Wania Duleba

Morphological abnormalities of foraminiferal tests in Brazilian environments: comparison between polluted and non-polluted areas

Abstract We investigated morphological abnormalities of Recent benthic foraminiferal tests in paralic environments of Brazil from two estuaries (Rio Guarau and Rio Una located in the tropical forest) which are not affected by human activities in comparison to one polluted estuary (Baixada Santista), and one hypersaline lagoon (Araruama). The highest percentage of abnormal tests occurred in Rio Una (29%) and was caused by decalcification/recalcification processes resulting from natural periodical acidification. In the Rio Guarau, percentages of abnormal tests reached 10%. The strong hydrodynamics in this estuary induced damage in living foraminiferal tests and the shape of the tests resulting from the regeneration of a damaged chamber, was often abnormal. In the lagoon of Araruama, percentages of abnormal tests reached 24%. Here, hypersalinity and strong salinity variations seem to perturb the test construction of foraminifers. In the most polluted estuary (Baixada Santista), lower percentages of abnormal tests occurred (0–7% with only one station reaching 12%). In this paralic environment, it is difficult to distinguish between the effect of natural stress and anthropogenic impact. Our study shows that higher percentages of abnormal tests occur in non-polluted areas than in polluted areas. Thus, the relative abundance of abnormal tests used as a bio-indicator of pollution in paralic environments, which are subject to strong natural stress, must be handled with care. Nevertheless, the relative abundance of abnormal tests is a useful proxy for the reconstruction of paleoecological changes in stressed paleoenvironments.

Gammaridean and caprellidean fauna from Brazil

This review of Brazilian Amphipod works is arranged in a chronological list and points out the significant works for each one of the four arbitrary periods. Besides that, this paper deals with the distribution of 83 species of Brazilian Gammaridea and Caprellidea in relation to bathymetry, substrate, latitude and thermal region.

Water stratification in coastal lagoons: its influence on foraminiferal assemblages in two Brazilian lagoons

Abstract Foraminiferal assemblages were studied in two Brazilian stratified lagoons: the restricted Cananeia–Iguape lagoon which exhibits inclined water stratification and the choked Lagoa da Conceicao, where strong horizontal stratification occurs during the rainy season. Water stratification has been shown to influence the distribution of foraminiferal assemblages. In the restricted lagoon, the transition from marine to continental water conditions induces a progressive change in foraminiferal assemblage, both horizontally and vertically. In the choked lagoon, the presence of two different water masses separated by a halocline leads to the presence of two distinct assemblages. The first, located in the depressions, characterized by the dominance of rotaliids indicates a stronger marine influence. The second, present in the shallow water, characterized by textulariids, indicates more restricted conditions. The dominance of calcareous species in the depressions, where organic rich sediments are potentially liable to dissolve calcareous tests shows that, even if it may greatly modify the thanatocoenoses, the dissolution does not destroy all the information. The differential impact of stratification on foraminiferal assemblages from these two sites clearly demonstrate: (1) that it is impossible to propose a universal model for foraminiferal distribution in lagoons; but (2) that the foraminiferal assemblages can provide valuable information for modern hydrodynamics and, with some caution, also for fossil lagoonal environments.

Distribution of benthic foraminifera in the southwestern zone of the estuarine-lagoonal system of Iguapé-Cananéia (Brasil)

One hundred species of benthic foraminifera were found in the study area (25oS - 48oW). The surface sediment of this lagoon contains from 0 to 3,000 tests per 50 cm3 and up to 32 species. The foraminifera fauna of the lagoonal system of Iguape-Cananeia is the richest among those described in other paralic environments of Brazil. The richness of foraminifera fauna can result from the strong marine influence in the Baia de Trapande. The foraminifera distribution in the study area is characterized by the occurrence of marine assemblages nearby the mouth, with a gradual increase in agglutinating species, such as,Ammotiwn salsum and Gaudryina exilis. In the confined areas, with low salinity, the assemblages are oligospecific and Milammina earlandi Is dominant. The abundance of Pararotalia in the Mar de Cananeia shows that this environment is less restricted than Mar de Cubatao, where the genus is absent. The distribution of foraminifera species shown to be also influenced by urbain sewages.