Mariculture System Research Articles

Seasonal variations of allocation strategy in carbon, nitrogen and phosphorus among tissues of male Mytilus coruscus are regulated by the gametogenic cycle: a case study in a mariculture system

This study examines the seasonal allocation strategy of carbon, nitrogen, and phosphorus in tissues of male Mytilus coruscus within a mariculture system at Gouqi Island, providing insights into the mussels' reproductive and nutritional adaptations. The reproductive cycle of mussels is bifurcated, with a resting phase in summer and active gametogenesis from autumn to spring. Digestive enzyme activity in mussels correlates negatively with food conditionality, especially when food is scarce in winter, enzyme activity is heightened to enhance nutrient extraction, whereas in summer, with an abundance of food, enzymatic activity is conserved for other physiological processes. This suggests an adaptive modulation to optimize energy allocation between growth, maintenance, and reproduction. Allometric growth analysis reveals that smaller mussels exhibit uniform nutrient allocation across tissues, focusing on somatic growth. In contrast, larger, mature mussels prioritize phosphorus utilization in gonads, indicative of reproductive investment. This shift aligns with the predictive adaptive response model, anticipating future reproductive demands by adjusting resource allocation. The study also identifies seasonal fluctuations in nutrient demand and allocation among tissues, with gonadal tissues showing preferential accumulation of nitrogen and phosphorus during mature phases. Although mussels preferentially allocate nutrients to the shell only in autumn, a consistent preferential accumulation of nitrogen and phosphorus to this critical structural component, highlighting the importance of these elements in biomineralization and shell maintenance. This research elucidates the complex interplay between environmental factors, physiological processes, and nutrient dynamics in male M. coruscus, and underscore the importance of considering seasonal variations in nutrient allocation for sustainable mariculture practices.

Stress and recovery of yellowtail kingfish (Seriola aureovittata) during Sea-land relay transportation: Biochemical, microecological and transcriptomic responses

Sea-land relay transportation (SRT) is a key part of the “land-based greenhouse + offshore net cage” mariculture system for yellowtail kingfish. In this study, the physiological status of yellowtail kingfish during SRT was assessed by determining serum biochemical indexes (levels of cortisol, glucose, and malondialdehyde (MDA), and activities of superoxide dismutase (SOD) and catalase (CAT)), the composition of intestinal microflora, and the liver transcriptome before (control), during, and after transportation (T1 and T2) and after recovery for 6 hours (6 h), 12 hours (12 h), 1 day (D1), 3 days (D3), and 7 days (D7). The results show that the serum cortisol and glucose levels, MDA level, and activities of SOD and CAT significantly increased during transportation, and decreased to similar levels to those in the control after 1 day of recovery. Bacteria including Acinetobacter, Enterobacter, and Comamonas accounted for more than 91 % of the microbial community in the gut of yellowtail kingfish, and these genera were associated with changes in serum glucose levels, indicating that they may help to alleviate the effects of transportation stress. Analyses of liver transcriptome data showed that significantly differentially expressed genes (DEGs) in the T2, D1, D3 and D7 groups were significantly enriched in the “Protein processing in the endoplasmic reticulum (ER)” pathway. At the end of transportation (T2 group), the ER-associated degradation (ERAD) pathway was activated, with up-regulation of hsp40, hsp70, and hsp90α. The transcript levels of these genes gradually returned to levels similar to those in the control during the recovery period. At the first day of recovery, the unfolded protein response imposed stress upon the ER, accompanied by significant down-regulation of PEPK and Calmin and significant up-regulation of CRT. The DEGs in the D3 group were enriched in the “ER”, “Steroid biosynthesis”, “Fatty acid degradation”, “PPAR signaling”, and “Fat digestion and absorption” pathways, whereas the number of DEGs related to lipid metabolism and stress pathways was significantly decreased in the D7 group. Our results indicate that hsp70 and hsp90α can be used as stress markers, and hsp40 can be used as a physio-metabolic recovery marker for yellowtail kingfish. These results show that, although serum indices recovered 24 hours after transportation, up to 3 days after transportation is an important period for recovery from transportation stress at the transcriptome level. “Protein processing in the ER pathway” is an important pathway regulating stress and recovery in yellowtail kingfish.

