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  • 1
    ISSN: 1573-5117
    Keywords: benthos ; Colorado ; fish ; coal mining ; periphyton ; stream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An aquatic biological survey was conducted in 1979–1980 to determine the effects of drainage from an active coal strip-mine on Trout Creek, in northwest Colorado, U.S.A. Sampling was conducted over four seasons at four stations for periphyton, benthic invertebrates and fish. Periphyton in Trout Creek changed in the relative abundance of algae divisions in no apparent relation to mining. Diatoms were the predominant division at all sites. Golden-brown algae were abundant in spring at the stations upstream and adjacent to the mine. Blue-green algae were relatively important at stations upstream and downstream of the mine in winter. Benthic invertebrates exhibited a progressive increase in density, biomass and number of taxa from the upstream station to the downstream station. Shannon-Wiener diversity index for bethic invertebrates decreased slightly downstream of mine drainage but remained indicative of a clean water community. Aquatic insects (especially Trichoptera) were the predominant invertebrates at all stations. Analysis of functional groups of benthic invertebrates revealed increased importance of collector species at the lower sites while shredders were most important upstream of the mine. Unlike the invertebrates, fish exhibited slightly lower biomass at the station adjacent to the mine. The decrease was due to fewer salmonids. However, salmonid density and biomass increased substantially at the station just downstream of the mine. Non-game species (suckers and minnows) increased in numbers downstream and were most abundant at the lowest station. This coal strip-mine had little discernable adverse effects on the periphyton and invertebrates of Trout Creek. Fish populations did not appear to be significantly affected by the mine. Apparently, the presence of settling ponds and a buffer zone of unmined land between the mine and the stream helped to minimize adverse effects.
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  • 2
    ISSN: 1573-5117
    Keywords: carbon dioxide ; 14C ; assimilation ; duckweed ; Spirodela polyrrhiza aquatic plant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Carbon dioxide assimilation by duckweed, S. polyrrhiza, was measured using a glass assimilation box and 14C-NaHCO3, under different pH conditions of water. S. polyrrhiza assimilates carbon dioxide from both air and water. The carbon assimilation from air is comparable to the assimilation from water under normal pH conditions.
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  • 3
    ISSN: 1573-5117
    Keywords: fish ; Siluriformes ; Sisoridae ; Thailand ; Burma ; new species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Erethistes maesotensis spec. nov. is described form the Mae Nam Moei, a tributary of the Salween River, near Mae Sot on the Thai-Burmese border.
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  • 4
    ISSN: 1573-5117
    Keywords: zooplankton ; Calanoida ; fecundity ; sex ratio ; reproductive rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study on the reproduction of M. laciniatus in Lake La Caldera during the ice-free period of the years 1975, 1976 and 1977 has been carried out. Values obtained as to sex ratio, production of spermatophores and eggs as well as fecundity and reproductive rates have allowed us to establish two well-differentiated periods in the breeding season of the population: A first period of maximum reproductive activity, at the beginning of the breeding season (before freezing of the lake), characterized by more males than females, a high rate of production of spermatophores and, generally, a low production of eggs and a low reproductive rate. A later period, following the thaw of the lake, and in which the population is composed mainly of nauplii and copepodids. Females dominate over males. Reproductive activity measured by the ratios of spermatophores per male and spermatophores per female is very limited. Conversely, high production of eggs and a high reproductive rate (most females are ovigerous) is observed. Mechanisms which determine both periods and their possible adaptive value, are discussed.
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  • 5
    ISSN: 1573-5117
    Keywords: heterotrophic assimilation ; amino acids ; diel variation ; carbon flux ; eutrophic lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Concentration of dissolved free amino acids (DFAA) and assimilation of the 5 most abundant DFAA (glutamic acid, serine, glycine, alanine and ornithine) were measured at 3-h intervals over 27 h in two Danish, eutrophic lakes. The carbon flux of the amino acid assimilation was compared with the major routes of carbon flux, including primary production, bacterial production and zooplankton grazing. In Frederiksborg Slotssø, the mean DFAA concentration was 275 nM with distinct peaks (up to 783 nM) 3 h after sunrise. Assimilation rates of the 5 amino acids amounted on the average to 2.03 µg Cl−1 h−1, but high values up to 7.41 µg Cl−1 h−1 occurred 3 h after sunrise and at midnight. The mean turnover time of the amino acid pools was 3.2 h. In Lake Mossø, the mean DFAA concentration was 592 nM with peak of 1 161 nM at dusk. The assimilation rate averaged 0.44 µg Cl−1 h−1, and the mean turnover time of the amino acid pools was 39 h. In Lake Mossø, similar turnover times of glutamic acid and serine were determined from the 14C-amino acid tracer technique and Michaelis-Menten uptake kinetics, indicating that the tracer technique gave reliable values of the actual assimilation. The average respiration percentages of the assimilated amino acids were 45% in Frederiksborg Slotssø and 51% in Lake Mossø. Extracellular organic carbon (EOC) released from the phytoplankton contributed DFAA to the water. In Lake Mossø, 81% of the ambient EOC pool was 〈700 daltons and 9.3% of the EOC was DFAA. This corresponded to about 2.4% of the DFAA pool. Bacterial productivity, determined by means of ‘frequency of dividing cells’ and 35S-SO4 dark uptake techniques gave similar results and constituted 4.5 and 3.7 µg Cl−1 h−1 in Frederiksborg Slotssø and Lake Mossø, respectively. The bacterial productivity suggested that DFAA were essential substrates to the bacteria, especially in Frederiksborg Slotssø. The zooplankton biomass in Frederiksborg Slotssø was six times larger than that in Lake Mossø, but cladocerans were dominant in both lakes. The zooplankton grazing probably was an important regulatory factor for the bacterial productivity.
