[Spatial pattern in larval distribution, settlement and growth of Crassostrea sikamea in Xiangshan Bay, Zhejiang Province, China]. / è±¡å±±æ¸¯ç†Šæœ¬ç‰¡è›Žå¹¼ä½“åˆ†å¸ƒã€é™„ç€åŠç”Ÿé•¿çš„ç©ºé—´æ ¼å±€.

The migration and settlement of oyster larvae significantly affect the distribution, recruitment, establishment and ecological services of oyster populations. We investigated the variations of Crassostrea sikamea larvae abundances between the two water layers and between the two experimental sites (seed bed and spawning bed) in Xiangshan Bay within a tidal cycle (9 sampling times), and explored the spatial patterns in larval settlement and spat growth at three intertidal zones (top, T; middle, M and bottom, B) of both experimental sites by a field settlement experiment. At the seed bed and spawning bed, oyster larvae abundance at the surface water significantly changed with sampling time. At the seed bed, oyster larvae abundance (20.8±5.6 larvae·L-1) was greatest at the high flood tide, and was significantly greater than that at the other eight sampling times. Contrasting results were found at the spawning bed where oyster larvae abundance was the lowest (0.1±0.1 larvae·L-1) at the high flood tide. At each site, oyster larvae abundance at the bottom water did not change within the tidal cycle. At the seed bed, total abundance, survival rate and shell height of the settled oysters significantly varied across intertidal zones, ranking as B>T=M for total oyster abundance, and T>M>B for survival rate and shell height. There was no significant difference in live spat abundance among intertidal zones. At the spawning bed, the total and live abundances, survival rate and shell height of the settled oysters had no difference among intertidal zones. Our results indicate that oyster larvae commonly settle at the high flood tide, and the abundance of settled spats are similar between seed bed and spawning bed.

[Purification function and ecological services value of Crassostrea sp. in Yangtze River estuary].

Oyster reef ecosystem is a natural decontamination plant of estuarine environment. This paper analyzed the bioaccumulation of heavy metals by Crassostrea sp. population at the dams of Yangtze River estuary, with its purification capacity and ecological services value assessed. The results indicated that Crassostrea sp. had a high capacity in bio-accumulating Cu, Zn and Cd, with the bio-concentration factor (BCF) and biota-sediment accumulation factor (BSAF) being (14.28 +/- 2.41) x 10(3), (12.75 +/- 2.02) x 10(3) and (14.51 +/- 3.71) x 10(3), and 26.78 +/- 4.53, 23.24 +/- 3.69 and 16.62 +/- 4.25, respectively. The bioaccumulation capacity decreased in the order of Cu > Zn > Cd > As > Pb > Hg. The total weight and fresh meat weight of the oyster at the dams of Yangtze River estuary were about 1.07 x 10(6) t and 1.75 x 10(5) t, respectively, and the total storage of nutrients and heavy metals were 1.462 x 10(6) kg N, 1 x 10(5) kg P, 24 745 kg Cu, 58 257 kg Zn, 609 kg Pb, 254 kg Cd, 0.18 kg Hg and 329 kg As. The total ecological services value of the oyster reef was estimated at about 8.27 x 10(6) RMB x a(-1), including habitat value of about 5.10 x 10(6) RMB x a(-1) and environmental value of about 3.17 x 10(6) RMB x a(-1). Such an environmental value was equivalent to the value of treating about 7.31 x 10(6) t combined sewage each year, and corresponded to a large municipal sewage plant with a treatment capacity about 20 000 t d(-1).

Prediction and setup of phytoplankton statistical model of Qiandaohu Lake.

This research considers the mathematical relationship between concentration of Chla and seven environmental factors, i.e. Lake water temperature (T), Secci-depth (SD), pH, DO, CODMn, Total Nitrogen (TN), Total Phosphorus (TP). Stepwise linear regression of 1997 to 1999 monitoring data at each sampling point of Qiandaohu Lake yielded the multivariate regression models presented in this paper. The concentration of Chla as simulation for the year 2000 by the regression model was similar to the observed value. The suggested mathematical relationship could be used to predict changes in the lakewater environment at any point in time. The results showed that SD, TP and pH were the most significant factors affecting Chla concentration.