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  • 1
    Electronic Resource
    Electronic Resource
    Effects of agricultural development on processing of tussock leaf litter in high country New Zealand streams (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. We compare the rates and mechanisms of processing of tussock (Chionochloa spp.) leaf litter in six New Zealand streams draining grassland catchments that contrast in the extent to which they have been developed for pasture.2. Rates of processing, measured as rate of weight loss of leaf packs and rate of leaf softening, were at the slow end of the spectrum for vascular plant processing. Processing was faster at developed sites, mediated mainly through the influence of oxidized nitrogen concentration on microbial activity.3. Few invertebrate shredders colonized leaf packs and it is unlikely that invertebrates had an appreciable effect on leaf processing in our study streams, which do not effectively retain leaf litter. Very small headwater tributaries appear to retain leaf litter and possess a more abundant shredder community.4. Measures of leaf processing in our six streams were significantly correlated with Petersen's (1992) RCE score of stream condition. We discuss the potential for using rate of leaf litter processing as a method of bioassessment.5. Even the most degraded stream in our study is classed as ‘good’ using the RCE inventory system. Human impact in the Taieri River is relatively small compared with the degradation observed in some parts of the world.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1994.tb01136.x
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  • 2
    Electronic Resource
    Electronic Resource
    Secondary production of chironomid communities in insecticide-treated and untreated headwater streams (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 24 (1990), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 〈list xml:id="l1" style="custom"〉1 Production of chironomid communities of three first order, Appalachian Mountain streams was estimated and the effects of an insecticide-induced disturbance on chironomid production was examined.2 Annual production of non-Tanypodinae chironomids in the streams during the first study year (no treatment) ranged from 1366 to 3636 mg m−2, while production of Tanypodinae chironomids ranged from 48 to 116 mg m −2. Production/biomass ratios ranged between 19 and 23 for non-Tanypodinae and from 6 to 7 for Tanypodinae chironomids.3 Insecticide applications resulted in significantly lower chironomid densities and biomass in the treated stream relative to the pretreatment year and reference stream. Annual production of non-Tanypodinae (703 mg m−2) and Tanypodinae (32 mg m −2) chironomids in the treated stream decreased by 64% and 67%, respectively, compared with the pretreatment year. In contrast, production of non-Tanypodinae (2084 mg m−2) increased by 34% and production of Tanypodinae (96 mg m−2) by 57% in the reference stream.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1990.tb00721.x
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  • 3
    Electronic Resource
    Electronic Resource
    Community structure of Trichoptera in a mountain stream: spatial patterns of production and functional organization (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 20 (1988), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Annual production was estimated for Trichoptera occurring in each of three distinct habitats of a mountain stream: bedrock-outcrops, riffles and pools. Production was greatest on bedrock-outcrops (2608 mg ash-free dry weight m−2), followed by riffles (1038) and pools (950).2. Annual production in bedrock-outcrops and pools was dominated by single functional groups, with collector-filterers and shredders contributing 73% and 75% of the annual production, respectively. Production in riffles was due primarily to shredders (46%), followed by collector-filterers (27%).3. Taking account of the amount of stream area occupied by each habitat type, total annual production was estimated at 1336 mg AFDW m−2. 53% of this production was attributable to four taxa: Parapsyche cardis Ross (25%), Pycnopsyche gentilis (MacLachlan) (10%), Neophylax mitchelli Carpenter (9%) and Rhyacophila nigrita Banks (9%).4. Habitat-weighted production was distributed among functional groups as follows: collector-filterers (41%), shredders (29%), engulfing-predators (15%), scrapers (13%) and collector-gatherers (2%).5. The distinct taxonomic and functional structures of trichopteran sub-communities were shaped by the distinct physical characteristics of their principal habitats. Bedrock-outcrops were characterized by low roughness and high current and were sites of low deposition or organic matter; thus the predominance of collector-filterers. In contrast, the other habitats of greater roughness (riffles) and/or lower current (pools) were sites of deposition of food (e.g. leaf litter) and greatest shredder production.6. By distinguishing discrete mesoscale habitats, each with a functionally distinct caddisfly sub-community, we speculate that small mountain streams provided the diverse physical templates essential for the evolution of the major feeding tactics (e.g. scraping, shredding, filter-feeding) of the. Trichoptera.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1988.tb00438.x
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  • 4
    Electronic Resource
    Electronic Resource
