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  • Florida lakes  (2)
  • diatoms  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Stable isotope (δ13C and δ15N) signatures of sedimented organic matter as indicators of historic lake trophic state (1999)
    Springer
    Journal of paleolimnology 22 (1999), S. 205-221 
    Details
    ISSN: 1573-0417
    Keywords: carbon isotopes ; diatoms ; lake management ; nitrogen isotopes ; phosphorus ; radium-226 ; sediments ; trophic state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We explored the use of carbon and nitrogen isotopes (δ13C and δ15N) in sedimented organic matter (OM) as proxy indicators of trophic state change in Florida lakes. Stable isotope data from four 210Pb-dated sediment cores were compared stratigraphically with established proxies for historical trophic state (diatom-inferred limnetic total phosphorus, sediment C/N ratio) and indicators of cultural disturbance (sediment total P and 226Ra activity). Diatom-based limnetic total P inferences indicate a transition from oligo-mesotrophy to meso-eutrophy in Clear Lake, and from eutrophy to hypereutrophy in Lakes Parker, Hollingsworth and Griffin. In cores from all four lakes, the carbon isotopic signature of accumulated OM generally tracks trophic state inferences and cultural impact assessments based on other variables. Oldest sediments in the records yield lower diatom-inferred total limnetic P concentrations and display relatively low δ13C values. In the Clear, Hollingsworth and Parker records, diatom-inferred nutrient concentrations increase after ca. AD 1900, and are associated stratigraphically with higher δ13C values in sediment OM. In the Lake Griffin core, both proxies display slight increases before ~1900, but highest values occur over the last ~100 years. As Lakes Clear, Hollingsworth and Parker became increasingly nutrient-enriched over the past century, the δ15N of sedimented organic matter decreased. This reflects, in part, the increasing relative contribution of nitrogen-fixing cyanobacteria to sedimented organic matter as primary productivity increased in these waterbodies. The Lake Griffin core displays a narrow range of both δ13C and δ15N values. Despite the complexity of carbon and nitrogen cycles in lakes, stratigraphic agreement between diatom-inferred changes in limnetic total P and the stable isotope signatures of sedimented OM suggests that δ13C and δ15N reflect shifts in historic lake trophic state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008078222806
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Paleolimnological evaluation of historical trophic state conditions in hypereutrophic Lake Thonotosassa, Florida, USA (1996)
    Springer
    Hydrobiologia 331 (1996), S. 143-152 
    Details
    ISSN: 1573-5117
    Keywords: diatoms ; lake management ; paleolimnology ; sediments ; trophic state ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We used paleolimnological methods to evaluate historical water quality in Lake Thonotosassa, Hillsborough County, Florida, USA. Sediment mapping shows that organic deposits are unevenly distributed in the lake. Two short (〈130 cm) sediment cores from the depositional zone were analyzed for radioisotopes (210Pb, 226Ra, and 137Cs), bulk density, organic matter concentration, nutrients (C,N,P), and diatoms. 210Pb results indicate that the profiles represent 〉 100 years of sediment accumulation. There is an abrupt change in sediment composition at about the turn of the century (∼80 cm depth), above which bulk density decreases and concentrations of organic matter, total C, total N, total P, and 226Ra activity increase. Diatom-based reconstructions of historical water-column trophic conditions indicate progressive nutrient enrichment in the lake during the past ∼100 years. Stratigraphic changes in diatom assemblages suggest that anthropogenic nutrient loading converted Lake Thonotosassa from a naturally eutrophic system to a hypereutrophic waterbody after ∼1900. Given the edaphic setting of Lake Thonotosassa, efforts to mitigate recent anthropogenic impacts will, at best, yield the eutrophic conditions that characterized the lake prior to human disturbance. This study illustrates the importance of paleolimnological data for targeting realistic water quality conditions when lake restoration is contemplated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025415
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  • 3
    Electronic Resource
    Electronic Resource
    Material transfer from water to sediment in Florida lakes (1986)
    Springer
    Hydrobiologia 143 (1986), S. 55-61 
    Details
    ISSN: 1573-5117
    Keywords: paleolimnology ; Florida lakes ; trophic state ; sediment chemistry ; accumulation rate ; 210Pb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We describe statistical relationships between chemical aspects of surficial sediments from 34 Florida lakes, and trophic state of the overlying waters. Trophic state is expressed by Carlson's TSI-Chl a. The objectives of the study are two-fold: 1) to understand processes that govern the transfer of material across the mudwater interface, and 2) to develop transfer functions for inferring historical TSI measures in chemically analyzed, 210Pb-dated cores. Simple regression of organic matter content or nutrient (C, N, P) concentration in surface sediments vs. TSI yields nonsignificant or weak positive correlations. However, using a novel application of 210Pb assay, net accumulation rates of the materials are estimated and show a better correlation with trophic state. Cation (Ca, Mg, Fe, K) and sulfur concentrations in surface muds are poorly related to corresponding TSI's. Net accumulation rates of these elements (Ca, Mg, Fe, K, S) are positively correlated (P 〈 0.01) with TSI-Chl a. Chemical data from the Florida surficial sediment survey suggest that inferred levels of past trophic state should be based on net accumulation rates of chemical constituents rather than their simple sediment concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026645
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  • 4
    Electronic Resource
    Electronic Resource
    Sedimentary records of accelerated nutrient loading in Florida lakes (1986)
    Springer
    Hydrobiologia 143 (1986), S. 49-53 
    Details
    ISSN: 1573-5117
    Keywords: paleolimnology ; eutrophication ; trophic state ; 210Pb ; transfer functions ; Florida lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transfer functions relating trophic state (Carlson's TSIchlorophyll-a) to present day accumulation rate of (1) nutrients, (2) cations, and (3) organic sediment, are computed using Binford's 210Pb-dilution method. As computed from surficial sediments of 27 lakes, former trophic states are reconstructed for recent (210Pb-dated) sedimentary histories of 14 lakes. Of the three kinds of models potentially available, model (3) (TSI vs. organic accumulation) is the weakest statistically, and may be unduly influenced by exceptional deposition and/or preservation of allochthonous organic matter. At present, however, it is the only model applicable to all 14 of the histories tested. Results are encouraging in that model accurately predicts observed TSI's in several mesotrophic and eutrophic lakes. Clearly significant increases (accelerations) are inferred only for a of the most eutrophic lakes of the set, while the model consistently overpredicts TSI's of the 7 most oligotrophic lakes. As Whitmore's diatom-assemblage index is a better predictor of TSI than is model (3) in the one eutrophic lake in which it has been tested, we expect more persuasive results when models (1) and (2) can be tested within a more complete set of analytical data. We were surprised to find 3 severely disturbed lakes among the 12 that show little or no acceleration in rate of eutrophication in recent decades, but we defer attempts at explanation until former nutrient loading can be tested by model (1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026644
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    Paper (German National Licenses)
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