Carlos Augusto França Schettini

The dynamics of a frictionally-dominated Amazonian estuary

A hidrodinâmica, morfologia e sedimentologia do estuario do Taperacu foram investigadas. Este e um entre varios estuarios do litoral amazonico que integram a maior extensao continua de manguezais do mundo, apresentando uma descarga de agua doce muito reduzida, atipica para a regiao. Os resultados revelam grandes bancos arenosos que ocupam em grande parte a porcao central do estuario. Areias muito finas e bem selecionadas de origem marinha prevalecem. Fases de enchente mais curtas, com velocidades de corrente substancialmente mais altas, sao observadas na porcao superior do estuario, como esperado para um estuario raso e dominado por friccao. Por outro lado, uma vazante mais intensa poderia ocorrer como resultado de grandes areas de manguezais associadas e intenso preenchimento estuarino, sendo que ambas as condicoes sao observadas no Taperacu. Neste caso, a prevalencia da enchente parece estar associada a ausencia de uma descarga fluvial efetiva. Alem disso, alguns canais de mare conectam o Taperacu com seu vizinho estuario do Caete, o que contribuiria para o dominio de enchente. Como um todo, os resultados demonstram uma complexa interacao de aspectos de configuracao (friccao, drenagem fluvial, conexoes com estuarios vizinhos, preenchimento e grandes areas intermareais) na determinacao dos padroes hidrodinâmicos, contribuindo para o entendimento dos estuarios da regiao amazonica.

Hidrodinâmica e transporte de material particulado em suspensão sazonal em um estuário dominado por maré: Estuário de Caravelas (BA)

The objective of the present paper is to characterize the hydrodynamics and the suspended particulate matter (SPM) in the Caravelas Estuary under different tidal and river regimes. Four hydrographic campaigns were carried out comprising a complete semi-diurnal tidal cycle, comprising neap and spring tidal phases, and during dry and wet seasons. Water level, current speed and direction, salinity, temperature and turbidity were recorded in an anchored station near to the estuarine mouth. The residual SPM flux and the mechanisms of transport were calculated. The higher SPM concentrations were recorded during the spring tidal phase. During neap tides, the net SPM flux was up-estuary, although with low scale. During spring tides the tidal currents are strongly ebb dominant, and the net flux can be either up- or down-estuary. The estuary was classified as well mixed or weakly stratified. The hydrography and the sediment balance are firstly modulated by the tidal range, and the fresh water inflow is negligible.

The circulation of the lower Capibaribe Estuary (Brazil) and its implications for the transport of scalars

O estuario do Rio Capibaribe e um corpo de agua que atravessa a Regiao Metropolitana de Recife (RMR), um dos maiores centros populacionais do Brasil, o que causa grande quantidade de carga de poluentes e baixa qualidade da agua. A entrada de agua doce a partir das aguas residuais da RMR pode contabilizar mais de tres vezes a contribuicao fluvial durante o periodo de baixa descarga. Este artigo investiga a hidrodinâmica e o potencial transporte de escalares particulados e dissolvidos neste estuario. Um experimento de campo foi realizado para registrar nivel da agua, velocidade de corrente, salinidade, temperatura e material particulado em suspensao (MPS) durante um ciclo de mare semidiurno completo. O experimento foi realizado em condicoes de baixa descarga e em condicoes de mare de sizigia. O estuario apresentou padrao de circulacao parcialmente estratificado. O transporte residual de agua e sal foi estuario acima, enquanto que o transporte residual de MPS foi estuario abaixo. Os primeiros sao entendidos como o efeito da complexa circulacao ao redor das ilhas que formam o baixo estuario, enquanto que o ultimo foi interpretado como devido a efeitos morfologicos que induzem a ressuspensao durante a vazante, a despeito da simetria entre correntes de enchente e vazante. Este mecanismo pode produzir transporte para a plataforma adjacente, mesmo durante periodos dominados pela mare, quando o oposto seria esperado.

