Contrasting responses of intertidal microphytobenthos and phytoplankton biomass and taxonomic composition to the nutrient loads in the Jiulong River Estuary

Microphytobenthos (MPB) and phytoplankton are important primary producers in the estuarial ecosystem, and their functions are critical to the ecosystem's biodiversity and environmental safety. The aim of this study was to compare the response of MPB and phytoplankton to the nutrient loads in a eutrophic estuary, which has seldom been studied. We used high‐performance liquid chromatography (HPLC) and CHEMTAX software to examine the biomass and taxonomic composition of both MPB and phytoplankton at Da‐yu Island (DYI) and Ji‐yu Island (JYI) in the Jiulong River Estuary from July 2010 to March 2012. The results showed that MPB chlorophyll a was low in the summer and high in the winter at both DYI and JYI, indicating a unimodal pattern. However, the phytoplankton chlorophyll a showed a mirrored pattern. Diatoms were the dominant class in both benthic and pelagic environments. Although redundancy analysis indicated that the effects of different environmental factors could not be easily separated, it is likely that phosphate and temperature were the most important factors regulating the seasonal patterns of MPB and phytoplankton diatoms, respectively. MPB and phytoplankton cyanobacteria was co‐limited by salinity and temperature. The high N/P ratio and low phosphate favored chlorophytes and cyanobacteria. Our study demonstrates the use of HPLC and CHEMTAX in an integrated survey of the spatial and temporal distribution patterns of MPB and phytoplankton in an estuarial ecosystem. The contrasting responses of MPB and phytoplankton to nutrient loads indicate the critical role of MPB in subtropical estuarial ecosystem function. The relationship between nutrients and MPB may indicate a significant contribution to carbon and nutrient cycling.     

Geographic variation in susceptibility of Chilo suppressalis (Lepidoptera: Pyralidae) to Bacillus thuringiensis toxins in China

Geographic variation in the susceptibility of the striped stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), in China to Bacillus thuringiensis (Bt) insecticidal crystal proteins Cry1Ac and Cry1Ab was studied to establish baseline information for comparing the future response of populations with increased exposure to Bt products. Rice is the major host of C. suppressalis, and Bt rice ma) be released in China in the near future. Twelve populations of the pest were collected from the major rice-growing regions of China. LC50 estimates were determined for all populations for Cry1Ac and for eight populations for Cry1Ab. The bioassay results indicated that the range of LC50 in neonate larvae to Cry1Ac and Cry1Ab was from approximately 15 to approximately 157 mg (AI)/L and approximately 2 to approximately 34 mg (AI)/L, respectively. LC50 values were lower for Cry1Ab than for Cry1Ac, and there was a significant positive correlation between the two toxins tested.     

Efficacy of transgenic cotton containing a cry1Ac gene from Bacillus thuringiensis against Helicoverpa armigera (Lepidoptera: Noctuidae) in northern China

NuCOTN 33B, a Bt transgenic variety of upland cotton (Gossypium hirsutum L.) expressing the insecticidal protein Cry1Ac from Bacillus thuringiensis Berliner sp. kurstaki, was evaluated for resistance to Helicoverpa armigera (Hübner) during 1998-2000 in northern China. The results indicated that there was no significant difference in egg densities between NuCOTN 33B and three nontransgenic varieties (DP5415, Zhongmian12, and Shiyuan321) during the season, although the survival of larvae on NuCOTN 33B seemed significantly reduced. High larval densities observed on non-Bt cotton appeared in great contrast to the low larval populations observed on NuCOTN 33B plants during the seasons. In an environment without insecticide sprays, the annual ginned cotton yields in NuCOTN 33B plots, ranging from 1391.17 to 1511.35 kg/ha, were significantly higher than those in non-Bt cotton (340.34-359.58 kg/ha). These high levels of field efficacy for NuCOTN 33B against H. armigera in northern China may pave the way for reduced pesticide applications and an expansion of alternative pest-control strategies.     