The potential seaweed resources assessment: Its cultivation prospect and future biofuel feedstock

Global issues on energy and fuel for sustainable development industrial and household system are a major concern in the world economy. Biofuel is a renewable energy source that can potentially be a replacement for fossil fuels. The utilization of algal biomass or seaweed organic matter is a good source of ethanol, methanol, biobutanol, and biodiesel. Malaysia’s waters recorded approximately 400 species of macroalgae, with several species found to be a potential source for biofuel application. An expedition study for the seaweed natural resources was carried out in December 2016 in coastal areas in Johor and Melaka, Peninsular Malaysia. Green seaweed, Ulva, large brown seaweed, Sargassum, and Gracilaria (red seaweed) are found in the selected study areas and these genera are listed as biofuel resources in the literature. The design of offshore mariculture system specifically for seaweed farming for biomass production for biofuel. The prototype was constructed and deployed in Bidong Island, Terengganu in 2016 before the monsoon. At the end of the monsoon period, the prototype is still stable in situ. Selected seaweed species with biofuel potential were trial cultivated on the system and the growth performance of the particular species was monitored. The suggested species for biofuel are Gracilaria and Ulva, while Kappaphycus is targeted for the food industry. Gracilaria and Ulva were also studied for their bioremediation potential and suitability to grow on the system. Gracilaria spp. was able to grow on the system, indicating the designed system is feasible for biomass production of seaweed. Further, the selected seaweed species can function as biofilters for the nutrients in the environment and acceptability for a wide salinity range meaning that the system can be applied in different locations such as estuary, inshore, or offshore. Seaweed biofuel and its subsequent advantage related to pollution-free energy generation is of critical importance.

Phytoplankton size structures and their interactive effects with nutrient conditions on sinking rates in a mariculture system

Phytoplankton size structures and their interactive effects with nutrient conditions on sinking rates in a mariculture system

The occurrence of pollutants in organisms and water of inland mariculture systems: Shrimp aquaculture is a procession of Microplastics accumulation

Microplastics (MPs) pollution in the ocean was widely concerned, but the current study on MPs pollution in the mariculture system is relatively lacking. This study researched the MPs pollution characteristics in water and shrimp at different stages of the pond and industrial aquaculture. The study shows that in the same aquaculture stage, MPs abundance in shrimp and water in pond aquaculture mode is higher than that in industrial aquaculture mode. The MPs pollution characteristics in shrimp and water show significant consistency. The hazard index of MPs in pond water and industrial models are 122 (Level Ⅲ) and 540 (Level Ⅲ), respectively, indicating that industrial aquaculture models may suffer from more severe MPs stress. The aquaculture period and mode significantly affected the MPs abundance of water and shrimp, but there was no interaction between the aquaculture period and mode. MPs abundance in shrimp show a significant relationship with the length of crustacean and weight. This study further enhanced the understanding of MPs pollution of water and organisms in different aquaculture modes at different stages, and warned MPs is widely spread in mariculture systems.

Rhamnolipid-assisted solid-phase denitrification process for enhanced nitrate removal of recirculating mariculture system water

Solid-phase denitrification (SPD) is a promising approach for treating recirculating mariculture systems (RMS) water, but its relatively slow nitrate removal rate presents a challenge. This study, for the first time, investigates the enhanced nitrate removal in the SPD process by rhamnolipid (RL) addition. The enhancement by RL addition (20 and 40 mg L−1) was significant and largely persisted even after RL dosing was stopped. Specifically, the nitrate removal in RL-assisted SPD reactors was enhanced by 1.7–2.6 and 1.9–2.1 times for influent NO3−-N concentrations of 100 and 200 mg L−1, respectively. The enhancement was attributed to the improved biofilm formation, as indicated by the increased contents of biomass and extracellular polymeric substances. Moreover, the abundances of denitrification and biofilm formation functional bacteria (Pseudomonas and Denitromonas) also increased. RL addition increased abundances of functional genes involved in carbon degradation and nitrate removal. The denitrification and assimilatory nitrate reduction pathways achieved nitrate removal together. Therefore, RL-assisted SPD presents a novel strategy for treating nitrate-rich RMS water.

