Rosildo Santos Paiva

Chemical composition of phytoplankton from the estuaries of Eastern Amazonia

Phytoplankton is important bioindicator of chemical and biological modifications of natural ecosystems. The objective of this study was to determine the total chemical composition of the phytoplankton of the Para and Mocajuba estuaries on the eastern coast of the Amazon region in the Brazilian state of Para. The chemical composition of the surface water, bottom sediments (total sample and bioavailable fraction), and the phytoplankton were determined by inductively coupled plasma optical emission spectrometry. Phytoplankton contained high concentrations of Ca, P, Mn, Fe, Zn, Al, Ba, and Pb. The phytoplankton of the Mocajuba estuary is rich in Fe (2,967-84,750 µg g -1 ), while those from the Para is rich in Al (1,216-15,389 µgg -1 ), probably reflecting divergent anthropogenic inputs. Both samples indicated a high bioconcentration factor derived from both the water and the bioavailable fraction, reflecting the efficiency of these organisms in the concentration of metals.

The mineralogy and chemistry of the German and Portuguese tiles used to face a historic building in the Amazon region and their natural susceptibility to tropical weathering

As proeminentes edificacoes da cidade de Belem foram revestidas durante o seculo 19 com azulejos produzidos em Portugal e Alemanha que ja apresentam distintos graus de degradacao. O Palacete Pinho e uma das mais importantes destas edificacoes e foi selecionado para se investigar a acao do clima tropical amazonico sobre a degradacao destes azulejos. Para atingir estes objetivos mapearam-se os azulejos desta edificacao visando identificar as modificacoes de origem orgânica e inorgânica e coletas de amostras para analises. Os minerais foram determinados por DRX, a composicao quimica por metodos classicos umidos e MEV/SED e os micro-organismos por microscopia. Os resultados obtidos mostram que os azulejos Portugueses e Alemaes sao distintos entre si. Enquanto o biscoito e composto de SiO2 e Al2O3, CaO foi encontrado apenas nos Portugueses. Os baixos conteudos de Na2O e K2O indicam adicao de materiais para reducao da temperatura de fusao. SiO2 e PbO compoem o vidrado, ja CoO e FeO foram adicionados como pigmentos. O biscoito dos azulejos Alemaes e constituido de quartzo, mullita e cristobalita, ao contrario do Portugues com quartzo, gehlenita, diopsidio, calcita e feldspatos. Os vidrados sao amorfos ao DRX. As diferencas quimicas e mineralogicas entre os azulejos Portugueses e Alemaes indicam que foram produzidos por materia prima distinta, bem como processo termal. As alteracoes relacionadas com o intemperismo sao as finas camadas de detritos (nos Alemaes), manchas de oxidacao, manchas escuras, descolamento do azulejo (no Portugues); perda de vidrado e biscoito tornando-se pulverulento como consequencia do estabelecimento de Cyanophyta e bacillariophyta (Portugues). As distintas feicoes de degradacao dos azulejos refletem as suas diferencas mineralogicas e quimicas expostas ao clima tropical Amazonico.

Considerações ecológicas sobre o zooplâncton do lago Bolonha, Belém, Pará, Brasil

Zooplankton population of the lake Bolonha were sampled in three stations in September of 1993. The objective was to determine the basic characteristics of the populations, as the composition and density of species, besides some environmental parameters. Fifty six species were determined, thirty of them were of Rotifera, nineteen Cladocera and seven Copepoda. Among Rotifera, the most frequent organisms were Brachionus zahniseri gessneri, Polyarthra vulgaris and Tricocerca similis, while enter Cladocera, Bosminopsis deitersi and Bosmina hagmanni were the most important in density terms. For Copepoda, the nauplii and copepodits they were the ones that presented the largerst densities, but Oithona amazonica and Notodiaptomus amazonicus deserve to be registered for they have also presented a great density. The lake Bolonha came with a great diversity of zooplanktonic organisms, needing, meantime of more intensive studies, because that number in biodiversity terms should increase considerable.