Aquaculture Ponds Research Articles

Temporal dynamics of protist communities and environmental factors in the horizontal flow-polyculture pond aquaculture model of Sinonovacula constricta

The horizontal flow (HF)–polyculture pond (PP) model has emerged as a new aquaculture model that has attracted considerable attention. The growth of Sinonovacula constricta in the HF is highly dependent on phytoplankton in the PP; however, the current understanding of the basic microbes in the HF-PP model research remains insufficient. To address this knowledge gap, we analyzed the temporal dynamics of protist communities in water and sediment samples obtained from the HF and PP in this study. In addition, we measured the temporal variations in physicochemical factors in these water and sediment samples. A comparison of water quality data between HF and PP revealed that HF effectively reduced the total nitrogen (TN) and total phosphorus (TP) levels in the polyculture ponds. Furthermore, Diatomea and Ciliophora were the predominant phyla in all samples. In the horizontal-flow water samples, significant alterations were observed over time in Skeletonema, Strombidium, and Gyrodinium genera. The dynamic pattern of the genus in the polyculture pond water (PPW) was similar to that in the horizontal flow water (HFW). Furthermore, Skeletonema abundance decreased over time in the horizontal flow sediment (HFS). Skeletonema and Cyclotella were dominant in polyculture pond sediment (PPS). There was a certain degree of community succession throughout the experiment in the HFW and PPW, but not in the HFS or PPS. Correlation analysis revealed that water temperature (WT), salinity(SAL)，dissolved oxygen (DO), pH, phosphate, and silicate played key roles in driving variations in the protist community. These findings contribute to our understanding of complex protist community dynamics within the HF-PP aquaculture model, shedding light on the roles of various environmental factors in shaping protist communities and water quality.

Complete genome sequence of aquaculture pond isolate, Bacillus velezensis M4019.

Bacillus velezensis is commonly found in soil and has various antibacterial activities against animal and plant pathogens. Here, we present the complete genome sequence of Bacillus velezensis strain M4019, isolated from a euryhaline aquaculture pond water in Yong-An, Kaohsiung City, Taiwan. This pond-water-derived isolate, unlike common soil-derived isolates, may provide potentially different adaptations and antimicrobial cues for future research.

Study on the purification of aquaculture tailwater under Sulfamethoxazole stress using algae-bacteria biofilms: Nutrient removal efficiency, microbial community, and ARGs

This study explored the dynamic processes of algae-bacteria biofilms in the remediation of aquaculture pond effluents as a novel treatment strategy. The purification capacity of the biofilms, changes in community composition, and their impact on the dissemination of antibiotic resistance genes (ARGs) were investigated under the application of sulfamethoxazole (SMX) at concentrations ranging from 100 to 1000 μg/L. The study also considered the factors influencing the abundance and diversity of ARGs and mobile genetic elements (MGEs) across different seasons, including the roles of environmental parameters and microbial community structure.The results showed that, although exposure to SMX reduced nutrient removal efficiency, photosynthetic activity, and increased oxidative stress levels, the biofilms maintained relatively high purification efficiency (with nutrient removal rates ranging from 67.62 % to 93.23 % and SMX removal rate reaching 50.13 % ± 12.34 %), demonstrating adaptability to SMX stress. Network analysis identified key microbial carriers responsible for ARG dissemination, highlighting the complex interactions between environmental factors, microbial communities, and resistance gene propagation. These findings enhance our understanding of biofilm-based water treatment systems and the seasonal factors affecting the dynamics of ARGs and MGEs.

