Jinhu Liu

Accumulation and oxidative stress biomarkers in Japanese flounder larvae and juveniles under chronic cadmium exposure.

This study investigated how Cd exposure affected oxidative biomarkers in Japanese flounder, Paralichthys olivaceus, at early life stages (ELS). Fish were exposed to waterborne Cd (0-48microg L(-1)) from embryonic to juvenile stages for 80days. Growth, Cd accumulation, activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), glutathione S-transferase (GST, EC 2.5.1.18), and levels of glutathione (GSH) and lipid peroxidation (LPO) were investigated at three developmental stages. Flounder growth decreased and Cd accumulation increased with increasing Cd concentration. In metamorphosing larvae, CAT and SOD activities were inhibited and GSH level was elevated, while LPO was enhanced by increasing Cd concentrations. CAT and GST activities of settling larvae were inhibited but GSH level was elevated at high Cd concentrations. In juveniles, SOD activity and LPO level were increased but GST activity was inhibited as Cd concentration increased. Antioxidants in flounder at ELS were able to develop ductile responses to defend against oxidative stress, but LPO fatally occurred due to Cd exposure. These biochemical parameters could be used as effective oxidative biomarkers for evaluating Cd contamination and toxicity in marine environments: CAT, SOD, GSH, and LPO for metamorphosing stage; CAT, GSH, and GST for settling stage; and SOD, GST, and LPO for juvenile stage.

Distribution and speciation of mercury in surficial sediments from main mangrove wetlands in China

The purpose of this study was to establish the distribution, speciation and bioavailability of mercury in mangrove sediments. A systemic survey of surficial sediments from 13 mangrove wetlands of China was carried out. Hg concentrations ranged from 2.3-903.6ngg(-1), with an average value of 189.4ngg(-1). Of the 13 areas surveyed, the Hg content in sediments was similar to background levels in 6 areas but was much higher in the other seven areas. Hg levels were affected by natural and anthropogenic factors, including terrestrial pollutants, geomorphic properties, and indirectly by economic status. Hg levels were positively correlated with organic matter, pH, and silt and clay fractions, but Hg was negatively correlated with sand fraction. In most mangrove wetlands, Hg existed primarily in the form of volatile Hg. Hg is easily bioaccumulated in mangrove wetlands and may be the natural source of Hg emissions to the atmosphere.

Short-term mercury exposure affecting the development and antioxidant biomarkers of Japanese flounder embryos and larvae.

This study investigated the acute and sub-lethal toxicities of waterborne mercuric chloride to Japanese flounder (Paralichthys olivaceus) embryos and larvae. Acute toxicity tests indicated that the 48-h LC(50) values of mercury to the embryos and larvae were 48.1 (32.8-63.6) and 99.4 (72.9-147.0) μg L(-1), respectively. Mercury could cause low hatching success, delayed hatching process, reduced growth at concentrations ≥20 μg L(-1), and induce reduced survival and higher morphological malformations at concentrations ≥40 μg L(-1) in the embryos and larvae. In sub-lethal toxicity test, superoxide dismutase (SOD) and catalase (CAT) activities, reduced glutathione (GSH) and malondialdehyde (MDA) contents of the larvae were significantly increased, while glutathione-S-transferase (GST) was decreased by 10 days of 0-10 μg Hg(2+)L(-1) exposure. These findings suggested that the hatching, survival, growth and antioxidant biomarkers of the flounder were sensitive to the highest mercury concentrations and could thereby serve as potential biomarkers for evaluating mercury contamination in the aquatic environment.

Bioaccumulation of heavy metals and health risk assessment in three benthic bivalves along the coast of Laizhou Bay, China

This study investigated the tissue- and species-specific bioaccumulation of heavy metals (Cr, Cu, Hg, Zn, As, Cd, and Pb) in three benthic bivalves (the ark shell, Scapharca subcrenata; the surf clam, Mactra veneriformis; and the Manila clam, Ruditapes philippinarum) collected from the coast of Laizhou Bay in the Bohai Sea. The results demonstrated that the visceral masses of the bivalves tended to accumulate heavy metals more efficiently than their muscles. The capacities of the bivalves to bioaccumulate metals followed a similar order: Cd>Hg>Zn=As>Cu>Cr=Pb. The conditions of metal contamination in the bivalves tended to be worse along the eastern coast than in other regions. Overall, the Manila clam was more severely contaminated by heavy metals than the surf clam and ark shell. Judging by the hazard quotients (HQ) of the metals in the muscles of the bivalves, the greatest hazard risk to human health comes primarily from As.

