Is Laguncularia racemosa more invasive than Sonneratia apetala in northern Fujian, China in terms of leaf energetic cost?

Laguncularia racemosa and Sonneratia apetala are fast-growing exotic mangrove species in Southern China and widely used for afforestation. However, the invasiveness of the two exotic species is still unclear. We compared structural and physiological traits and energy-use related traits between L. racemosa and S. apetala, and with two natives (Kandelia obovata and Aegiceras corniculatum) in northern Fujian. Results showed that leaf construction cost based on mass (CCM) and caloric values of L. racemosa were significantly lower than S. apetala, and the two natives had highest CCM. Because lower CCM, L. racemosa grew faster with a taller height (4.83 m) and wider ground diameter circumference (40.03 cm) than S. apetala (4.43 m tall and 35.63 cm wide) and the two natives (2.42 m tall and 26.78 cm wide). These findings indicated that L. racemosa could be more invasive than S. apetala in mangrove forests in northern Fujian, China where it still grew well, which deserves more attention.

Structure and function of soil microbial community in artificially planted Sonneratia apetala and S. caseolaris forests at different stand ages in Shenzhen Bay, China.

The present study examined the relationships between soil characteristics, microbial community structure and function in the forests artificially planted with exotic Sonneratia apetala at stand ages of 1-, 2-, 7-, 10- and 14-years and Sonneratia caseolaris of 1-, 4-, 7-, 10- and 14-years in Futian National Nature Reserve, Shenzhen Bay, China. The 7-years old forests of both Sonneratia species reached peak growth and had the highest content of nitrogen and phosphorus, enzymatic activities, including dehydrogenase, cellulase, phosphatase, urease and ß-glucosidase, except arylsulphatase which increased continuously with stand ages. The microbial community structure reflected by phospholipid fatty acid (PLFA) profiles also reached the maximum value in the 7-years old forests and soil bacterial PLFAs in both forests were significantly higher than fungal PLFAs. The canonical correlation analysis revealed that differences in microbial structural variables were significantly correlated to the differences in their functional variables, and the highest correlation was found between the soil enzymatic activities and the content of carbon and nitrogen.

Removal of antibiotics from wastewater by sewage treatment facilities in Hong Kong and Shenzhen, China.

Concentrations of nine antibiotics [erythromycin-H(2)O (ERY-H(2)O); trimethoprim (TMP); tetracycline (TET); norfloxacin (NOR); penicillin G (PEN G); penicillin V (PEN V); cefalexin (CLX); cefotaxim (CTX); and cefazolin (CFZ)] were measured in influent and effluent samples from four sewage treatment plants (STPs) in Hong Kong as well as in influent samples from one STP in Shenzhen. Levels of PEN V and CFZ were below method detection limits in all of the samples analyzed. CLX concentrations were the highest in most of the Hong Kong samples, ranging from 670 to 2900 ng/L and 240 to 1800 ng/L in influent and effluent samples, respectively, but CLX was not detected in the samples from Shenzhen. Comparatively lower concentrations were observed for ERY-H(2)O (470-810 ng/L) and TET (96-1300 ng/L) in the influent samples from all STPs in Hong Kong. CTX was found to be the dominant antibiotic in the Shenzhen STP influents with a mean concentration of 1100 ng/L, but occurred at lower concentrations in Hong Kong sewage. These results likely reflect regional variations in the prescription and use patterns of antibiotics between Hong Kong and Shenzhen. Antibiotic removal efficiencies depended on their chemical properties and the wastewater treatment processes used. In general, relatively higher removal efficiencies were observed for NOR (5-78%) and TET (7-73%), which are readily adsorbed to particulate matter, while lower removal efficiencies were observed for ERY-H(2)O (9-19%), which is relatively persistent in the environment. Antibiotics were removed more efficiently at Hong Kong STPs employing secondary treatment processes compared with those using primary treatment only. Concentrations of NOR measured in effluents from STPs in Hong Kong were lower than the predicted no-effect concentration of 8000 ng/L determined in a previous study. Therefore, concentrations of antibiotics measured in this preliminary study would be unlikely to cause adverse effects on microorganisms used in wastewater treatment processes at the sampled STPs.

Removal of pyrene by different microalgal species.

The efficiency of seven microalgal species, namely, Chlamydomonas sp., Chlorella miniata, Chlorella vulgaris, Scenedesmus platydiscus, Scenedesmus quadricauda, Selenastrum capricornutum, and Synechosystis sp. to remove pyrene from solution varied from species to species. According to the 6-hour, 12-hour, and 7-day exposure data, S. capricornutum was the most efficient species in the removal of pyrene, followed by S. platydiscus (a local isolate), and the least effective species was C. vulgaris. For all species, the removal was very rapid in the first 3 to 6 hours of treatment, and no significant difference was found between live and dead cells of C. miniata, C. vulgaris and S. capricornutum, indicating that the initial removal was due to passive physico-chemical biosorption. More than 65% of the pyrene adsorbed was bound on cell wall materials of S. capricornutum, suggesting the major binding sites were on cell walls. The pyrene removal was also dependent on the concentration of algal biomass used, the more the biomass the higher the removal percentages. In addition to biosorption, pyrene was accumulated and transformed inside live cells. In 7-day S. capricornutum culture, pyrene was not detected in either culture medium or algal pellets, and pyrene might have been completely transformed by this species. The degree of bioaccumulation and biotransformation was species specific.