Intra-tidal variation of stratification in a semi-arid estuary under the impact of flow regulation

O rio Jaguaribe e o maior rio do semi-arido brasileiro, constituindo uma importante fonte de agua para o estado do Ceara. Na decada de 1990 entrou em operacao o Acude do Castanhao com o objetivo de regularizar a vazao do rio Jaguaribe, o qual obteve grande sucesso. Como consequencia foi alterado o regime hidrodinâmico do estuario, o qual atualmente nao esta mais sujeito a variabilidade climatologica anual de estacoes seca e chuvosa. O presente trabalho apresenta uma avaliacao da mudanca do regime hidrologico antes e apos a construcao do acude, e investiga a estrutura de estratificacao da densidade nos estuarios. Foi realizado um experimento de campo em novembro de 2009, no fim da estacao seca, quando a salinidade e temperatura da agua foram monitorados em diferentes niveis durante tres ciclos de mare. A variacao temporal da salinidade e temperatura durante os ciclos de mare foram de 16 psu e 1,5oC, respectivamente. A salinidade chegou a apresentar variacao vertical de 4 unidades, enquanto que a variacao da temperatura foi bem inferior. Foram calculados parâmetros indicadores da estratificacao a partir da densidade: coeficiente de estratificacao; frequencia de Brunt-Vaisala; e a anomalia da energia potencial. Os resultados mostraram que os parâmetros comportam-se da mesma maneira, apenas com diferenca da magnitude relativa de seus valores. A estrutura vertical do estuario apresentou estratificacao pronunciada durante a fase de vazante da mare, e verticalmente homogenea na fase de enchente da mare e durante a preamar. Dada as condicoes presentes, com vazao regularizada, o estuario apresenta padrao de estratificacao parcialmente misturado e hiposalino, quando seria esperado uma condicao bem misturada e hipersalina para o periodo estudado.

The environmental impacts of one of the largest tailing dam failures worldwide

The impacts of the SAMARCO iron tailing spill along more than 650 km, between the dam and the plume of the Doce River in the Atlantic, were assessed by the determination of toxic metals. The tailing spill caused a substantial increase in suspended sediment loads (up to 33,000 mg L−1), in addition to large depositions of waste along the Doce basin. The highest estimated transport of dissolved metals was observed for Fe (58.8 μg s−1), Ba (37.9 μg s−1) and Al (25.0 μg s−1). Sediments reached the highest enrichment factors (EFs) for Hg (4,234), Co (133), Fe (43), and Ni (16), whereas As (55), Ba (64), Cr (16), Cu (17), Mn (41), Pb (38) and Zn (82) highest EFs were observed for suspended particulate matter (SPM). Iron, As, Hg, Mn exceeded sediment quality guidelines. Therefore, the risk of occurrence of adverse effects is highly possible, not only due to the dam failure, but also due to the Fe mining and the artisan Au mining. Heavy rain episodes will likely cause enhanced erosion, remobilization, and transport of contaminated particles, sustaining high inputs of SPM and metals for the years to come and threatening the ecosystem services.

Observation of an Estuarine Turbidity Maximum in the Highly Impacted Capibaribe Estuary, Brazil

