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  • Articles  (5)
  • paleolimnology  (5)
  • Guatemala
  • sediment geochemistry
  • Springer  (5)
  • 1995-1999  (5)
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  • Articles  (5)
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  • Springer  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    A multi-proxy study of Holocene environmental change in the Maya Lowlands of Peten, Guatemala (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 139-159 
    Details
    ISSN: 1573-0417
    Keywords: geochemistry ; Guatemala ; Holocene ; lakesediment ; Maya ; magnetic susceptibility ; paleolimnology ; pollen ; stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We used multiple variables in a sediment core from Lake Peten-Itza, Peten, Guatemala, to infer Holocene climate change and human influence on the regional environment. Multiple proxies including pollen, stable isotope geochemistry, elemental composition, and magnetic susceptibility in samples from the same core allow differentiation of natural versus anthropogenic environmental changes. Core chronology is based on AMS 14C measurement of terrestrial wood and charcoal and thus avoids the vagaries of hard-water-lake error. During the earliest Holocene, prior to ∼9000 14C yr BP, the coring site was not covered by water and all proxies suggest that climatic conditions were relatively dry. Water covered the coring site by ∼9000 14C yr BP, coinciding with filling of other lakes in Peten and farther north on the Yucatan Peninsula. During the early Holocene (∼9000 to ∼6800 14C yr BP), pollen data suggest moist conditions, but high δ 18O values are indicative of relatively high E/P. This apparent discrepancy may be due to a greater fractional loss of the lake's water budget to evaporation during the early stages of lake filling. Nonetheless, conditions were moist enough to support semi-deciduous lowland forest. Decrease in δ 18O values and associated change in ostracod species at ∼6800 14C yr BP suggest a transition to even moister conditions. Decline in lowland forest taxa beginning ∼5780 14C yr BP may indicate early human disturbance. By ∼2800 14C yr BP, Maya impact on the environment is documented by accelerated forest clearance and associated soil erosion. Multiple proxies indicate forest recovery and soil stabilization beginning ∼1100 to 1000 14C yr BP, following the collapse of Classic Maya civilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007968508262
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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
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Spatial and temporal patterns of sediment and nutrient accumulation in shallow lakes of the Upper St. Johns River Basin, Florida (1998)
    Springer
    Wetlands ecology and management 6 (1998), S. 221-240 
    Details
    ISSN: 1572-9834
    Keywords: Florida ; lake ; 210Pb dating ; macrophytes ; nutrients ; paleolimnology ; river ; sediment ; wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We used paleolimnological methods to investigate spatial and temporal patterns of bulk sediment and nutrient (C, N, P) accumulation in Lakes Hell ‘n’ Blazes (A = 154 ha, zmax = 240 cm), Sawgrass (A = 195 ha, zmax = 157 cm) and Washington (A = 1766 ha, zmax = 322 cm), in the Upper St. Johns River Basin, Florida. The study was designed to evaluate long-term changes in sedimentation and nutrient storage in the basin, and was one component of a larger project addressing flood control, wetland restoration, and water quality improvement. These three study lakes are wide, shallow waterbodies in the upper reaches of the St. Johns River channel. Sediment mapping indicates soft, organic deposits are distributed uniformly throughout Lakes Hell ‘n’ Blazes and Sawgrass. In contrast, much of Lake Washington is characterized by sandy bottom, and organic sediment is largely restricted to the north end of the lake. Lakes Hell ‘n’ Blazes and Sawgrass are effective sediment traps because dense submersed macrophytes and their associated epiphytes reduce flow velocity, intercept suspended particles, and utilize dissolved nutrients. Abundant Hydrilla, combined with short fetch, prevents resuspension and downstream transport of sediments. Larger Lake Washington is probably wind-mixed and resuspended organic sediments are redeposited to downstream sites. 210Pb-dated sediment cores show that organic sediment accumulation began in all three lakes before 1900, but that bulk sediment and nutrient accumulation rates have generally increased since then. The increases are probably attributable, in part, to anthropogenic activities including 1) hydrologic modifications that reduced flow rates in the channel, 2) discharge of nutrient-rich waters from urban, agricultural and ranching areas, and, 3) introduction and periodic herbicide treatment of the exotic macrophytes Eichhornia and Hydrilla.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008408030256
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