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  • 1
    Electronic Resource
    Electronic Resource
    Extracellular enzyme activity associated with suspended matter in the River Rhine (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 26 (1991), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Spatial and temporal variations in exoenzymatic proteolysis and alkaline phosphatase activity in the River Rhine were measured fluorometrically using L-leucyi (ß-naphthylamide and methylumbelliferyl phosphate (MUFP), respectively, as test substances.2. Extracellular proteolytic activity measured in the lower 150-km reach of the river during 1988 followed the changes in the concentration of particulate nitrogen associated with the occurrence of phytoplankton blooms. Alkaline phosphatase activity was not related to the concentration of particulate phosphate and correlated weakly with particulate nitrogen and phytoplankton concentrations.3. Seasonal observations (1989) in the lower River Rhine and transport studies in a 660-km-long reach of the river (1990) indicated that the variations in the exoenzyme activities were unrelated (or not closely related) to fluctuating bacterial numbers. Exoproteolytic activity correlated well with thymidine incorporation and algal density, confirming indications in the literature that the exoenzyme activity is related to the overall metabolic rate of the bacterial populations.4. The exoproteolytic activities in the Rhine are similar to the highest observed in eutrophic freshwaters, indicating a rapid turnover of proteins in the river. Bacterial phosphatase activities, measured with MUFP, were similar to those in the few marine and inland waters studied so far. However, phosphate-limited algal blooms, such as reported for the plume of the Rhine in the North Sea, are likely to contribute substantially to hydrolysis of natural organic phosphates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1991.tb01415.x
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  • 2
    Electronic Resource
    Electronic Resource
    Seasonal variation in composition and production of planktonic communities in the lower River Rhine (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 32 (1994), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The composition and activity of phytoplankton, zooplankton and bacterioplankton in the lower River Rhine were measured in 1990 as part of an international biological inventory of the river. A seasonal study was carried out on two stations: one in the river mouth (km 1019) and one at the German/Dutch border (km 863).2. High densities of phytoplankton (with up to 140 μg chlorophyll a 1-−1) and occasional depletion of dissolved silicate were observed at the upstream station. Phosphate concentrations were also lowered during blooms.3. Phytoplankton blooms, dominated by a few species of centric diatoms, declined one order of magnitude during downstream transport. During non-bloom conditions (low) algal densities were maintained during transport, or increased slightly, indicating the suitability of the river reach for algal growth.4. Bacterial cell number and production (measured by the 3H-thymidine method) showed a broad summer maximum with activity peaks (0.5 nK 〈 M thymidine h−1) coincident with declining phytoplankton blooms. Winter values of bacterial production (0.02–0.05 n 〈 Mh−1) were substantial, probably as a result of allochthonous input of organic matter.5. Rotifers and crustaceans made up the greater part of the zooplankton biovolume, but at the upstream station the contribution of Dreissena larvae and rhizopods was also substantial. High zooplankton biovolumes, of over 500 × 106μm31-−1, were observed only during the phytoplankton spring bloom.6. Quantitative relationships between the high phytoplankton production (2.1–3.4 gCm−2 day−1), the high bacterial substrate uptake (0.5–1gCm−2 day−1), and grazing were analysed for the growing season 1990. Algal grazing by metazoan herbivores was substantial only during spring, while the role of phagotrophic microplankton and cell lysis were indicated as major factors responsible for the downstream decline of phytoplankton blooms in the lower Rhine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1994.tb01144.x
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  • 3
    Electronic Resource
    Electronic Resource
    Phosphate regime structures species composition in cultured phototrophic biofilms (2004)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The effect of phosphate on species composition in biofilms was studied under three different phosphate regimes (0.5, 5 and 50 μm) in two different multi species communities: one composed of the four diatom species Melosira varians, Nitzschia perminuta, Navicula trivialis and Achnanthes lanceolata and one containing these diatom species plus the two cyanobacterial species Leptolyngbya foveolarum and Cylindrospermum stagnale.2. Algal growth in monocultures and mixtures was measured as chlorophyll a and PAM fluorimetry was applied to document density and physiological condition of the two main groups of photosynthetic organisms in mixed cultures.3. In phosphate-replete communities, a single species dominated the community (N. perminuta in the diatom mixture and L. foveolarum in the all species mixture), while in the phosphate-deprived communities several species persisted, in spite of severe phosphate limitation.4. We conclude that high supply of phosphate enables the species L. foveolarum, and to a lesser extent N. perminuta, to overgrow biofilm consortia, facilitated by their filamentous growth form, motility or the excretion of inhibitors. The persistence of several species under a low phosphate regime is explained by a less intense interspecific interaction in low-density biofilms. This clarifies field observations published previously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01189.x
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  • 4
    Electronic Resource
    Electronic Resource
    Observations and experiments on the population dynamics of epipelic diatoms from an estuarine mudflat
    Amsterdam : Elsevier
    Estuarine and Coastal Marine Science 14 (1982), S. 471-487 
    Details
    ISSN: 0302-3524
    Keywords: Ems estuary ; algal culture ; benthos ; micro-algae ; population dynamics ; productivity
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Geography , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0302-3524(82)80071-6
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  • 5
    Electronic Resource
    Electronic Resource
    Chronic ecotoxicity of Zn and Pb to the zebra mussel Dreissena polymorpha
    Amsterdam : Elsevier
    Aquatic Toxicology 30 (1994), S. 77-89 
    Details
    ISSN: 0166-445X
    Keywords: Dreissena polymorpha ; Filtration rate ; Lead ; Metal accumulation ; Mussel ; Zinc
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0166-445X(94)90007-8
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  • 6
    Electronic Resource
    Electronic Resource
    Translocation of Microbenthic Algal Assemblages Used for In Situ Analysis of Metal Pollution in Rivers (1999)