Degradation of Emamectin Benzoate in the Aquaculture Pond Environment under Tropical Climatic Condition

Emamectin Benzoate (EMB), is an anti-parasitic drug, commonly used in aquaculture for prevention and control of parasitic infestations. The drug enters the environment through uneaten feed and faeces, ultimately accumulating in aquaculture pond sediment. Present study reports the influence of abiotic factors like, sunlight exposure (2,454 to 117,500 lux), pH, salinity and soil texture on the degradation of EMB in aquaculture pond water and sediment as per Organization for Economic Cooperation and Development (OECD). Results showed that the degradation of EMB in both water and sediment followed first-order kinetics, resulting in half-life of 5.6 days in water and 12.4 days in sediment when exposed to natural sunlight. Higher degradation of EMB was observed under alkaline conditions (pH 8.5) and at lower salinity (0.5ppt). EMB degradation is accelerated in loamy sand soil when exposed to sunlight. Results of the study suggest that in countries like India, where ample sunlight exposure is prevalent throughout the year, EMB degradation in aquaculture pond environment occurs at a rapid pace reducing the risk of accumulation in water or sediment.

Assessing sediment CO2 effluxes in the coastal ecosystem of North Sumatra, Indonesia

Coastal wetlands including mangrove play a vital role in regulating the local and global carbon cycle. Coastal areas contribute greatly to the carbon exchange process due to the complex interactions that occur between the atmosphere, land, and oceans. One of the important components in coastal carbon dynamics is CO2 gas exchange between soil, water and the atmosphere. This study aims to assess CO2 efflux across various land covers (namely natural mangrove, restored mangrove, and converted mangroves to oil palm and aquaculture pond) in the coastal areas of North Sumatra Province, and analyze the effect of sea tides and ebbs on the rate of CO2 efflux and their connection with the number and area of macrozoobenthos burrows. We applied direct sampling by using the static closed chamber method attached to portable CO2 analyzer. The mean of CO2 efflux in natural mangrove forest land covers was 866±585 mgCO2/m2/h during low tide conditions and 1137±792 mgCO2/m2/h during high tide conditions, followed by oil palm plantations at 760.71±341 mgCO2/m2/h, restored mangroves during low tide of 575.24±326 mgCO2/m2/h and 597.11±180 mg CO2/m2/h during high tide conditions, and the lowest was recorded in ponds at 588.55±358 mgCO2/m2/h. Further, we observed that tidal conditions affect the magnitudes of CO2 efflux in natural and restored mangrove forests, and we did not observe similar pattern in oil palms and ponds since these land covers were not influenced by regular tidal input. We also observed that no significant relationship between the number and area of macrozoobenthos burrows and CO2 efflux. Our findings suggest that CO2 effluxes in coastal wetlands are highly dynamic and presumably driven by complex factors and therefore, understanding their magnitudes and drivers requires extensive measurement covering large spatial and temporal scales.

Variability in N2O emission controls among different ponds within a hilly watershed

While it is well established that small water bodies like ponds play a disproportionately large role in contributing to N2O emissions, few studies have focused on lowland ponds in hilly watersheds. Here, we explored the characteristics of N2O concentrations and emissions from various typical ponds (village, tea, forested, and aquaculture ponds) in a hilly watershed and examined the specific controls influencing N2O production. Our findings revealed that tea ponds exhibited the highest N2O flux (8.42 ± 8.23 μmol m-2 d-1), which was 2.8 to 3.3 times greater than other types of ponds. Remarkable seasonal variations were observed in tea and forested ponds due to the seasonality of nutrient-enriched runoff, whereas such variations were less pronounced in village and aquaculture ponds. Key factors such as nitrogen levels, temperature, and dissolved oxygen (DO) emerged as the primary controls of N2O concentrations in ponds, heavily influenced by land use and human activities in their drainage areas. Specifically, N2O production in tea and aquaculture ponds was driven by N inputs from fertilization and feed, respectively, while DO levels governed the process in village and forested ponds, influenced by abundant algae and forest vegetation. This study emphasizes that environmental factors predominantly drive N2O production in ponds within hilly watersheds, but land use in the pond drainages acts as an indirect yet crucial influence. This highlights the need for future research to develop targeted emission reduction strategies based on land use to effectively mitigate N2O emissions, promising a path toward more sustainable and climate-friendly watershed management.

