摘要:

AbstractThe annual cycles ofDaphnia carinatain three fish‐free ponds in southern New Zealand (Quarry, Taieri and Raupo Ponds) are described. Although breeding was continuous, the populations were frequently dominated by distinct cohorts and there was a sexual phase in spring. Growth rates, particularly in Quarry Pond, were often slow, and clutch sizes generally small. Egg and neonate sizes changed seasonally, but changes were not closely related to clutch sizes and body lengths. In Taieri Pond and Raupo Pond someD. carinatagrew to 6.14 mm and carried clutches of up to 154 eggs. The potentially high fecundity associated with large size makesD. carinataa good coloniser, but our studies showed that it also survives well in poor food conditions by growing slowly and producing only 1–2 eggs per clutch.D. carinatashowed marked seasonal polymorphism in tailspine length and development of head crests. In winter, crests were absent and tailspines were short and varied little with body length. Crests were first apparent, and tailspines began to elongate, in early spring, before the first appearance of a notonectid,Anisops wakefieldi.By midsummer, tailspines had increased markedly with body length but the slope of the relationship declined in autumn. Laboratory trials showed that both tailspine length and crest development increased in the presence ofAnisops.These increases may be due to water‐soluble factor(s) produced byAn

ISSN:0020-9309    

DOI:10.1002/iroh.19940790402

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY

摘要:

AbstractFour size classes of both sexes of laboratory‐culturedStreptocephalus proboscideus(post‐metanauplii 4.7±0.4; juvenile virgins 8.7±0.7; adults I 13.8±0.9, and adults II 22.07±1.1 mm) were fed five concentrations (20 to 320 ml−1) ofAnuraeopsis fissa, or six concentrations (20 to 640 ml−1) in adults I and adults II, for 30 minutes. Post‐metanauplii consumed at maximum 66±9 rotifers ind.−1min.−1(mean±S.D.) while the largest adult females maximally ingested 347±37 rotifers min.−1.Regardless of predator size and sex, prey consumption was dependent on prey density. Functional response curves either plateaued or declined at 320 prey ml−1in post‐metanauplii, juveniles and adults I, and at 640 ml−1in adults II. Females consumed c. 40% more prey than males. On a daily basis, adult II females consumed up to 1.05 mg rotifer dry weight (10% of their own body weight) while post‐metanauplii consumed up to 0.2 mg DW (100% of their body weight). Intermediate stages had intermediate consumption rates. Filtration rates indicated that a fully grownS. proboscideusmay filter as much as 2 1 of water per day, suggesting that fairy shrimps, in their natural environm

ISSN:0020-9309    

DOI:10.1002/iroh.19940790403

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19940790404

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY

摘要:

AbstractThe colonization and succession of the macrozoobenthos in a polyhumic, winter‐regulated reservoir, Lake Kyrkösjärvi in Western Finland (62° 45′N, 22°48′E, A = 6.4 km2at summer HW, zmean= 2.5 m and zmax= 7 m) was studied from its filling in 1981 until 1989 (in 1981–83, 1986 and 1989). The zoobenthos was sampled over the whole reservoir bottom using qualitative and quantitative methods during three open‐water seasons and winter samples were taken in the regulated and submerged areas during the maximum draw down (2 m) in March‐April.Colonization during the first summer revealed two phases. The first phase featured dominance of actively swimming and adult‐dispersing taxa. The second phase was characterized by a mass occurence (high abundance and biomass) of chironomids (Chironomus, Glyptotendipes) and the isopodAsellus aquaticus. Asellusoriginated in a small bog pond in the northern outlet basin, and it was the dominant zoobenthic species during the study period. The species ofChironomus, most of them pool inhabitants of natural waters, succeeded each other.In the later study years, when the zoobenthos at the sites was determined more by habitat (spatially) than by the succession (temporally), the reservoir bottom could be divided into three areas: a) deep areas, ≧3 m, with an increasing occurrence of lacustrine species (eutrophic or dystrophic), b) shallower organic bottoms, ≦ 2 m, with many pool‐inhabiting and eurytopic species, and c) some eroded areas in the shallow littoral, ≦ 0.5 m, where lacustrine species became common.Water‐level regulation in winter killed only a small proportion of the fauna in the organic‐rich peatland and forest bottom areas representing the majority of the regulated zone. Hence, the regulated areas had almost everywhere high abundance and biomass values throughout the year, deviating from the results found by other authors in strongly regulated lakes, which have maximum values j

