An assessment of the wealth of information given by sponge spicules as a paleoenvironmental tool: The case of two lakes in northeast (Brazil)

Abstract

This study aimed to test the use of inland sponge spicules as proxy data for a Holocene paleoenvironmental reconstruction of the Trairí River valley, in the state of Rio Grande do Norte, in Northeast Brazil. Spicules were recovered from sediments from two core samples obtained from Lake Fumo and Lake Urtiga, at depths of 0.60 m and 0.96 m, respectively. The following analyses were carried out: phytolith morphotype classification, isotope data (δ13C, δ15N‰), radiocarbon dating (AMS), grain size analysis, sediment morphoscopy, and percentage of soil organic matter. Environmental reconstruction indicated seasons with dry and rainy conditions 1940 years BP. Isotope data pointed to the presence of plants (C3 and C4) and algae. Phytolith classification indicated that Poaceae, Cyperaceae, Arecaceae and/or Bromeliaceae occurred at the location. Spicules from the inland sponges Heterorotula fistula; Ephydatia sp.; Dosilia pydanieli; Corvoheteromeyenia heterosclera; Tubella variabilis; Radiospongilla inesi; and Anheteromeyenia sp. were found in the core samples. Reconstruction based on isotope, phytolith and sedimentology results was compared with the spicule data and only D. pydanieli and H. fistula confirmed the other proxy information.