Wetland mapping in the Liaohe River Estuary using multi-source remote sensing image feature selection

ABSTRACT As a crucial node in the East Asia–Australasia migratory bird network, the Liaohe River Estuary Wetland (LREW) contributes significantly to coastal ecological balance and biodiversity. Accurate and timely mapping of the LREW is essential for monitoring ecological changes and understanding shifts in the wetland’s ecosystem structure and functions. In this study, an innovative approach that integrates radar (Sentinel-1), optical (Sentinel-2), and DEM data on Google Earth Engine (GEE) is proposed to achieve a more optimized and accurate wetland mapping. Recursive Feature Elimination (RFE) is employed to improve feature collection, facilitating the construction of an optimal feature set for Random Forest (RF) classification to extract detailed LREW information. Mapping conducted from 2017 to 2023 using the proposed approach demonstrates its effectiveness and stability in mapping the LREW, achieving overall accuracies ranging from 89.84% to 93.73% and Kappa from 0.85 to 0.91. Compared to single-source methods, the integration of multi-source data substantially enhances mapping accuracy, while RF-RFE effectively eliminates redundant features, further refining classification precision. Texture features (Sum Average, SAVG) and the Water Index 2019 (WI2019) were found to significantly influence wetland mapping. The importance of different feature types is ranked as follows: spectral features > vegetation/water body index > PCA features > SAR texture features > red-edge index > other spectral index > spectral texture features > backscatter coefficient > H-Alpha. During the study period, the wetland area increased from 849.60 km2 to 979.49 km2. This expansion was caused primarily by wetland protection policies that led to the dismantling of coastal aquaculture ponds, resulting in a reduction of 90.28 km2 in waterbodies over 7 years, with many areas transitioning to tidal flats and Suaeda salsa habitats. In conclusion, the proposed method is effective in mapping the LRE wetlands and provides reliable data support for wetland ecological protection and restoration.

Optimal balance of organic detritus and feed for fish growth and water quality improvement through regulating nutrients cycling

In order to explore the effects of different feed composition on the nutrient level and microbial loop structure in aquaculture ponds, a field simulation experiment in aquaculture ponds was conducted by adding different proportions (0%, 20%, 40% and 60%) of bagasse to fish feed for combined feeding. The addition of bagasse significantly reduced the levels of various forms of nitrogen and phosphorus in the water, especially with the addition of 60% bagasse. In the treatments without addition and with 20% bagasse added, nitrogen and phosphorus levels remained relatively high, which should be attributed to the decomposition of feed and the release of sediment, ultimately stimulating the abundant reproduction of algae. Bacterial growth was limited due to insufficient supply of organic carbon, and the growth of fish relied more on the components of the feed. With the addition of 60% bagasse, the high organic carbon and low nitrogen and phosphorus levels could not support the growth of phytoplankton, bacteria, and zooplankton. It is inferred that organic carbon may be more degraded into carbon dioxide, ultimately limiting the growth of fish. Adding 40% bagasse achieved a balanced level of carbon, nitrogen, and phosphorus, establishing a healthy and stable microbial loop structure (including phytoplankton, bacteria, and zooplankton). Most nutrients were converted into plankton, which then became natural food for fish, ensuring complete nutrient utilization. This is beneficial for both water quality improvement and fish reproduction. Therefore, adding a moderate proportion of bagasse to the feed can maximize the effects of water quality improvement, fish reproduction, and even the quality of fish meat.

