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  • 1
    Electronic Resource
    Electronic Resource
    A sedimentary record of human disturbance from Lake Miragoane, Haiti (1988)
    Springer
    Journal of paleolimnology 1 (1988), S. 85-97 
    Details
    ISSN: 1573-0417
    Keywords: land-water interactions ; limnology ; paleolimnology ; 210Pb ; sediment geochemistry ; West Indies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Lake Miragoane, Haiti is one of the largest, natural freshwater lakes in the Caribbean (A=7.06 km2, zmax=41.0 m, conductivity = 350 μS cm−1). Lake waters are dominated by calcium and bicarbonate ions. The lake was thermally stratified, and oxygen profiles were clinograde during summer visits in 1983 and 1985. A 72-cm mud-water interface core was taken near the center of the lake and dated with 210Pb. The local 210Pb fallout rate is low (0.09 pCi cm−2 yr−1), about 20% of the global average. Bulk sedimentation rates ranged from 0.008 to 0.030 g cm−2 yr−1 during the past 130 years (0–8 cm depth). Sediment geochemistry and pollen have been analyzed in the topmost 58 cm of the section. Tentative ages were assigned to the core by extrapolation of 210Pb dates. According to this preliminary chronology, the bottom part of the core (58–30 cm) records pre-Columbian sedimentation (1000–500 B.P.) and contains pollen evidence of intact, dry and mesic forest. Pre-Columbian deposits are rich in organic matter (x = 30%) and relatively poor in carbonates (x = 15% as CO2). The top 30 cm of the core preserve the record since European contact (500 B.P. to present). Pollen data reveal two episodes of deforestation following European arrival. Consequent soil erosion is documented by a decrease in organic matter content (x = 15%) and an increase in carbonates (x = 27% as CO2). Surficial sediments reflect the widespread deforestation and soil loss that characterize the watershed today.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196066
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  • 2
    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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  • 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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