Occurrence and distribution of phthalate esters in freshwater aquaculture fish ponds in Pearl River Delta, China.

The concentrations, congener profiles and spatial distribution of 13 phthalate esters (PAEs) in the freshwater fish ponds in the Pearl River Delta (PRD) region were investigated in water and sediment samples collect from 22 sites during Jul. 2016-Sept. 2017. The di-2-ethylhexyl phthalate (DEHP) was the predominant compounds in both water and sediment samples, accounting for 70.1% and 66.1% of ∑PAEs, respectively. The DEHP concentrations in the water samples collected from the sites of Zhongshan (35.7 µg/L), Jingmen (17.3 µg/L) and Nanhai (14.2 µg/L) were higher than that collected from other sampling sites (p <0.05), and exceed the Chinese environmental quality standards for surface water (DEHP, 8.00 µg/L). The concentrations of ΣPAEs (mean and median were 11.8 mg/kg dw and 7.95 mg/kg dw) in sediment was higher than that in sediment of river and estuary in the PRD region (p <0.05). The median concentrations of DEHP and di-n-butyl phthalate (DBP) exceeded recommend environmental risk limit (ERL) that posed a potential risk to the aquaculture fish pond environment in the PRD.

Food wastes as fish feeds for polyculture of low-trophic-level fish: bioaccumulation and health risk assessments of heavy metals in the cultured fish.

The major purpose of this study was to use different types of food wastes which serve as the major sources of protein to replace the fish meal used in fish feeds to produce quality fish. Two types of food waste-based feed pellets FW A (with cereals) and FW B (with cereals and meat products) and the commercial feed Jinfeng® were used to culture fingerlings of three low-trophic-level fish species: bighead carp, grass carp, and mud carp (in the ratio of 1:3:1) for 1 year period in the Sha Tau Kok Organic Farm in Hong Kong. Heavy metal concentrations in all of the fish species fed with food waste pellets and commercial pellets in Sha Tau Kok fish ponds were all below the local and international maximum permissible levels in food. Health risk assessments indicated that human consumption of the fish fed with food waste feed pellets was safe for the Hong Kong residents. The present results revealed that recycling of food waste for cultivating low-trophic-level fish (mainly herbivores and detritus feeders) is feasible, and at the same time will ease the disposal pressure of food waste, a common problem of densely populated cities like Hong Kong.

The use of food waste-based diets and Napier grass to culture grass carp: growth performance and contaminants contained in cultured fish.

The present study used commercial feeds, food waste feeds, Napier grass, and mixed feeds (food waste feed to Napier grass ratio, 1:10) to feed grass carp (Ctenopharyngodon idellus). The results indicated that grass carp fed with food waste feeds and mix feeds achieved growth performance (based on specific growth rate and feed conversion ratio) that was similar to commercial feeds (p > 0.05). Concentrations of metalloid/metals in food waste feeds and polycyclic aromatic hydrocarbons (PAHs) in Napier grass were relatively higher than other types of fish feeds (p < 0.05). However, most of the metalloid/metals and PAH levels in fish fed with four types of fish feeds were not significantly different (p > 0.05). These findings show that food waste feeds are suitable for using in the production of fish feed and Napier grass can be served as supplemental feeds for grass carp, and hence reducing the production cost.

Environmental mercury concentrations in cultured low-trophic-level fish using food waste-based diets.