Optimization of water supply parameters for enhanced thermal uniformity in aquaculture ponds under varied working conditions: An experimental study

Aquaculture ponds are critical for the successful rearing of fish larvae, and achieving consistent temperature distribution within these systems is essential for optimal growth conditions. This study explores methods for precise temperature regulation on both the water and atmospheric sides of the pond ecosystem. Based on the original design, systematic changes were made to parameters such as water supply pipe layout, bend angles, perforation rates, and working conditions. Metrics including average temperature, average temperature difference, and extreme temperature difference were utilized to extensively discuss the impacts of these parameters. Through this, temperature distributions across five distinct water supply layouts were analyzed, and the impacts of four different bending angles and perforation rates were evaluated using optimized configurations. Our findings demonstrate that a water supply layout radius of 2000 mm, coupled with a 60° bending angle and a 25 % perforation rate, increased overall temperature uniformity in the pond by 5 %. Additionally, seasonal variations significantly impact temperature distribution in ponds, particularly with different extreme temperature differences observed in winter and summer. Compared to the transitional season and summer, the average temperature difference in the pond during winter decreased by 30 % and 45 %, respectively. It was further revealed that winter conditions naturally yield more uniform water-side temperatures, making seasonal fluctuations irrelevant in determining optimal perforation rates. After the implementation of a water agitator, the average extreme temperature difference decreased from 0.6 K to 0.52 K. In the shallow water layer, the water agitator reduced the extreme temperature difference in the pond by 26 %. The use of water agitators has enhanced thermal uniformity in ponds, thereby improving the growth environment for fish larvae and providing valuable insights for environmental management in aquaculture.

Optimization of water supply parameters for enhanced thermal uniformity in aquaculture ponds: An experimental study based on orthogonal experimental design

The temperature distribution in aquaculture ponds plays a crucial role in the rearing of fish larvae. To achieve a more uniform temperature distribution in the pond and alleviate the problem of thermal stratification, precise control of pond temperature is essential. A recirculating aquaculture pond was taken as the test object. Single-factor experiments and orthogonal experiments were conducted to comprehensively test the aquaculture pond's water supply pipe layout, bend angle, perforation rate, and environmental conditions. Three evaluation indicators were used to analyze the temperature distribution of the aquaculture pond under various water supply pipe structures, leading to the identification of optimal structural configurations. The optimal structure I, obtained from single-factor experiments, was determined to be 2.5 m, 50 %, and 60°, while the optimal structure II, derived from orthogonal experiments, was 1.25 m, 75 %, and 30°. Both optimized structures exhibited significant temperature fluctuations in the pond during the summer season. However, Structure II demonstrated the lowest average temperature difference in the winter season, indicating its superior adaptability during winter. Moreover, Structure II could provide higher temperatures for shallow areas with depths greater than 600 mm, making it more suitable for fish larvae cultivation. Additionally, local devices effectively decreased temperature variations by 17.5 % within the pond. Furthermore, energy consumption output was evaluated for different operational conditions. The results showed that Structure II had the lowest energy consumption output during the summer season. In contrast, during the winter season, the energy consumption output increased by approximately 12 %, indicating significant energy-saving potential in aquaculture ponds during winter.

Efficacy of Terminalia arjuna (Roxb.) bark extracts against Salmonella sp. isolated from aquaculture ponds

The present study was conducted to determine the efficacy of Terminalia arjuna bark extracts against Salmonella sp. isolated from 15 aquaculture ponds located adjacent to Bangladesh Agricultural University, Mymensingh. T. arjuna barks was dried, powdered and extracted using cold water (polar) and hexane (non-polar) and stored at 10ºC while Salmonella sp. were isolated using SS (Salmonella Shigella) Agar and selected 2 isolates were confirmed by Hi Assorted biochemical test kit. Antimicrobial activities of the bark extract of T. arjuna against fifteen selected isolates of Salmonella were then determined. Two of those selected isolates (Sa-2 and Sa-5) shown zone of inhibition against crude bark extract (hexane extract) of T. arjuna. The isolates were also screened for antibiotic resistance to eleven antibiotics. Salmonella isolates were serotyped and the antimicrobial resistance was determined by a disk diffusion method. About 100% of the isolates were resistant to antibiotic discs among which ampicillin (10 μg), and chloramphenicol (30 μg) showed 15%, azithromycin (10 μg) showed 45%, erythromycin (15 μg) showed 60%, tetracycline (10 μg) showed 40%, ampicillin (10 μg) showed 100%, doxycycline (30 μg) showed 46.67%, kanamycin (30 μg) and gentamycin (10 μg) showed 6%, streptomycin (25 μg) and ciprofloxacin (10 μg) showed 20%, and cefotaxime (30 μg) showed 30% resistant to isolated Salmonella sp. and all Salmonella sp. isolates were found to be 100% resistant to cold water extract but sensitive to hexane extract of T. arjuna. The study showed hexane extract of T. arjuna would be potential, ecofriendly and biodegradable herbal medicine to control multi drug resistant Salmonella sp. as well as aquaculture health management. Res. Agric. Livest. Fish. Vol. 11, No. 2, August 2024: 255-269