Start-up of solid-phase denitrification process for treatment of nitrate-rich water in recirculating mariculture system: Carbon source selection and nitrate removal mechanism

Efficient nitrate removal from recirculating mariculture system (RMS) water is of significance since high concentration of nitrate would cause chronic health effects on aquatic organisms and eutrophication. Solid-phase denitrification (SPD) is a safer and more sustainable approach than conventional heterotrophic denitrification by dosing liquid carbon sources. Thus, its application for treating nitrate-rich RMS water was investigated in this study. Poly 3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) was identified with the best nitrate removal among four kinds of carbon sources. PHBV-filled reactors started with mariculture, municipal and mixing sludges (at the ratio of 1:1) and fed with 200 mg L-1 nitrate-rich RMS water all achieved over 81% nitrate removals with a HRT of 4 days. The dissolved organic carbon concentrations of the reactors were in the range of 3–9 mg L-1. Arcobacter, Halomonas, and Psedomonas were dominant genera responsible for nitrate removal in different reactors. Metagenomic analyses indicate that both denitrification and assimilatory nitrate reduction (ANR) are the main contributors to nitrate removals. Metagenomic results illustrated nirB/D cooperated with nasA may perform ANR pathway, which transformed nitrate to ammonia for biosynthesis. These results indicate that SPD could be a safer alternative for treating nitrate-rich RMS water, and provide new insights into nitrogen metabolism pathways in SPD process.

Mariculture structure adjustment to achieve China's carbon neutrality and mitigate climate change

China is responsible for the biggest shellfish and macroalgae production in the world. In this study, comprehensive methods were used to assess the CO2 release and sequestration by maricultured shellfish and macroalgae in China. Through considering CaCO3 production and CO2 release coefficient (Φ, moles of CO2 released per mole of CaCO3 formed) in different waters, we find that cultured shellfish released 0.741 ± 0.008 Tg C yr−1 through calcification based on the data of 2016–2020. In addition to calcification, maricultured shellfish released 0.580 ± 0.004 Tg C yr−1 by respiration. Meanwhile, shellfish sequestered 0.145 ± 0.001 and 0.0387 ± 0.0004 Tg C yr−1 organic carbon in sediments and shells, respectively. Therefore, the net released CO2 by maricultured shellfish was 1.136 ± 0.011 Tg C yr−1, which is about four times higher than that maricultured macroalgae could sequester (0.280 ± 0.010 Tg C yr−1). To achieve carbon neutrality within the mariculture system, shellfish culture may need to be restricted and meanwhile the expansion of macroalgae cultivation should be carried out. The mean carbon sequestration rate of seven kinds of macroalgae was 174 ± 6 g m−2 yr−1 while some cultivated macroalgae had higher CO2 sequestration rates, e.g. 356 ± 24 g C m−2 yr−1 for Gracilariopsis lemaneiformis and 331 ± 17 g C m−2 yr−1 for Undaria pinnatifida. In scenario 0.5 (CCUS (Carbon Capture, Utilization and Storage) sequesters 0.5 Gt CO2 per year), using macroalgae culture cannot achieve China's carbon neutrality by 2060 but in scenarios 1.0 and 1.5 (CCUS sequesters 1.0 and 1.5 Gt CO2 per year, respectively) it is feasible to achieve carbon neutrality using some macroalgae species with high carbon sequestration rates. This study provides important insights into how to develop mariculture in the context of carbon-neutrality and climate change mitigation.

Effects of Dietary Lysine Level on Growth Performance and Protein Metabolism in Juvenile Leopard Coral Grouper (Plectropomus leopardus).

