摘要:

SUMMARY.1.Daphnia pulexgrown in the cell‐free filtrate of a log phase culture ofAnabaena flos‐aquaeshowed lower fitness as measured by filtering rate, survivorship and reproduction than did individuals in a control treatment. This suggests that the extracellular metabolites of some algae may have considerable adaptive value as a herbivore deterrent.2. Heating of the cell‐free filtrate neutralized the inhibitory effect on filtering rate, but increased the depression of reproduetive rate. This suggests the presence of a variety of bioactive compounds which may inhibit specific herbivore func

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1983.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARY.1, An apparatus has been described that is suitable for potentiometric measurement of carbon dioxide flux in photosynthesizing shoots of submerged aquatic macrophytes2. The procedure, based on methods described by Tailing (1973) for measurement of phytoplankton photosynthesis, relies upon the continuous pH‐statting of the solution surrounding the tissues. The pH of the solution is monitored by electrodes from a pH meter which is linked to an auto‐titrator. The rise in pH during photosynthesis is then compensated tor by controlled, small titrant additions of CO2‐ennched solution (titrant water). This replaces the CO2removed by the tissues without affecting the total alkalinity of the solution. If the concentration of CO2in the titrant water, and the volume of titrant added arc known precisely, the CO2flux can be calculated.3. Total alkalinity, total CO2and free‐CO2acidity of the bathing solutions and titrant waters are estimated by Gran titrations and the pH: tilre‐volume data pairs are analysed by computer to provide rapid data feed‐back. A modification to Tailing's equation for calculation of F1functions has been necessary for accurate calibration of the CO2enriched tilrant water.4. The photosynthesis cuvette, which is surrounded by a water‐jacket, is approximately I dm3in capacity and has six compartments for the shoots. An impeller at the base of the cuvette rapidly mixes and cycles the bathing solution and flushes it over the tissues.5. Information on temperature, light flux density, oxygen concentration. pH and titre‐volume is continuously recorded into a data‐logger and is fed into a computer which is programmed for data analyses.6. Results from a typical experiment show the system to be sound and the method has considerable potential, especially in the study of aquatic plant photosynthesis

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1983.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARY.1. Invertebrates and fish were surveyed during October 1976 in thirty‐four stony riffle stream sites in Ashdown Forest, Sussex.2. A variety of physicochemical factors were also measured in an attempt to assess the importance of each in determining the distribution of species and the structure of communities.3. Three analytical techniques—stepwise multiple regression analysis, ordination and community classification—revealed that the structure of these communities was strongly related to variation in stream pH. Acid sites had low numbers of individuals, low species richness and low equitabilities. Summer temperature and stream discharge also appeared to play significant roles. The pattern of catchment land use was shown to have an important bearing on stream pH.4. In the most acid sites only collectors, shredders and predators occurred. In more basic sites the number of species in collector and predator categories increased and these were joined by grazer/scrapers and filter feeders.5. A theoretical basis for explaining stream community structure is disc

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1983.tb00011.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARY.1. As three previous comparative studies of deep‐water samplers for benthic macroinvertebrates in rivers highlighted the need for a quantitative sampler for use on stony substrata, a new air‐lift sampler was developed. It can be operated from a small boat by two people, weighs 13.5–20.0 kg, depending on the length of riser used, and extends the maximum range of substrata that may be sampled quantitatively from 16–32 mm to 128—256 mm. The sampling area is isolated by forcing a collecting cylinder into the substratum, and rapid evacuation of the contents is assisted by a vibrator.2. All the major specifications of the sampler were determined experimentally in a large tank using three sizes of substrata and plastic pellets to represent invertebrates. The sampler performed accurately to a depth of at least 8 cm on substrata ranging from gravel (2–4 mm) to large stones (32–36 mm long).3. The performance of the sampler was compared with that of a Ponar grab and Pearsonel at.air‐lift sampler at two sites on a large river and also with a Naturalist's dredge and a diver‐operated Hess‐Waters sampler at one of the sites where there were large stones up to 280 mm long. In terms of both mean taxa per sample and mean numbers m−2, samples taken using the new air‐lift sampler provided estimates comparable to or belter than those obtained

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1983.tb00012.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARY.1. The rate and nature of colonization of ball‐clay ponds by aquatic macrophytes and macroinvertebrates were studied by comparing communities present in a scries of ten ponds of similar dimensions, but of different ages, ranging from 6 months to 15 years.2. Multivariate analyses of the biotic data distinguished between‘neutral’and‘acid’ponds; further analyses concentrated on the former type.3. Initial colonization of neutral ponds was rapid with a predictable sequence of species arrival, probably reflecting short dispersal distances. Variations in macroinvertebrate invasion times were related to dispersal strategy and ability. As the pond aged, successional changes, linked with macrophyte colonization, produced a shift in dominance from algivores and predators towards epiphyton grazers and detritivores. Some evidence of succession of species within invertebrate orders was found.4. Low pH affected colonization principally by preventing the establishment of acid‐intolerant immigrant species, but also by retarding succession.5. It is concluded that non‐interactive models of insular colonization, with constant immigration and extinction rates, are of limited applicability to pond colonization in te

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1983.tb00013.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARY.1. AdultHygrotusbeetles were collected from about 400 localities out of 621 sampled in the Netherlands. Distribution of the three Dutch species of this genus has been related to different environmental variables, principally by use of the Index of Representation (I.R.).2.Hygrotus decoratusis an acidophilous and haloxenous species. It inhabits small water bodies such as peat‐ditches, reed‐lands and overgrown ditches where emergent plants are abundant.Hygrotus inaequalisoccurs in all of the habitats studied and has no clear preferences or aversions with respect to the environmental variables examined.Hygrotus versicolorinhabits permanent water bodies such as clay‐ and sand‐canals which have a rich growth of submerged plants and a weak current. The species has a significant preference for waters with a pH between 7.1 and 8.0 and a chlorinity between 60 and 200 mg 1‐−1.3.H. decoratusandH. versicolorrarely co‐exist because of their different environmental requirements, but both species often co‐exist withH. inaequalis.Structural environmental variables such as water depth and abundance and growth‐form of the aquatic plants play a greater role than chemical factors in habitat select

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1983.tb00014.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARY.1. The reproductive cycle and growth ofCraterocephalus marjoriaeandCraterocephalus stercusmuscarum(Atherinidae) were studied in Brisbane, south‐eastern Queensland, over a 17‐month period (1981–82).2. Both species had a 5‐month breeding season in spring and summer, with a breeding peak in spring (September‐October). Multiple spawning occurred but life time fecundity was not determined.3. Gonosomatic index values and mean fecundity per female were higher inCraterocephalus marjoriaethan inC. stercusmuscarum.Fecundity increased with body length in both species according to the relationship,F=aLb.Growth rates were similar and growth was adequately described by the von Bertalanffy equation. Both species grew rapidly during the first year and reached maturity the following season. Reproductive strategies are considered in relation to seasonal flooding in the streams

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1983.tb00015.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Book review in this article:Sly, P.G. (Ed.) (1982)Sediment/Freshwater Interaction: Proceedings of the Second International Symposium.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1983.tb00016.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY