Heavy metals in riverine/estuarine sediments from an aquaculture wetland in metropolitan areas, China: Characterization, bioavailability and probabilistic ecological risk.

Aquaculture wetlands, particularly those located within urban areas, are fragile ecosystems due to urban and aquaculture impacts. However, to date, there are no reports on the combined toxicity of heavy metal mixtures in aquatic biota in sediments from aquaculture wetlands in metropolitan areas. Thus, the characterization, bioavailability, and ecological probability risk of heavy metals were studied in the riverine/estuarine sediments of the Rongjiang River in an aquaculture wetland in Chaoshan metropolis, South China. In the study area, the average total concentrations (mg/kg) were 2.38 (Cd), 113.40 (Pb), 88.27 (Cr), 148.25 (Ni), 62.08 (Cu), 125.18 (Zn), 45,636.44 (Fe), and 797.18 (Mn), with the Cd pollution being regarded as extremely serious based on the enrichment factor (EF). There are two main sources of heavy metals in the study area; Ni, Pb, Zn, Fe and Mn are mainly from domestic waste, while Cr, Cd and Cu are possibly associated with industrial production activities. The bioavailability of most heavy metals accounted for more than 20% of the total concentration. The combined toxicity of heavy metal mixtures based on probabilistic risk assessment suggests that the surface sediments of the Rongjiang River and its estuary had a 15.71% probability of toxic effects on aquatic biota.

Micro-CT and SEM investigation of sound absorption structure and chambers in the otoliths of Giant Panda fish species - Chinese Bahaba (Bahaba taipingensis).

As a critically endangered (CR) fish species, Chinese Bahaba is a unique "Giant Panda" fish species in China and has been listed among the national first-class wildlife protection animals and China's top 10 genetic resources of aquatic products since 2021. This fish species is of high commercial value because its swim bladder is commonly used in traditional Chinese medicine. Its otoliths are the sensory organs immersed in the endolymph for maintaining its balance and hearing. However, rare information has been reported on the sound absorption structure and chambers of otoliths of such "Giant Panda" fish. The big "C" groove was found in the fish's front sagittal otolith with the crystal cluster in the back sagittal otolith, the former of which is a 3D layered structure, that is constructed by elongated prismatic crystals. Besides, there are numerous small holes and adhesion material in this 3D layered structure, where many chambers were also found, indicating that some specific sounds may be captured by this structure and these chambers may then amplify such sounds at a certain wavelength. This finding could be of great importance for protecting and conserving this critically endangered species.

The complete mitochondrial genome of the tropical oyster Saccostrea echinata (Bivalvia: Ostreidae) from the South China Sea.

Saccostrea echinata is a rock perched oyster with wide distribution and tremendous potential for commercial mariculture. However, the taxonomy of this genus is confused. In this study, we described the complete mitochondrial genome of medium-sized form of Saccostrea echinata. The genome is 16,282 bp in length, encoding the standard set of 12 protein-coding genes (PCGs), 23 tRNA genes, and two rRNA genes, with circular organization. The overall base composition of the whole mitochondrial genome was A (26.78%), T (36.64%), G (21.99%), and C (14.59%) with an AT bias of 63.42%. The longest PCG of these species was ND5, whereas the shortest was ND4L.

The complete mitochondrial genome of middle-sized form of Sthenoteuthis oualaniensis (Cephalopoda: Ommastrephidae) from the South China Sea.

The purpleback flying squid (Sthenoteuthis oualaniensis) is a pelagic squid with tremendous potential for commercial exploitation. Sthenoteuthis oualaniensis comprises two forms in the South China Sea, medium-sized form and dwarf form. In this study, we described the complete mitochondrial genome of medium-sized form of S. oualaniensis. The genome is 20,309 bp in length, encoding the standard set of 13 protein-coding genes, 20 tRNA genes, and two rRNA genes, with circular organization. The overall base composition of the whole mitochondrial genome was A (35.86%), T (33.36%), G (11.63%), and C (19.15%) with an AT bias of 69.22%. The longest protein-coding gene of these species was ND5, whereas the shortest ATP8.

Diversity of marine planktonic ostracods in South China Sea: a DNA taxonomy approach.

Ostracods (Crustacea, Ostracoda) are small bivalved crustaceans, contributing over 200 described species to the marine zooplankton community. They are widely distributed and are relatively abundant components of the mesozooplankton, playing an important role in the transport of organic matter to deep layers. However, identification of ostracods based on micro-morphological characters is extremely difficult and time-consuming. Previous fragmentary taxonomic studies of ostracods in the South China Sea (SCA), were based solely on morphology. Here, by analysing the mitochondrial COI gene, we explore the taxa across the SCA using molecular tools for the first time. Our results show that sequence divergence among species varies within a large range, from 12.93% to 35.82%. Sixteen of the taxonomic units recovered by DNA taxonomy agree well with morphology, but Paraconchoecia oblonga, Conchoecia magna and Halocypris brevirostris split into two clades each, each of which contains cryptic species.

Beryllium in riverine/estuarine sediments from a typical aquaculture wetland, China: Bioavailability and probabilistic ecological risk.

Beryllium (Be) is of a significant concern because of its mutagenic and carcinogenic properties. However, reports on presences of Be in sediments from aquaculture areas still remain unknown. This study investigated the total concentration and bioavailability of Be in the surface sediments from Rongjiang River and its estuary in a large-scale aquaculture wetland in Chaoshan metropolis, South China; together with its probabilistic ecological risks posed to aquatic organisms. The total and bioavailable concentrations of Be were in the range of 5.11-8.02 and 0.23-0.33 mg/kg, respectively. Total concentration of Be mainly originated from anthropogenic source and bioavailable Be was <6% of the total concentration of Be. The probabilistic ecological risk assessment based on bioavailable concentration of Be showed that surface sediments of Rongjiang River and its estuary had a low (2.91%) probability of toxic effect to aquatic organisms.

Changes of the Macrobenthic Faunal Community with Stand Age of a Non-native Mangrove Species in Futian Mangrove National Nature Reserve, Guangdong, China.

Ya-Fang Li, Fei-Yan Du, Yang-Guang Gu, Jia-Jia Ning, and Liang-Gen Wang (2017) Sonneratia apetala, a non-native superior rapidly growing mangrove species with wide environmental tolerance, has been introduced to Futian National Nature Reserve in Shenzhen, Guangdong, China, for mangrove restoration since 1993. However, the community structure of the associated macrobenthic fauna, a vital component of energy ow and nutrient recycling, remains obscure. The present study analyzed the macrobenthic faunal community, associated habitat characteristics and physico-chemical properties of sediment in rehabilitated S. apetala forests at stand ages of 8, 9, 14, 16 and 20 years from November 2014 to May 2015. Habitat complexity and stand structural heterogeneity varied with stand age. Sediment physico-chemical properties were similar for all stands analyzed, although soil organic matter (SOM) content was significantly higher in the 20-year-old stand than in others. Shannon-Weaver (H') and Pielou's evenness (J) indices of macrobenthic fauna were highest in 14- and 16-year- old stands, respectively, and lowest in 8-year-old stands. In contrast, abundance and biomass peaked in 8-year- old stands and were lowest in 16-year-old stands. Multivariate analysis (cluster, ANOSIM and SIMPER) showed that the macrobenthic faunal community in the 20-year-old stand was different from other stand ages because of a greater abundance of small-sized mollusks and opportunistic species. Spearman correlation analysis showed that H' was positively correlated with salinity. The distance-based linear model suggested that SOM was a significant predictor variable correlated with the macrobenthic faunal community. However, SOM was the only significant predictor variable explaining 12.7% of the total variation; this implies that the spatial variation of the macrobenthic faunal community here was mostly independent of the sediment properties measured. Therefore, we conclude that habitat characteristics such as vegetation characteristics can potentially explain the majority of the variation.

Heavy metals in fish tissues/stomach contents in four marine wild commercially valuable fish species from the western continental shelf of South China Sea.

The concentrations of heavy metals (Cd, Pb, Cr, Ni, Cu and Zn) were determined in four commercially valuable fish species (Thunnus obesus, Decapterus lajang, Cubiceps squamiceps and Priacanthus macracanthus), collected in the western continental shelf of the South China Sea. Concentrations of Cd, Pb, Cr, Ni, Cu, and Zn in fish muscles were 0.006-0.050, 0.13-0.68, 0.18-0.85, 0.11-0.25, 0.12-0.77, and 2.41-4.73µg/g, wet weight, respectively. Concentrations of heavy metals in all species were below their acceptable daily upper limit, suggesting human consumption of these wild fish species may be safe, with health risk assessment based on the target hazard quotients (THQ) and total THQ, indicating no significant adverse health effects with consumption. The average concentrations of Zn were higher in gills than in stomach contents, backbones or muscle, while conversely, the other heavy metals had higher concentrations in stomach contents than in other tissues.

Fuzzy comprehensive assessment of heavy metals and Pb isotopic signature in surface sediments from a bay under serious anthropogenic influences: Daya Bay, China.

The fuzzy comprehensive assessment was undertaken to evaluate the marine sediment quality in Daya Bay, China based on the monitoring data of 2015 and China National Standard for Marine Sediment Quality (GB 18668-2002). The results demonstrated that the average metal concentrations (mg/kg) were 0.08 (Cd), 51.30 (Pb), 91.30 (Cr), 29.63 (Cu), 143.42 (Zn), 0.03 (Hg), and 7.31 (As), which were clearly higher with respect to their corresponding background values. Cr was the major pollutant based weight matrices calculated. Taken as whole, the membership degree of class I was a range from 0.65 to 1, suggesting that the marine sediment quality in Daya Bay belongs to class I. Pb stable isotopic analysis coupled with geographic information system (GIS) approach showed the sedimentary Pb mainly originated from petrochemical industry at northwest coast of Daya Bay.