In this study, different types of food wastes were used as the major source of protein to replace the fish meal in fish feeds to produce quality fish (polyculture of different freshwater fish). During October 2011-April 2012, the concentrations of Hg in water, suspended particulate matter, and sediment of the three experimental fish ponds located in Sha Tau Kok Organic Farm were monitored, and the results were similar to or lower than those detected in commercial fish ponds around the Pearl River Delta (PRD) region (by comparing data of previous and present studies). Health risk assessments indicated that human consumption of grass carp (Ctenopharyngodon idellus), a herbivore which fed food waste feed pellets would be safer than other fish species: mud carp (Cirrhina molitorella), bighead carp (Hypophthalmichthys nobilis), and largemouth bass (Lepomis macrochirus). Due to the lower species diversity and substantially shorter food chains of the polyculture system consisting of only three fish species, the extent of Hg biomagnification was significantly lower than other polyculture ponds around PRD. Furthermore, the use of food waste instead of fish meal (mainly consisted of contaminated trash fish) further reduced the mercury accumulation in the cultured fish.

[Residues and health risk assessment of sulfonamides in sediment and fish from typical marine aquaculture regions of Guangdong Province, China].

Concentrations of sulfonamides including sulfadiazine (SDZ), sulfadimidin (SM2) and sulfamethoxazole (SMX) in sediments, muscle and liver tissues of 7 kinds of fish species collected from two marine aquaculture regions along the coast of Guangdong Provice were determined by high performance liquid chromatography (HPLC) equipped with a ultraviolet detector. Assessment of the health risks were conducted based on the values of maximum residue limits (MRL) and acceptable daily intake (ADI). The results showed that sulfonamides were found in all the sediment samples. The concentrations (dry wet) ranged from 2.1 - 35.2 ng x g(-1), the detected frequency of the 3 sulfonamide antibiotics ranked as SDZ (85.7%) > SM2 (71.4%) > SMX (28.6%). The detection rate of sulfonamides in samples from Daya Bay was higher than that from Hailing Island. Higher concentrations were detected in liver tissues rather than in muscle tissues (P < 0.05). The residues of SDZ, SM2 and SMX in fish muscle tissues (wet weight) ranged from 11.6-37.9, 16.3-27.8 and 4.9-20.0 ng x g(-1), respectively. The calculated daily intakes of sulfonamides in the present study ranged from 3.37-36.72 ng x kg(-1), which accounted for 0.007% -0.073% of the ADI (50 microg x kg(-1)). Health risks to human body were negligible as the estimated intake was less than 1% ADI, therefore the security of dietary was high.

Replacing fish meal by food waste in feed pellets to culture lower trophic level fish containing acceptable levels of organochlorine pesticides: health risk assessments.

The present study used food waste (collected from local hotels and restaurants) feed pellets in polyculture of low-trophic level fish [bighead (Aristichtys nobilis), grass carp (Ctenopharyngodon idellus), and mud carp (Cirrhina molitorella)] aiming at producing safe and quality products for local consumption. The results indicated that grass carp (hexachlorocyclohexanes (HCHs) <0.03; dichlorodiphenyltrichloroethanes (DDTs) 1.42-3.34 ng/g ww) and bighead carp (HCHs<0.03; DDTs 1.55-2.56 ng/g ww) fed with food waste feed pellets were relatively free of organochlorine pesticides (OCPs). The experimental ponds (water and sediment) were relatively free of OCPs, lowering the possibility of biomagnification of OCPs in the food chains within the ponds. The raw concentrations of OCPs extracted from the fish were not in the bioavailable form, which would ultimately reach bloodstream and exert adverse effects on human body. Health risk assessments based on digestible concentrations are commonly regarded as a more accurate method. The results of health risk assessments based on raw and digestible concentrations showed that the fish fed with food waste feed pellets were safe for consumption from the OCP perspective.

[Preliminary studies on the occurrence of antibiotic resistance genes in typical aquaculture area of the Pearl River Estuary].

