Análise de espículas de esponjas como indicadores paleoambientais em sedimentos lacustres no oeste da Bahia

Abstract

-ANALYSIS OF SPONGE SPICULES AS PALEOENVIRONMENTAL INDICATORS IN WESTERN BAHIA LACUSTRINE SEDIMENTS.The use of sponge spicules in sediments as proxy data has been successful in paleoenvironmental reconstructions. We recovered two sedimentary cores in two ponds located in San Francisco lowland in Western Bahia to understand the paleoclimatic and the lacustrine system dynamics. Sedimentary facies and granulometric analysis were perfomed. Also, organic matter content and presence of diatoms frustules were studied, besides the identification and quantification of sponge spicules detected in sediments, which were dated by 14 C. The sediment age ranged between 8410 to 3929 yrs cal BP, corresponding to the Holocene. Sponge spicules of the following species were found: Dosilia pydanieli, Heterorotula fistula, Metania spinata, Oncoslera sp., Radiospongilla inesi and Tubella variabilis. Analysis of the results suggest that the two lakes have a standardized climate pattern alternating between drier and wetter climates in relation to the current climate condition. However, the two lakes differ regarding the sedimentation rate and the microfossil content the pond of the northern portion showed lentic and lotic alternated phases, indicating a paleodrainage at the beginning of the upper Holocene, while the evidences in the southern pond of the lake system there are only lentic phases. Such evidences suggest that other physiographic factors and climate influenced the dynamics of these lakes, such as structure, litholog and tectonics of the ponds substrates.Key words: Quaternary, Holocene, San Francisco lowland, sponges.RESUMO -A utilização de espículas de esponjas em sedimentos como dado proxy vem obtendo sucesso em proposições de reconstruções paleoambientais. Para compreender as condições paleoclimáticas e dinâmicas do sistema lacustre, localizado na Depressão do São Francisco, no oeste do estado da Bahia, foram recuperados dois testemunhos em duas lagoas. Foram realizadas análises de fácies, ensaios granulométricos, de conteúdo de matéria orgânica e presença de diatomáceas, além da identificação e quantificação de espículas de esponjas detectadas nos sedimentos holocênicos, que foram datados por 14 C. A idade das amostras dos sedimentos variou entre 8.410 a 3.929 cal. AP. Foram encontradas espículas das esponjas Dosilia pydanieli, Heterorotula fistula, Metania spinata, Oncoslera sp, Radiospongilla inesi e Tubella variabilis. As análises sugerem que as duas lagoas tiveram situações climáticas com alternância entre fases mais secas e mais úmidas em relação ao clima atual. No entanto, as duas lagoas diferem no que tange à taxa de sedimentação e conteúdo microfossilífero. Para a lagoa da porção norte os resultados evidenciaram alternância de fases lênticas e lóticas, indicando uma paleodrenagem no início do Holoceno superior, enquanto as evidências da lagoa ao sul do sistema lacustre indicam apenas fases lênticas. Tais evidências sugerem que outros fatores fisiográficos, além do clima, influenciaram a dinâmica dessas la...

Sponge spicule and phytolith evidence for Late Quaternary environmental changes in the tropical Pantanal wetlands of western Brazil

“…Sponges respond to local environmental conditions, and they are particularly sensitive to changes associated with flowing versus stagnant waters and transport distance. For example, sponge assemblages marked by robust structures (e.g., megascleres) and a high degree of fragmentation are most consistent with long distance fluvial transport, whereas a biodiverse assemblage of delicate spicules suggests a local lacustrine population under stable conditions (Wilding and Drees, 1968;Sifeddine et al, 2001;Santos et al, 2016). The development of a spongiofacies in Unit V indicates that the environmental conditions at LN were a shallow lake with abundant macrophytes on its margins.…”

Utilizing sponge spicules in taxonomic, ecological and environmental reconstructions: a review

“…Even though the authors recognized the presence of three sponge species in their assemblage, they did not explore whether their occurrence is indicative of an important environmental information (water pH, conductivity). The most comprehensive assessment of the use of freshwater sponge spicules for paleoenvironmental reconstructions was conducted in riverine and lentic systems in Caatinga ( Santos et al, 2016 ) and Pantanal wetlands ecosystems ( McGlue et al, 2012 ; Kuerten et al, 2013 ; Rasbold et al, 2019b ) in Brazil. Parolin, Volkmer-Ribeiro & Stevaux (2007 , 2008) , Guerreiro et al (2013) and Zviejkovski et al (2017) focused mostly on reconstructing the history of lake sediments on colluvial-alluvial terraces in the Upper Paraná River, while Rasbold et al (2019a) investigated the history of island deposits.…”

La colonización española en Sudamérica: Estudio del primer asentamiento en la Cuenca del Plata mediante el registro de los microrrestos biosilíceos

“…En cuanto a las espículas de espongiarios dulceacuícolas, se consideró el morfotipo más abundante para el recuento, el cual posee grandes dimensiones, lisos y de extremos aguzados, con un canalículo que lo recorre en sentido longitudinal. Se estableció su abundancia en relación con la mayor/menor disponibilidad hídrica en el ambiente (Barbosa Dos Santos et al 2016). Las diatomeas se consideraron según el criterio de presencia/ausencia, y su abundancia se interpretó como aumento/disminución de la humedad en el ambiente de depositación (López Fuerte y Siqueiros Beltrones 2011; y Tabla 1).…”