防海胆食害藻礁的设计及实验研究     

田涛  张秀梅  张沛东  杨宝清  陈勇 《中国海洋大学学报(自然科学版)》2008,38(1):68-72

人工藻礁是进行藻场建设的重要手段,但由于海胆等食藻类生物的摄食,将会影响藻类的生长,从而影响人工藻场的建设效果.为解决人工藻场建设中海胆的食害问题,从礁体自身设计出发,实验设计了8种不同形状的藻礁,选用光棘球海胆和中间球海胆为实验对象,观察比较了不同形状藻礁对海胆攀爬的阻碍效果,实验发现:侧周面为锯齿形或侧周面缠挂多孔柔性材料的礁型可有效阻止海胆攀爬,起到防止海胆摄食礁顶藻类的目的.研究结果为人工藻礁的设计提供了参考依据.  相似文献   

Experimental studies on the role of planktivorous fishes in the elimination ofMicrocystis bloom from Donghu Lake using enclosure method     

Xie Ping 《中国海洋湖沼学报》1996,14(3):193-204

The hypertrophic subtropic Donghu Lake's dense water bloom (of mainlyMicrocystis, Anabaena andOscillatoria) that occurred annually from the beginning of the 1970s, has disappeared since 1985. The influence of planktivorous fishes (silver and bighead carps) on the water bloom was studied for three years using the enclosure method. The enclosures stocked densely with bighead and/or silver carp were free of water bloom during the experimental period. The water bloom that appeared in the fish-free enclosures was completely eliminated in 10–20 days by introduction of silver and/or bighead carp(grass carp was not effective in controlling water bloom). This study showed clearly that grazing pressure by planktivorous fishes is a key factor in eliminating water bloom from the lake. This work was supported by FEBL (State Key Laboratory for Freshwater Ecology and Biotechnology of China) funds and by the National Natural Science Foundation of China (Grant No., 3937014).  相似文献   

Increased benthic grazing: An alternative explanation for low phytoplankton biomass in northern San Francisco Bay during the 1976–1977 drought     

Frederic H. Nichols 《Estuarine, Coastal and Shelf Science》1985,21(3):379-388

Among the consequences of extremely low river flow into northern San Francisco Bay during a two-year drought were (1) a gradual increase in salinity, (2) an unusual decline in chlorophyll a concentration, and (3) the upstream migration of estuarine benthic invertebrates to the normally brackish area of the bay. Total abundance in the benthos at a shallow monitoring site increased from a normal 2000 to greater than 20 000 individuals m^?2 during the summer of 1977, presumably in response to the increased salinity. Estimated filtration rates derived from equations in the literature for one of the species, the suspended-feeding bivalve Mya arenaria ranged from 1 to 4 m³ m^?2 day^?1 during 1977 depending on abundance and mean size on sampling dates. Because water depth at this site is less than 2 m, Mya could have filtered all of the particles (including diatoms) from the water column on the order of once per day. Several other immigrant species undoubtedly contributed to the removal of particles from the near-bottom water as well. Increased benthic grazing, therefore, could have accounted for the anomalously low phytoplankton biomass observed during the drought. These results suggest that during periods of prolonged low river flow and increased salinity benthic food webs could become more important than planktonic food webs in the upper part of the estuary.  相似文献   

THE POSSIBILITIES AND REALITIES ON THE REMANAGEMENT OF DESERTIFIED LANDS IN THE TRANSITIONAL ZONE BETWEEN THE DRY-FARMING AREA AND THE GRAZING AREA IN NORTH CHINA     

朱震达  刘恕  杨有林 《中国地理科学(英文版)》1991,1(1):30-41

The desertification process is rapidly developing at present and 61.5% of the land area in the zone are already desertified.Among the desertified lands, 26.9% are seriously desertified, 25% most seriously desertified and 47.4% are the lands where desertification is under way. They are caused by over-reclamation for farming, over-grazing, unreasonable collection of firewood,the destruction of vegetation and the misuse of water resources. Under the ecological environment in semi-arid zone,the degraded environment process possesses the ability of restoring to its original status as soon as the interruption of excessive human activities are eliminated. The fencing- and-self-cultivating method is an effective measure adopted universally in semi-arid zone to cure the desertified lands.The desertified lands can be readjusted and controlled easily if other controlling measures are supplemented. The fundamental ways to control desertification are to utilize rationally the resources, to readjust the existing land  相似文献   

从若干典型地区的研究对近十余年来中国土地沙漠化演变趋势的分析   总被引：23，自引：3，他引：23  

朱震达  王涛 《地理学报》1990,(4)

土地沙漠化是当前世界上一个重要的生态环境问题,在我国也存在着严重的土地沙漠化问题。50年代末至70年代中期,我国沙漠化土地以每年1560km~2的速度扩大。近10余年来其总的趋势仍在发展,平均每年以2100km~2的速度蔓延。目前,全国已经沙漠化了的土地面积达19.70×10~4km~2以上,其中以沙质草原农垦区和能源基地附近的情况最为严重。实例说明,沙漠化土地在采取必要的措施之后,不仅可以防止其蔓延,而且还可以重新恢复其生产潜力成为农牧业用地。  相似文献   