Occurrence and risk assessment of quinolones and sulfonamides in freshwater aquaculture ponds in Northeast Zhejiang, China

Antibiotics play an essential role in the aquaculture industry, but their overuse and weak degradability inevitably lead to light to severe residues in natural and aquaculture environments. Most studies were interested in the occurrence, distribution, and ecological risks of a limited number of antibiotics in natural environments (rivers, lakes, and coastal regions) with a minor focus on antibiotic presence in either water, sediments, or organisms in aquaculture environments located in specific regions. In this study, we conducted a comprehensive investigation into the occurrence and distribution of up to 32 antibiotics [including 15 quinolones (QNs) and 17 sulfonamides (SAs)] in organisms and their corresponding environmental matrices from 26 freshwater aquaculture ponds in Northeast Zhejiang, China. A total of 13, 9, 7, and 7 antibiotics were detected in pond water, sediments, feeds, and aquaculture organisms, respectively, with concentration ranges of 0.6–92.2 ng/L, 0.4–1169.3 ng/g dw, <LOD–17.5 ng/g dw, and < LOD–234.3 ng/g ww, respectively, where enrofloxacin (ENR) was the main component in different matrix samples, with a proportion range of 51 %–88 %. There were differences in the predominant antibiotic and concentration abundance among fishponds, shrimp ponds, crab ponds, and turtle ponds. Feed was likely one of the most essential source of antibiotics in freshwater aquaculture ponds. The risk quotient (RQ) results revealed that ciprofloxacin (CIP) and ENR showed high risks to algae in water at the maximum measured concentrations and norfloxacin (NOR), CIP, ENR, and ofloxacin (OFL) exhibited high risks in sediments. However, the joint probability curve (JPC) showed acceptable risk in water. On the basis of the calculated hazard quotients (HQ < 1), the risk of human antibiotic ingestion through aquaculture organisms was acceptable. These results suggest that the rational control of antibiotic use is necessary for human health and ecological security.

Characteristics and regulatory mechanisms of net ecosystem CO2 exchange at the water-air interface in coastal aquaculture ponds

Coastal aquaculture ponds represented a biogeochemical hotspot in the global carbon cycle. However, there was a limited understanding of their dynamics. In this study, the eddy covariance (EC) technique was applied to quantify the net ecosystem CO2 exchange (NEE) over coastal aquaculture ponds in the Liaohe River estuary in northern China during 2020, aiming to investigate and quantify the carbon exchange characteristics of this region. The results showed that (a) a predominant “U” shaped diurnal NEE pattern throughout the year. During the sea cucumber monoculture phase, the ponds exhibited a consistent daytime carbon sink and nighttime carbon source pattern. In contrast, during the shrimp and sea cucumber polyculture phase, the ponds mostly remained in a net carbon sink state. (b) NEE was negatively correlated with photosynthetically active radiation (PAR), air temperature (Tair), and wind speed (WS), while showing a positive correlation with atmospheric pressure (AP). (c) Overall, the entire study area (complex underlying surfaces) functioned as a carbon sink in 2020, with a total net carbon sequestration of 281.533 g C·m−2. This was approximately four times greater than the restored wetlands that naturally formed from decommissioned coastal aquaculture ponds. Adjusting for surface heterogeneity revealed that the complex surfaces led to a 34.28 % underestimation of the aquaculture region's unit area carbon sequestration capacity. This study was crucial for assessing the carbon cycling and sequestration functions of coastal aquaculture pond ecosystems and provided a scientific basis for related ecological restoration projects.