    Springer
    Archives of environmental contamination and toxicology 37 (1999), S. 19-28 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. Effects of metal pollution from a zinc factory on microbenthic algal communities were assessed in three neighboring streams on the Dutch-Belgian border. Diatom species composition was experimentally related to water quality by transferring racks with colonized glass discs from a polluted stream to a reference stream and vice versa. The succession of species and the changes in biomass and metal accumulation were measured during experiments in spring, autumn, and winter. Metal concentrations and dry weight in translocated biofilms tended to conform with those in local biofilms within an incubation time of 14 to 18 days. Bray-Curtis similarity values from the different communities indicated that diatom communities responded more completely to the metal-polluted conditions than to the reference water quality. Cymbella minuta, Diatoma vulgare var. ehrenbergii, Navicula sp., and Melosira varians had a lower percentage in assemblages placed in the metal-polluted streams. In contrast, Pinnularia sp. and Neidium ampliatum decreased in assemblages from the polluted streams that were transferred to the reference stream. Achnanthes minutissima and Navicula seminulum (N. atomus) proliferated on any translocation, possibly reflecting an opportunistic strategy and a high tolerance for Zn and Cd. The behavior of the species in relation to metal pollution generally accorded with observations in the literature. However, it seems that metal tolerance is not the only selective factor, and other ecological variables may also influence the composition of microphytobenthic communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449900485
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  • 7
    Electronic Resource
    Electronic Resource
    Alterations in life-history traits of Chironomus riparius (diptera) obtained from metal contaminated rivers (1995)
    Springer
    Archives of environmental contamination and toxicology 29 (1995), S. 469-475 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Cadmium tolerance in field populations of the midge Chironomus riparius was studied by comparing the effects of chronic cadmium exposure on several life-history parameters using first generation, laboratory-reared animals. Differences between populations of C. riparius were therefore assumed to have a genetic basis. Field populations naturally exposed to metals were less sensitive to cadmium compared to unexposed populations, when larval development time and hatchability of the egg masses were measured. However, larval mortality still increased with cadmium exposure and no differences between exposed and unexposed populations were observed. Furthermore, life-history patterns differed between metal tolerant and nontolerant populations grown under control conditions. Metal tolerant populations were characterized by a high control mortality (50%) or an increased larval development time (with 30%). The results, therefore, indicated the presence of costs of tolerance, while a direct selection on certain life-history characteristics due to metal pollution was absent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208376
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  • 8
    Electronic Resource
    Electronic Resource
    Induced Metal Tolerance in Microbenthic Communities from Three Lowland Rivers with Different Metal Loads (1999)
    Springer
    Archives of environmental contamination and toxicology 36 (1999), S. 384-391 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The response of microbenthic communities to sustained metal stress was studied in three lowland rivers with different levels of pollution. Tolerance against zinc and cadmium was determined in short-term toxicity tests with microbenthic assemblages colonizing glass discs. Photosynthetic activity served as an endpoint in tests for algae, whereas for bacteria thymidine incorporation was determined. For bacterial assemblages from unpolluted locations, EC50 values in short-term tests ranged between 6.7 and 56.2 μM zinc, and 8.7 and 25.5 μM cadmium, respectively. Bacterial assemblages from the two most polluted sites were significantly more tolerant for zinc (EC50: 994 μM and 〉1,000 μM) and cadmium (EC50: 218 μM and 154 μM). Results indicated a shift in community composition toward pollution-adapted organisms when a threshold concentration of 1 μM zinc is exceeded. Although an increasing community tolerance was also indicated for algae, EC50 values for microbenthic algae from all sites exceeded in most cases the highest metal concentrations tested (Zn: 1,000 μM; Cd: 320 μM). Since species composition of algal assemblages was found to change at much lower metal levels, it is concluded that short-term toxicity tests measuring photosynthesis inhibition do not reflect well the long-term effects of these metals. Toxic effects of metals on both algal and bacterial assemblages are attenuated by precipitation and complexing capacities of the biofilm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006610
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  • 9
    Electronic Resource
    Electronic Resource
    Short-Term Ecotoxicity of a Mixture of Five Metals to the Zebra Mussel Dreissena polymorpha (1999)
    Springer
    Bulletin of environmental contamination and toxicology 63 (1999), S. 805-812 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001289901050
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  • 10
    Electronic Resource
    Electronic Resource
    Salinity tolerance of benthic estuarine diatoms as tested with a rapid polarographic measurement of photosynthesis (1976)
    Springer
    Marine biology 39 (1976), S. 11-18 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurements of net photosynthesis of benthic estuarine diatoms were made by polarographic registration of oxygen saturation. A measuring cell was constructed in which media with salinities of 2.0 to 100.7‰ were pumped over the algae between measurements. Diatoms from unialgal cultures and mixed populations from intertidal flats appeared to be highly tolerant of extreme salinities. During short-term exposures (20 min) the net photosynthesis of the algae did not drop below 70% of the initial values, within the salinity range 4.0 to 60.0‰. Prolonged exposure (up to 6 h) gave essentially the same results. Populations of benthic diatoms, sampled from field stations with mean salinities of about 30, 12, and below 5‰, showed only gradual differences in their tolerance of salinities between 2.0 and 33.7‰. Two species, Navicula arenaria and Nitzschia sigma, were cultured in media ranging in salinity from 8.0 to 45.0‰ and from 2.0 to 45‰, respectively. The tolerance to changing salinity was only slightly affected by the salinity of the medium in the preculture. The role of salinity in the production and distribution of intertidal diatoms is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395587
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