Molybdate Addition Mitigates Hydrogen Sulfide Production in Shrimp Pond Sediments During Long-Term Organic Waste Accumulation

核心概念

Molybdate addition can effectively mitigate hydrogen sulfide production in shrimp pond sediments by inhibiting sulfate reduction, even during long-term organic waste accumulation.

要約

The study investigated the potential of molybdate to mitigate hydrogen sulfide (H2S) production in shrimp pond sediments over a 61-day period simulating the final stage of a full shrimp growth cycle. An experimental shrimp pond model was used to assess the impact of 5 mg/L (M5) and 25 mg/L (M25) molybdate additions compared to a control treatment (no molybdate).
Key findings:

Molybdate partially mitigated H2S production in the sediment and delayed its transfer to the bulk liquid by pushing the higher sulfide concentration zone towards deeper sediment layers.
The M25 treatment showed a 46% lower H2S concentration in the bulk liquid compared to the control on day 35, when peak H2S levels were observed.
Molybdate treatment, especially at 25 mg/L, significantly impacted the overall microbial community composition, with a higher relative abundance of sulfate-reducing bacteria (SRB) compared to the control.
Combining amplicon sequencing and flow cytometry data revealed that molybdate treatments had a higher absolute abundance of the Desulfobacterota phylum, which contains many SRB, despite the lower H2S production.
The increased abundance of SRB in molybdate treatments may be due to a shift in their energy metabolism, as molybdate can partially inactivate key enzymes involved in sulfate reduction.
Overall, molybdate shows promise as a mitigation strategy against sulfide accumulation in shrimp pond sediments during long-term organic waste buildup, by directly steering the microbial community composition and activity.

統計

Molybdate concentrations in the bulk liquid decreased by 53 ± 1% in the M25 treatment and 5-15% in the M5 treatment by the end of the experiment.
Residual sulfate concentrations in the bulk liquid gradually decreased over time, with no clear differences between treatments.
The maximum H2S concentration in the sediment was 69 ± 11% and 60 ± 39% lower in the M5 and M25 treatments, respectively, compared to the control on day 44.

引用

"Molybdate addition partially mitigated H2S production in the sediment, and delayed its transfer to the bulk liquid by pushing the higher sulphide concentration zone towards deeper sediment layers."
"Molybdate treatment at 25 mg/L significantly impacted the overall microbial community composition and treated samples (5 and 25 mg/L molybdate) had about 50% higher relative abundance of sulphate reducing bacteria than the control (no molybdate) treatment."
"An overall increasing trend in time was observed for the Desulfobacterota phylum, including the samples treated with molybdate."

抽出されたキーインサイト

Molybdate delays sulphide formation in the sediment and transfer to the bulk liquid in a model shrimp pond

by Torun,F., Ho... 場所 www.biorxiv.org 11-17-2023

https://www.biorxiv.org/content/10.1101/2023.11.16.567380v3

深掘り質問

How would the addition of microalgae in the shrimp pond system affect the efficacy of molybdate in mitigating sulfide production?

The addition of microalgae in the shrimp pond system could potentially impact the efficacy of molybdate in mitigating sulfide production in several ways. Microalgae play a crucial role in the pond ecosystem by photosynthesizing and producing oxygen, which can help maintain higher dissolved oxygen levels in the water column. This increased oxygenation can create a more aerobic environment, inhibiting the growth of sulfate-reducing bacteria (SRB) responsible for sulfide production.
Additionally, microalgae can consume carbon dioxide and release oxygen during photosynthesis, which can lead to an increase in pH levels in the water. Higher pH levels can reduce the toxicity of hydrogen sulfide (H2S) to shrimp and other organisms in the pond. This reduction in H2S toxicity can further support the health and growth of the shrimp population.
However, the presence of microalgae can also introduce complexities to the system. While microalgae can contribute to oxygenation and pH regulation, they can also compete with molybdate for nutrients in the water. This competition may affect the availability and effectiveness of molybdate in inhibiting sulfate reduction and sulfide production. Therefore, the interaction between molybdate, microalgae, and other components of the pond ecosystem would need to be carefully monitored and managed to optimize sulfide mitigation strategies.

What are the potential long-term ecological impacts of repeated molybdate addition in shrimp ponds, particularly on the overall pond ecosystem and surrounding environment?

Repeated molybdate addition in shrimp ponds for sulfide mitigation could have several potential long-term ecological impacts on the overall pond ecosystem and surrounding environment.

Microbial Community Shifts: Continuous molybdate addition may lead to long-term shifts in the microbial community composition in the pond sediment. While molybdate can inhibit sulfate-reducing bacteria (SRB), repeated exposure may select for molybdate-resistant SRB strains or other microbial populations that could impact nutrient cycling and ecosystem dynamics.

Nutrient Cycling: Molybdate addition can disrupt the natural sulfur cycle in the pond ecosystem. Sulfate reduction is a key process in nutrient cycling, and prolonged inhibition of this process could alter nutrient availability and cycling patterns in the pond, potentially affecting primary productivity and overall ecosystem health.

Biodiversity: Changes in microbial communities and nutrient dynamics due to molybdate addition may have cascading effects on the biodiversity of the pond ecosystem. Shifts in microbial populations can impact the food web structure, with potential consequences for higher trophic levels such as shrimp and other aquatic organisms.

Water Quality: Molybdate itself can have direct effects on water quality parameters. Monitoring the concentrations of molybdate and its potential accumulation in the pond water is essential to prevent unintended consequences on water quality and aquatic life.

Ecosystem Resilience: Over-reliance on molybdate for sulfide mitigation could reduce the natural resilience of the pond ecosystem to environmental stressors. Ecosystems that are overly dependent on external interventions may become less adaptable to changes and more vulnerable to disturbances.

Overall, the long-term ecological impacts of repeated molybdate addition in shrimp ponds underscore the importance of sustainable aquaculture practices that consider the broader ecosystem dynamics and aim to minimize potential disruptions to natural processes.

Could the increased abundance of sulfate-reducing bacteria in molybdate-treated samples be leveraged for other applications, such as bioremediation of sulfate-contaminated environments?

The increased abundance of sulfate-reducing bacteria (SRB) in molybdate-treated samples could indeed be leveraged for other applications, such as bioremediation of sulfate-contaminated environments. SRB are known for their ability to reduce sulfate to sulfide under anaerobic conditions, a process that can be harnessed for various bioremediation purposes.

Sulfate Reduction: The enhanced population of SRB in molybdate-treated samples indicates their metabolic activity and potential for sulfate reduction. In sulfate-contaminated environments, these bacteria can facilitate the conversion of sulfate into sulfide, which can aid in the remediation of sulfate pollution.

Metal Bioremediation: SRB are also involved in metal bioremediation processes. They can interact with heavy metals and metalloids, forming metal sulfides that are less soluble and more easily precipitated. This mechanism can be utilized for the removal of toxic metals from contaminated sites.

Biogeochemical Cycling: SRB play a crucial role in the biogeochemical cycling of sulfur compounds. By leveraging the metabolic capabilities of SRB, bioremediation strategies can be designed to target specific pollutants and enhance natural sulfur cycling processes in contaminated environments.

Anaerobic Digestion: SRB are commonly found in anaerobic digestion processes, where they contribute to the breakdown of organic matter and the production of biogas. The increased abundance of SRB in molybdate-treated samples could be beneficial for optimizing anaerobic digestion systems for waste treatment and energy production.

By understanding and manipulating the metabolic activities of SRB, particularly in the presence of molybdate, innovative bioremediation strategies can be developed to address various environmental challenges, ranging from sulfate contamination to metal remediation and organic waste management.