A summary of a long-term research of Lake Kinneret zooplankton distribution is presented. During 1969-2002 several prominent changes have been recorded in the Kinneret ecosystem. This paper is an attempt aimed at anal...A summary of a long-term research of Lake Kinneret zooplankton distribution is presented. During 1969-2002 several prominent changes have been recorded in the Kinneret ecosystem. This paper is an attempt aimed at analyzing the impact of these ecological changes on the zooplankton communities. The impacts of Phytoplankton, Bacteria, Protozoa, Temperature, Nutrient composition and fish predation on zooplankton dynamics are analyzed. It was found that periodical fluctuations of zooplankton density were mostly affected by fish predation as well as by temperature increase and food availability. Ecological conditions in Lake Kinneret have been modified since early 1990’s and the new conditions were consequently accompanied by zooplankton Homeostatic response. Moreover, as a result of the ecological changes fish intensified their pressure on zoo-plankton. The flexibility of food resource preference by zooplankton enabled its existence but fish predation predominantly controlled their density.展开更多
Sea ice in the western Antarctic Peninsula （WAP） region is both highly variable and rapidly changing. In the Palmer Station region, the ice season duration has decreased by 92 d since 1978. The sea-ice changes affec...Sea ice in the western Antarctic Peninsula （WAP） region is both highly variable and rapidly changing. In the Palmer Station region, the ice season duration has decreased by 92 d since 1978. The sea-ice changes affect ocean stratification and freshwater balance and in turn impact every component of the polar marine ecosystem. Long-term observations from the WAP nearshore and offshore regions show a pattern of chlorophyll （Chl） variability with three to five years of negative Chl anomalies interrupted by one or two years of positive anomalies （high and low Chl regimes）. Both field observations and results from an inverse food-web model show that these high and low Chl regimes differed significantly from each other, with high primary productivity and net community production （NCP） and other rates associated with the high Chl years and low rates with low Chl years. Gross primary production rates （GPP） averaged 30 mmolC.m^-2.d^-1 in the low Chl years and 100 mmolC.m-2.d1 in the high Chl years. Both large and small phytoplankton were more abundant and more productive in high Chl years than in low Chl years. Similarly, krill were more important as grazers in high Chl years, but did not differ from microzooplankton in high or low Chl years. Microzooplankton did not differ between high and low Chl years. Net community production differed significantly between high and low Chl years, but mobilized a similar proportion of GPP in both high and low Chl years. The composition of the NCP was uniform in high and low Chl years. These results emphasize the importance of microbial components in the WAP plankton system and suggest that food webs dominated by small phytoplankton can have pathways that funnel production into NCP, and likely, export.展开更多
The dynamics and performance of soil biota during forest rotation were studied in monoculture beech stands forming a chronosequence of four different age-classes(30,62,111,153 yr).Biomass was monitored in major groups...The dynamics and performance of soil biota during forest rotation were studied in monoculture beech stands forming a chronosequence of four different age-classes(30,62,111,153 yr).Biomass was monitored in major groups of microflora,microfauna,mesofauna,and macrofauna.Resource availability(litter layer,soil organic mater),biomass of the two dominant decomposer groups(microflora,earthworms)as well as the biomass of mesofauna and microfauna were found to remain quite stable during forest succession.Nevertheless,the marked increase of the biomasses of primary decomposers(fungi,saprophagous macroinvertebrates)in the 62-year-old stand,followed by an increase of the biomasses of macropredators in the 111-year-old stand,indicate substantial changes of several components of edaphic communities during forest development.However,constant values of soil respiration suggest that the overall performance of the soil food web does not change during beech forest succession.Thus,the decomposer system of lowland managed beech forests on calcareous soils seems to be very stable over time.We suggest that earthworm activity might have masked impacts of forest development on other soil biota and led to an astounding stability of decomposer assemblages during beech forest rotation.展开更多