Traditional and quantitative PCR techniques were used to determine the occurrence and quantities of ARGs, including three types of genes resistant to sulfonamide, seven for tetracycline resistance and one for quinolone resistance, as well as one integron gene in typical aquaculture of the Pearl River Estuary. The results showed that all genes except for tetW were detectable in the aquaculture environment, and sull, sul2 and int1 were the most frequently detected genes (detectable percentage, 100% ). Relative abundances of ARGs increased with the prolongation of rearing time under the same aquaculture pattern, suggesting a cumulative effect. Moreover, the occurrences of ARGs in the ponds were different with different aquaculture patterns, indicating that the aquaculture pattern might play an important role in the abundances and distributions of ARGs. Relative abundances of intl, as a horizontal mobile genetic element, were significantly correlated to the levels of sull and the total ARGs (P < 0. 05). The total concentration of antibiotics exhibited a good positive correlation with the total concentration of ARGs in sediments (P <0. 05). All results elucidated that extensive residues of antibiotics in the aquaculture substantially increased the abundances of ARGs probably owning to the induction of horizontal gene transfer of ARGs among bacteria.

Toxic effects of triclosan on the detoxification system and breeding of Daphnia magna.

The toxic effects of different concentrations of Triclosan (TCS) (1-128 µg/L) on Daphnia magna (D. magna) were investigated by acute (48 h) and chronic (21-day) toxicity tests. The response of antioxidase system and Phase I metabolism process of D. magna exposed to TCS were investigated by measuring a series of biomarkers including glutathione S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), 7-ethoxyresorufin O-deethylase (EROD), Erythromycin N-demethylase (ERND) and Aminopyrine N-demethylase (APND). The 48 h LC50 of TCS was 330 µg/L for D. magna. In the chronic test, total number of neonates per female, body length and the intrinsic rate of natural increase (r) of D. magna increased at the low exposure concentrations (1-16 µg/L) and decreased at the high concentrations (64-128 µg/L), while the total number of molting per adult decreased continually. The GST and CAT activities showed no significant increase in all treatments, and SOD activities were induced after 24-h exposure and inhibited after 48-h exposure at 4-128 µg/L of concentrations. The MDA content increased after 6-h exposure but decreased after 48-h exposure at 4-128 µg/L. EROD activities initially increased after 6-h exposure, but decreased after 24 and 48-h exposure, ERND and APND activities showed a similar temporal pattern among different treatments groups. SOD, MDA and APND were sensitive to TCS, thus they are suitable as potential biomarkers for the exposure to TCS.

Risk assessments of human exposure to bioaccessible phthalate esters through market fish consumption.

The bioaccessibility of phthalate esters in 20 fish species collected from Hong Kong market was evaluated using an in vitro gastrointestinal model. The ∑phthalate ester concentration detected in fresh water fish ranged from 1.66 to 3.14µg/g wet weight (ww) and in marine fish ranged from 1.57 to 7.10µg/g ww, respectively. di-2-Ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP) were the predominant compounds in both freshwater fish and marine fish. The digestible concentrations of phthalate esters ranged from 0.20 to 1.23µg/g ww (mean 0.35µg/g ww), and account for 2.44 to 45.5% (mean 16.8%) for raw concentrations of phthalate esters. In the present study, the accumulation ratio Rnn value of all phthalate esters was greater than 1 except for diisobutyl phthalate (DIBP), DBP and di-n-hexyl phthalate (DHP), suggesting that these phthalate esters could be accumulated during gastrointestinal digestion. Based on this health risk assessment, most of fish species were considered safe for consumption, however Hong Kong residents should take caution when consuming Mud carp and Bighead carp.

Toxic effects of erythromycin, ciprofloxacin and sulfamethoxazole exposure to the antioxidant system in Pseudokirchneriella subcapitata.