Estuarine turbidity maxima (ETM) are features present in some estuaries where the concentration of suspended particulate matter (SPM) is higher than elsewhere along the fresh-marine water transition in the estuarine domain (POSTMA, 1967; SCHUBEL, 1968; GEYER, 1993; DYER, 1995). The presence of ETM has important ecological implications: since they occur at places where there is an accumulation of organic matter: bacterioplancton and zooplankton dynamics in estuaries is affected by ETM behavior (CRUMP; BAROSS, 1996; MORGAN et al., 1997). ETM are also important in the pollutants dynamics of an estuary, mainly for those that occur adsorbed to fine clayey sediments (BRUNK et al., 1996). ETM are formed and maintained as the result of complex interactions between river discharge, tidal dynamics and gravitational circulation (DYER, 1988). The concentration of SPM in the ETM varies over time on tidal, sinodical and seasonal time scales (GRABEMANN et al., 1997). ETM have been studied in many estuaries abroad (ALLEN et al., 1980; GELFENBAUM, 1983; UNCLES et al., 1994; WOLANSKI et al., 1995). In some estuaries they are of an ephemeral nature (KISTNER; PETTIGREW, 2001), while in other cases they do not occur at all (SCHETTINI; TOLDO JUNIOR, 2006; SCHETTINI et al., 2006). The physics underlying the formation of the ETM has been studied using both analytical and numerical models (GEYER, 1993; JAY; MUSIAK, 1994; BURCHARD; BAUMERT, 1998; YU et al., 2014) in which the effect of gravitational circulation and tidal pumping is of primary importance, with a high degree of interaction between the flow and the bed. Most ETM have been reported in meso or macro-tidal estuaries. As regards the Brazilian coast, it is not expected to find ETM in the Southeastern and Southern Regions basically because the tidal regime is microtidal. Some papers have reported ETM processes in Paranagua Bay (PR) (e.g., RIBEIRO et al., 2011), although the higher turbidity zone in that estuary is linked rather to re-suspension due to tidal currents (MANTOVANELLI et al., 2004) than to the occurrence of a true ETM. Other studies on SPM in southern Brazilian estuaries have not reported the presence of ETM (SCHETTINI; TOLDO JUNIOR, 2006; D´AQUINO et al., 2010). On the other hand, meso and macro tides occur on the shores of the Northeastern and Northern Regions, where there would be a greater likelihood of observing ETM. Nevertheless, there are not many studies of the fine sediment dynamics of this area, and the few that are available do not report the presence of ETM. The fine sediment dynamics of the Caravelas estuary, Bahia has been assessed (SCHETTINI; MIRANDA, 2010; SCHETTINI et al., 2013), despite the fact that this estuary presents a very small freshwater inflow, and the major source of sediments is the inner shelf. Such conditions are unfavorable to the formation of ETM. The eastern shores of Para seem to present favorable conditions for the formation of ETM, and a single survey carried out in the Caete estuary has shown a feature in the longitudinal distribution of SPM which fits in with what is expected of an ETM (ASP et al., 2012), even though it has not yet been assessed.A series of surveys has been carried out in the Capibaribe estuary since 2012 to investigate its circulation, fine sediment transport, deposition patterns and recent environmental evolution. The main appeal of and reason for these assessments was the fact that the Capibaribe estuary is a relatively small system (~ 10 km

Effect of shellfish culture on phytodetritus vertical fluxes in tropical waters: southern Brazil

O cultivo de moluscos ao longo da costa de Santa Catarina tem crescido de forma acelerada nos ultimos anos. Embora os beneficios sejam muitos, varios tipos de impactos ambientais podem ser decorrentes do cultivo de moluscos. Desta forma, o sucesso da atividade depende de fatores que envolvem a capacidade suporte do meio e do grau que o ambiente e impactado. Um dos mais evidentes impactos associados ao cultivo de moluscos marinhos e o aumento da taxa de fluxo vertical de particulas associado a reducao da biomassa fitoplanctonica na coluna de agua. O fluxo vertical de fitodetritos produzidos em uma area de cultivo foi avaliado por meio de analise por cromatografia liquida de alta eficiencia (CLAE) de pigmentos fotossinteticos e produtos de degradacao do material coletado por armadilhas de sedimento. Os resultados indicam que o cultivo de moluscos aumenta em media 5 vezes o fluxo vertical de fitodetritos, sendo que a maior parte da degradacao da c1orofila-a ocorre na forma de feoforbideos. Dado o expressivo fluxo vertical de fitodetritos, comparado a pequena biomassa na coluna de agua, sugere-se que o fitopl ncton a1OOono, trazido por processos advectivos, e importante para a manutencao do crescimento dos moluscos na area estudada.