ISSN:0020-9309    

DOI:10.1002/iroh.19940790405

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY

摘要:

AbstractFactors affecting the processing rate of packs of southern sassafras (Atherosperma moschatum) leaves were investigated in an Australian cool temperate rainforest stream pool. Processing rate was strongly influenced by pack weight fitting a linear inverse relationship. Processing was not significantly (p>0.05) affected by whether the packs were placed on bricks or free on the stream bed. Free packs, but not packs on bricks, were processed more rapidly near the bank than in midstream (p = 0.050). Packs placed in 300 μm mesh bags, with one side unsealed were processed at the same rate as packs attached to bricks or free on the stream bed, but packs in sealed 300 μm mesh bags were processed significantly more slowly (p<10−4). Abscissed leaves were processed significantly more slowly than fresh leaves (p<10−5) and at a rate not significantly different to leaves sealed in mesh bags (p = 0.197). There was no consistent pattern of difference between processing rates in summer and winter. The results indicate that the size of litter packs may be a more important factor in influencing processing rate estimates than the method of attachment of the packs. The slow rate of processing of abscissed leaves compared with fresh leaves indicates that they were at most, slightly influenced by stream shredders. The absence of a consistent pattern of difference between summer and winter processing rates is consistent with the results of previous litter processing studies from southeastern Australia although no clear causal factor can be ident

ISSN:0020-9309    

DOI:10.1002/iroh.19940790406

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY

摘要:

AbstractThe seasonal succession of macrophyte communities on temporarily flooded wetlands in the Pantanal of Poconé was investigated by general surveys of the region and by semi‐quantitative surveys conducted on an area of 2500 m2with a gradient of water depth steep enough to permit a correlation of the species diversity with the depth and duration of flooding. The tropical wet‐and‐dry climate is the main determinant of the regional ecological conditions, and the seasonal variations of the physical and chemical factors, including the alternation between aquatic and terrestrial conditions over most of the area, produce a pronounced seasonal succession. During all of the seasons, the occurrence and growth of the plant species on the area surveyed was found to be inversely correlated with the water depth, but the statistical significance of the findings varied during the course of the year. The plant species are discussed individually, since little or nothing had previously been reported about the autecology of several of them. In addition, a general survey is made of the common aquatic and wetland plant species encountered in the region. On sites temporarily inundated during the course of the year, there is usually a succession of vegetation involving purely terrestrial and aquatic species as well as short‐lived annuals that appear only during the transition period from wet to dry and perennials with seasonal periods of dormancy during periods of excessive

ISSN:0020-9309    

DOI:10.1002/iroh.19940790407

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19940790408

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY

摘要:

AbstractCommunity structure of soft‐bottom macrobenthos from Newport Submarine Canyon, California, was compared to that on the adjoining shelf. Four hypotheses involving sediment characteristics, community structure, benthic feeding types and seasonal population fluctuations were posed. Results indicated that there were statistically significant differences between the canyon and adjoining shelf. Although there were differences in sediment geochemistry between the canyon and shelf, sediment type played the major role influencing differences in community structure and feeding. Operation of a shelf outfall has not demonstrably changed the canyon soft‐bottom macrobenthos for at least 16 years and probably closer to 27 ye

ISSN:0020-9309    

DOI:10.1002/iroh.19940790409

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY

摘要:

AbstractStudies on the Mediterranean Undercurrent in the Gulf of Cádiz showed that bacterial abundance and biomass as well as heterotrophic activity were higher in the water of Mediterranean origin in 500–800 m depth than in the adjacent Atlantic water. Upwelling processes off Mauretania and Portugal were accompanied by high bacterial numbers (bacterial plate counts) in the mixed surface layer. Changes in the qualitative composition of the bacterial flora in the waters off West Africa and in the Arabian Gulf were explained by the introduction of dust from desert regions into the sea by aeolian transport. In the Western Baltic migration of fish was detected by the presence of special bacteria, which normally live on or in these animals. Regions with complex hydrographic structures such as the Western and Central Baltic Sea revealed interesting relationships between bacteriological abundance and activity on the one hand and characteristic physical and chemical properties, such as origin, salinity and O2/H2S‐content, on the other. The importance of bacteriological variables for the characterization of different water bodies is discu

ISSN:0020-9309    

DOI:10.1002/iroh.19940790410

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19940790411

出版商:Akademie Verlag, Berlin    

年代:1994

数据来源: WILEY