摘要:

SUMMARY.1. Populations ofDaphnia galeata mendotaeandD. retrocurvawere exposed for one generation to predators enclosed in mesh bags. The exposedDaphniashowed adaptive morphological changes that mimic cyclomorphosis in nature. The invertebrate predatorsChaoborusandNotonectainduced longer helmets, while the fishLepomisinduced shorter bodies but had no effect on helmet length. Longer tail spines (relative to body length) were induced byNotonectaandLepomis.2. The responses ofD. retrocurvawere influenced by algae concentration, with the more extreme responses occurring at a higher food concentration and higher lipid index.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1988.tb00332.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARY.1. This study links maximum biomass from eighteen aquatic macrophyte communities in the Eastern Townships of Quebec, Canada, to sediment characteristics: chemically exchangeable nitrogen, phosphorus and potassium, per cent organic matter, water content and texture, and to biotic variables: number of species and depth of maximum biomass.2. Total biomass was positively and significantly related to sediment potassium content and to sediment texture.3. Sediment nitrogen and potassium levels are correlated in the spring but not at the end of the growing season.4. It appears that sediment potassium is a surrogate variable for the availability of sediment nitrogen which has been shown to limit aquatic macrophyte growth in this area.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1988.tb00333.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SUMMARY.1. Changes in zoopiankton composition and abundance in Lake le Roux, a turbid subtropical reservoir on the Orange River in South Africa, were correlated with changes in water transparency (related to suspended sediment levels) during a 7 year field study. Results of radiotracer studies of the effect of mineral turbidity on zooplankton feeding rates which potentially influence competitive ability, and thus community structure, are reported here.2. Feeding rates of five zooplankters were very variable, but consistently declined with rising turbidity: rates of decline differed between species. A regression estimate of the critical turbidity threshold at which food intake matched the estimated respiratory need was derived for each species. This yielded the following “turbidity‐tolerance” ranking:Moina brachiataJurine>Metadiaptomus meridianus(van Douwe) ×Daphnia gibbaMethuen>D. barbataWeltner>D. longispinaO. F. Muller. The consistency between this ranking and one based upon abundance‐transparency relationships in the field study suggests that community structure is related to differential feeding capabilities, although other influences are not excluded.3. Tests onD. gibbaandM. meridianusfailed to reveal any detectable feeding rate saturation (incipient limiting food level) below 1.2mg 1−1C. The relative reduction in feeding rates at elevated turbidity was nearly 3 times greater for the daphnid than the copepod over a range of food concentrations, and considerably reduces the competitive ability of this (and other) daphnids. The turbidity tolerance disparity betweenMoinaand the daphnids demonstrates a more complex situation than a simple copepod/cladoceran dichotomy. These findings and their implieations are discussed in relation to wider features of zooplankt

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1988.tb00334.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Books review in this article:Kirk. J.T.O.(1987)Light and Photosynthesis in Aquatic EcosystemsMance, G.(1987)Pollution Threat of Heavy Metals in Aquatic EnvirontmentsSpencer‐Jones, D&Wade, M.(1986)Aquatic Plants – A Guide to Recogni

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1988.tb00335.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1988.tb00336.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY