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  • 11
    Electronic Resource
    Electronic Resource
    Surface water chemistry. Reply to comments (1989)
    s.l. : American Chemical Society
    Environmental science & technology 23 (1989), S. 754-759 
    Details
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/es00065a003
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  • 12
    Electronic Resource
    Electronic Resource
    Importance of hydrogen ions and aluminium in regulating the structure and function of stream ecosystems: an experimental test (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 18 (1987), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1365-2427.1987.tb01293.x
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  • 13
    Electronic Resource
    Electronic Resource
    Contradictory results from different methods for measuring direction of insect flight (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. 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01266.x
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  • 14
    Electronic Resource
    Electronic Resource
    Controls on periphyton biomass in heterotrophic streams (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. Headwater streams of the Hubbard Brook Experimental Forest (HBEF) are typically characterised by a periphyton assemblage of low biomass and diversity. However, periphyton blooms have been observed following catchment deforestation experiments and occasionally during the annual spring thaw before canopy leaf-out.2. There is pronounced seasonal variation in both nutrient and light availability in HBEF streams. Stream water nitrogen (N) concentrations and light levels are higher before canopy leaf-out and after leaf senescence and are lower during the growing season. Periphyton accrual rates also change seasonally; they are highest in spring prior to leaf-out and significantly lower during summer and in autumn.3. Periphyton biomass rarely responded positively to in-situ experimental enrichment with nitrogen or phosphorus. In the summer, nutrient enrichment overall had no effect on periphyton biomass, while outside the growing season N enrichment had inhibitory effects on periphyton.4. Despite these experimental results, surveys of ambient chlorophyll a concentrations in streams across the HBEF demonstrated no relationship between streamwater dissolved inorganic N or P concentrations and benthic chlorophyll a.5. Our results suggest that HBEF periphyton communities are not closely regulated by nutrient availability, even during periods of high light availability. The inhibitory effects of nutrient enrichment outside the growing season are interesting, but further research is necessary to elucidate the mechanisms driving these responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2426.2003.01161.x
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  • 15
    Electronic Resource
    Electronic Resource
    Biomass and annual production of the freshwater mussel Elliptio complanata in an oligotrophic softwater lake (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 11 (1981), S. 0 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1981.tb01275.x
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  • 16
    Electronic Resource
    Electronic Resource
    Stable isotopes identify dispersal patterns of stonefly populations living along stream corridors (2005)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 50 (2005), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Populations in different locations can exchange individuals depending on the distribution and connectivity of suitable habitat, and the dispersal capabilities and behaviour of the organisms. We used an isotopic tracer, 15N, to label stoneflies (Leuctra ferruginea) to determine the extent of adult flight along stream corridors and between streams where their larvae live.2. In four mass, mark-capture experiments we added 15NH4Cl continuously for several weeks to label specific regions of streams within the Hubbard Brook Experimental Forest, NH, U.S.A. We collected adult stoneflies along the labelled streams (up to 1.5 km of stream length), on transects through the forest away from labelled sections (up to 500 m), and along an 800-m reach of adjacent tributary that flows into a labelled stream.3. Of 966 individual adult stoneflies collected and analysed for 15N, 20% were labelled. Most labelled stoneflies were captured along stream corridors and had flown upstream a mean distance of 211 m; the net movement of the population (upstream + downstream) estimated from the midpoint of the labelled sections was 126 m upstream. The furthest male and female travelled approximately 730 m and approximately 663 m upstream, respectively. We also captured labelled mature females along an unlabelled tributary and along a forest transect 500 m from the labelled stream, thus demonstrating cross-watershed dispersal.4. We conclude that the adjacent forest was not a barrier to dispersal between catchments, and adult dispersal linked stonefly populations among streams across a landscape within one generation. Our data on the extent of adult dispersal provide a basis for a conceptual model identifying the boundaries of these populations, whose larvae are restricted to stream channels, and whose females must return to streams to oviposit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2005.01387.x
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  • 17
    Electronic Resource
    Electronic Resource
    The influence of dissolved nutrients and particulate organic matter quality on microbial respiration and biomass in a forest stream (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Although dissolved nutrients and the quality of particulate organic matter (POM) influence microbial processes in aquatic systems, these factors have rarely been considered simultaneously. We manipulated dissolved nutrient concentrations and POM type in three contiguous reaches (reference, nitrogen, nitrogen + phosphorus) of a low nutrient, third-order stream at Hubbard Brook Experimental Forest (U.S.A). In each reach we placed species of leaves (mean C : N of 68 and C : P of 2284) and wood (mean C : N of 721 and C : P of 60 654) that differed in elemental composition. We measured the respiration and biomass of microbes associated with this POM before and after nutrient addition.2. Before nutrient addition, microbial respiration rates and biomass were higher for leaves than for wood. Respiration rates of microbes associated with wood showed a larger response to increased dissolved nutrient concentrations than respiration rates of microbes associated with leaves, suggesting that the response of microbes to increased dissolved nutrients was influenced by the quality of their substrate.3. Overall, dissolved nutrients had strong positive effects on microbial respiration and fungal, but not bacterial, biomass, indicating that microbial respiration and fungi were nutrient limited. The concentration of nitrate in the enriched reaches was within the range of natural variation in forest streams, suggesting that natural variation in nitrate among forest streams influences carbon mineralisation and fungal biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01141.x
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  • 18
    Electronic Resource
    Electronic Resource
    Biogeochemical responses of two forest streams to a 2-month calcium addition (2001)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 46 (2001), S. 0 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00660.x
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  • 19
    Electronic Resource
    Electronic Resource
    Buffering an Acidic Stream in New Hampshire with a Silicate Mineral (2004)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Restoration ecology 12 (2004), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ground and pelletized Wollastonite (Wo; CaSiO3) was added to a 50-m reach of an anthropogenically acidified stream within the Hubbard Brook Experimental Forest, New Hampshire, to evaluate its buffering and restoration potential. The Wo was highly effective in raising the pH, acid-neutralizing capacity (ANC), dissolved inorganic carbon (DIC), and Ca2+ concentrations of the stream water, but during the short duration of the experiment had no discernable effect on the stream biota. After initial, spike-like fluctuations in pH and concentrations of ANC, DIC, and Ca2+, the relatively slow dissolution rates of the Wo dampened extreme concentrations and contributed to relatively long-lasting (4 months) amelioration of streamwater acidity. Changes in concentrations of Ca2+, dissolved Si, ANC, and DIC were inversely related to streamflow. After several high, stream-discharge events, concentrations quickly and consistently returned to pre-event conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1061-2971.2004.00357.x
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  • 20
    Electronic Resource
    Electronic Resource
    Decrease in precipitation acidity resulting from decreased SO 2− 4 concentration (1987)
    [s.l.] : Nature Publishing Group
    Nature 325 (1987), S. 244-246 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] During the 20-year period 1964-1983, decreases in concentration and deposition of SOj" (Fig. la) in precipitation at HBEF have been attributed to decreases in SO2 emissions in the northeastern and midwestern USA (Environmental Protection Agency regions I, II and V)10'11. Significant decreasing ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/325244a0
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