%0 Journal Article
%T Paleolimnological studies of Laguna Chica of San Pedro (VIII Region): Diatoms, hydrocarbons and fatty acid records Estudio Paleolimnol車gico de Laguna Chica de San Pedro (VIII Regi車n): Diatomeas, hidrocarburos y 芍cidos grasos
%A ROBERTO URRUTIA
%A SABBE KOEN
%A FABIOLA CRUCES
%A KARLA POZO
%J Revista chilena de historia natural
%D 2000
%I Springer
%X Diatom, hydrocarbons and fatty acid sedimentary records were used for reconstructing the recent (last 150 years) palaeolimnological history of Laguna Chica of San Pedro (Concepci車n, VIII Regi車n, Chile). Cluster analyses (Constrained Incremental Sum of Squares) on the diatom data revealed three distinct periods. The first period (1883-1940's) showed a pronounced increase in sedimentation rate and a slight increase in organic matter accumulation. In this period, eutrophic species (Aulacoseira granulata and Staurosira construens) became increasingly dominant. From the 1940s until the 1970s the diatom signal is more equivocal: after the initial decrease in the relative abundance of A. granulata and S. construens their numbers fluctuate without a clear pattern. Sedimentation rates strongly fluctuate in this period. From 1978 onwards eutrophic species are in decline while indicators of oligotrophic conditions, such as Cyclotella stelligera and Aulacoseira distans, become more abundant. This shift in the lake trophic status could not be attributed to a reduction in the nutrient load from the catchment and we hypothesize that the invasion of the lake by the submersed macrophyte Egeria densa has altered nutrient availability to the plankton communities. This is in agreement with the hydrocarbons and fatty acid analyses which demonstrate a shift in carbon number distributions from short chain alkanes and alkanoic acids (typical for microalgae) to long chain molecules (characteristic for higher plants) in the upper layers of the lake sediment Se realiz車 la reconstrucci車n hist車rica de los 迆ltimos 150 a os de Laguna Chica de San Pedro (Concepci車n, VIII Regi車n, Chile), a trav谷s de la utilizaci車n de los restos de diatomeas, hidrocarburos y 芍cidos grasos contenidos en la columna de sedimento. El an芍lisis estratigr芍fico de las diatomeas revel車 la presencia de tres per赤odos diferentes. El primer per赤odo (1883-1940's), mostr車 un marcado aumento de las tasas de sedimentaci車n y un leve aumento en la acumulaci車n de materia org芍nica; en este per赤odo se registra un incremento de las especies eutr車ficas (Aulacoseira granulata y Staurosira construens). Desde los a os cuarenta hasta la d谷cada del setenta el cambio en la comunidad de diatomeas fue m芍s evidente y las tasas de sedimentaci車n variaron fuertemente. A partir de 1978 disminuyen las especies eutr車ficas y aumentan las indicadoras de condiciones oligotr車ficas (Cyclotella stelligera y Aulacoseira distans). El cambio en el estado tr車fico del lago, no se atribuye a una reducci車n de los aportes de nutrientes desde la cuenca, si
%K diatomeas
%K hidrocarburos
%K 芍cidos grasos
%K paleolimnolog赤a
%K uso del suelo
%K diatoms
%K hydrocarbons
%K fatty acids
%K paleolimnology
%K land use
%U http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2000000400014