Evidence for biotic control of Australian reservoir phytoplankton communities and the potential for applied biomanipulation

Although some concerns have been expressed with respect to the applicability of biomanipulation to Australian reservoirs and other inland waters, no major obstacles were found in this review. The previous doubts stimulated research, which has provided evidence for unexpected mechanisms of food web interactions, such as positive effects of small copepods on planktonic algae, higher than usual grazing potential of cladoceran communities, and direct positive effects of planktivores on phytoplankton. Further research into zooplankton-cyanobacteria interactions should indicate how widespread is the previously reported ability of some southern hemisphere crustaceans to benefit at a population level from feeding on cyanobacteria. Quantitative fisheries acoustics, which has not been widely used in biomanipulation trials before, is a promising new tool in the assessment of the biomass of planktivorous fish in the pelagic zone of reservoirs.     

在线生物监测技术用于典型农药突发性污染的研究

水源水突发性污染监测技术是当前的研究重点,导致突发性污染事故的末知污染物可通过暴露于污染的水生生物行为改变来实现在线生物监测.通过48 h暴露,以标准水为对照,研究了经差分滤除以后,大型蚤在一定农药浓度下的相对行为变化,进一步说明生物行为生态学变化在水体生物监测中的指示作用.研究结果表明,在不同浓度百菌清、除草醚和溴氰菊酯的作用下,大型蚤的运动行为强度会发生剧烈变化,并呈现明显的剂量-效应关系.在一定浓度的农药暴露中,暴露生物的行为强度在经历一个短暂的突增后,会随暴露时间增加而逐步减弱.因此,通过监测大型蚤运动相对行为变化,可以实现对百菌清、除草醚和溴氰菊酯农药污染事故的在线生物监测.     

Changes in the Crustacean Communities of the Central Basin of Lake Erie during the First Full Year of the Bythotrephes longimanus Invasion

The exotic predatory cladoceran Bythotrephes longimanus was first observed in Lake Erie on 19 September, 1985. During the early summer immediately prior to its appearance, the cladoceran community in the central basin of Lake Erie was characterized by large populations of Bosmina longirostris, Eubosmina coregoni, Daphnia mendotae, and Daphnia retrocurva, with the latter three species persisting throughout August and September, along with Diaphanosoma spp. Community composition during early summer 1986 was similar to that of the previous year, but densities of all cladocerans decreased dramatically coincident with the appearance of Bythotrephes in mid-July, and remained suppressed throughout August and September. Only D. mendotae was present in appreciable numbers during this period; from mid-July through the end of August, 86-98% of cladoceran biomass (exclusive of Bythotrephes and Leptodora) was contributed by D. mendotae. Densities of Leptodora and Bythotrephes showed a strikingly inverse relationship, both temporally and spatially, during 1986. Size frequency distributions of D. mendotae exhibited an immediate shift towards extremely large ( > 2.5 mm) individuals coincident with Bythotrephes’ appearance in 1986, suggesting an upper size limit to efficient prey utilization by Bythotrephes. These results suggest that Bythotrephes can have substantial impacts both on cladoceran community composition, and on the size distributions of individual species.     

Grazing by a resident macrozooplankton community and non-resident Daphnia carinata King: A preliminary in situ incubation study

A 24 h incubation study was conducted in situ in Manly Dam reservoir, Sydney, Australia. The study aimed to evaluate the relative effectiveness of grazing on phytoplankton by a resident macrozooplankton community, dominated by the cladoceran Ceriodaphnia and some copepods, in comparison with grazing by added, non-resident Daphnia carinata in the absence of the resident macrozooplankton community. Although there was some variability in the measured grazing rates among incubation bottles (volume: 1.28 L), D. carinata with a mean body size of 30.8 μg dry weight were more efficient grazers than the reservoir macrozooplankton community with a mean body size of 2.5 μg dry weight. The weight-specific clearance rate of D. carinata was 2–65 times higher than that of the resident reservoir community for five taxa of reservoir phytoplankton examined. In comparing the evidence from the literature on the limited ability of D. carinata to graze on cyanobacteria, a management strategy using D. carinata for the reduction of phytoplankton biomass may need to be considered separately from one designed to specifically control undesirable taxa, such as the cyanobacteria Microcystis and Anabaena .     

Limnological features of Funil Reservoir (R.J., Brazil) and indicator properties of rotifers and cladocerans of the zooplankton community

Funil Reservoir receives inflow from a highly industrialized region and acts as a natural sink to pollutants. Among the consequences of the uncontrolled nutrient loading is the constant presence and periodic heavy blooms of Microcystis aeruginosa . This study verified limnological features and zooplankton assemblage of the Funil Reservoir focusing on the environmental-indicator properties of rotifers and cladocerans. The summer bloom of M. aeruginosa caused reductions in water transparency, nitrate and orthophosphate concentrations and raises in chlorophyll a , pH, dissolved oxygen and chemical oxygen demand values. All zooplankton species presented spatial and temporal variations with the exception of the copepods, which were present in all samples. According to canonical correspondence analysis, ammonium was the variable most related to zooplankton variability and different Rotifera and Cladocera assemblages indicated distinct environment conditions. Rotifer taxa associated with increases of water temperature and chlorophyll a concentration were found with high densities during M. aeruginosa blooms. Species of rotifer and cladocerans are suggested as indicators that can be used to identify different physical and chemical gradients or eutrophic increases in Funil Reservoir.     