Losses and destabilization of soil organic carbon stocks in coastal wetlands converted into aquaculture ponds.

Coastal-wetlands play a crucial role as carbon (C) reservoirs on Earth due to their C pool composition and functional sink, making them significant for mitigating global climate change. However, due to the development and utilization of wetland resources, many wetlands have been transformed into other land-use types. The current study focuses on the alterations in soil organic-C (SOC) in coastal-wetlands following reclamation into aquaculture ponds. We conducted sampling at 11 different coastal-wetlands along the tropical to temperate regions of the China coast. Each site included two community types, one with solely native species (Suaeda salsa, Phragmites australis and Mangroves) and the other with an adjacent reclaimed aquaculture pond. Across these 11 locations we compared SOC stock, active OC fractions, and soil physicochemical properties between coastal wetlands and aquaculture ponds. We observed that different soil uses, sampling sites, and their interaction had significant effects on SOC and its stock (p < .05). Reclamation significantly declined SOC concentration at depths of 0-15 cm and 15-30 cm by 35.5% and 30.3%, respectively, and also decreased SOC stock at 0-15 cm and 15-30 cm depths by 29.1% and 37.9%, respectively. Similar trends were evident for SOC stock, labile organic-C, dissolved organic-C and microbial biomass organic-C concentrations (p < .05), indicating soil C-destabilization and losses from soil following conversion. Soils in aquaculture ponds exhibited higher bulk density (BD; 11.3%) and lower levels of salinity (61.0%), soil water content (SWC; 11.7%), total nitrogen (TN) concentration (23.8%) and available-nitrogen concentration (37.7%; p < .05) than coastal-wetlands. Redundancy-analysis revealed that pH, BD and TN concentration were the key variables most linked with temporal variations in SOC fractions and stock between two land use types. This study provides a theoretical basis for the rational utilization and management of wetland resources, the achievement of an environment-friendly society, and the preservation of multiple service functions within wetland ecosystems.

A deep learning model for estimating body weight of live pacific white shrimp in a clay pond shrimp aquaculture

This paper presents a novel approach to address the essential challenge of accurately determining the total weight of shrimp within aquaculture ponds. Precise weight estimation is crucial in mitigating issues of overfeeding and underfeeding, thus enhancing efficiency and productivity in shrimp farming. The proposed system leverages image processing techniques to detect individual live shrimp and extract pertinent features for weight estimation within a clay pond environment. Specifically, an automated feed tray captures images of live shrimp, which are then processed using a combination of Detectron2, PyTorch, and CUDA (Compute Unified Device Architecture) for individual shrimp detection. Essential features such as area, perimeter, width, length, and posture are extracted through image analysis, enabling accurate estimation of shrimp weight. An Artificial Neural Network (ANN) model, utilizing these features, accurately predicts shrimp weight with a coefficient of determination (R2) of 94.50% when incorporating all extracted features. Furthermore, our system integrates a user-friendly web application that empowers farmers to monitor shrimp weight trends, facilitating precision feeding strategies and effective farm management. This study contributes a low-cost solution using a deep learning model to estimate the weight of live Pacific white shrimp in clay ponds, enabling daily weight calculations, helping farmers optimize feed quantities, providing shrimp size distribution insights, and reducing the Feed Conversion Ratio (FCR) for greater profitability. The procedure for shrimp feature extraction is also provided, including the calculation of shrimp length and width, as well as shrimp posture classification.