海洋浮游细菌生长率和被摄食的研究综述   总被引：2，自引：0，他引：2  

张武昌  赵丽  陈雪  赵苑  董逸  李海波  肖天 《海洋科学》2016,40(5):151-158

海洋浮游细菌利用海水中的溶解有机碳合成自身物质,是海洋浮游生态系统的二次生产者。微型浮游动物是细菌的主要摄食者,也是细菌生产向较高营养级传递的中介。研究海洋浮游细菌的生长率和被(微型浮游动物的)摄食率对理解海洋浮游生态系统的功能具有重要作用。本文综述了利用改变海水中生物类群组成(或功能)的培养方法研究海洋浮游细菌生长率和被摄食率的历程和现状,为我国的同类研究提供借鉴。改变海水中生物类群组成(或功能)进行培养的方法有海水分粒级培养、海水稀释培养和添加选择性抑制剂培养。这些方法各有其局限性,应用并不广泛。细菌及其主要摄食者异养鞭毛虫群落在自然海区和实验室内都有生长周期,鞭毛虫的生长周期落后于细菌,因此细菌的生长率有时会小于被摄食率,有时会大于被摄食率。我国这方面的研究相对落后,应值得引起重视,建议从海水稀释培养法入手开展相关研究。  相似文献   

Riparian management and stream bank erosion in New Zealand     

AO Hughes 《新西兰海洋与淡水研究杂志》2016,50(2):277-290

Improvements in riparian management, such as shrub/tree planting and livestock exclusion, are often assumed to result in reduced stream bank erosion and associated catchment sediment yield. Studies that quantify the effectiveness of riparian interventions aimed at reducing bank erosion and river sediment yields are, however, rare. This paper discusses how bank erosion processes can vary throughout catchments (with particular reference to their scale dependence) and hence how the effectiveness of different riparian interventions can be variable. The findings of known published accounts of the effectiveness of riparian management interventions for reducing stream bank erosion in New Zealand are also summarised. Only nine relevant studies were identified and most used qualitative or semi-quantitative analysis methods. Most studies compared stream banks in pasture catchments (with unlimited livestock access) with stream banks where livestock were excluded and riparian shrubs/trees were present. Many studies reported that managed stream banks were in better condition than unmanaged banks. The exclusion of livestock from riparian areas was generally reported as the principal factor in the measured improvements or differences. Only two studies specifically attributed reduced stream bank erosion to the presence of riparian vegetation. The dearth of research identified here highlights the need for further quantitative studies to determine the effectiveness of riparian management measures for reducing bank erosion.  相似文献   

Filter-feeding ascidians (Ciona intestinalis) in a shallow cove: Implications of hydrodynamics for grazing impact     

Hans Ulrik Riisgård  Carsten Jürgensen  Torben Clausen 《Journal of Sea Research》1996,35(4):293-300

The grazing impact by a dense population of filter-feeding ascidians Ciona intestinalis on horizontally flowing water (driven by density circulation) in a shallow cove (Kertinge Nor, Denmark) has been described and quantified by means of a simple one-dimensional numerical model. The agreement between observations and modelled predictions was satisfactory. The applied numerical model has the following analytical solution in the idealized case: Cx = C₀e^−(fx/Y₂), where C_x = algal concentration at a downstream distance x, C₀ = initial concentration, f = F/v_c; F = area specific population filtration rate; v_c = current velocity; Y₂ = depth of mixed layer below halocline. The numerical model quantifies the actual grazing impact while the analytical model illustrates the governing physics in well-known terms. To describe situations with no current (i.e. stagnant water), we performed simulation studies in the laboratory and measured vertical profiles of algal cells over filter-feeding C. intestinalis. The results showed that phytoplankton became reduced in a near-bottom water layer of 20–30 cm thickness. Such water layers may develop in stagnant water (calm days and no advective currents), thus uncoupling the pelagic food and the filter feeders which within a short time will experience extremely meagre food conditions.  相似文献   

三亚湾夏秋两季微型浮游动物摄食研究     

苏强  黄良民  谭烨辉  王汉奎  董俊德  周伟华  胡友木 《海洋通报》2007,26(6):19-25

根据2005年8月和11月的调查资料,利用现场稀释法,以叶绿素a为检测对象,分别对三亚湾海区夏秋两季微型浮游动物的摄食情况进行研究。结果表明,夏秋两季浮游植物瞬时生长率(k)分别为0.9~1.32/d和1.81~3.30/d,而微型浮游动物的摄食率(g)则为0.85~1.79/d和1.29~2.57/d。对浮游植物现存量和初级生产力的摄食压力分别是,夏季为57.26%~83.30%和78.13%~140.38%,秋季为72.47%~92.35%和86.65%~97.90%。秋季微型浮游动物以微型浮游植物为其主要食物来源,其摄食率和对初级生产力的摄食压力最高,平均分别为1.09/d和107.98%;微型浮游植物的瞬时生长率也是最高的,平均为0.94/d,为浮游植物群体的主要组成部分。在三亚湾夏秋两季可把微型浮游动物作为控制浮游植物生长的重要影响因子之一,同时与秋季相比,夏季微型浮游动物在物质循环和能量流动方面起到更显著的作用。  相似文献   

Effects of food concentration and diet on chromophoric dissolved organic matter accumulation and fluorescent composition during grazing experiments with the copepod Calanus finmarchicus     

Urban-Rich  Juanita; McCarty  James T; Shailer  Mark 《ICES Journal of Marine Science》2004,61(4):542-551

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