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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Effects of omnivorous shrimp in a montane tropical stream: sediment removal, disturbance of sessile invertebrates and enhancement of understory algal biomass (1993)
    Springer
    Oecologia 93 (1993), S. 1-11 
    Details
    ISSN: 1432-1939
    Keywords: Tropical stream ; Community structure ; Sedimentation ; Shrimp ; Algal periphyton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Freshwater shrimp dominate the faunal biomass of many headwater tropical streams: however, their role in community organization is unclear. Enclosure/exclosure experiments in a montane Puerto Rican stream examined direct and indirect effects of two dominant taxa of atyid (Atyidae) shrimp, Atya lanipes Holthuis and Xiphocaris elongata Guerin-Meneville. Both shrimp taxa caused significant reductions in sediment cover on rock substrata, reducing sedimentation and enhancing algal biovolume on clay tiles in cages. When tiles incubated in shrimp exclosures for 2 wks were placed outside of cages, atyid shrimp removed 100% of the sediment cover within a 30 min observation period. Atyid shrimp appear to play an important role in stream recovery after high discharge events by rapidly removing sediments and detritus deposited on benthic substrata in pools. We evaluated the mechanism by which A. lanipes influences algae and benthic insects by comparing patterns of algal biomass, taxonomic composition, and insect abundance between shrimp-exclusion and shrimp-presence treatments both with and without manual sediment removal. The shrimp exclusion treatment without manual sediment removal bad significantly lower algal biomass and greater sedimentation than all other treatments. The treatment in which shrimp were excluded but sediment was manually removed, however, accrued almost the same algal biovolume as the shrimp enclosure treatment, supporting the hypothesis that sediment removal enhances the biovolume of understory algal taxa. Algal community composition was similar between stream bottom bedrock exposed to natural densities of shrimp and all experimental treatments for both Atya and Xiphocaris: a diatom community strongly dominated (78–95%) by the adnate taxon, Achnanthes lanceolata Breb ex. Kutz. Atyid shrimp are important in determining the distribution and abundance of benthic insects through both direct and indirect effects. Sessile, retreat-building chironomid larvae (Chironomidae: Diptera) are negatively affected by both A. lanipes and X. elongata, through direct removal by foraging activities and/or indirectly through depression of sediment resources available to larvae for the construction of retreats. In constrast, the mobile grazer, Cloeodes maculipes (Baetidae: Ephemeroptera) was not adversely affected and atyid shrimp have the potential to exert positive indirect effects on this taxon by facilitating its exploitation of algal resources and/or through enhancement of understory algal food resources through sediment removal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00321183
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  • 3
    Electronic Resource
    Electronic Resource
    Inter-annual Fidelity to Summer Feeding Sites in Arctic Grayling (2000)
    Springer
    Environmental biology of fishes 59 (2000), S. 319-327 
    Details
    ISSN: 1573-5133
    Keywords: Thymallus arcticus ; river fertilization ; tagging ; habitat quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Inter-annual fidelity to summer feeding sites was assessed in adult Arctic grayling, Thymallus arcticus, in the Kuparuk River, Alaska using long-term (15 years) records of individually tagged fish. The Kuparuk River has been the site of a long-term fertilization experiment which allowed us to evaluate the effects of habitat quality on site fidelity. Fidelity to the entire 5 km experimental reach, the reference or fertilized zone of the river and to specific river locations was examined. On average, 32% of the arctic grayling caught in the experimental reach were recaptured within the reach in subsequent years. Grayling that returned to the reach displayed strong fidelity to river zones as well as to specific sites on the river. More than half of the fish were recaptured within 300 meters of the site where they were captured in previous years. There was no significant difference in fidelity to either the reference or the more productive fertilized zone. Unexpectedly, fidelity was unrelated to fish size (29–43 cm TL) or previous summer’s growth. Strong site fidelity appears to be an adaptation to a short summer during which sufficient resources must be acquired to sustain the fish through the long (9 month) Arctic winter leaving little time to explore alternative locations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007626507936
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  • 4
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    Structural and functional aspects of treated mine water and aquaculture effluent streams (2007)
    Springer
    Details
    Publication Date: 2007-03-03
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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  • 5
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    Effects of omnivorous shrimp in a montane tropical stream: sediment removal, disturbance of sessile invertebrates and enhancement of understory algal biomass (1993)
    Springer
    Details
    Publication Date: 1993-02-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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  • 6
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    Long-term survival of adult Arctic grayling (Thymallus arcticus) in the Kuparuk River, Alaska (2005)
    National Research Council Canada
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © National Research Council Canada, 2004. This article is posted here by permission of National Research Council Canada for personal use, not for redistribution. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences 61 (2004): 1954-1964, doi:10.1139/F04-126.
    Description: In many long-lived species such as Arctic grayling (Thymallus arcticus), population growth rate is most sensitive to changes in adult survival probabilities. Understanding the factors that regulate adult survival in this species should provide insight into the population dynamics of this and other long-lived Arctic species. Using the program MARK, we analyzed 17 years of mark–recapture data to estimate survival rates for Arctic grayling in the Kuparuk River, Alaska, from 1985 to 2000. Mean annual survival rates overall ranged from 0.39 to 1.0 and averaged 0.71 ± 0.05 for resident and 0.75 ± 0.05 for nonresident fish. Spending the summer in the more productive fertilized zone of the experimental reach had no influence on survival despite higher productivity on all trophic levels and consistently higher growth rates in Arctic grayling. None of the environmental (stream temperature, discharge, winter severity, and incidence of drought) or population parameters (growth, condition factor, and mean fish size) that we examined explained significant amounts of variance in survival rates. The lack of responsiveness of survival to annual environmental conditions was unexpected and suggests that multiyear factors or life history tactics that maintain survival at the expense of growth and fecundity likely determine survival.
    Description: This research was supported by National Science Foundation grants OPP-9911278 and DEB-9810222 in conjunction with the Long-term Ecological Research Program.
    Keywords: Arctic grayling ; Thymallus arcticus ; Adult survival probabilities
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: 423997 bytes
    Format: application/pdf
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