An 8-week feeding trial was conducted to evaluate the effects of dietary lysine level on growth performance and protein metabolism of juvenile leopard coral grouper (Plectropomus leopardus) and thereby obtained the optimal dietary lysine requirement of P. leopardus. Six isoproteic and isolipidic experimental diets were formulated to contain 1.10%, 1.69%, 2.30%, 3.08%, 3.56%, and 4.36% lysine of diets, respectively. Each diet was assigned at random to triplicate groups of 25 juveniles (initial mean weight is 10.57 g) per tank in a flow-through mariculture system maintained at 27-30°C. Dietary inclusion of 2.30-3.08% lysine improved the weight gain rate (WGR) and specific growth rate and decreased the feed conversion ratio (FCR) of juveniles (P < 0.05). The intestinal digestive enzyme (trypsin, amylase, and lipase) activities were overall enhanced by dietary inclusion of 3.08-3.56% lysine (P < 0.05). The mammalian target of rapamycin (mTOR) signaling pathway was activated in fish fed diets with 1.69-2.30% lysine by upregulating the relative expression levels of hepatic TOR and S6K1 (p70 ribosomal protein S6 kinase 1) but downregulating the relative expression level of hepatic 4E-BP2 (eIF4E-binding protein 2). Conversely, the amino acid response signaling pathway was inhibited in fish fed diet with 2.30% lysine by downregulating the relative expression levels of hepatic GCN2 (general control nondepressible 2), ATF3 (activating transcription factor 3), ATF4a (activating transcription factor 4a), and ATF4b (activating transcription factor 4b). Additionally, dietary 1.69-3.08% lysine enhanced the plasma total protein level and hepatic lysine α-ketoglutarate reductase activity but depressed the blood urea nitrogen level and hepatic adenosine monophosphate deaminase activity (P < 0.05). Moreover, dietary 3.08% lysine increased the contents of whole-body crude protein and total amino acids, while 1.69%-4.36% lysine depressed the whole-body lipid content (P < 0.05). These results indicated that optimal dietary lysine increased the digestive enzyme activities, promoted protein synthesis but depressed protein degradation, and thereby improved the growth performance of P. leopardus. Based on the second-order polynomial model, the optimal lysine requirement of juvenile P. leopardus for WGR, FCR, and lysine deposition was 2.60%-2.97% of diets (4.91%-5.60% of dietary protein).

Temporal variations, distribution, and dissemination of antibiotic resistance genes and changes of bacterial communities in a biofloc-based zero-water-exchange mariculture system

Antibiotic resistance genes (ARGs) have obtained an increasing number of global concerns for the severe risks they pose to food safety and public health. Studies have investigated the concentrations and distribution of ARGs in the environment. However, the distribution and dissemination of ARGs, the bacterial communities, and the key influencing factors during the entire rearing period in the biofloc-based zero-water-exchange mariculture system (BBZWEMS) remain unclear. The current study investigated the concentrations, temporal variations, distribution, and dissemination of ARGs, the changes in the bacterial communities, as well as the key influencing factors during the rearing period in the BBZWEMS. Sul1 and sul2 were dominant ARGs. Total concentrations of ARGs followed a trend of decrease in pond water, while they followed a trend of increase in source water, biofloc, and shrimp gut. Total concentrations of targeted ARGs in the water source were higher than those in the pond water and biofloc samples for each corresponding rearing stage by 2.25–122.97-fold (p < 0.05). The bacterial communities in biofloc and pond water did not change much, while they changed considerably in the shrimp gut samples during the rearing period. Pearson correlation, redundancy analysis, and multivariable linear regression analysis showed that suspended substances and Planctomycetes were positively correlated with the concentrations of ARGs (p < 0.05). The current study indicates that the water source may be a critical source of ARGs, and that suspended substances is a key factor influencing the distribution and dissemination of ARGs in the BBZWEMS. Early intervention measures on ARGs in water sources should be implemented to aid in the prevention and control of resistance genes in aquaculture industry, and reduce the potential risks of ARGs to public health and food safety.

