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  • 1
    Electronic Resource
    Electronic Resource
    Application of a 15N tracer to simulate and track the fate of atmospherically deposited N in the coastal forests of the Waquoit Bay Watershed, Cape Cod, Massachusetts (1997)
    Springer
    Oecologia 112 (1997), S. 393-402 
    Details
    ISSN: 1432-1939
    Keywords: Key words15N tracer ; Atmospheric deposition ; Soil texture ; N retention ; Microbial uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined patterns of N retention in the coastal forests of the Waquoit Bay watershed on Cape Cod, Masschusetts using 15N tracer techniques. A solution of 99.6% enriched 15N -NO3 −, at a concentration similar to that of background throughfall, was applied to forest plots established along a gradient of soil texture to simulate and track the fate of throughfall NO3 − deposition. The tracer solution was applied to replicate plots during both the spring and fall to examine seasonal differences in ecosystem retention. 15N enrichment was subsequently measured in litter, O2 horizon, 0–15 cm mineral soil, fine roots, microbial biomass in the O2 horizon and mineral soil, and lysimeter leachate over a 6 month period following each application. The O2 horizon contained the largest fraction of 15N in all sites immediately following the spring application (19–45%) but was less important following the fall application (10–25%). The mineral soil N pool generally contained the largest fraction of applied 15N (7–28%) in all sites at the end of both 6-month sampling periods. Microbial uptake of applied 15N provided an initial barrier against leaching loss as well as a mechanism for its long-term incorporation into soil organic matter. Microbial processing was less important in the most coarsely textured site, perhaps as a result of lower substrate availability and smaller microbial pool sizes. The highest cumulative leaching losses of applied 15N were observed in the coarse sand site (40, 51%) followed by the fine sand (13, 43%) and loamy sand (4, 19%) sites for the spring and fall applications, respectively. More than 90% of all 15N captured in lysimeters occurred within two days following the applications, and 25–43% of all 15N captured in lysimeters after 2 days was in the form of dissolved organic nitrogen (DON) indicating that it had been assimilated by microbes prior to leaching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050325
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  • 2
    Electronic Resource
    Electronic Resource
    Mussels as bioindicators of trace metal pollution in the Danube Delta of Romania (1999)
    Springer
    Hydrobiologia 392 (1999), S. 143-158 
    Details
    ISSN: 1573-5117
    Keywords: biogeochemistry ; metals ; mussels ; bioindicators ; delta ; Romania
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Specimens of mussels species Anodonta anatina, Unio pictorum, U. tumidus and surfical sediment samples were collected in the summers of 1994 and 1995 from twelve lakes in the Danube Delta, Romania. Whole mussel tissues were analyzed for metals (Ag, As, Cd, Co, Cu, Cr, Ni, Pb, Se and Zn), and sediment samples were subjected to weak acid extraction and to a sequential extraction procedure, and analyzed for Cr, Cu, Ni and Zn. Total mean Cu and Ag concentrations were statistically greater in Unio species than in Anodonta species, but other metal levels did not significantly differ between mussel species. There was a ten fold variation for Cd and Pb and five fold variation for Zn, Ag and Co concentrations in mussels among lakes. Mean concentrations of As, Cu, Se and Zn in mussel tissues varied two fold among lakes. Zn, Co and Cd concentrations in mussels were significantly negatively correlated with distance gradients from the origin of the Delta and with distance from main channels of the Danube. Other metal concentrations in mussels did not correlate with either distance gradient. Trace metal levels in mussel tissues were correlated with those in weak acid and in sequential extractions of sediment. Zn concentrations in the carbonate fraction was the best predictor of Zn concentrations in mussels. Cu and Ni levels in the organic matter and sulfide fraction were the best estimators of Cu and Ni concentrations in mussels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003555130831
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