    Production and litter processing by crayfish in an Appalachian mountain stream (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: SUMMARY 1. Mean annual density and biomass (B̄) of Cambarus bartonii in an Appalachian mountain stream (U.S.A.) was 12 individuals m−2 and 1669 mg (ash-free dry weight) m−2.2. Annual production (P) of C bartonii was 961 mg AFDW m−2. Despite high biomass, low growth rates resulted in low production and a low P/B̄ ratio of 0.58.3. While C bartonii constituted 61% of the total macroinvertebrate biomass, it contributed only 13% of annual community secondary production.4. Litter processing was positively related to temperature and crayfish size. Cambariis bartotnii was estimated to comminute 36 g m−2 y−1 of leaf litter (〉1 mm2) to 24 g m−〉2 y−1 fine particulate material (〈1 mm2). The annual pattern of litter comminution by crayfish was regulated by temperature. As a result, 〉5()% of shredding activity by crayfish occurred from June to September which was also the period of lowest litter standing crops and activity of other shredding macroinvertebrates.5. We speculate that during summer crayfish play an important role in temperate woodland streams by converting slowly processed leaf litter species (e.g. Rhododendron) to fine particles which are then available to collector-gatherers (e.g. Chironomidae, Oligochaeta).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1987.tb01314.x
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  • 5
    Electronic Resource
    Electronic Resource
    Book Reviews (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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01045_2.x
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  • 6
    Electronic Resource
    Electronic Resource
    Responses of a beaded Arctic stream to short-term N and P fertilisation (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. Oligotrophic Arctic streams are likely to be sensitive to changes in hydrology and nutrient inputs predicted to occur as a consequence of future climate and land use change. To investigate the potential consequences of nutrient enrichment for low-order Arctic streams, we added ammonium-N and phosphorous to a second-order beaded, tundra stream on Alaska's north slope. We measured responses in nutrient chemistry, chlorophyll a standing crop, and in the breakdown and macroinvertebrate colonisation of leaf litter over a 38-day summer period.2. During the addition, nutrient concentrations immediately downstream of the dripper averaged 6.4 μm ammonium-N and 0.45 μm soluble reactive P. Concentrations upstream of the dripper averaged 0.54 μm ammonium-N and 0.03 μm soluble reactive P. Uptake of both nutrients was rapid. Concentrations were reduced on average to 28% (ammonium-N) and 15% (inorganic P) of maximum values within 1500 m. Standing crops of chlorophyll a on standardised samplers were significantly higher by the end of the experiment. Breakdown rates of senescent willow (Salix sp.) and sedge (Carex sp.) litter and associated fungal biomass were also significantly increased by nutrient addition.3. Fertilisation resulted in four- to sevenfold higher macroinvertebrate abundance and two- to fourfold higher macroinvertebrate biomass in litter bags, as well as an increase in late-summer body mass of larval Nemoura stoneflies.4. Our results are consistent with those of similar studies of larger streams in the high-Arctic region. Based on our short-term experiment, increased inputs of nutrients into these ecosystems, whether caused by climate change or more local disturbance, are likely to have profound ecological consequences. Longer-term effects of enrichment, and their interaction with other components of future change in climate or land use, are more difficult to assess.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01319.x
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  • 7
    Electronic Resource
    Electronic Resource
    Life history and production of Paranephrops zealandicus in a forest stream, with comments about the sustainable harvest of a freshwater crayfish (1999)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 42 (1999), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Life history and production were assessed for the crayfish Paranephrops zealandicus in three reaches of a headwater stream with a catchment of regenerating coniferous-broadleaf forest in the south-east of the South Island of New Zealand.2. Crayfish density ranged from 3 to 4 m−2 in riffles and 4–12 m−2 in pools, depending on reach. Crayfish biomass (4–33 g AFDW m−2) and annual production (2–11 g AFDW m−2) were high compared with values reported elsewhere, while P:B ratio was low (0.33–0.43). This substantial production was dependent primarily upon high biomass rather than high growth rate.3. The crayfish of this population rank amongst the longest lived and slowest growing ever recorded. Individuals estimated to be 16+ year of age were not uncommon. Females became reproductively active at 6+ year. Fewer than 4% of females carried eggs, and young remained attached to females for at least 15 months.4. We propose that characteristics of this population are the consequence of a cool thermal regime (mean daily stream temperature = 7.0 °C, range 1.8–11.9 °C), and that low biomass turnover and poor reproductive rate precludes any sustainable commercial harvest of crayfish from streams in New Zealand with similar thermal regimes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1999.00482.x
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  • 8
    Electronic Resource
    Electronic Resource
    Catchment land-use, macroinvertebrates and detritus processing in headwater streams: taxonomic richness versus function (2002)
    Oxford UK : Blackwell Science Ltd.