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  • 6
    ISSN: 1573-5117
    Keywords: Chaoborus ; coexistence ; life cycles ; feeding ; growth rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Crawford Lake, a small meromictic water body in southern Ontario, Canada, the life cycles of planktonic Chaoborus flavicans and C. punctipennis were out of phase by about two months, the former pupating from mid May through mid June and the latter from July through September. C. flavicans possibly produced a second annual generation. Fourth instars of both species were strong diel migrators and occupied similar strata at most times. C. punctipennis fourth instar diet consisted almost entirely of rotifers. C. flavicans ate rotifers but fed heavily also on daphnids in May and August. C. punctipennis fourth instars showed little growth until early spring, possibly owing to a sparseness of rotifers, then grew rapidly until pupation. C. flavicans had a slow, but relatively constant growth rate at all times during the open water season, presumably because its greater mouth gape allowed it a wider range of food items.
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  • 7
    ISSN: 1573-5117
    Keywords: phytoplankton ; macrophyte decline ; light limitation ; competition ; littoral
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A dramatic decline in biomass and areal coverage of the submersed macrophyte Myriophyllum spicatum in Lake Wingra, Wisconsin, USA during the mid-1970's is documented using aerial photography, vegetation surveys, and quadrat biomass sampling. Over the same period, light penetration as measured by Secchi disc transparency and extinction coefficient decreased substantially. During this period, extinction coefficient was closely correlated with chlorophyll a levels implicating phytoplankton as the major source of decreased light penetration. A growth model for M. spicatum predicts a substantial decline in macrophyte biomass when extinction coefficient is increased to the levels reported since 1977. Available data do not show whether the phytoplankton increase preceeded or followed the macrophyte decline. Nonetheless it is clear that phytoplankton growth can account for a substantial portion of the decline and that macrophyte recovery will be difficult given the phytoplankton-induced decrease in water clarity.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 107 (1983), S. 193-201 
    ISSN: 1573-5117
    Keywords: Nematoda ; Oncholaimus ; Sahara ; freshwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oncholaimus sahariensis sp.n. is described from an oasis in the Algerian Sahara. It differs from O. aquaedulcis Schneider, 1937 and O. deconincki Heyns & Coomans, 1977, the only other freshwater species in the genus, in the more posteriorly situated vulva, the spicules which are longer than in O. deconincki but shorter than in O. aquaedulcis, and various other characteristics. The new species is unusual in that the whole female reproductive system as well as the demanian system are located on the left side of the intestine, whereas the reproductive system is normally to the right in Oncholaimoidea. Problems concerning the validity and differentiation of Oncholaimium Cobb, 1930 are discussed, at the same time explaining why the new species is placed in Oncholaimus rather than in Oncholaimium.
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  • 9
    ISSN: 1573-5117
    Keywords: aquatic drift ; black flies ; sibling species ; periodicity ; running water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Larval (5th-final instar) drift patterns of five species of black flies (Prosimulium mixtum, Stegopterna mutata, Simulium tuberosum FG, S. vittatum IIIL-1, and S. vittatum IS-7) were analyzed. The diel drift patterns were not species-specific, but consistently exhibited a marked increase after sunset, preceded by a period of minimal drift. The drift minimum generally occurred during or shortly after the period of maximum water temperature. Larvae showed significantly more nocturnal than diurnal drift. Pupal drift was attributed to accidental detachment from the substrate. Adult drift was over 90% diurnal and usually composed primarily of teneral individuals. Upstream larval movements of the S. vittatum and S. tuberosum complexes were each less than 6.5% of the total upstream and downstream larval movements. The proportion of parasitized larvae of the S. vittatum and S. tuberosum complexes was generally higher in the benthos than in the drift. Based in part on data included in a thesis submitted by the senior author to The Pennsylvania State University in partial fulfillment of the requirements for the Ph. D. degree.
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  • 10
    ISSN: 1573-5117
    Keywords: lakes ; eutrophication ; phytoplankton populations ; Asterionella formosa ; Tabellaria fenestrata ; bioassays ; nutrient growth limitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Laboratory batch experiments with dilute phytoplankton communities were carried out to determine growth-limiting nutrients and the degree of growth limitation for Asterionella formosa, Hass., Tabellaria fenestrata (Lyngb.) Kütz. and red species of Oscillatoria under specific temperature and light conditions. Water samples from five Norwegian lakes with average epilimnetic total phosphorus concentrations ranging from 5 to 30 µg P per 1 were investigated. Both enrichment and transplant experiments were carried out. In samples from the most oligotrophic lakes (Lake Randsfjorden and Lake Tyrifjorden) phosphorus was found to be the growth-limiting nutrient. In samples from Lake Mjøsa silicate was also growth-limiting for the diatoms, while nitrogen could be limiting for both asterionella and Oscillatoria from Lake Steinsfjorden. Phosphorus was often the only limiting nutrient determined for Oscillatoria in Lake Gjersjøen (the most eutrophic of the lakes). In samples from this lake, however, Asterionella was also growth-limited directly or indirectly as a result of high (pH 〉 9). This was also found for Asterionella and Tabellaria from lake Mjøsa by means of transplant experiments. Oscillatoria from Lake Gjersjøen could not grow in filtered water from Lake Mjøsa but obtained maximum growth rate after addition of phosphate and chelated iron in combination.
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