Patrícia P. B. Eichler

FORAMINIFERAL ASSEMBLAGES IN A HYPERSALINE LAGOON, ARARUAMA (R.J.) BRAZIL

Foraminiferal assemblages were studied in 93 samples collected in the lagoon of Araruama and in the adjacent area. The lagoon of Araruama is one of the largest hypersaline lagoons in the world, with a salinity range of 52–65 ‰. Historical reports show that the lagoon has been hypersaline since at least the 16th century. Foraminiferal assemblages are dominated by miliolids, mainly Triloculina oblonga, and rotaliids, with Ammonia tepida and the less abundant Cribroelphidium excavatum var. selseyense . Textulariids are almost absent. This assemblage is similar to those usually reported from hypersaline lagoons with sandy carbonate-rich sediments and from salt marshes. A high proportion of aberrant tests was observed. Anthropogenic stresses do not seem to be responsible for these morphological abnormalities, which are attributed to high salinity conditions and to changes of salinity. However, the higher proportion of Ammonia tepida in the more impacted northern part of the lagoon is probably due to human impact.

Foraminifera as indicators of marine pollutant contamination on the inner continental shelf of southern Brazil

Analyses of living foraminiferal and environmental parameters near an outfall at Mar Grosso Beach (Laguna, SC, Brazil) demonstrate its usefulness as indicators of domestic sewage pollution. The low species diversity may be due to sand accumulation in the central part. Higher diversity was noted closer to the mouth of Laguna estuarine system where reduced salinity and higher temperatures indicate freshwater influence, suggesting a relationship between increased diversity and greater availability of terrestrial food. On the basis of foraminiferal diversity and average coliform count the higher values are closer to the mouth of the estuarine system and under the influence of the outfall. Due to the effect of local hydrodynamics, the particulate organic waste derived from the outfall does not settle down locally, and thus, do not accumulate nearby. Our hypothesis is that the fine material derived from the outfall is accumulating on the southwestern and northwestern parts of the beach.

The investigation of a mixed carbonate-siliciclastic shelf, NE Brazil: side-scan sonar imagery, underwater photography, and surface-sediment data

Side-scan sonar imagery and underwater photography, coupled with bathymetric and sedimentologic data, revealed noteworthy features and the interplay of multiple processes on the north-eastern Brazilian continental shelf. The high-resolution data cover a 500 km2 area of the shallow (~70 m) and narrow (~40 km) shelf, which comprises the submerged portion of the Potiguar Basin; the area includes the partially filled incised valley of the ancient Acu River.The seafloor imagery was integrated with 673 surface sediment samples to distinguish boundaries within the mixed siliciclastic-carbonate region. The sediment grain size increases from nearshore, muddy, siliciclastic sediments to biogenic, coarse sand and gravel on the outer shelf. Carbonate-rich sediment predominates, except on the eastern margin of the Acu Incised Valley (AIV), the nearshore zone and estuary mouths. The AIV is filled mainly with muddy sediments reworked from the latest transgressive deposits. Bedform configurations indicate bottom currents associated with tidal and wave-driven currents.Mixing processes are controlled by the interplay of high hydrodynamic energy regime and shelf physiography. Special attention was paid to the middle and outer shelves, where a large field of newly found reefs occurs between 20 and 50 m depths. The reef substrate is composed of limestones, probably belonging to the Guamare Formation.SCUBA dive inspections revealed benthic colonies (corals: Montastraea cavernosa, Porites astreoides, Siderastrea stellata; sponges: Scopalina ruetzleri, Callyspongia vaginalis, Ectyoplasia ferox, Ircinia sp., Spirastrella sp., Aiolochroia sp.) over fossil reefs. A preliminary examination of the foraminiferal species showed a Caribbean-type reef community, including Amphisorus hemprichii, Amphistegina gibbosa, Archaias angulatus, Heterostegina antillarum, Homotrema rubra, Peneroplis carinatus and P. proteus.

Aspectos sedimentológicos do talude continental setentrional do Rio Grande do Norte, NE do Brasil

Os taludes continentais das regioes norte e nordeste brasileira carecem de dados e conhecimento e representam um ecossistema de importância economica e ambiental. O objetivo deste estudo e avaliar a sedimentologia do talude continental da Bacia Potiguar, nordeste do Brasil. As amostras foram coletadas com amostrador box-corer e foram analisadas quanto a granulometria, teor de carbonato de calcio e teor de materia orgânica. Analises de microscopia eletronica de varredura e difratometria de raios X tambem foram realizadas a fim de reconhecer os constituintes sedimentares das amostras em questao. A cobertura sedimentar apresenta diminuicao do tamanho de grao a medida que a profundidade aumenta e e representada por quatro facies sedimentares: silte, silte arenosa, areia siltosa e areia com cascalho. O teor de carbonato de calcio e moderado a alto (37-93,2 %) e o teor de materia orgânica e baixo (4,6-14,5 %). O talude continental e considerado misto, pois os sedimentos sao compostos por siliciclasticos e bioclasticos. Dentre os siliciclasticos destacam-se Quartzo e Argilominerais. Os minerais acessorios sao Ilmenita, Zircao, Titanita, Muscovita, Biotita, Glauconita, Estaurolita, Cordierita, Siderita, Rutilo, Magnetita, Turmalina, Pirita, Monazita e Barita. Bioclasticos sao representados pelos briozoarios, esponjas, foraminiferos, anelideos (tubos de poliquetas), nematodas, moluscos e diatomaceas. A presenca de minerais estaveis (Zircao, Turmalina e Rutilo) indica a contribuicao dos rios Acu e Apodi atraves dos vales incisos e canyons submarinos na sedimentacao da area de estudo.

Marine Pollution-Environmental Indicators in Marine Meiofauna from Brazil

To assess the primary stresses that affect environmental quality, recent benthic foraminiferal distribution in Brazilian domestic outfalls of Baixada Santista, Sao Paulo State (Santos Bay, Long Beach, Gurauja Cove), close to oil refineries in Todos Santos Bay (BA), Guanabara Bay (RJ), and Sao Sebastiao Channel, and from environments polluted by pesticides in Laguna (SC) were compared through foraminifera species in 250 sediment samples.