    Freshwater biology 47 (2002), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. We used a litter bag technique to assess the effect of catchment land-use (forest, wetland, agriculture, urban) on the processing of red maple (Acer rubrum L.) litter in 17 streams in Maine, U.S.A. Litter processing by fungi was predicted to increase with nutrient concentrations along a gradient of land use, from relatively unmodified to highly modified. Litter processing by litter-shredding macroinvertebrates was predicted to decline along this gradient because of a decline in their taxonomic richness and biomass.2. Land use was associated with the anticipated gradient in nutrient and macroinvertebrate attributes, and a significant relationship was found between land use and nitrate concentration. There was, however, no significant relationship between land use and soluble reactive phosphorus (SRP) concentration. Similarly, shredder taxonomic richness was significantly related to land use type, whereas shredder biomass showed no significant relationship to land use.3. Attributes of the shredder assemblage structure and nutrient concentrations were both strong determinants of litter processing. Increasing biomass and taxonomic richness of shredders was significantly related to increasing rates of litter mass loss. Increasing concentrations of nitrate and SRP were significantly related to increasing rates of litter softening below threshold concentrations (approximately 0.20 mg NO3-N L–1 and 5 μg SRP L–1).4. The potentially additive effects of nitrate and SRP concentrations or shredder richness and biomass on litter processing rates were confounded by the lack of significant correlation between these pairs of variables. Consequently, rates of litter processing (as rates of softening or mass loss) did not vary systematically among different land use regimes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2002.00812.x
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  • 9
    Electronic Resource
    Electronic Resource
    Temporal shift in contribution of terrestrial organic matter to consumer production in a grassland river (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. We used stable isotopes to study the temporal (early summer versus autumn) pattern of use of terrestrial and aquatic sources of organic carbon by consumers in two bedrock-confined reaches of a grassland river in New Zealand. 
2. The major sources of organic carbon available to primary consumers were expected to be terrestrial leaf-litter and biofilm from the stream channel. These putative carbon sources showed no significant change in mean δ13C between summer and autumn. Leaf litter (mean δ13C〈−26.25) was depleted in 13C compared to biofilm (mean δ13C〉−19.92). 
3. In contrast to leaf litter and biofilm, the δ13C of consumers changed over time, being enriched in 13C in the autumn compared with early summer. Both the magnitude (〉5‰ in some cases) and rapidity of this shift (〈3 months) was surprising. 
4. A two-source mixing model indicated that, during early summer, terrestrial carbon comprised〉 50% of tissue carbon for 15 of the 17 taxa of aquatic consumers analysed. During autumn, terrestrial carbon comprised〉 50% of the tissue carbon of only five of 25 taxa. Because the mean δ13C of putative food sources was consistent over time, the shift in δ13C values for consumers is attributed to a change in relative amounts of terrestrial and aquatic carbon available for consumption. 
5. Because seston consists of a mixture of many particles of diverse origin, it may provide an integrated measure of catchment-wide sources of organic matter entering a stream channel. Like the tissues of most consumers, mean δ13C values for seston showed a significant shift toward 13C enrichment. This indicated that the relative availability of terrestrial carbon decreased from summer to autumn. 
6. The actual quantity of carbon contributed to the stream food-web by this potential terrestrial–aquatic link is unknown. Although terrestrial carbon may comprise a high proportion of the tissue carbon of consumers prior to summer, the majority of secondary production (and carbon sequestration) probably occurs during early summer as a consequence of rising temperature and high quality food in the form of biofilm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00648.x
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  • 10
    Electronic Resource
    Electronic Resource
    Ecosystem-level evidence for top-down and bottom-up control of production in a grassland stream system (1998)
    Springer
    Oecologia 115 (1998), S. 173-183 
    Details
    ISSN: 1432-1939
    Keywords: Key words Predation ; Food webs ; Trophic cascades ; Invertebrates ; Fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ecosystem-wide effects of introduced brown trout (Salmo trutta L.) and native river galaxias (Galaxiaseldoni McDowall) were studied by analysing ecosystem production budgets for two adjacent tributaries of a grassland stream-system in the South Island of New Zealand. One tributary was inhabited by brown trout, the other by river galaxias. No other fish species were present in either stream. The budget for the river galaxias stream indicated little top-down control of invertebrates by fish predation (river galaxias consumed ∼18% of available prey production). A large proportion of annual net primary production was required to support production by invertebrates (invertebrates consumed an average of ∼75% of available primary production), and mean surplus primary production (i.e. not consumed) was not significantly different from zero. Primary and secondary production were presumably mutually limiting in this system (i.e. controlled by simultaneous top-down and bottom-up mechanisms). In contrast, the budget for the brown trout stream indicated extreme top-down control of invertebrate populations by fish predation; essentially all invertebrate production (∼100%) was required to support trout production. Invertebrate production required only a minor portion of annual net primary production (∼21%) and primary production was presumably controlled by mechanisms other than grazing (e.g. sloughing, nutrient limitation). Predatory invertebrates had little quantitative effect on prey populations in either stream. Recent experimental studies of invertebrate behaviour, fish behaviour, and food-web structure in New Zealand streams with physically stable channels indicate that a trophic cascade should be observed in streams inhabited by brown trout, in contrast to those inhabited by native fish. The results reported here provide ecosystem-level evidence supporting this prediction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050505
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