Zhiquan Liu

Application of macrobenthic diversity to estimate ecological health of artificial oyster reef in Yangtze Estuary, China.

In this study, several macrobenthic diversity investigations were performed in Yangtze Estuary Oyster Reef, the largest artificial oyster reef in China, from 2012 to 2014. The sampling sites of the south branch showed considerably higher diversity than those of the north branch. The richness measures exhibited a significant increasing trend from low- to high-salinity zone; however, the evenness measures were typically high in the middle-salinity zone. During the past decade, the results were combined with historical data to detect the changes in macrobenthos. The variation in substrate organisms and macrobenthic diversity followed a steady trend after a major fluctuation. Redundancy analysis indicated that the water salinity and substrate factors were the main indicators that influence macrobenthic distribution. All sampling sites in the south branch were protected by a nature reserve. However, the N2 and N6 sites in the north branch were subjected to severe and mild human interventions, respectively.

Loss and self-restoration of macrobenthic diversity in reclamation habitats of estuarine islands in Yangtze Estuary, China

In this study, macrobenthic diversity data were collected from intertidal habitats of island wetlands in Yangtze Estuary before and after reclamation. Three survey regions based on habitat features were investigated: protected region, normal region, and self-restored region. The pattern of diversity variation showed a sharp decrease in reclamation sites and an obvious increase in vegetated sites of the self-restored region before and after reclamation. A declining trend in habitat health was observed in reclamation sites, but the degree of perturbation was relatively weaker in protected region than in normal region. The vegetated site showed a better self-restoration of biodiversity than the bald site. These results suggest that reclamation may have a negative influence on biodiversity and habitat health status in the intertidal wetland. Also, there is a possibility of self-restoration in tidal flats disturbed by reclamation and the resistance effect in nature reserve may reduce the disturbances resulting from reclamation.

Accumulation of polystyrene microplastics in juvenile Eriocheir sinensis and oxidative stress effects in the liver

As a widespread and ubiquitous pollutant of marine ecosystems, microplastic has the potential to become an emerging global threat for aquatic organisms. The present study aims to elucidate the effects of microplastics on the growth, accumulation and oxidative stress response in the liver of Eriocheir sinensis. Fluorescent microplastic particles (diameter = 0.5 μm) accumulated in the gill, liver and gut tissues of E. sinensis were investigated when crabs were exposed to a concentration of 40000 μg/L for 7 days. A 21 day toxicity test suggested that the rate of weight gain, specific growth rate, and hepatosomatic index of E. sinensis decreased with increasing microplastic concentration (0 μg/L, 40 μg/L, 400 μg/L, 4000 μg/L and 40000 μg/L). The activities of AChE and GPT in crabs exposed to microplastics were lower than those in control group. GOT activity increased significantly after exposure to a low concentration of microplastics and then decreased continuously with increasing microplastic concentrations. The activities of superoxide dismutase (SOD), aspartate transaminase (GOT), glutathione (GSH), and glutathione peroxidase (GPx) increased in specimens exposed to low concentrations of microplastics (40 and 400 μg/L) compared to the control and decreased in organisms exposed to high concentrations (4000 and 40000 μg/L). In contrast, the activities of acetylcholinesterase, catalase (CAT), and alanine aminotransferase were significantly lower in the organisms exposed to microplastics compared to control animals. Upon exposure to increasing microplastic concentrations, the expression of genes encoding the antioxidants SOD, CAT, GPx and glutathione S-transferase in the liver decreased after first increasing. Exposure to microplastics increased the expression of the gene encoding p38 in the MAPK signaling pathway and significantly decreased the expressions of genes encoding ERK, AKT, and MEK. The results of this study demonstrate that microplastics can accumulate in the tissues of E. sinensis and negatively affect growth. In addition, exposure to microplastics causes damage and induces oxidative stress in the hepatopancreas of E. sinensis. The findings provide basic biological data for environmental and human risk assessments of microplastics of high concern.

Effects of cadmium on lipid metabolism in female estuarine crab, Chiromantes dehaani

Due to the nature of their habitat, which contains a high level of pollutants, estuarine crabs are at great risk of exposure to contaminants such as cadmium. Thus, in this study, the effects of cadmium on lipid metabolism were investigated in estuarine crab Chiromantes dehaani. Adult female estuarine crabs were randomly exposed to 0.05, 0.1, 0.5, and 1mg/L of CdCl2 for 7, 14 and 21days, after which the lipid contents of the hepatopancreas and ovary were measured. Also, the substance contents and the activities of the enzyme in lipid digestion, lipid synthesis and lipid transport metabolism were analyzed. The results showed that the lipid contents in the hepatopancreas and ovary of the exposed crabs decreased after prolonged exposure to cadmium compared to the control. The lipase activity decreased while the activities of fatty acid synthase and acetyl coenzyme A in the hepatopancreas increased on day 7 but decreased on days 14 and 21. Moreover, the change in non-esterified fatty acid level was similar to fatty acid synthase. The level of low-density lipoprotein increased in the exposed crabs compared to the control group while the level of high-density lipoprotein and the activity of lipoprotein lipase decreased at a higher concentration of cadmium and longer exposure time. These observations suggest that cadmium decreases the lipid content by weakening the ability of digestion, transportation and synthase of lipid, thus affecting hepatopancreas and ovary indices.

