Effect of orange solid waste diet on flesh quality and metabolic profile of common carp (Cyprinus carpio).

In this study, we aimed to evaluate the effects of solid waste of Citrus sinensis (SWC) supplementation in diet on common carp (Cyprinus carpio) flesh quality and the potential mechanisms underlying these effects. Four diets, each with different levels of SWC (0%, 5%, 10%, and 15%), were formulated and administered to C. carpio (48.83 ± 5.59 g) for 60 days. The results showed that SWC diet significantly enhanced specific growth rate, muscle sweetness (via sweet amino acids and sweet molecules), and the nutritional value of fish meat (increased protein, α-vitamin E, and allopurinol). Chromatography-mass spectrometry analyses indicated that SWC supplementation increased the essential amino acid content in the diet. In addition, SWC diet promoted biosynthesis of non-essential amino acids in muscle by enhancing glycolysis and the tricarboxylic acid cycle. In conclusion, SWC could be a cost-effective solution for providing nutritious and flavourful aquatic products.

Effects of stress on school bullying behavior among secondary school students: Moderating effects of gender and grade level.

This study investigated the effects of stress on school bullying behaviors among middle school students, and the moderating role of gender and grade level in this relationship. To this end, the Olweus Child Bullying Questionnaire (OBVQ) secondary school version of the child bullying questionnaire and the stressor scale for secondary school students were used to survey 3,566 secondary school students in Guizhou Province, and the data were statistically analyzed. Results showed that stress was significantly and positively associated with school bullying among secondary school students. Furthermore, both gender and grade moderated the relationship between stress and school bullying, showing that boys and middle school children are more likely to engage in bullying than girls and high school students, respectively. The results of the study provide a theoretical basis for the prevention and intervention of school bullying behaviors among middle school students.

Ocean acidification induces tissue-specific interactions with copper toxicity on antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818).

Toxicity of contaminants in organisms under ocean acidification (OA) has attracted increasing attention in ecotoxicological studies. This study investigated how pCO2-driven OA affected waterborne copper (Cu) toxicity in antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818). Clams were continuously exposed to Cu at ambient relevant (0/no metal exposure, 10 and 50 µg L-1) and polluted-high (100 µg L-1) concentrations in unacidified (pH 8.10) and acidified (pH 7.70/moderate OA and 7.30/extreme OA) seawater for 21 days. Following coexposure, metal bioaccumulation and responses of antioxidant defence-related biomarkers to OA and Cu coexposure were investigated. Results showed that metal bioaccumulation was positively correlated with waterborne metal concentrations but was not notably influenced by OA conditions. Both Cu and OA affected the antioxidant responses to environmental stress. Additionally, OA induced tissue-specific interactions with Cu on antioxidant defences, varying with exposure conditions. In unacidified seawater, antioxidant biomarkers were activated to defend against oxidative stress induced by Cu and prevented clams from lipid peroxidation (LPO or MDA), but failed to defend against DNA damage (8-OHdG). OA exacerbated Cu toxicity in antioxidant defences and increased LPO levels in tissues. Gills and viscera adopted adaptive antioxidant defence strategies to manage oxidative stress, with the former being more vulnerable to oxidative stress than the latter. MDA and 8-OHdG were sensitive to OA and Cu exposure, respectively, and were useful bioindicators for assessing oxidative stress. Integrated biomarker response (IBR) and PCA can reflect the integrative responses of antioxidant biomarkers to environmental stress and illuminate the contributions of specific biomarkers to antioxidant defence strategies. The findings provided insights for understanding antioxidant defences against metal toxicity in marine bivalves under OA scenarios, which is essential into managing wild populations.

Application of hybrid electrocoagulation-filtration methods in the pretreatment of marine aquaculture wastewater.

The aim of this study was to provide technical means and data support for enhancing the filtration pretreatment capacity of a recirculating aquaculture system. A continuous flow electrocoagulation (EC)-filtration system was designed and its application in the pretreatment of marine aquaculture wastewater was studied. The influences of anode combination modes, hydraulic retention times (HRTs) of the EC reactor and filter pore sizes on the water treatment capacity were investigated. Results showed that EC could significantly enhance the treatment efficiency of the filtration equipment used in subsequent steps. Al-Fe electrodes used as anode led to better processing capacity of this system, and the optimum anode was 3Al + Fe. With the increase of HRT and decrease of filter pore size, the enhanced effect of the EC process on the filter was more obvious. When the current density was 19.22 A/m2, the anode was 3Al + Fe, the HRT was 4.5 min and the filter pore size was 45 µm, the removal efficiency of the system for Vibrio, chemical oxygen demand, total ammonia nitrogen, nitrite nitrogen (NO2--N), nitrate nitrogen (NO3--N) and total nitrogen was 69.55 ± 0.93%, 48.99 ± 1.42%, 57.06 ± 1.28%, 34.09 ± 2.27%, 18.47 ± 1.88% and 55.26 ± 1.42%, respectively, and the energy consumption was (26.25 ± 4.95) × 10-3kWh/m3.

The biofilteration ability of oysters (Crassostrea gigas) to reduce Aeromonas salmonicida in salmon culture.

Pathogen contamination in the environment is inevitable with the rapid development of intensive aquaculture. Therefore, alternative ecofriendly biological strategies to control pathogenic bacteria are required. However, our aim was to investigate the ability of oysters (Crassostrea gigas) to filter the important opportunistic pathogen, Aeromonas salmonicida (strain C4), using a green fluorescent protein tag (GFP) in the Atlantic salmon (Salmo salar) farming wastewater. Hence, A. salmonicida removal efficiency and ingestion rate were detected in two different oyster stages (larvae and adults). To evaluate the practical performance of oysters as A. salmonicida biofilter, adult oysters were applied to an integrated constructed wetlands system (ICWS) and their long-term C4-GFP removal efficiency was recorded for 60 days. Overall, our results clearly indicated that oysters had substantial A. salmonicida removal ability via their ingestion process when observed under a fluorescent microscope. Approximately 88-95% of C4-GFP was removed by oyster larvae at an ingestion rate of 6.4 × 103-6.2 × 105 CFU/h·ind, while 79-92% of C4-GFP was removed by adult oysters at an ingestion rate of 2.1 × 104-3.1 × 106 CFU/h·ind. Furthermore, 57.9 ± 17.2% of C4-GFP removal efficiency was achieved when oysters were applied to ICWS. We, therefore, concluded that using oysters as a biofilter represents an effective alternative for removing A. salmonicida from aquaculture wastewater. However, the fate of oysters after ingesting the pathogenic bacteria, acting as a potential reservoir or vector for pathogens, is still debatable. This research provides the basis for the application of oysters as a biofilter to remove pathogens from aquaculture wastewater in industrialized production.

A feeding model of oyster larvae (Crassostrea angulata).

There is a need to develop more efficient rearing systems for the aquaculture of economically important bivalves, such as oysters. Here, we constructed a model that describes the feeding behavior of larval Crassostrea angulata oysters and tested it in an experimental setting. Larval ingestion rate is closely correlated with larval length. Based on our model, we showed that larval swimming speed, velum diameter and the filtration coefficient, which also determine the ingestion rate, are also correlated with larval length. Our model integrates morphological, locomotory and feeding behavior parameters to establish a relation between them and so provides a mathematical way to describe variation in the feeding behavior of bivalve larvae. The results of this study could facilitate the precise management of the aquaculture of bivalve larvae, in particular the optimum prey density and feeding rate of these important organisms.