Hydrocarbons in sediments along a tropical estuary-shelf transition area: Sources and spatial distribution

Estuaries generally act as sediment traps and may retain a range of contaminants associated to this matrix. Aliphatic hydrocarbons (AHs) were investigated in Capibaribe Estuarine System and adjacent shelf, Northeast of Brazil, to evaluate the contamination and to better understand its functionality related to the coast. Fourteen sediment samples were analyzed, using gas chromatography with flame ionization detection. Total AHs concentrations ranged from 7.5 to 190.3μgg-1 and n-alkanes ranged from below detection limit (<DL) to 9.47μgg-1. The highest concentrations were in the upper portion of the estuary, which receives domestic and industrial effluents. The observed UCM and other geochemical markers, indicated contamination by petroleum hydrocarbons. The concentration decrease (about 90%) towards the adjacent shelf suggested an estuarine high retention capacity but dilution and degradation processes cannot be neglected. Similar AHs characteristics reported in sediments from the adjacent shelf suggested that this system may also export contaminants.

SPATIAL AND TEMPORAL VARIATION OF THE ZOOPLANKTON COMMUNITY IN THE AREA OF INFLUENCE OF THE ITAJAÍ-AÇU RIVER, SC (BRAZIL)

On the north coast of the State of Santa Catarina (Brazil), the Itajai-Acu River mouth shows a low-saline water plume on the internal shelf with strong density gradients. This oceanographic condition has a possible influence over the pelagic community, and it has been little investigated on the Brazilian coast. The present work seeks to evaluate the spatial and temporal variations of the zooplankton community in the area of influence of the Itajai-acu River, and its relations with the abiotic forces of temperature (seasonal variation) and salinity of the river plume. For this purpose, 14 monthly oceanographic cruises were carried out during the years 2002 and 2003, to obtain physical and chemical parameters, and zooplankton hauls in 9 sampling points. The zooplankton analyses were carried out at the lowest taxon possible to characterize the resident community of the river mouth. It was observed that the zooplankton presented the highest densities in winter and spring. The species with higher densities and frequencies of occurrence were Paracalanus quasimodo, Parvocalanus crassirostris, Acartia lilijeborgi, Temora stylifera, T. turbinata, and Penilia avirostris, indicating a prevalence in this region, of Tropical Water from the Brazil Current and greater similarity with the coastal community of the Southeast region of Brazil. However, even for the species typical of Tropical Water, there were alterations in dominance of the species, due to the seasonality and level of flow rate of the river on the salinity of the internal shelf of the study area.

Caracterização oceanográfica e do transporte de sedimentos em suspensão no estuário do Rio Mampituba, SC

The Mampituba River drains a watershed with 1,200 km2 in area, having its springs in the Serra Geral and debouching to the Atlantic Ocean at city of Torres, after running a 62 km long course. It has a mean discharge of 18.6 m3.s-1, a mean depth around 4 m and is under a microtidal regime. An oceanographic campaign was carried out at May 17th, 2008, when water level, currents, salinity and suspended sediment concentration were recorded during two tidal cycles(25 hours). The water level presented a decreasing trend during the campaign, and the mean tidal range was 0.4 m, with flood dominated asymmetry. The current pattern was bi-directional with mean ebb and flood velocity of 0.33 and 0.13 m.s-1, respectively. The estuarine stratification followed the tide, with the salt wedge intrusion extending 5 km up-estuary. The total salt transport was 1.11 kg.m-1.s-1 out to the estuary. The fluvial discharge component accounted for 98% of the seaward transport, whereas the landward transport had 51% due to the gravitational circulation, 26% due to tidal correlation and 19% due to tidal pumping. The suspended sediments transport was mainly due to the gravitational circulation, which accounted for 83% of the total transport. The Mampituba River estuary hydrodynamics responds mainly to the river, presenting a highly stratified behavior.