Cloning, expression and localization of the Daphnia carinata transformer gene DcarTra during different reproductive stages

In this study, the full-length cDNA of the Transformer (Tra) gene from the common freshwater species Daphnia carinata (DcarTra; GenBank accession no. KJ735445) was cloned using primers based on homologous sequences and rapid amplification of cDNA ends (RACE). The relative expression and localization of DcarTra and the cellular abundance of the DcarTra protein during different sexual phases were subsequently investigated. The full-length DcarTra cDNA was 1620 bp with an ORF of 1143 bp encoding a 380 amino acid polypeptide. Phylogenetic analysis identified closely related genes in Daphnia magna and Daphnia pulex, and more distantly related genes in other insects. Quantitative PCR showed that DcarTra expression was highest in males, followed by sexual females, and lowest in parthenogenetic females. Whole-mount in situ hybridization showed that DcarTra was mainly expressed in the thoracic limbs, ovaries and rectum in parthenogenetic females, and in the joints of second antennae, ovaries, rectum and ventral processes in sexual females. Western blotting showed two differently phosphorylated forms of the Tra protein. When Tra is phosphorylated, DcarTra protein levels were much higher in males than in two females. Otherwise, when Tra is dephosphorylated, the highest Tra protein levels were in sexual females, which revealed that D. carinata can control the sexual transition via these two forms. Together these results suggest that DcarTra plays significant roles in the reproductive transformation of D. carinata and dephosphorylation of DcarTra may be the trigger for females to transform into males.

Different effects of reclamation methods on macrobenthos community structure in the Yangtze Estuary, China

The effects of enclosed, semi-closed, and opened reclamation methods on the macrobenthos community structure were investigated. Compared with their paired controls, water salinity decreased sharply in the enclosed reclamation region with no apparent change in the opened reclamation region. Declining species and biodiversity was observed in the reclamation regions, but the extent of this declining trend was weaker in the semi-closed and opened reclamations than in the enclosed reclamation region. The ABC curve indicated that the enclosed reclamation was disturbed, whereas the semi-closed and opened reclamations were undisturbed. Taken together, these results suggest that reclamation may have a negative effect on the community and health status of macrobenthos in the intertidal wetlands of the Yangtze Estuary. Semi-closed and opened reclamation methods may mitigate the problem of a salinity decrease caused by enclosed reclamation, while also having a relatively weaker negative effect on community structure and wetland habitat.

Age-dependent survival, stress defense, and AMPK in Daphnia pulex after short-term exposure to a polystyrene nanoplastic

The widespread occurrence and accumulation of micro- and nanoplastics in aquatic environments has become a growing global concern. Generally, natural aquatic populations are characterized by a variety of multi-structured age groups, for which physiological and biochemical responses typically differ. The freshwater cladoceran, Daphnia pulex, is a model species used extensively in environmental monitoring studies and ecotoxicology testing. Here, the effects of a polystyrene nanoplastic on the physiological changes (i.e., survival) and expression levels of stress defense genes (i.e., those encoding antioxidant-mediated and heat shock proteins) in this freshwater flea were measured. Results from acute bioassays were used to determine the respective nanoplastic LC50 values for five age groups (1-, 4-, 7-, 14- and 21-day-old individuals): the obtained values for the 1- and 21-day-old D. pulex groups were similar (i.e., not significantly different). The expression levels of genes encoding key stress defense enzymes and proteins-SOD, CAT, GST, GPx, HSP70, and HSP90-were influenced by the nanoplastic in all the age groups, but not in the same way for each. Significant differences were observed among all age groups in their expression of the gene encoding the energy-sensing enzyme AMPK (adenosine monophosphate-activated protein kinase) α, β, and γ following exposure to the nanoplastic. Moreover, the expression of AMPK α was significantly increased in the 1-, 7-, and 21-day-old individuals exposed to nanoplastic relative to the control group. Together, these results indicate that age in D. pulex affects the sensitivity of its individuals to pollution from this nanoplastic, primarily via alterations to vital physiological and biochemical processes, such as cellular energy homeostasis and oxidation, which were demonstrated in vivo. We speculate that such age-related effects may extend to other nanoplastics and forms of pollution in D. pulex and perhaps similar marine organisms.

Macrobenthic community characteristics and ecological health of a constructed intertidal oyster reef in the Yangtze Estuary, China

Development of substrate organisms (oysters, barnacles) and the health of a monitored oyster reef were investigated in the Yangtze Estuary. Very low salinity suppressed oyster survival. Nevertheless, middle- to high-salinity significantly increased the abundance and biomass of substrate organisms, and macrobenthos species and diversity. Long-term variation in substrate organisms was steady after a major fluctuation, yet the macrobenthic community structure lagged behind that of oysters. Overall, the oyster reef was in a healthy state. The M-AMBI results showed that its ecological status under high-salinity was better than medium-salinity conditions. Redundancy analysis indicated these results were associated with changes in water salinity and substrate factors. Taken together, our results suggest this constructed intertidal oyster reef has had a positive effect on the community and health status of macrobenthos in the Yangtze Estuary. Further, these ecological benefits increased going from medium- to high-salinity waters, but were generally absent under low salinity.