, low molecular weight organic compounds that may be important for sea cucumber nutrition.…”

The effect of resource quality on the growth of Holothuria scabra during aquaculture waste bioremediation

“…Sediment microbial communities are primarily net heterotrophic systems that link energy transfer to higher trophic levels; therefore recycling nutrients in situ may provide a viable means to intensively culture deposit feeders with a higher overall efficiency (Schroeder, 1987). Furthermore, prior research (Robinson et al, 2015;Robinson et al, 2016) demonstrated that redox-stratified sediment supported faster growth rates and a higher biomass yield of Holothuria scabra relative to fully oxic sediment, indicating that heterotrophic systems are more favourable for deposit feeder growth.…”

Assimilation of shrimp farm sediment by Holothuria scabra: a coupled fatty acid and stable isotope approach

“…Slater and Carton 2007;Watanabe et al, 2012;Neofitou et al, 2019;Zamora et al, 2016). In particular, their ability to selectively extract specific components of sedimentary organic matter, such as bacteria, nitrogen and transparent exopolymer particles (Moriarty 1982;Roberts et al, 2003;Robinson et al, 2016;Sadeghi-Nassaj et al, 2018), may suggest that their use in co-culture systems is relevant. Indeed, their use can contribute to remediate or manage the risks associated with pond sediment degradation in aquaculture ponds, where high densities and/or dystrophy conditions typically result in animal health issues (Lemonnier et al, 2006;Lemonnier, 2007).…”