摘要
20 0 0年 8月在香港牛尾海 ( A站 )和龙鼓水道 ( B站 )的 2个典型站位采样 ,用半现场的稀释法研究了夏季香港水域浮游植物的生长率和微型浮游动物对浮游植物的摄食压力等。结果表明 :A、B站浮游植物主要以硅藻为主 ,但 A站甲藻比重比 B站要高。A站 <5 μm的微型浮游植物比 B站要少 ,从细胞大小上 B站的浮游植物更易被微型浮游动物所摄食。A站微型浮游动物类群主要以异养鞭毛藻为主 ,而 B站为砂壳纤毛虫 ,其细胞丰度分别为 770和 62 0 ind./L。 A、B站浮游植物碳 /叶绿素 a浓度比率分别为 2 7.1 5和88.66。 A站浮游植物的内禀生长率相似于 B站 ,分别为 1 .0 4和 0 .98d- 1。浮游植物在 A站的净生长率是0 .33d- 1,而在 B站则出现了负增长 ,其净生长率是 - 0 .5 8d- 1。微型浮游动物在 A、B站的摄食率分别为0 .71和 1 .5 6d- 1,摄食压力分别占到了浮游植物现存量的 1 43.7%和 2 0 9.7% ,初级生产力的 78.6%和1 2 6.6% ,对浮游植物碳的摄食率分别达到 35 1和 5 5 2 μg C/( L·d)。A站的浮游植物生长要高于 B站 ,B站的微型浮游动物摄食压力要明显高于 A站。与其它海区比较香港水域微型浮游动物摄食压力处于中等水平。
Two typical stations, the Port Shelter (station A) and Urmston Rcad (s tation B) in Hong Kong, were chosen as sites for phytoplankton growth and microz ooplankton herbivory studies which were completed using a semi- in situ dil ution experiment in August 2000. PFW (particle-free water) was used to dilute sea wa t er to five target dilutions of 0%, 20%, 40%, 60% and 80%. The microzooplankton g razing rate and phytoplankton growth rate were estimated by the linear regressio n of AGR (apparent growth rate) versus ADF (actual dilution factor). The grazing impact on phytoplankton by microzooplankton was estimated by calculating phytop lankton net growth rate, percentage of phytoplankton standing stock ingested, pe rcentage of prey potential production ingested, and ingestion rate of phytoplank ton carbon. The phytoplankton carbon was estimated by converting the cell biovol ume to carbon using assumed carbon conversion factors. At stations A and B, diatoms were dominant in the phytoplankton community, but when the species richness and cell abundance were completed, dinoflagellates we re more important in stations A than B. The dominant phytoplankton species were Chaetoceros curvisetus, Thalassionema frauenfeldii, and Chaetoceros lorenz ianus at station A, and Lauderia annulata, Thalassionema frauenfeldii, and Dityl um sol at station B. The phytoplankton assemblage at station A was characteri stic of coastal warm water species, while brackish water species could be found in the p hytoplankton assemblage at station B. The light conditions were good but the nut rient conditions (ammonium, phosphate, nitrate plus nitrite, and silicate were 0 .30, 0.23, 0.56, 0.69 μm respectively) were poor at station A. In contrast, lig ht conditions were poor and nutrient conditions (ammonium, phosphate, nitrate pl us nitrite, and silicate were 3.42, 1.06, 49.57, 46.15 μM respectively) wer e go od at station B. The < 5 μm fraction of phytoplankton in station A (24.3%) was less than station B (40.9%). This indicated that, according to cell size, the p h ytoplankter at station B was more easily preyed upon than that of station A. Het erotrophic dinoflagellates were the major component of microzooplankton at stati on A, and tintinnids were also commonly present in the microzooplankton sample. At station B, however, tintinnids were a major component of microzooplankton and few copepod nauplii were found. Microzooplankton abundances were 770 and 620 in d./L at stations A and B respectively. The carbon:chlorophyll a ratios were 27. 1 5 and 88.66 at stations A and B respectively. The dilution experiment results s h owed that phytoplankton instantaneous growth rates were 1.04 and 0.98 d-1 at sta tions A and B respectively. The net growth rate was 0.33 d-1 at station A , which was greater than that of -0.58 d-1at station B. The microzooplankton gra zing ra tes were 0.71 and 1.56 d-1, percentages of phytoplankton standing crop i ngested by microzooplankton were 143.7% and 209.7%, percentages of phytoplankton poten ti al production ingested by microzooplankton were 78.6% and 126.6%, microzooplan kt on ingestion rates of phytoplankton carbon were 351 and 552 μgC/(L·d) at stati o ns A and B respectively. This demonstrated that the phytoplankton growth rate at station A was greater than at station B, and microzooplankton grazing pressure was less than that of station B. We can also deduce that the grazing pressure of tintinnids was higher than that of heterotrophic dinoflagellates. In spite of t he good nutrient conditions at station B, high microzooplankton grazing pressure plus low light condition made the standing crop of phytoplankton at station B ( chlorophyll a concentration is 9.00μg/L) lower than at station A (chlorophyll a concentration is 2.97μg/L). Compared with the other regions around the world, the microzooplankton grazing pressure in Hong Kong waters was in the middle of t he range of measurements elsewhere. The results of the long-time controlled dilution experiments (3 days) under da rk conditions showed that
出处
《生态学报》
CAS
CSCD
北大核心
2003年第4期712-724,共13页
Acta Ecologica Sinica
基金
香港科技大学 PREPP资助项目
国家基础研究与重点资助项目 (批准号 :2 0 0 1 CB4 0 970 2 )
中国科学院创新资助项目 ( KZCX2 -2 0 6)~~