Evaluation of the natural refuge function for Helicoverpa arnigera (Lepidoptera: Noctuidae) within Bacillus thuringiensis transgenic cotton growing areas in north China

The density of Helicoverpa armigera (Hübner) populations on Bacillus thuringiensis Berliner (Bt) transgenic cotton, corn, peanut, and soybean; differences in its development on Bt cotton and common (nontransgenic) cotton; and the potential for mating among populations from Bt cotton fields and other crop fields were investigated in the suburbs of Xinxiang City (Henan Province) and Langfang City (Hebei Province) in the southern and northern parts of north China, respectively. Although development of H. armigera on Bt cotton was much slower than on common cotton, there was a still high probability of mating between populations from Bt cotton and other sources due to the scattered emergence pattern of H. armigera adults, and overlap of the second and third generations. In a cotton and corn growing region, early and late planted corn provided suitable refugia for the third and fourth generations of H. armigera, but not for the second generation. In a cotton and soybean/ peanut mix system, noncotton crops provided a natural refugia from the second- to fourth-generation H. armigera, but function of the refuge would closely depend on the proportion of Bt cotton. Consequently, it may be necessary to compensate the original mixed cropping patterns in different areas for delaying resistance development of H. armigera to Bt cotton.     

Flight potential of Lygus lucorum (Meyer-Dür) (Heteroptera: Miridae)

Lygus lucorum (Meyer-Dür) is a key pest of Bt cotton in China. This study reports on its flight potential examined by a flight-mill system. We found that 10-d-old mated females engaged in flight over the greatest distance (40.1 +/- 5.2 km) and duration (7.7 +/- 1.0 h) in 24-h flight assays in relation to age, sex, and mating status. Optimum temperature for flight was 20 degrees C, and optimum relative humidity was 75% RH. Flight potential of 10-d-old mated females under the optimum conditions (20 degrees C and 75% RH) was tested continuously for 48 h. Results showed that the flight distance amounted to 67.3 +/- 9.7 km, with a maximum distance of 151.3 km. This study shows that L. lucorum has the potential to undertake long-distance flight. The information will help in the development of the forecast and management of L. lucorum.     

Unexpected CH4 emission from the Three Gorges Reservoir and its implications

Until the end of last century, scientists began to show their concern about greenhouse gas emission from reservoirs and questioned the “green credential” of hydroelectric dams since then. Through measurements along the channel of the TGR, an unexpectedly low CH₄ emission rate was recently observed from the surface of the TGR, much lower than our assumed estimate before. Moreover, the rate from the TGR is lower than that from many hydroelectric reservoirs. One possible reason for such a low emission rate is that lack of substrates supplied by decomposed vegetation limits the CH₄ production in the sediment of the TGR because of vegetation clearance since 2002 before impounding, whose primary purpose is to conserve the water quality. These results indicated that TGR is not a hotspot of CH₄ emission. On a broader sense, it also indicated that removal of flooded vegetation would help to decrease CH₄ emission from dam reservoirs before impounding, especially in the drawdown area.     

Unexpected CH4 emission from the Three Gorges Reservoir and its implications

Until the end of last century, scientists began to show their concern about greenhouse gas emission from reservoirs and questioned the “green credential” of hydroelectric dams since then. Through measurements along the channel of the TGR, an unexpectedly low CH₄ emission rate was recently observed from the surface of the TGR, much lower than our assumed estimate before. Moreover, the rate from the TGR is lower than that from many hydroelectric reservoirs. One possible reason for such a low emission rate is that lack of substrates supplied by decomposed vegetation limits the CH₄ production in the sediment of the TGR because of vegetation clearance since 2002 before impounding, whose primary purpose is to conserve the water quality. These results indicated that TGR is not a hotspot of CH₄ emission. On a broader sense, it also indicated that removal of flooded vegetation would help to decrease CH₄ emission from dam reservoirs before impounding, especially in the drawdown area.     

Benzothieno[3,2-b]indole derivatives as potent selective estrogen receptor modulators

A series of estrogen receptor ligands based on benzothieno[3,2-b]indole were synthesized and their binding affinity for estrogen receptor subtypes (ERalpha and ERbeta) and effects on mouse uterus and bone were evaluated. Some of these compounds showed strong binding affinity to ER and significantly increased the bone mineral density of ovariectomized mice.