Monitoring water quality parameters impacted by Indonesia’s weather using internet of things

Increasing need for food resources, State of Indonesia to strive to maximize the output of food production. Not only in agriculture but also aquaculture results are also trying to be improved. This is also supported by the increase of Indonesia’s national fish consumption rate from 50.69 Kg per capita in 2018 to 55.37 Kg per capita in 2021. Recent aquaculture research only explored topics about monitoring the cultivation environment. But there have been no studies exploring how bad the impact of weather on the process of farming. Hence, this study aims to measure the influence of weather on freshwater aquaculture pond water quality and analyze its impact on fish growth namely Oreochromis Sp., using pH sensors and dissolved oxygen (DO). Then a weather simulation was carried out based on Indonesia’s tropical climate, which majorly consists of sunny and rainy weather. The experimental results indicate the instability of the pH value during the rainy period. DO values tend to decrease at the end of periods of sunny weather. Moreover, fish growth analysis showed that there was a decrease in food conversion ratio (FCR) by 0.956, specific growth rate (SGR) by 2.13% and survival rate (SR) by 5.715% during rainy weather.

Soil remediation and nano-biosilica: a potential combination to improve the environmental quality of brackishwater aquaculture ponds affected by acid sulfate soils.

The successful management of ASS-affected brackishwater aquaculture ponds necessitates overcoming associated environmental limitations. This study investigated the potential application of nano-biosilica from rice husk ash (RHA) and soil remediation techniques to improve the environmental quality of ASS-affected brackishwater ponds. The study followed a completely randomized design (CRD) with four treatments and three replicates. The treatments comprised applying soil remediation, nano-biosilica fertilizer, and their combination. The study generally revealed that the combination of soil remediation technique and RHA-driven nano-biosilica improved the water quality of ASS-affected brackishwater ponds. Soil remediation improved water quality by reducing acidity levels. However, excessive lime application as an integral part of the remediation might release acidity and toxic metals into water, potentially increasing calcium-phosphorus fixation. Despite liming potential negative consequences, if mixed with nano-biosilica could increase diatom-phytoplankton growth by reducing dissolved Al and Fe levels while boosting P and Si availability. Liming could also help boost diatom photosynthesis and inhibit unwanted algae blooms by decreasing water turbidity and increasing sunlight penetration. This study emphasized that the effectiveness of nano-biosilica in promoting diatom growth depends on appropriate nitrogen (N) and phosphorus (P) concentrations and ratios, which should not be a limiting factor. However, the required N/P concentration and ratio are only met if the remediation method is effectively implemented. The combination of nano-biosilica and soil remediation treatment maintained SiO2 concentrations above the average natural seawater concentration; however, availability may be limited due to complexes containing Ca, Al, Mg, and Fe. Regularly applying cost-effective nano-biosilica fertilizer in combination with N and P fertilizers is recommended to enhance water remediation efficiency by boosting Si availability and decreasing the toxicity of dissolved toxic metal ions.

Significant temporal variability leads to estimation bias in greenhouse gas emissions from aquaculture pond systems

Rising demand for aquatic products has expanded aquaculture, significantly elevating greenhouse gas (GHG) emissions from the aquaculture ponds. However, the emission estimation shows huge uncertainty. This study employed a meta-analysis of 1060 datasets of CO2, CH4 and N2O fluxes to examine how temporal variability affects GHG emissions from China's aquaculture ponds and to identify key environmental drivers. The results reveal that China’s aquaculture ponds are significant sources of GHGs to the atmosphere, with fluxes of CO2, CH4, and N2O from coastal pond systems at 5.50, 7.41 mg m² h⁻¹, and 16.72 μg m² h⁻¹ during the farming period, and −8.96, 4.33 mg m² h⁻¹, and 44.98 μg m² h⁻¹ during the non-farming period, respectively. Regarding inland pond systems, the fluxes of CO2, CH4, and N2O were 50.48, 5.19 mg m² h⁻¹, and 36.35 μg m² h⁻¹ during farming period, and 0.90, 1.03 mg m² h⁻¹, and 51.46 μg m² h⁻¹ during non-farming period, respectively. Total GHG annual emissions were 42.17 Tg CO2-eq over a 100-year time scale, predominantly from CH4 at 74.11 %, with CO2 contributing to 9.63 %, and N2O to 6.63 %. Post-cultivation drainage significantly shifts biogeochemical conditions and emission patterns, reducing total GHG emissions. Ignoring the non-farming period leads to overestimated CO2 and CH4 emissions, and underestimated N2O emissions. Our study provides new insights into GHG estimation from aquaculture ponds, highlighting the importance of considering temporal variability in GHG inventories, and supporting the development of management-based mitigation strategies.