The Genetic and Phenotypic Diversity of Bacillus spp. from the Mariculture System in China and Their Potential Function against Pathogenic Vibrio

Bacillus spp. could be one of the most suitable substitutes for the control and prevention of aquatic diseases. The occurrence of species population, antimicrobial character, and virulence diversity in Bacillus spp. recovered from the mariculture system in China between 2009 and 2021 were investigated, screening for probiotic Bacillus strains with good biological safety that can inhibit Vibrio parahaemolyticus, V. alginolyticus, V. harveyi, V. owensii, V. campbellii. The results showed that 116 Bacillus isolates were divided into 24 species, and the top three species were B. subtilis (37/116), B. velezensis (28/116), and B. amyloliquefaciens (10/116). Among the 116 Bacillus isolates, 32.8% were effective against V. parahaemolyticus, 30.1% for V. alginolyticus, 60.3% for V. harveyi, 69.8% for V. owensii and 74.1% for V. campbellii. More than 62% of Bacillus isolates were susceptible to florfenicol, doxycycline and tetracycline, etc., and 26/116 Bacillus isolates were found to be multiple-antibiotic-resistant (MAR), with MARI values ranging from 0 to 0.06. Eighteen kinds of antibiotic resistance genes were tested; only tetB, blaTEM, and blaZ were detected. And 9 isolates in 2 Bacillus species were excluded by 6/10 kinds of Bacillus-related toxin gene (hblA, hblC, nheB, nheC, entFM, cykK). Bio-safety testing indicated that three kinds of probiotics were good probiotic candidates to prevent Vibriosis. These results provide comprehensive genetic diversity, potential risks, and probiotic characteristics of Bacillus in the mariculture system in China, and provide basic support for green and healthy development of aquatic industry.

Dietary Histamine Impairs the Digestive Physiology Function and Muscle Quality of Hybrid Grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂).

An 8-week feeding experiment was conducted to investigate the effect of dietary histamine on growth performance, digestive physiology function and muscle quality in a hybrid grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂). Seven isoproteic (50%) and isolipidic (11%) diets were prepared with various histamine inclusion levels of 0, 30, 60, 120, 240, 480 and 960 mg/kg in diets (actual contents were 72.33, 99.56, 138.60, 225.35, 404.12, 662.12 and 1245.38 mg/kg), respectively. Each diet was randomly assigned to triplicates of 30 juveniles (average body weight 14.78 g) per tank in a flow-through mariculture system. The increase in the dietary histamine level up to 1245.38 mg/kg made no significant difference on the growth rate and feed utilization of the grouper. However, the increased histamine content linearly decreased the activities of digestive enzymes, while no differences were observed in groups with low levels of histamine (≤404.12 mg/kg). Similarly, high levels of histamine (≥404.12 mg/kg) significantly damaged the gastric and intestinal mucosa, disrupted the intestinal tight junction structure, and raised the serum diamine oxidase activity and endotoxin level. Meanwhile, high doses of histamine (≥662.12 mg/kg) significantly reduced the activities of antioxidant enzymes, upregulated the relative expression of Kelch-like ECH-associated protein 1, and hardened and yellowed the dorsal muscle of grouper. These results showed that dietary histamine was detrimental to the digestive physiology function and muscle quality of the grouper, although it did compromise its growth performance.

Multi-Costimulatory Pathways Drive the Antagonistic Pseudoalteromonas piscicida against the Dominant Pathogenic Vibrio harveyi in Mariculture: Insights from Proteomics and Metabolomics.