We tested antioxidant responses of the green microalga Pseudokirchneriella subcapitata exposed to different concentrations of the three antibiotics erythromycin (ETM), ciprofloxacin (CPF) and sulfamethoxazole (SMZ). Measurements included the level of lipid peroxidation, the total antioxidative capacity and three major antioxidant mechanisms: the ascorbate-glutathione cycle, the xanthophyll cycle and the enzyme activities of catalase (CAT), superoxide dismutase (SOD), guaiacol glutathione peroxidase (GPX) and glutathione-S-transferase (GST). Three antibiotics significantly affect the antioxidant system of P. subcapitata, but in different ways the alga was more tolerant to CPF and SMZ exposures than to ETM exposure. ETM caused reductions in AsA and GSH biosynthesis, ascorbate-glutathione cycle, xanthophylls cycle and antioxidant enzyme activities. The toxicity of CPF seems to be mainly overcome via induction of the ascorbate-glutathione cycle and CAT, SOD and GPX activities, while the toxicity of SMZ on the photosynthetic apparatus is predominantly reduced by the xanthophyll cycle and GST activity.

Trophic relationships and health risk assessments of trace metals in the aquaculture pond ecosystem of Pearl River Delta, China.

Cadmium, lead, zinc, Chromium, copper, nickel and manganese in sediments and in aquatic organisms were collected from the aquaculture pond ecosystem of the Pearl River Delta (PRD), China and analyzed to evaluate bioaccumulation and trophic transfer in food chains, as well as the potential health risk of exposure to the Hong Kong residents via dietary intake of these aquatic products. The results revealed that based on the biota-sediment accumulation factor, omnivorous fish and zooplankton accumulated more trace metals from sediment than carnivorous fish. Concentrations of seven trace metals in aquaculture pond of PRD significantly decreased with increasing trophic levels, showing that these trace metals were trophically diluted in predatory and omnivorous food chains. The hazard index values of all fish species were smaller than 1 for adults and children, indicating there was no health risk from the multiple metals via ingestion of the freshwater fish for the inhabitants.

Arsenic contamination in the freshwater fish ponds of Pearl River Delta: bioaccumulation and health risk assessment.

This study investigated the extent of arsenic (As) contamination in five common species of freshwater fish (northern snakehead [Channa argus], mandrarin fish [Siniperca chuatsi], largemouth bass [Lepomis macrochirous], bighead carp [Aristichthys nobilis] and grass carp [Ctenopharyngodon idellus]) and their associated fish pond sediments collected from 18 freshwater fish ponds around the Pearl River Delta (PRD). The total As concentrations detected in fish muscle and sediment in freshwater ponds around the PRD were 0.05-3.01 mg kg(-1) wet weight (w. wt) and 8.41-22.76 mg kg(-1) dry weight (d. wt), respectively. In addition, the As content was positively correlated (p < 0.05) to total organic carbon (TOC) contents in sediments. Biota sediment accumulation factor (BSAF) showed that omnivorous fish and zooplankton accumulated higher concentrations of heavy metals from the sediment than carnivorous fish. In addition, feeding habits of fish also influence As accumulation in different fish species. In this study, two typical food chains of the aquaculture ponds were selected for investigation: (1) omnivorous food chain (zooplankton, grass carp and bighead carp) and (2) predatory food chain (zooplankton, mud carp and mandarin fish). Significant linear relationships were obtained between log As and δ (15)N. The slope of the regression (-0.066 and -0.078) of the log transformed As concentrations and δ (15)N values, as biomagnifications power, indicated there was no magnification or diminution of As from lower trophic levels (zooplankton) to fish in the aquaculture ponds. Consumption of largemouth bass, northern snakehead and bighead carp might impose health risks of Hong Kong residents consuming these fish to the local population, due to the fact that its cancer risk (CR) value exceeded the upper limit of the acceptable risk levels (10(-4)) stipulated by the USEPA.

Physiological responses of three marine microalgae exposed to cypermethrin.