Food of Young-of-the-Year Lake Trout (Salvelinus Namaycush) in Presque Isle Harbor,Lake Superior

The food habits of young lake trout (Salvelinus namaycush) were studied by examining the digestive tracts of 293 young-of-the-year collected in Presque Isle Harbor, Lake Superior. Lake trout in the 25 to 27-mm length range started to eat food organisms before all of their yolk material was absorbed. Organisms consumed by the 25 to 27-mm young-of-the-year included Chironomidae, Copepoda (Harpacticoida, Calanoida, Cyclopoida), and Cladocerea (Daphnia spp., Bosmina sp., Chydorus sp.). Chironomid pupae and chironomid larvae accounted for 74% and 5%, respectively, of the total volume of food eaten by the young lake trout in Presque Isle Harbor. Although copepods, cladocerans, and mysids were present in many stomachs, their contribution to the total volume of food was only 15%. Some lake trout in the 32 to 54-mm length range had consumed fry of sculpin (Cottus spp.) or rainbow smelt (Osmerus mordax), but the overall contribution of fish fry to the total volume of food was only 4% (frequency of occurrence, 10%). The lake trout in Presque Isle Harbor fed heavily on planktonic organisms, sparingly on benthic organisms, and were opportunistic feeders that appeared to prey on whatever forage organisms were available in the shallow nearshore waters.     

Role of Daphnia in the decomposition of organic matter in the surface layer of Lake Biwa

To examine the role of Daphnia in the decomposition and elimination of organic carbon at the surface layer, organic matter from Lake Biwa was incubated with and without Daphnia at 20°C in the dark for 15 days in May, July and October. In all of the experiments, total organic carbon decreased during the incubation, regardless of treatment; however, the net effect of Daphnia on this decrease differed among experiments. Daphnia stimulated the decrease in particulate organic carbon in two out of three experiments. Bacterial abundance was higher in treatments with Daphnia than in treatments without Daphnia in all experiments. Higher bacterial abundance in treatments with Daphnia could not be explained fully by zooplankton grazing effects on phagotrophic protozoans, rather Daphnia seemed to stimulate bacterial growth by supplying substrates for that growth. The results of the present study suggest that Daphnia reduces sinking flux, not only by direct grazing, but also by the channelling of particulate organic carbon into dissolved forms that are then available for bacterial growth.     

饮用水中余氯对大型蚤的急性和慢性毒性

目前我国饮用水生产过程中普遍采用氯消毒,在去除一些有害微生物的同时,会形成一定浓度的余氯。为了监测余氯对用于在线监测的水生生物产生的毒性效应,讨论了饮用水中余氯对大型蚤的急性和慢性毒性。当余氯为0.16 mg/L时,大型蚤24 h存活率为100%,48 h存活率为90%;当余氯达到0.32 mg/L时,大型蚤48 h存活率为30%。在最小致死剂量(MLD=0.16 mg/L) 暴露下,40 d慢性毒性结果显示水中余氯对大型蚤生长和生殖影响显著。因此,可用于实现在线连续监测过量投加后水中高浓度的余氯。而当大型蚤用于毒性的在线生物监测(如突发性事故监测), 或用于监测水质大幅度变化时,应考虑首先消除水中余氯对动物行为生态的影响。     

大型溞和日本青鳉在水质在线生物安全预警应用中的比较

讨论了利用大型溞和日本青鳉作为受试生物,通过在线监测两种受试生物行为变化反映水质变化状况的优缺点.结果表明:首先,大型溞对水体污染比日本青鳉更敏感,针对某些污染物的监测水平甚至高于国家地表水标准的限值,而日本青鳉反应水平处于10倍以上地表水标准;其次,在连续监测过程中,大型溞行为变化未表现明显的昼夜规律性,而日本青鳉行为变化具有更明显的生物钟现象;第三,在连续在线监测过程中,大型溞持续监测只能维持7天左右,其续航能力明显弱于日本青鳉的30天以上监测周期.     

饮用水生产中突发性有机磷农药污染事故的在线生物监测

饮用水生产中可能因为水源污染或人为投加的有机磷农药而使水质发生突发性变化,可以利用生物暴露于有机磷农药时运动行为的变化在线预警这类突发性污染事故。研究了大型蚤在不同浓度有机磷农药作用下的行为变化规律。研究结果表明,不同浓度对硫磷、马拉硫磷和敌百虫条件下,大型蚤的运动行为会发生剧烈变化,其强度随水中有机磷农药的浓度和暴露时间增加而逐步减弱;即使在这三种有机磷农药的水相浓度远低于《地表水环境质量标准》(GB 3838—2002)的情况下, 仍然可以观察到大型蚤运动行为的改变,因此可以对突发性有机磷农药污染事故实现安全预警。