Toxicity of short-term copper exposure to early life stages of red sea bream, Pagrus major.

Acute (0, 0.1, 0.2, 0.4, 0.8, 1.6 mg Cu/L) and chronic (0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12 mg Cu/L) toxicity tests of Cu with embryonic and larval red sea bream, Pagrus major, were carried out to investigate their biological responses to Cu exposure in static water at 18 +/- 1 degrees C (dissolved organic carbon, 1.8 +/- 0.65 mg C/L; hardness, 6,183 +/- 360 mg CaCO3/L; salinity, 33 +/- 1 per thousand). The 24- and 48-h LC50 (median lethal concentration) values of Cu for embryos were 0.23 and 0.15 mg/L, whereas the 48-, 72-, and 96-h LC50 values for larvae were 0.52, 0.19, and 0.13 mg/L, respectively, suggesting that embryos were more sensitive to Cu toxicity than larvae. Copper exposures at > or =0.06 mg concentrations caused low hatching success, a delay in the time to hatching of embryos, and reductions in the growth and yolk absorption of the larvae, whereas high mortality and morphological malformations occurred in the embryos and larvae at > or =0.08 mg/L concentrations. Copper concentration did not significantly affect the heart rate of the embryos, but it significantly decreased the heart rate of the newly hatched larvae when the Cu concentration was > or =0.08 mg/L, suggesting that Cu at high concentrations could induce heartbeat disturbances in red sea bream more easily at the larval stage than at the embryonic stage. Hatching success, time to hatching, growth rate, morphological abnormality, yolk absorption, and heart rate were Cu concentration-dependent and could be effective endpoints for evaluating Cu toxicity to the early life stages of red sea bream in nature.

Zinc and copper bioaccumulation in fish from Laizhou Bay, the Bohai Sea

Zinc (Zn) and copper (Cu) concentrations were determined in the tissues (muscle, stomach, liver, gills, skin, and gonads) of five commercial fish species (mullet Liza haematocheilus, flathead Platycephalus indicus, mackerel Scomberomorus niphonius, silver pomfret Pampus argenteus, and sea bass Lateolabrax japonicus) from Laizhou Bay in the Bohai Sea. Metal bioaccumulation was highest in the metabolically active tissues of the gonads and liver. Bioconcentration factors for Zn were higher in all tissues (gonads 44.35, stomach 7.73, gills 7.72, liver 5.61, skin 4.88, and muscle 1.63) than the corresponding values for Cu (gonads 3.50, stomach 3.00, gills 1.60, liver 5.43, skin 1.50, and muscle 0.93). Mackerel tissues accumulated metal to higher concentrations than did other fish species, but bioaccumulation levels were not significantly correlated with the trophic levels of the fish. Zn and Cu concentrations in the tissues were generally negatively correlated with fish length, except for a few tissues of sea bass. Risk assessment based on national and international permissible limits and provisional tolerances for weekly intake of Zn and Cu revealed that the concentrations of these two metals in muscle were relatively low and would not pose hazards to human health.

Application of otolith shape analysis for stock discrimination and species identification of five goby species (Perciformes: Gobiidae) in the northern Chinese coastal waters

We tested the use of otolith shape analysis to discriminate between species and stocks of five goby species (Ctenotrypauchen chinensis, Odontamblyopus lacepedii, Amblychaeturichthys hexanema, Chaeturichthys stigmatias, and Acanthogobius hasta) found in northern Chinese coastal waters. The five species were well differentiated with high overall classification success using shape indices (83.7%), elliptic Fourier coefficients (98.6%), or the combination of both methods (94.9%). However, shape analysis alone was only moderately successful at discriminating among the four stocks (Liaodong Bay, LD; Bohai Bay, BH; Huanghe (Yellow) River estuary HRE, and Jiaozhou Bay, JZ stocks) of A. hasta (50%–54%) and C. stigmatias (65.7%–75.8%). For these two species, shape analysis was moderately successful at discriminating the HRE or JZ stocks from other stocks, but failed to effectively identify the LD and BH stocks. A large number of otoliths were misclassified between the HRE and JZ stocks, which are geographically well separated. The classification success for stock discrimination was higher using elliptic Fourier coefficients alone (70.2%) or in combination with shape indices (75.8%) than using only shape indices (65.7%) in C. stigmatias whereas there was little difference among the three methods for A. hasta. Our results supported the common belief that otolith shape analysis is generally more effective for interspecific identification than intraspecific discrimination. Moreover, compared with shape indices analysis, Fourier analysis improves classification success during inter- and intra-species discrimination by otolith shape analysis, although this did not necessarily always occur in all fish species.

