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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © Inter-Research, 2008. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 369 (2008): 193-204, doi:10.3354/meps07644.
    Description: Salt marshes are important coastal ecosystems whose trophic function can be monitored with stable isotopes of abundant fish biosentinel species such as the mummichog Fundulus heteroclitus and the Atlantic silverside Menidia menidia. We compared movement patterns and feeding biology of these species in the summers of 1999 and 2000 in the Rowley River salt marsh estuary north of Boston, Massachusetts, USA. A 15N tracer addition experiment showed that fish of both species were more resident than transient, with mummichogs resident at scales of 1 km or less. Natural abundance stable isotope C, N, and S distributions showed that mummichogs feed more strongly in the benthic food web while silversides feed more in the planktonic food web, with % benthic feeding respectively averaging 58 ± 5 and 32 ± 3% (mean ± 95% confidence limit, CL). For both species, isotope results indicated considerable individual specialization in foraging behavior, likely related to use of channel habitat versus use of the marsh. Power analysis showed that measuring 3 composite samples each comprising 10 to 15 individual fish should provide relatively low errors of 0.5‰ (95% CL) or less around stable isotope averages. Use of such composite samples in monitoring programs will allow detection of significant temporal and spatial changes in benthic-planktonic coupling for salt marsh ecosystems, as recorded in average fish diets. Analyzing some individual fish also is recommended to obtain more detailed information on fish food sources, feeding specializations, and end-member isotope values used in estimating importance of benthic and planktonic food sources.
    Description: This work was supported by Louisiana SeaGrant Projects R/CEH-13 and R-EFH-07, NOAA MULTISTRESS award 16OP2670, and NSF award DEB 9815598 and BES SGER award 0553138-001.
    Keywords: Stable isotope analysis ; Salt marsh ; Fish ; Monitoring ; Power analysis ; Benthic microalgae ; Spartina
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © Inter-Research, 2008. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 354 (2008): 35-46, doi:10.3354/meps07170.
    Description: We examined the effects of increased nutrient availability on nitrogen (N) dynamics in dominant New England salt marsh plants (tall and stunted Spartina alterniflora and S. patens) using paired large-scale nutrient and 15NO3– tracer additions. This study is one component of a long-term, large-scale, salt marsh nutrient and trophic manipulation study (the Trophic Cascades and Interacting Control Processes in a Detritus-based Aquatic Ecosystem [TIDE] Project). We compared physiological variables of plants in fertilized (~17× ambient N and P in incoming tidal water) and reference marsh systems to quantify NO3– uptake and uptake efficiency, allocation of N to tissues, end-of-season N resorption, leaf litter quality and other potential responses to increased nutrient availability. Reference system plants sequestered ~24.5 g NO3-N ha–1 d–1 in aboveground pools during mid-summer, while fertilized plants sequestered ~140 g NO3-N ha–1 d–1. However, NO3– uptake efficiency (% of total incoming NO3-N sequestered aboveground) was higher in the reference system (16.8%) than in the fertilized system (2.6%), suggesting that our fertilization rate (~70 µM NO3– in incoming water) approaches or exceeds the uptake saturation point for this vegetation community. Leaf litter quality was clearly affected by N availability; N resorption efficiency was lower in all plants of the fertilized system; senesced leaves from the fertilized creek contained ~43% (tall S. alterniflora), 23% (stunted S. alterniflora) and 15% (S. patens) more N per unit biomass than reference creek leaves.
    Description: This work was funded by National Science Foundation Grant DEB 0213767 and OCE 9726921.
    Description: 2013-02-07
    Keywords: Spartina alterniflora ; Spartina patens ; Plant ecophysiology ; Eutrophication ; Nitrogen isotopes ; Nitrogen cycling ; Marsh ecosystem
    Repository Name: Woods Hole Open Access Server
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  • 3
    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.
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  • 4
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The Lotic Intersite Nitrogen eXperiment (LINX) was a coordinated study of the relationships between North American biomes and factors governing ammonium uptake in streams. Our objective was to relate inter-biome variability of ammonium uptake to physical, chemical and biological processes.2. Data were collected from 11 streams ranging from arctic to tropical and from desert to rainforest. Measurements at each site included physical, hydraulic and chemical characteristics, biological parameters, whole-stream metabolism and ammonium uptake. Ammonium uptake was measured by injection of 15N-ammonium and downstream measurements of 15N-ammonium concentration.3. We found no general, statistically significant relationships that explained the variability in ammonium uptake among sites. However, this approach does not account for the multiple mechanisms of ammonium uptake in streams. When we estimated biological demand for inorganic nitrogen based on our measurements of in-stream metabolism, we found good correspondence between calculated nitrogen demand and measured assimilative nitrogen uptake.4. Nitrogen uptake varied little among sites, reflecting metabolic compensation in streams in a variety of distinctly different biomes (autotrophic production is high where allochthonous inputs are relatively low and vice versa).5. Both autotrophic and heterotrophic metabolism require nitrogen and these biotic processes dominate inorganic nitrogen retention in streams. Factors that affect the relative balance of autotrophic and heterotrophic metabolism indirectly control inorganic nitrogen uptake.
    Type of Medium: Electronic Resource
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