Aquacultural source of nitrous oxide revealed by nitrogen isotopes

The rapid expansion of coastal aquaculture has led to an increase in the coverage of aquaculture ponds, where intense feed-derived nitrogen is causing significant emissions of nitrous oxide (N2O). Multiple N2O production pathways and the relative importance of water column vs. sedimentary production in aquaculture ponds remain uncertain. Clarifying these pathways is vital for sustainable aquaculture development. Using 15N-labeled dissolved inorganic nitrogen, the pathways and rates of N2O production in subtropical aquaculture ponds located in south China, cultivating whiteleg shrimp, Japanese seabass, and giant river prawn, were successfully characterized. Total N2O production rates ranged from 6 to 70 µmol-N m−2 d−1, with the shrimp pond exhibiting the highest total N2O production rates, followed by ponds for seabass and prawn. These differences are primarily due to varying feed amounts causing differences in dissolved nutrients in water column and sediment. Particularly, nutrient and organic matter accumulation at the surface sediment stimulated N2O production. The oxygenated sediment on a centimeter scale could produce substantially more N2O compared to the water column above on a meter scale. Partial denitrification, i.e., nitrate and nitrite reduction to N2O, was more important (> 60 %) for N2O production in aquaculture ponds. The availability of nitrite is likely a major factor driving partial denitrification for both sedimentary and water column N2O production.

Mangrove wetland recovery enhances soil carbon sequestration capacity of soil aggregates and microbial network stability in southeastern China

Mangrove wetlands are highly productive ecosystems in tropical and subtropical coastal zones, play crucial roles in water purification, biodiversity maintenance, and carbon sequestration. Recent years have seen the implementation of pond return initiatives, which have facilitated the gradual recovery of mangrove areas in China. However, the implications of these initiatives for soil aggregate stability, microbial community structure, and network interactions remain unclear. This study assesses the impacts of converting ponds to mangroves—both in natural and artificially restored settings—on soil aggregate stability and microbial networks at typical mangrove restoration sites along China's southeastern coast. Our observations confirmed our hypothesis that pond-to-mangrove conversions resulted in an increase in the proportion of large aggregates (>0.25 mm), improved soil aggregate structural stability, and increased carbon sequestration. However, mangrove recovery led to a decrease in the abundance and diversity of soil fungi communities. In terms of co-occurrence networks, naturally restored mangrove wetlands exhibited more nodes and edges. The naturally recovered mangrove wetlands demonstrated a higher level of community symbiosis compared to those that were manually restored. Conversely, bacterial networks showed a different pattern, with significant shifts in key taxa related to carbon sequestration functions. For instance, the proportion of bacterial Desulfobacterota and fungi Basidiomycota in natural recovery mangrove increased by 15.03 % and 7.82 %, respectively, compared with that in aquaculture ponds. Soil fungi and bacteria communities, as well as carbon sequestration by aggregates, were all positively correlated with soil total carbon content (P < 0.05). Both bacterial and fungal communities contributed to soil aggregate stability. Our study highlights the complex relationships between soil microbial communities, aggregate stability, and the carbon cycle before and after land-use changes. These findings underscore the potential benefits of restoring mangrove wetlands, as such efforts can enhance carbon storage capacity and significantly contribute to climate change mitigation.