INALI   02622
INSTITUTO NACIONAL DE LIMNOLOGIA
Unidad Ejecutora - UE
artículos
Título:
Spicules of the Freshwater Sponge Ephydatia facunda Indicate Lagoonal Paleoenvironment at the Pampas of Buenos Aires Province, Argentina
Autor/es:
C. VOLKMER RIBEIRO, I. EZCURRA DE DRAGO AND M. PAROLIN
Revista:
JOURNAL OF COASTAL RESEARCH
Editorial:
Griffith University
Referencias:
Lugar: Gold Coast; Año: 2008 vol. 50 p. 449 - 452
ISSN:
0749-0208
Resumen:
Sediments dredged at the site Puente de la Tropa, by the banks along the middle reach of River Luján (34º34´40"S-59º08´14"W), northeastern Pampas of Buenos Aires Province, Argentina, which were seen to contain sponge spicules and diatoms, were 14C dated as 4,000 (80 cm) and 11,000 (222cm) yr B.P. Portions of the sediments were boiled in nitric acid, throughly washed in tap water to remove all organic materials. The resulted suspended clean silicious materials were dropped on glass slides, dried, embedded with Entellan and covered with cover slips. Abundat gemmular spicules of the freshwater sponge Ephydatia facunda (Weltner, 1895), were seen in the samples dated of 11.060 e 10.420 yr B.P. The spicules were associated to diatoms, besides a rich gastropod, ostracod faunas, plus silicofitolites and fish bones. Hyalodiscus subtilis Hyalodiscus (Bailey) a brackish, benthic diatom dominated the diatomological flora. The detected taxocenosis comes to indicate the existence of a past pleistocenic lagoonal environment at this area. The remarkable presence of E. facunda enforces this interpretation as the species has been proved to actually thrive in coastal lagoonal brackish to fresh water rivers and swampy areas at the Brazilian and Argentinian ocean border. The species was seen to bear a strong relationship to the enrichment by floating meadows occurring at such areas, the corresponding organic enrichment of the waters and sediments and the reduction of the free water column.