摘要:

SUMMARY.1. Trichopteran populations below a dam on the River Tuntang (Central Java) and on intake screens above the dam consisted almost exclusively ofAmphipsyche meridiana.Larvae on dam screens were in tightly packed aggregations, with greater densities in deeper water, and were predominantly fourth or fifth instars during the period of observation. Below the dam, 40% of larvae were in the first three instars. Larvae at the dam screens were heavier and yielded larger emerging adults which contained more eggs per female.2. Mean net mesh sizes of fifth instar larvae varied greatly from 34×26 μm to 125×106 μm with larger meshes having progressively thicker strands. It is suggested that larger mesh size may be positively correlated with faster flow rates. The dinoflagellatePeridinium, commonly found in the guts of larvae below the dam, was virtually absent in dam screen larvae, possibly due to mesh size differences.3. The behaviour of larvae in aggregations was observed in a laboratory flow channel. After experimental destruction of feeding nets, larvae immediately ingested silk prior to the construction of a new net. Nets were spun in a‘figure 8’fashion, and took between 11 and 30 min to complete. Stridulation between larvae occurred frequently and may be related to the defence of silk reserves within terr

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00017.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.(1) The average benthic density ofPeltoperla mariain an undisturbed southern Appalachian stream was more than twice that of a nearby stream draining a previously clear‐cul catchment in its tenth year of natural secondary succession.(2)Peltoperlaproduction estimates, using three methods, do not show a significant difference in production between streams draining the two catchments. We attribute these results to quicker growth and slightly higher densities of larger nymphs in the disturbed stream. Production estimates for the disturbed stream ranged from 498 to 560 mg (ash free dry weight) m−2y−1while those for the undisturbed stream were 41–4–515 mg m−2y−1.(3) Our results reinforce the view that conclusions based solely upon numerical densities may lead to erroneus interpretations about the roles organisms play in ecosystems.(4) Annual frass production by this shredder is about 20 times (10 g m−2y−1) the secondary prod

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00018.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. A macroinvertebrale survey of various habitats (e.g. riffles, pools, tree roots) at sixteen sites in the Teifi catchment in September 1981 yielded 217 taxa excluding Hydracarina and Chironomidae.2. Sites with the greatest number of habitats were generally rich in taxa and supported the highest number of ‘rare’ species, the latter generally being associated with vegetation. However, species were not generally restricted to particular habitats although ecdyonurid mayflies predominated in riffles and one leptocerid caddisfly was principally collected from tree roots.3. Four groups of taxa which characterized three habitat groups were established using classification procedures and it was concluded that three habitat types (eroding, depositing and vegetation) should be sampled to describe adequately the macroinvertebrate fauna at each site.4. Three attributes (species richness, species rarity and site uniqueness) were used to establish the conservational value of each site; in general, the main river and one lowland tributary were of highest conservational significance.5. Multiple regression analyses were used to establish significant relationships between the three attributes and environmental features such as number of habitats, altitude, river width, pH and total hardness. Such relationships may facilitate a rapid assessment of resource value without expensive biological sur

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00019.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.(1) A study was made of the biology ofChrysichthys auratus, a bottom‐feeding omnivore, in Tiga Lake, a man‐made lake in Northern Nigeria.(2) Ripe females were present from April to September, coinciding with the hot season and rise in water level. First spawning took place at age II in females. No ripe males were found, and this was attributed to their spatial separation. Absolute fecundity was related to length and ranged from 327 to 1466 in forty‐six females.(3) Hyaline rings on the centra of lumbar vertebrae were counted to age 235 fish. The first ring is laid down at the end of the second year, after which the rings were formed annually, probably during the breeding season. The fish live for up to 6 years. There is a good fit of the growth curve to the von Bertalanffy equation. Growth is slow and a smaller maximum size is attained than in r

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00020.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Of the various approaches to studying species‐abundance patterns in aquatic ecosystems (particularly streams) the logseries distribution is the most appropriate. The distribution parameter, α, is readily estimated and goodness‐of‐fit of the model to the data can be estimated.2. A method exists which uses a to calculate an index of similarity from which cluster dendrograms can be constructed and the clusters tested for significant differences. Assumptions and calculations are presented.3. Procedures are illustrated, with examples from Idaho streams, and approaches to interpreting the results are included.4. Studies of stream macro invertebrates can fulfill the assumptions of the logseries distribution but cannot meet those of commonly used diversity i

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00021.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. The relationship between microbial ATP and biomass‐ carbon in the near surface waters (0.5–5 m) of eight New Zealand lakes was studied to determine the constancy of the carbon:ATP ratio under natural growth conditions. Concentrations of microbial carbon were estimated indirectly from cell volume determinations.2. The carbon:ATP ratio remained reasonably constant (interquartile range 248–291,n= 50), except during periods of nitrogen/phosphorus deficiency when carbon: ATP ratios increased to values greater than 400.3. During periods of nitrogen/phosphorus sufficiency, corresponding estimates of microbial ATP and biomass‐carbon were strongly correlated (r=0.97,n=47) and related by the equation carbon = (287±20) ATP‐(22±41) where carbon and ATP are expressed in mg m−3. From this relationship an average carbon:ATP ratio of 267 (SE=5) was calculated.4. This ratio was not significantly affected by the relative proportions of bacterial and algal biomass in the surface water samples. However, because of the marked deviation of the carbon:ATP ratio during periods of nitrogen/phosphorus deficiency, the routine use of ATP as a biomass indicator i

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00022.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Between February and September 1974, concentrations of fulvic and humic acids in waters from a cryoboreal region of the Precambrian Shield in Quebec varied between 0.5–6.1 mg 1−1and 0.1–6.5 mg 1−1respectively. Whereas the fulvic acids usually remained relatively constant during this period, humic acids showed appreciable increases.2. The number and weight average molecular weights of the fulvic acids (∼5000 and ∼22,000 daltons respectively) were lower than those of the humic acids (∼20,000 and ∼75,000 daltons respectively). The average molecular weight of the aquatic humic matter often decreased during late summer and early autumn. During spring floods the molecular weight of fulvic acids increased and that of humic acids declined.3. Because the aquatic humic acids were more intensely coloured than fulvic acids, they contributed more than 30% of the colour of the water even though they accounted for only 15% of the concentration of humic matter. The colour intensity of both fulvic and humic acids generally appeared to increase during the latter part of the summer, when there was normally a decrease in the value of the colour quotient (E4/E6ratio), indicating the accumulation in the waters of more hu

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00023.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Invertebrate movement was monitored in a parkland marsh in central Alberta, Canada, for 24 h periods every 2 weeks during the ice‐free season. Stationary plankton nets captured organisms moving towards or away from shore.2. Movement occurred throughout the sampling programme, particularly during the warm summer months. Most organisms were night active and exhibited directional movements.Hyalella azteca(Saussure) andCaenis simulansMcDunnough constituted most of the catch.3. Although there was a significant positive seasonal relationship between maximum water temperature and total numbers of animals captured. no physical factor appeared to control movement on a daily basi

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00024.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Basic physical and morphometric data are presented for sixty‐five lochs on the Shetland Islands. The interrelations between loch dimensions are comparable to those recorded elsewhere in Scotland, but the smaller lochs on Shetland tend to be somewhat shallower, and the large lochs somewhat deeper than usual.2. The results of a multivariate analysis show that most of the physical variables measured in the field are closely correlated with easily measured map attribute

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00025.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Book reviewe in this article:Schiemer, F.(Ed.) (1983)Limnology of Parakrama Samudra, Sri Lanka.Developments in Hydrobiology.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00026.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY