Seasonal changes in imposex and tissue burden of butyltin compounds in Thais clavigera populations along the coastal area of Mirs Bay, China

We assessed the current status of tributyltin (TBT) contamination of Thais clavigera (Gastropoda) along the coastal area of Mirs Bay, China for the first time. The snail samples were collected from 10 different sites in the summer (June) and winter (December) of 2006, respectively. They were analyzed for imposex status, i.e. relative penis size index (RPSI) and vas deferens sequence index (VDSI), followed by quantification of butyltins in their tissues. Most of the collected females suffered from imposex, but the level of butyltin contamination varied with the distance from Yantian Port, which is currently the fourth busiest container port in the world. The tissue concentration of TBT varied with season. For a particular site, the winter samples in general contained much higher concentration of TBT than the summer samples. RPSI, VDSI and organotin concentrations were higher in T. clavigera collected from sites closer to the Port, such as the Seafood Street and Kat O. Both RPSI and VDSI were positively correlated with the tissue burden of tributyltin. VDSI exhibited little seasonal variability, whereas RPSI showed marked seasonal variability, with lower values in the summer samples. The current results will serve as an important reference for long-term monitoring of butyltin contamination in this area.     

香港东北部托罗港湾水环境评价

Uncontrolled discharges of municipal sewage, agricultural wastes and industrial effluents in the past decades have upset the ecosystems, caused frequent occurrences of red tides, and resulted in a loss of inland and coastal amenity values of the land-locked embayment of Tolo Harbour and the related river systems. This paper provides a review of the established relevant legislations and sewage management facilities for environmental conservation, and the current status of water environment in the Tolo Harbour Water Control Zone.     

Ciliate communities in a constructed mangrove wetland for wastewater treatment

In wetlands constructed for treating municipal and industrial wastewater, including mangroves, the effect of wastewater discharged on the substrate has often been neglected. Ciliates, an important group of protozoa, are sensitive to pollutants and any changes in ciliate diversity and community structure reflects the habitat quality. The ciliate communities at six sections along a constructed mangrove belt (33 m in length) planted with Aegicerascorniculatum were investigated in Shenzhen, South China. In all samples collected in both rainy and dry seasons, 183 ciliate species were observed. Most species (56%) were free-swimming forms, while only 10.8% were sessile ciliates. The abundance and species number of ciliates were both found to decrease from the anterior (the wastewater inlet) to the posterior (the outlet) parts of the wetland belt, indicating that organic matter and bacteria in wastewater, which served as food for most ciliates, were gradually removed by the constructed wetland. The r/K (number of r- and K-selected species) ratios at the six sections were relatively small, between 0.2 and 0.4, whereas the C/P (abundance of colpodids and polyhymenophorans) quotient at some sections was higher than 1. These results indicate that although most of the environments along the constructed wetland belt were not stressful for ciliate communities, there were habitats that favored colpodids in high abundances.     

Hydrodynamic response of a pneumatic floating platform

This paper describes a numerical approach to model the dynamic response of a pneumatic floating platform, and the laboratory experiments and parametric study to verify the numerical results. The pneumatic platform is composed of an array of open-bottom vertical cylinders trapping pressurized air that displaces the water. The cylinder diameter is assumed to be small compared to the wavelength and the water inside each cylinder oscillates as a piston. These assumptions simplify the mathematical formulation in that the bottom of the platform can be treated as a continuous surface on which the source distribution method can be applied. In the laboratory experiments, the compressibility and displacement of the trapped air are modeled by a spring and float assembly. The comparison between the numerical and experimental results indicates favorable agreement. The oscillation of the water columns and the overall dynamic characteristics of the platform are illustrated and discussed in the parametric study.     

Effects of heavy metals on oxygen consumption and ammonia excretion in green-lipped mussels (Perna viridis)

Physiological responses (oxygen consumption and ammonia excretion) of the green-lipped mussel (Perna viridis) exposed to four concentrations of Cd (0.15, 0.32, 0.70 and 1.50 ppm) and four concentrations of Zn (0.60, 1.29, 2.79 and 6.00 ppm) were monitored for 21 days. Changes occurred in the ammonia excretion rates and O:N ratios with individual mussels experiencing different metal concentrations over time. Oxygen consumption rate decreased significantly with time for Cd-exposed individuals and also decreased significantly with the interaction between the concentration of Zn and time for Zn-exposed individuals. Although low O:N ratios (<30) were obtained in most of the treatments, no predictable correlation was found between concentrations of metals and values of O:N obtained. The value of using O:N ratio as a stress index is questioned.     

Size effects of suspended particles on gill damage in green-lipped mussel Perna viridis

The green-lipped mussels Perna viridis were exposed to <500 μm suspended solids (SS) with concentrations of 0 (control), 250, 500, 750 and 1000 mg/L for 14 days, followed by transferring to clean, filtered seawater for 28 days. Results of scanning microscopy showed significantly higher damages to the cilia on the frontal surface of the gill filaments than that on the abfrontal surface in both demibranchs. Percent ciliary depletion varied with SS concentrations and time. No sign of recovery of the gill filaments was observed after the mussels were transferred to clean seawater. In a second experiment, mussels were exposed to SS with size range from <63, >125–<250 and >250–<500 μm at 600 mg/L, together with a control (0 mg/L) for 14 days, followed by transferring to clean, filtered seawater for 28 days. Results of scanning microscopy showed significant ciliary damages in both the ascending and descending lamellae under the three particle size groups as compared with the control. Percent depletion of frontal cilia was most serious for the >250–<500 μm size group and least for the <63 μm size group. However, percent depletion of abfrontal cilia was most serious for the >125–<250 μm size group and least for the <63 μm size group. No recovery of ciliary damages was observed. The effects of particle size of suspended sediments on the morphological damages of gill filaments in the green-lipped mussels were discussed.