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  • 11
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 18 (1987), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Experiments simulating spring acidic snowmelt episodes were conducted to determine the effects of short-term inputs of H+ and Al on the chemistry and biology of a poorly buffered mountain stream. HC1 and A1C13 were added in separate experiments to first- to third-order reaches of a New Hampshire stream.2. Cation exchange and Aln+ dissolution reactions neutralized experimentally added H +, whereas groundwater dilution was insignificant. Mobilized Ca++, Mg++ and Aln+ concentrations progressively increased from third- to first-order reaches during HC1 additions. Mobilization of Ca++ and Mg++ was greater during A1C13 than HC1 addition.3. Total phosphorus was mobilized from stream sediments during both HCI and A1C13 addition. Dissolved organic carbon (DOC) decreased during A1C13 addition in the second-order but not in the third-order reach. DOC concentration decreased during HCI addition only when Aln + mobilized from the stream bottom was 〉0.28 mg AI 11.4. Production of foam at the water surface during AlCl3 addition to a second-order and HCl addition to a first-order reach indicated a reduction in surface tension of the streamwater and may be related to complexation reactions between Al and DOC at low pH (4–5).5. Mayfly nymphs and blackfly and chironomid larvae drifted at greater rates from HCl- and AlCl3treated sections of first- and second-order streams than from corresponding reference areas.6. When stream pH was lowered to 5.25–5.5 by HCI alone (15 μg monomeric inorganic Al l−1), the behaviour of aquatic invertebrates did not change, but pH reduced to the same range during Al additions (280μg Al 1−1) did affect it. Therefore, fluctuating aluminium concentrations in low-order streams at a pH range of 4.5–5.5 may alter the biology and geochemistry of poorly buffered waters.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Stream ecologists have been puzzled by the apparent paradox that invertebrate populations persist in headwater streams despite the high frequency with which individuals drift downstream. To resolve this ‘drift paradox’, directions and distances of both larval and adult movement must be identified. Using over 50 interception traps in combination with results from several mark–capture experiments using 15N as a label, we tested the assumption that interception traps accurately represent the ultimate direction of adult insect flight.2. In several streams in the Hubbard Brook Experimental Forest, 76% of 15N-labelled stoneflies (Leuctra ferruginea) had flown upstream from where they emerged to where they were captured. In contrast, over 60% of stoneflies were flying downstream when captured, i.e. on the upstream side of an interception trap.3. The instantaneous direction, as indicated by the side of the interception trap on which they were captured, indicated the ultimate flight direction for fewer than 1/3 of the individuals captured. Thus, such traps did not accurately reflect the ultimate flight patterns of individuals, as indicated by mark–capture data.4. Conclusions drawn from interception trap counts regarding the direction of movement and the distribution and persistence of populations may need to be re-evaluated. We suggest that better tracking methods, including mass mark–capture studies using stable isotopes, be used to evaluate the potentially complex patterns of adult insect movement and the consequences of that movement for individuals and populations.
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  • 13
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Environmental science & technology 19 (1985), S. 646-648 
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Environmental science & technology 23 (1989), S. 137-143 
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
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  • 16
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Environmental science & technology 23 (1989), S. 362-365 
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
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  • 17
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Environmental science & technology 23 (1989), S. 754-759 
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
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  • 18
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 46 (2001), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Calcium (Ca) has been lost from forest soils at the Hubbard Brook Experimental Forest (HBEF) because of decreased atmospheric input of Ca and high input of acid anions. Through time, this Ca loss has led to low streamwater Ca concentration and this change may affect stream ecosystem processes. 
2. To test both the biogeochemical response of streams to increased calcium concentration and the role of streams in retaining calcium lost from soils, we added c. 120 μeq Ca L−1 as CaCl2 to two second-order streams at HBEF for 2 months. One stream (buffered) also received an equivalent amount of NaHCO3 to simulate the increase in pH and alkalinity if Ca were added with associated HCO3− ion. The other stream (unbuffered) received only CaCl2. We collected water samples along a transect above and below the addition site at 11 dates: two before, seven during, and two after the addition. 
3. Increase in pH in the buffered stream ranged from 5.6 to about 7.0 in the treated section. There was a net uptake of Ca on all sampling dates during the addition and these uptake rates were positively related to pH. Between 10 and 50% of the added Ca was taken up during the release in the 80-m study reach. In the unbuffered stream, there was net uptake of Ca on only two dates, suggesting lower Ca uptake. 
4. Water samples collected after the addition was stopped showed that a small fraction of the added Ca desorbed from sediments; the remainder was apparently in longer-term storage in the sediments. No Ca desorbed from the stream sediments in the unbuffered stream, showing that sorption/desorption may be controlled by a pH-induced increase in the number of exchange sites. 
5. These streams appeared to be a significant sink for Ca over a 2-month time scale, and thus, change in streamwater Ca during a year may be due to processing of Ca within the stream channel, as well as to changes in inputs from the catchment.
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  • 19
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. An extensive survey of Mirror Lake, New Hampshire, was carried out by divers with SCUBA to assess the importance of the freshwater mussel Elliptio complanata in this softwater lake ecosystem. Density (0.032 adults m−2), biomass (52 mg m−2 as dry organic matter) and annual production (6.4 mg m−2 as dry organic matter) of the mussel population are low when compared with results from other studies, corresponding with the general observation that mussels are scarce in soft, oligotrophic waters. We reject the traditional view that the low mussel density is a result of low calcium concentrations in Mirror Lake, and propose that mussel populations may be regulated by a scarcity of appropriate fish hosts in unproductive lakes. Elliptio complanata is probably not important in the metabolism or biochemistry of the Mirror Lake ecosystem.
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  • 20
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 292 (1981), S. 329-331 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Areas affected by acid precipitation are often located in northern latitudes where snow accumulates during long, cold winters. Snowmelt in spring then releases a large quantity of water and ions to streams and lakes14'15. For example, on average, 54% of the annual streamwater discharge within the ...
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