根据20072008年在南海北部(107°00'120°00'E、17°00'23°30'N)进行的海洋生态综合调查数据,应用Ecopath with Ecosim软件构建了南海北部生态系统的生态通道模型,并通过模型分析了南海北部海洋生态...根据20072008年在南海北部(107°00'120°00'E、17°00'23°30'N)进行的海洋生态综合调查数据,应用Ecopath with Ecosim软件构建了南海北部生态系统的生态通道模型,并通过模型分析了南海北部海洋生态系统的食物网结构、能量流动和系统的总体特征,并简要总结过度捕捞生态系统的基本特征。结果表明,南海北部海洋生态系统以捕食食物链为主要能流通道,初级生产者是系统能量的主要来源。各功能群的营养级范围为13.99,哺乳动物占据了最高的营养层,平均渔获物营养级为2.93。利用生态网络分析,系统的能量流动主要有6级,来自初级生产者的能流效率为12.6%,来自碎屑的转换效率为10.4%,平均能量转换效率为11.5%。系统连接指数(Connectance Index,CI)和系统杂食指数(System Omnivory Index,SOI)分别为0.290和0.239;Finn’s循环指数(Finn’scy cling index,FCI)和系统平均路径长度(Finn’s mean path length,MPL)分别为4.380和2.476;总初级生产力/总呼吸为2.596,综合研究表明当前南海北部海洋生态系统处于不成熟阶段。展开更多
文摘A summary of a long-term research of Lake Kinneret zooplankton distribution is presented. During 1969-2002 several prominent changes have been recorded in the Kinneret ecosystem. This paper is an attempt aimed at analyzing the impact of these ecological changes on the zooplankton communities. The impacts of Phytoplankton, Bacteria, Protozoa, Temperature, Nutrient composition and fish predation on zooplankton dynamics are analyzed. It was found that periodical fluctuations of zooplankton density were mostly affected by fish predation as well as by temperature increase and food availability. Ecological conditions in Lake Kinneret have been modified since early 1990’s and the new conditions were consequently accompanied by zooplankton Homeostatic response. Moreover, as a result of the ecological changes fish intensified their pressure on zoo-plankton. The flexibility of food resource preference by zooplankton enabled its existence but fish predation predominantly controlled their density.
基金supported by NSF Polar Programs awards ANT-1344502 and PLR-1440435 to HWD at Lamont-Doherty Earth ObservatorySFS and SCD were supported partly by Woods Hole Oceanographic Institution
文摘Sea ice in the western Antarctic Peninsula （WAP） region is both highly variable and rapidly changing. In the Palmer Station region, the ice season duration has decreased by 92 d since 1978. The sea-ice changes affect ocean stratification and freshwater balance and in turn impact every component of the polar marine ecosystem. Long-term observations from the WAP nearshore and offshore regions show a pattern of chlorophyll （Chl） variability with three to five years of negative Chl anomalies interrupted by one or two years of positive anomalies （high and low Chl regimes）. Both field observations and results from an inverse food-web model show that these high and low Chl regimes differed significantly from each other, with high primary productivity and net community production （NCP） and other rates associated with the high Chl years and low rates with low Chl years. Gross primary production rates （GPP） averaged 30 mmolC.m^-2.d^-1 in the low Chl years and 100 mmolC.m-2.d1 in the high Chl years. Both large and small phytoplankton were more abundant and more productive in high Chl years than in low Chl years. Similarly, krill were more important as grazers in high Chl years, but did not differ from microzooplankton in high or low Chl years. Microzooplankton did not differ between high and low Chl years. Net community production differed significantly between high and low Chl years, but mobilized a similar proportion of GPP in both high and low Chl years. The composition of the NCP was uniform in high and low Chl years. These results emphasize the importance of microbial components in the WAP plankton system and suggest that food webs dominated by small phytoplankton can have pathways that funnel production into NCP, and likely, export.
基金funded by the EU in the context of the FORCAST project
文摘The dynamics and performance of soil biota during forest rotation were studied in monoculture beech stands forming a chronosequence of four different age-classes(30,62,111,153 yr).Biomass was monitored in major groups of microflora,microfauna,mesofauna,and macrofauna.Resource availability(litter layer,soil organic mater),biomass of the two dominant decomposer groups(microflora,earthworms)as well as the biomass of mesofauna and microfauna were found to remain quite stable during forest succession.Nevertheless,the marked increase of the biomasses of primary decomposers(fungi,saprophagous macroinvertebrates)in the 62-year-old stand,followed by an increase of the biomasses of macropredators in the 111-year-old stand,indicate substantial changes of several components of edaphic communities during forest development.However,constant values of soil respiration suggest that the overall performance of the soil food web does not change during beech forest succession.Thus,the decomposer system of lowland managed beech forests on calcareous soils seems to be very stable over time.We suggest that earthworm activity might have masked impacts of forest development on other soil biota and led to an astounding stability of decomposer assemblages during beech forest rotation.