Vibrio harveyi is the dominant pathogen in mariculture, and biocontrol of this pathogen using antagonistic probiotics is a long-standing biological challenge. Here, Pseudoalteromonas piscicida WCPW15003 as a probiotic effectively antagonized dominant pathogenic V. harveyi in a mariculture, with a growth-of-inhibition ratio of 6.3 h-1. The antagonistic activities of cells and intracellular components of WCPW15003 made a greater contribution to the antagonistic process than did extracellular metabolites and caused the dominance of WCPW15003 during the antagonistic process in vitro. WCPW15003 was safe for the pearl gentian grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatus) and, as a consequence of the antagonistic effect on V. harveyi, protected the fish from an immune response in vivo. A comprehensive combined proteomics and metabolomics analysis of antagonistic WCPW15003 and pathogenic V. harveyi in a coculture compared to a monoculture was performed to investigate the antagonistic molecular mechanisms. The results showed that during the antagonistic process, WCPW15003 in a coculture had significantly downregulated metabolic pathways for histidine metabolism, arginine biosynthesis, and phenylalanine metabolism, and upregulated glycerophospholipid metabolism, leading to a competitive advantage against the co-occurring species, V. harveyi. This defined a mechanism by which multi-costimulatory pathways drove P. piscicida WCPW15003 against V. harveyi. IMPORTANCE V. harveyi as a dominant pathogen has become a major hazard in mariculture development and seafood safety, and biocontrol of this pathogen using antagonistic probiotic agents is a long-standing biological challenge. P. piscicida WCPW15003 has promise as a novel, safe, and effective bioagent for specifically inhibiting dominant pathogenic V. harveyi and protects mariculture animals from infection by this pathogen by moderating the host immune response, which is heavily driven by multi-costimulatory pathways in a coculture of WCPW15003 and V. harveyi. This work identified a direction for comprehensively elucidating the molecular mechanism of WCPW15003 antagonism against the dominant pathogen in mariculture using modern molecular biology techniques and provided deep insights into the advantages and potential of this antagonistic probiotic against V. harveyi for the construction of an environmentally friendly, recirculating mariculture system.

Physiology, metabolism, antibiotic resistance, and genetic diversity of Harveyi clade bacteria isolated from coastal mariculture system in China in the last two decades

Vibrio bacteria, particularly members of the Harveyi clade, are the most important pathogens of aquatic organisms that cause significant economic losses in the world. It is difficult to provide specific data on taxa of the Harveyi clade for biological research and prevention strategies. Therefore, we conducted an extensive phenotypic and antibiotic resistance study, as well as phylogenetic and molecular typing of 192 isolates of the Harveyi clade collection from 2000 to 2020 with a typical interannual difference from a coastal area in China. The isolates had a significant interspecific genetic and antibiotic resistance diversity. Based on the multilocus sequence analysis (MLSA) of housekeeping genes (gyrB, pyrH, recA, and atpA), 192 Harveyi clade isolates were rapidly and accurately classified into 10 species. The population of these isolates was composed of 95 sequence types (STs), of which 92 STs were newly identified, indicating a high degree of genetic diversity. ST327 ranked first, accounting for 11.5% of the total number of isolates (22 out of 192), followed by ST215 with 6.25%, while 63 STs included single isolates. At the metabolic level, the physiological and biochemical experiments revealed that all the Harveyi clade isolates were positive for oxidase and negative for melibiose. The isolates showed a varied tolerance to 11 antibiotics. No isolates were resistant to neomycin. The percentages of sulfadimidine-resistant strains (61 out of 192), sulfadiazine (44 out of 192), sulfamonomethoxine (44 out of 192), sulfamethoxazole (33 out of 192), thiamphenicol (34 out of 192), ciprofloxacin (52 out of 192), and enrofloxacin (31 out of 192) were 31.77%, 22.92%, 22.92%, 17.19%, 17.71%, 27.08%, and 16.15%, respectively. A proportion of 61.8% of the isolates presented a multiple antibiotic resistance index (MARI) lower than 0.1, indicating that the risk of antibiotic resistance transmission of most of the Harveyi clade is low in mariculture systems in China. These results provide substantial data to support further studies on the identification and genetic and metabolic diversity of Harveyi clade isolates in mariculture systems in China.

Anode modification of sediment microbial fuel cells (SMFC) towards bioremediating mariculture wastewater

Remediation of mariculture wastewater is of great practical importance. In this study, sediment microbial fuel cells (SMFCs) were adopted and carbon felt anodes were modified to enhance COD and ammonia removal in mariculture system. The results showed that the SMFC anode with 5 % (w/w) graphene oxide (GO) coating performed best in pollutants removal and electricity generation. The maximum power density approached 132 mW/m2, nearly 4.5 times higher than the unmodified anode. The removal efficiency of COD and ammonia reached 82.1 % and 95.8 % respectively, both improved compared with the control and chemical modification. The modified anode effectively enriched the electrogenic Sulfurovum and Lactobacillus and thus led to a significant improvement in the electrochemical performance of SMFC. This study demonstrates the successful application of SMFCs with GO modified anodes in the in-situ removing pollutants and SMFCs present obvious remediation potential on the contaminated mariculture inhabitant.

