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  • 1
    Electronic Resource
    Electronic Resource
    Paleolimnology forum (1995)
    Springer
    Journal of paleolimnology 13 (1995), S. 293-293 
    Details
    ISSN: 1573-0417
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682772
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  • 2
    Electronic Resource
    Electronic Resource
    A multi-proxy trophic state reconstruction for shallow Orange Lake, Florida, USA: possible influence of macrophytes on limnetic nutrient concentrations (1999)
    Springer
    Journal of paleolimnology 21 (1999), S. 215-233 
    Details
    ISSN: 1573-0417
    Keywords: Florida ; geochemistry ; 210Pb dating ; macrophytes ; nutrients ; paleolimnology ; sediments ; shallow lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We retrieved four sediment cores from shallow, eutrophic, macrophyte-dominated Orange Lake (A = 51.4 km2, zmax 〈5 m, zmean 〈 2 m), north-central Florida, USA. The 210Pb-dated profiles were used to evaluate spatial and temporal patterns of bulk sediment and nutrient accumulation in the limnetic zone and to infer historical changes in lake trophic state. Bulk density, organic matter, total carbon, total nitrogen, total phosphorus and non-apatite inorganic phosphorus (NAIP) concentrations displayed stratigraphic similarities among three of four cores, as did accumulation rates of bulk sediment, organic matter and nutrients. Accumulation rates were slower at the fourth site. Nutrients showed generally increasing rates of accumulation since the turn of the century. Percentages of periphytic diatom taxa increased progressively in the cores after ~ 1930. Diatom-inferred limnetic total P trends were similar among profiles. Eutrophic conditions were inferred for the period prior to the turn of the century. The lake was hypereutrophic in the early decades of the 1900s, but inferred limnetic total P values declined after ~ 1930. Declining inferred limnetic total P trends for the last 60--70 years were accompanied by concomitant increases in accumulation rates of total P and NAIP on the lake bottom. Several lines of evidence suggest that after ~ 1930, phosphorus entering Orange Lake was increasingly utilized by submersed macrophytes. Paleolimnological records from Orange Lake highlight the importance of using multiple sediment variables to infer past trophic state and suggest that aquatic macrophytes can play a role in regulating water-column nutrient concentrations in shallow, warm-temperate lakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008079500375
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    The Diatoms: Applications for the Environmental and Earth Sciences (2000)
    Springer
    Journal of paleolimnology 24 (2000), S. 241-242 
    Details
    ISSN: 1573-0417
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008141120458
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  • 5
    Electronic Resource
    Electronic Resource
    Highly variable sediment distribution in shallow, wind-stressed lakes: a case for sediment-mapping surveys in paleolimnological studies (1996)
    Springer
    Journal of paleolimnology 15 (1996), S. 207-221 
    Details
    ISSN: 1573-0417
    Keywords: sediments ; paleolimnology ; sediment distribution ; sediment mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We examine sediment distribution patterns in seven Florida lakes and discuss implications for paleolimnological studies of shallow, subtropical lakes. The study lakes are highly productive and should exhibit thick organic sediment deposits, but organic sediments are often grossly lacking because basins are shallow, and frequent mixing, lack of stratification, and warm temperatures lead to breakdown of organic material. Organic sediment distribution patterns are highly variable. We observe three types of distribution patterns. When organic sediments are abundant, there may be (1) uniform sediment distribution. In lakes lacking organic sediments, there are (2) distribution to deeper areas if present, or (3) distribution to peripheral areas and embayments when deep waters are absent. We advocate the use of systematic mapping surveys to locate optimal coring sites for paleolimnological studies of shallow, wind-stressed lakes. Because numerous factors affect diagenesis and sediment redistribution, sediment abundance and location are not predictable. Sediment chronologies may be discontinuous and disturbed even in accumulation zones. The extent to which sedimentary records are discontinuous or disturbed is not quantifiable in any practical manner. 210Pb and 137Cs radioisotopic profiles provide qualitative evidence of the degree of stratigraphic disturbance. Total excess 210Pb inventories show that sediments are focused into depositional zones when sediment distribution is uneven. Excess 210Pb inventories are not informative about the completeness of sedimentary profiles unless small inventories suggest discontinuous sedimentation or erosional events. We present examples of disturbed and undisturbed profiles, and discuss how we use radioisotopic and geochemical evidence, and multiple cores to assess stratigraphic continuity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213041
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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Sedimentary diatom concentrations and accumulation rates as predictors of lake trophic state (1991)
    Springer
    Hydrobiologia 214 (1991), S. 163-169 
    Details
    ISSN: 1573-5117
    Keywords: diatoms ; trophic state ; paleolimnology ; Florida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diatom concentrations in surface sediments are positively correlated with limnetic chlorophyll a concentrations in Florida (USA) lakes. Using this relationship, I examine models that provide quantitative inferences for trophic state in historical applications. The best model predicts chlorophyll a trophic state index (TSI) values from log-transformed diatom concentrations and explains approximately half the variance in the dependent variable. Diatom accumulation rates are not better than sedimentary diatom concentrations as predictors of TSI. The entire diatom assemblage is as sensitive an indicator of TSI as are the planktonic diatoms alone. A model that considers the ecological preferences of specific taxa was found to be a better predictor than the model based on total diatom concentration. The sedimentary diatom concentration model provides a useful method for assessing historical changes in primary productivity, except in lakes where factors (e.g., silica limitation, blue-green bacterial inhibition) limited diatom production, or post-depositional changes removed sedimentary diatoms. TSI inferences are presented for sediment cores from two Florida lakes, one of which demonstrates a problematic application, and the other of which does not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050946
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  • 9
    Electronic Resource
    Electronic Resource
    Paleolimnology of Qilu Hu, Yunnan Province, China (1991)
    Springer
    Hydrobiologia 214 (1991), S. 333-340 
    Details
    ISSN: 1573-5117
    Keywords: China ; limnology ; paleolimnology ; Pleistocene ; sediment geochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Qilu Hu is a large (A = 36.9 km2), shallow (zmax = 6.8 m) lake that lies at an elevation of 1797 m above msl on the Yunnan Plateau, southern China. Lake waters are hard (Mg = 3.2m eq L−1, Ca = 1.3 meq L−1 ), fresh (conductivity = 380 μS cm −1), and productive (Secchi 〈 40 cm). An 11-m sediment core has a basal 14C age of 30960 ± 860 B.P. Sediments between 11 m and 6 m are high in % dry weight, rich in clay components Al2O3, Fe2O3, K2O, MgO, and low in organic C (≤6.1%), carbonate-C (〈1.0%), total N (〈3.2 mg g−1), and total S (〈-1.7 mg g−1). Diatoms and pollen indicate open-water conditions between 9.0 m and 6.0 m (1342011790 B.P.). Above 6.0 m, CaCO3 and organic matter concentrations increase relative to clastics. The transition marks a change to shallow-water conditions as inferred from diatoms and pollen, and probably reflects a shift to drier climate. Uppermost (80-0 cm) red clays were deposited rapidly, probably as a consequence of recent (decades to centuries) riparian disturbances (e.g. agriculture, lake-bottom reclamation, urban development). Dates assigned to events in the Qilu Hu profile are tentative because of potential hard-water-lake error.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050968
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