On new species and records of Hydroidomedusae from the Changjiang River Estuary and its adjacent waters

Forty-nine species of Hydroidomedusae are identified. Two new species and new records are described.

Distribution of ammonia-oxidizing Betaproteobacteria community in surface sediment off the Changjiang River Estuary in summer

The spatial distribution of ammonia-oxidizing Betaproteobacteria （βAOB） was investigated by FISH （fluorescence in situ hybridization） and DGGE （denaturing gradient get electrophoresis） techniques in the sediment off the Changjiang River Estuary. Sediment samples were collected from eight stations in June before the formation of hypoxia zone in 2006. The abundance of βAOB ranged from 1.87× 10^5 to 3.53×10^5 cells/g of sediment. βAOB abundance did not present a negative correlation with salinity, whereas salinity was implicated as the primary factor affecting nitrification rates. The DGGE profiles of PCR-amplified amoA gene fragments revealed that the βAOB community structure of sample S2 separated from other samples at the level of 40% similarity. The variations in composition ofβAOB were significantly correlated with the salinity, temperature, absorption ability of sediments and TOC. The statistical analysis indicates that theβAOB abundance was a main factor to influence nitrification rates with an influence ratio of 87.7% at the level of 40% biodiversity similarity. Considering the good correlation between βAOB abundance and nitrification estimates, the abundance and diversity of βAOB community could be expected as an indirect index of nitrification activity at the study sea area in summer.

Nutrient concentrations and fluxes in the Changjiang Estuary during summer

In June 2003 and 2006 concentrations of nutrient were determined in the Changjiang Estuary. The data indicated that phosphate and nitrate did not behave conservatively in the estuary, but silicate behaved conservatively. An important mobilization of phosphate and nitrate was observed from the river up to halfway in the estuary. Both input flux （from river to estuary） and output flux （from estuary to coastal zone） of phosphate, silicate and nitrate were calculated from statistical interpretations of the salinity profiles. There was a large discrepancy between input and output fluxes of phosphate and nitrate. The river fluxes of silicate, phosphate and nitrate （fr） are augmented 5.3%, 28.9% and 36.6% in June 2003 and 1.0%, 62.5%, 31.7% in June 2006 by internal inputs （fi）.The phosphate and nitrate fluxes are enhanced through the estuarine process, while silicate flux is unaltered. The authors present some long-term data for nutrient concentrations and the ratios of silicon to nitrogen to phosphorus in the Changjiang Estuary. Silicate level falled in the last two decades, while concentration of nitrate increased. Phosphate concentration had no significant change.

Allelopathic inhibition on red tide microalgae Skeletonema costatum by five macroalgal extracts

This study aims to identify effective antialgal allelochemicals from marine macroalgae that inhibit the growth of red tide microalgae.Practically,new algicidal agents were developed to control red tide.The growth inhibitory effects of 5 marine macroalgae Porphyra tenera,Laminaria japonica,Ulva pertusa,Enteromorpha clathrata,and Undaria pinnatifida on Skeletonema costatum were evaluated by adding crude seawater extracts of macroalgal dry tissue into the culture medium containing S.costatum.The half-effective concentrations at 120 h(EC_(50),120 h)of the seawater extracts were 0.6,0.9,1.0,1.0,and 4.7 g/L for the five macroalgae above,respectively.E.clathrata,L.japonica and U.pertusa showed strong allelopathic effect on the growth of S.costatum.There have been no previous reports with regard to the allelopathic effects of the former two macroalgae so far.The possible allelochemicals of 21 compounds of the E.clathrata were detected using Gas chromatography-mass spectrometry(GC-MS)analysis.Unsaturated fatty acids,acrylic acid(C_(3)H_(4)O_(2)),and linolenic acid(C_(18)H_(30)O_(2))were the most likely allelochemicals in E.clathrata.