Ecosystem Services of Ecosystem Approach to Mariculture: Providing an Unprecedented Opportunity for the Reform of China’s Sustainable Aquaculture

China is the biggest provider of mariculture products, and the industry is still growing rapidly. Increasing scientific evidence indicates that mariculture may provide valuable ecosystem goods and services in China. Here, we performed a systematic literature review of studies with the aim of understanding the ecosystem services of mariculture and a comprehensive review of ecosystem approaches that may improve mariculture ecosystem services and goods in China. We highlight four ecosystem services functions in China, including food supply, nutrient extraction, carbon sequestration, and biodiversity conservation. Given the further reform of China’s mariculture, we outlined several ecosystem approaches including integrated multi-trophic aquaculture (IMTA), carrying capacity assessment and monitoring, marine spatial planning, and waste treatment and recirculating mariculture system. We conclude that the ecosystem services of the ecosystem approach to mariculture provide an unprecedented opportunity for the reform of China’s sustainable aquaculture. Finally, a synthesis of sustainable development of mariculture, along with the five recommendations for future mariculture development in China, is outlined.

DEVELOPMENT OF INSTITUTIONAL SUPPORT OF MARICULTURE IN UKRAINE: IMPLEMENTATION OF INTERNATIONAL EXPERIENCE

Topicality. The UN Summit on Global Goals and the 2030 Agenda for Sustainable Development identifies the need to address poverty and hunger, human rights, and long-term protection of the planet and its natural resources. The development of the economy should be aimed both at a single goal and to represent a multifunctional system that covers their achievements in an interdependent set. Building a blue economy in the context of sustainability is crucial not only for the Summit's global goal of 14 " Life below water", but also for the goals of resources, poverty, health, justice and prosperity. This is especially true of island and coastal states, where the seas and oceans provide daily life, livelihoods, economic opportunities in poverty and food shortages. Sustainable development of mariculture can provide significant potential for increasing revenues and contributions of the industry to the national economy. With the right approach to location, development, management and regulation, the mariculture industry can bring economic, environmental and social benefits. Mariculture as a highly productive industry based on sustainable development practices is the key to food and environmental security, a sustainable seafood supply chain and significant socio-economic benefits for coastal areas. For the effective development of mariculture, as for any economic sector, a stable basis is needed as an institutional support, which in Ukraine, unfortunately, is not characterized by a high enough level. The current state of affairs, trends and identified problems actualize the purpose of scientific research. Aim and tasks. The purpose of the study is to assess the institutional support for the development of mariculture in Ukraine and study international experience in this field in the context of its implementation in national practice. The main objectives of the study are: to study the features of the theoretical and applied basis of the development of the mariculture system in the domestic and international context, in order to identify opportunities for implementation of international experience in Ukraine; to analyze the domestic institutional context of mariculture development and the legal framework for mariculture development in countries with long traditions of marine organisms and in countries where this industry did not previously exist; to develop conclusions on the current state of institutional support and recommendations for the development of mariculture in Ukraine on the basis of compliance with international requirements and justify the possibility of their implementation. Research results. The scientific novelty of the study is that the author proposed the definition of "mariculture", an algorithm for the development of institutional support of mariculture in Ukraine based on the implementation of international norms and principles (subjective, object and spatial sphere) based on the experience of the European Union. world leaders in the development of mariculture and countries with a short tradition of growing marine organisms or where this industry did not previously exist. Conclusion. A detailed interpretation of mariculture based on the characteristics of the industry presented in the texts of the existing legal framework of Ukraine, European Union countries, world leaders in mariculture, dictionaries and works of prominent Ukrainian and foreign scientists. An algorithm for the development of institutional support for mariculture in Ukraine has been developed.