The effects of cypermethrin on physiological responses of three typical marine microalgal species Skeletonema costatum (Bacillariophyceae), Scrippsiella trochoidea (Dinophyceae), and Chattonella marina (Raphidophyceae), were investigated by 96-h growth tests in a batch-culture system. The 96-h median inhibition concentrations (IC(50)) were 71.4, 205, and 191 µg L(-1) for S. costatum, S. trochoidea, and C. marina, respectively. Quick and significant physiological responses occurred when algal cells were exposed to cypermethrin, and all biochemical parameters varied significantly within 6- or 12-h exposure. Cypermethrin affected algal growth, protein content, and superoxide dismutase (SOD) activity by stimulation at low concentrations (1, 5 µg L(-1)) and inhibition at high concentrations (>50 µg L(-1)). A general increase in malondialdehyde (MDA) level was observed in all test groups, which suggested that the toxic effects of cypermethrin were probably exerted through free radical generation. These results suggest that the activation of SOD and promotion of protein at early exposure are important to counteract the oxidative stress induced by cypermethrin, and the inactivation of SOD may be crucial to the growth inhibition of microalgae by cypermethrin.

Source and profile of paralytic shellfish poisoning toxins in shellfish in Daya Bay, South China Sea.

Changes in cell density and cyst flux of Alexandrium tamarense, paralytic shellfish poisoning (PSP) toxin contents in shellfishes, and environmental parameters were measured in two stations in Daya Bay, South China Sea from March 2005 to July 2006. Vegetative cells of A. tamarense occurred sporadically; however, they presented abundantly during the winter months. Meanwhile, cyst flux reached its maximum level just following the peak abundance of motile cells. The PSP contents in shellfish were generally low, but higher in winter with the maximum of 14,015 µg STX equiv./kg. The majority of toxins were found in digestive glands, with a maximum of 66,227 µg STX equiv./kg. There were significant positive relationships between toxin level and vegetative cell density and cyst flux. This indicates that vegetative cells and cysts of Alexandrium significantly influenced PSP level, and could be an important source of PSP toxins in shellfish during winter.

Toxicological effects of cypermethrin to marine phytoplankton in a co-culture system under laboratory conditions.

The growth of three marine phytoplankton species Skeletonema costatum, Scrippsiella trochoidea and Chattonella marina and the response of the antioxidant defense system have been investigated on exposure to commercial cypermethrin for 96 h and 32 days in a co-culture system. Growth of the three species was generally comparable over 96 h with an inoculation of 1:3:6.5 (C. marina:S. trochoidea:S. costatum), with stimulation at 5 µg l(-1) and inhibition under higher concentrations (50, 100 µg l(-1)). However, when inoculating at ratios of 1:1:1 during a 32 day test, S. costatum became the most sensitive species and was significantly inhibited in all test groups under the dual stresses of cypermethrin and interspecies competition. The growth of C. marina was significantly inhibited at the concentrations higher than 5 µg l(-1), while the growth of S. trochoidea was significantly promoted at low concentrations. Superoxide dismutase (SOD) activities significantly increased during 6-12 h exposure periods in test treatments at low concentrations, and enhanced in the control as well due to interspecies competition. The lipid peroxidation product malondialdehyde was enhanced at high concentrations, but did not increase in control and low concentration cultures with high SOD activities, indicating that algal cells activated the antioxidant enzymes promptly to protect the cells from lipid membrane damage. Results from this study suggested that cypermethrin pollution in maricultural sea waters might lead to a shift in phytoplankton community structure from diatom to harmful dinoflagellate species, and thus potentially stimulatory for harmful algal blooms.

Toxic effects of erythromycin, ciprofloxacin and sulfamethoxazole on photosynthetic apparatus in Selenastrum capricornutum.

The effects of three antibiotics (erythromycin, ciprofloxacin and sulfamethoxazole) on photosynthesis process of Selenastrum capricornutum were investigated by determining a battery of parameters including photosynthetic rate, chlorophyll fluorescence, Hill reaction, and ribulose-1.5-bisphosphate carboxylase activity, etc. The results indicated that three antibiotics could significantly inhibit the physiological progress including primary photochemistry, electron transport, photophosphorylation and carbon assimilation. Erythromycin could induce acute toxic effects at the concentration of 0.06 mg L(-1), while the same results were exhibited for ciprofloxacin and sulfamethoxazole at higher than 1.0 mg L(-1). Erythromycin was considerably more toxic than ciprofloxacin and sulfamethoxazole and may pose a higher potential risk to the aquatic ecosystem. Some indices like chlorophyll fluorescence, Mg(2+)-ATPase activity and RuBPCase activity showed a high specificity and sensitivity to the exposure of erythromycin, and may be potentially used as candidate biomarkers for the exposure of the macrolide antibiotics.