Species- and tissue-specific mercury bioaccumulation in five fish species from Laizhou Bay in the Bohai Sea of China

Mercury (Hg) concentrations in the tissues (muscle, stomach, liver, gills, skin, and gonads) of five fish species (mullet Liza ha em atocheil us, flathead fish Platycephalus indicus, sea bass Lateolabraxjaponic u s, mackerel Scomberomorus niphonius and silver pomfret Pampus argenteus) collected from Laizhou Bay in the Bohai Sea of China were investigated. The results indicate that Hg bioaccumulation in the five fish was tissue-specific, with the highest levels in the muscle and liver, followed by the stomach and gonads. The lowest levels were found in the gills and skin. Fish at higher trophic levels (flathead fish and sea bass) exhibited higher Hg concentrations than consumers at lower trophic levels. Mercury bioaccumulation tended to be positively correlated with fish length in mullet, silver pomfret, mackerel, and flathead fish, but was negatively correlated with fish length in sea bass. The Hg concentrations in the muscles of all fish species in Laizhou Bay were within the permissible limits of food safety set by national and international criteria. However, the suggesting maximum consumption of sea bass is 263 g per week for human health.

Size-dependent predation of fish larvae by jellyfish: an experimental evaluation exemplified with the flounder Paralichthys olivaceus larvae and the moon jellyfish Aurelia aurita medusae

This study evaluates the size-dependent predation of fish larvae by jellyfish, exemplified with flounder Paralichthys olivaceus and moon jellyfish Aurelia aurita under laboratory conditions. The effects of some environmental factors on the size-dependent predation were also investigated. The results indicate that the predation rate increased with larval development, until the larvae had developed the ability to actively avoid predation at approximately 11-day post-hatching and decreased thereafter. This suggests a size-dependent predation on the fish larvae. Water temperature and predator size significantly affected the predation rate of the medusae on the fish larvae, but the temperature and size effects were markedly reduced as the larvae reached post-larval stage. These findings suggest that water temperature and jellyfish size interacted with the ontogenetic development of the fish larvae to affect the predation rates. The presence of alternative prey Artemia salina, could alleviate the predation rate on the fish larvae, whereas light conditions showed no effects on the predation rate. Due to their overlaps in spatial and temporal distributions along the north Chinese coast, jellyfish are likely to prey upon flounder larvae and thus affect the recruitment of the wild fish populations.

Comparison of otolith shape descriptors and morphometrics for stock discrimination of yellow croaker along the Chinese coast

This study compared and evaluated the efficiency of two otolith shape descriptors (i.e., the elliptic Fourier transform (EFT) and discrete wavelet transform (DWT)) and morphometrics for stock discrimination. To accomplish this, sample fish from three stocks of yellow croaker Larimichthys polyactis along the Chinese coast (LDB stock from the Liaodong Bay of the Bohai Sea, JZB stock from the Jiaozhou Bay of the Yellow Sea and CJE stock from the Changjiang River estuary of the East China Sea) were used for otolith morphology analyses. The results showed that morphometrics produced an overall classification success rate of 70.8% in contrast with success rates of 80.0% or 82.0% obtained using EFT or DWT, respectively. This suggests that the two shape descriptors comparably discriminated among the stocks and performed more efficiently than morphometrics. During data adjustment and acquisition, some size variables were excluded from the subsequent discriminant analysis for stock discrimination because they were statistically “ineffective,” which could reduce the efficiency of morphometrics and lead to relatively low overall classification success. Both EFT and DWT retain the contour coefficients and thus provide a detailed description of otolith shape, which could improve discriminatory efficiency compared with morphometrics.