Small-sized salt-tolerant denitrifying and phosphorus removal aerobic granular sludge cultivated with mariculture waste solids to treat synthetic mariculture wastewater

The mariculture waste solids generated in mariculture system were harmlessly reused to cultivate salt-tolerant aerobic granular sludge to further treat synthetic mariculture wastewater. Salt-tolerant aerobic granules with small size (~350 µm) were obtained after 45 days in an anaerobic/aerobic/anoxic sequencing batch reactor. The functional microorganisms were efficiently enriched as high nitrogen and phosphate removal efficiencies of 96.1% and 97.2% respectively were obtained after granulation. Loosely bound protein was conducive to form initial granules. EPS barely changed after granulation. The microbial richness and diversity of mariculture waste solids decreased during the granulation process. Dominant microorganisms were different between young granules and matured granules. Many genera which proliferated in young granules were uncompetitive and reduced or eliminated after granulation. Genera of unclassified_f __Rhodobacteraceae, unclassified_f __Flavobacteriaceae and Ilumatobacter related to phosphorus removal process. Denitrification was mainly performed by denitrifying phosphorus accumulating organisms, denitrifying glycogen accumulating organisms and autotrophic denitrifiers after granulation under saline condition.

Environmental and economic assessment of mariculture systems using a high share of renewable energy sources

Increased demand for fish products has resulted in greater investment in and modernization of the aquaculture sector. These processes have led to higher energy needs of aquaculture farms globally, resulting in their greater environmental impact. Fossil fuel is the main power source in aquaculture, and its combustion generates a large amount of Greenhouse Gases (GHGs) and other emissions. This paper considers the use of renewable energy sources (RESs) in mariculture systems to ensure at the same time cost-effective and environmentally friendly powering options. This paper investigates an alternative solution which relocates the majority of equipment and tasks from a mariculture vessel to a barge to reduce the energy demands of the vessel and to significantly lessen emissions of the system. The solution includes the full electrification of the workboat and the installation of PV cells and a wind turbine onboard the barge, combined with a diesel generator in an integrated power system. A Life-Cycle Assessment (LCA) was performed to evaluate the considered power system configurations from an environmental point of view, while a Life-Cycle Cost Assessment (LCCA) was performed to evaluate the economic performance of the proposed solutions. The results of the implementation of RESs in the mariculture system indicate an emission reduction of about 20% and an increase in capital costs by 0.61%. Feed reduction and the use of electricity in an alternative mariculture farm design in Croatia increase profitability by 4% in most cases.

Antibiotics, antibiotic resistance genes and microbial community in grouper mariculture

Increasing use of feed and medicine in mariculture could cause negative environmental impacts such as habitat modification, microbial disease development and antibiotic resistance. Here we investigated contamination of antibiotics and antibiotic resistance genes (ARGs), and composition of microbial community in grouper mariculture systems in Hainan province, China. Results showed detection of various antibiotic residues with the dominance of fluoroquinolones and tetracyclines in the six grouper cultivation systems. The concentrations of the detected antibiotics in the grouper mariculture water were significantly higher than those in the original seawater. Some of the detected antibiotics such as enrofloxacin, ciprofloxacin, ofloxacin, oxytetracycline and erythromycin in the mariculture water and/or sediment would pose high resistance selection risks. Sulfonamides resistance genes sul1 and sul2 were found to be predominant in water and sediment, while tetracycline resistance genes were prevalent in fish gill and gut. The dominant bacterial phyla in water and sediments were Bacteroides, Actinomycetes, and Proteobacteria, while the dominant ones in fish gill and gut were the Proteobacteria. Genera of Vibrio and Mycobacterium in the core microbiota were important zoonotic pathogens, and there was a significant positive correlation between Vibrio and ARGs. Phyla of Proteobacteria, Actinomyces, and Cyanobacteria were positively correlated to ARGs, indicating that these microorganisms are potential hosts of ARGs. The putative functions of microbiome related to antibiotic resistance and human diseases were significantly higher in fish than in the mariculture environment. This study suggests that mariculture system is a reservoir of ARGs, and the use of antibiotics in mariculture could induce the increase of antibiotic resistance and the prevalence of opportunistic pathogens.