Mercury biomagnification in the aquaculture pond ecosystem in the Pearl River Delta.

This is the first study to investigate the rate of mercury (Hg) biomagnification in the aquaculture pond ecosystem of the Pearl River Delta (PRD), China, by analyzing total mercury (THg) and methyl mercury (MeHg) concentrations in various species of fish at different trophic levels (TLs). Species representing a gradient of trophic positions in the aquaculture pond food chains were chosen for analyzing THg and MeHg concentrations. In this study, there were two kinds of the aquaculture pond food chains: (1) omnivorous (fish feeds, zooplankton, grass carp [Ctenopharyngodon idellus], and bighead carp [Aristichthys nobilis]) and (2) predatory (zooplankton, mud carp [Cirrhina molitorella], and mandarin fish [Siniperca kneri]). Bighead carp and mandarin fish had the highest MeHg and THg concentrations, i.e., an order of magnitude higher than other species, in their respective food chains. More than 90% of the THg concentrations detected in bighead carp, mandarin fish, and mud carp were in the methylated form. In this study, %MeHg increased with TLs and MeHg concentrations, reflecting that MeHg is the dominant chemical species of Hg accumulated in higher concentrations in biota, especially biota associated with higher TLs in the food chains. The trophic magnification factors were 2.32 and 2.60 for MeHg and 1.94 and 2.03 for THg in omnivorous and predatory food chains, respectively, in PRD. Hg concentrations in fish tissue correlated to Hg levels in the ambient environment, and sediment seemed to be the major source for Hg accumulated in fish. In addition, feeding habit also affected Hg accumulation in different fish species. Four significant linear relationships were obtained between log-THg and δ(15)N and between log-MeHg and δ(15)N. The slope of the regression equations, as biomagnification power, was smaller in magnitude compared with those reported for temperate and arctic marine and freshwater ecosystems, indicating that THg and MeHg biomagnifications were lower in this PRD subtropical aquaculture pond ecosystem. This was probably due to low Hg bioavailability at lower TLs as well as individual feeding behavior of fish.

[Investigation of quinolones in aquaculture environment of the Pearl River Delta].

The concentrations and distributions of three sorts of quinolones (norfloxacin, ciprofloxacin and enorfloxacin) in water, sediments and the tissues of 8 kinds of fishes from 7 sites in Pearl River Delta aquaculture regions (freshwater and marine) were determined by high performance liquid chromatography (HPLC) with fluorescence detector. Results showed that no quinolones were found in either fresh waterborne or marine water. Norfloxacin, ciprofloxacin and enorfloxacin in sediments collected from freshwater aquaculture region ranged from 5.03-13.28, 3.64-9.32 and 0-7.13 ng x g(-1), respectively, ranged from 1.88-8.81, 0-1.09 ng x g(-1) in marine aquaculture area, respectively. Enorfloxacin were not found in sediments from marine aquaculture. Three kinds of quinolones in liver tissues were higher than that in muscle tissues. The residues of norfloxacin, ciprofloxacin and enorfloxacin in fish muscle tissues ranged from 1.95-100.54, 0.48-33.26 and 1.18-51.89 ng x g(-1), respectively. The concentration of pharmaceuticals in fish tissues were ranked by size as following: norfloxacin, ciprofloxacin and enofloxacin. Higher concentration of quinolones was found in fish from freshwater aquaculture than marine aquaculture.