C.A.R. Silva

Metals reservoir in a red mangrove forest.

This study presents heavy metal concentrations and distributions in a mangrove forest in Sepetiba Bay, Rio de Janeiro. Sediments are the main reservoir of the total metal contained in mangrove studied: 99 percent for Mn; 100 percent for Fe; 100 percent for Zn; 99 percent for Cu; 100 percent for Cr and 100 percent for Pb and Cd. Rhizophora mangle biomass contained less than 1 percent of reservoir. Within the biotic compartment, perennial tissues accounted for almost all of the metals present in biomass. The results indicate that mangrove may act as an efficient metal trap in tropical coastal environments.

Factors affecting the hydrochemistry of a mangrove tidal creek, sepetiba bay, Brazil

We studied the porewater chemistry, and spatial and temporal variation of mangrove creek hydrochemistry. Except for nitrate porewater, the concentrations of nutrients we analysed were higher than for creek water. Groundwater is a source of silica and phosphate, whereas total alkalinity and ammonium are related to mangrove porewater migration to the creek. Open bay waters contribute chlorine, dissolved oxygen and elevated pH. The results also suggest that nitrate is related to nitrification inside the creek. During flood tides, salinity, chlorine, dissolved oxygen and pH increase, whereas total alkalinity decreases. This pattern is reversed at ebb tides. Silica, phosphate, nitrate and ammonium show an erratic behaviour during the tidal cycle. Tidal dynamics, precipitation events and nitrification inside the creek were identified as major control factors and an estimate of tidal exchanges indicate that the system is in an equilibrium state.

Biomonitoring of trace metal contamination in the Potengi Estuary, Natal (Brazil), using the oyster Crassostrea rhizophorae, a local food source

The oyster Crassostrea rhizophorae was collected in September 1997 from 10 stations along the Potengi estuary, Natal, Brazil, a mangrove-lined estuary receiving anthropogenic inputs of trace metals. C. rhizophorae is a net accumulator of trace metals and can be used as a biomonitor, the accumulated soft tissue concentrations representing integrated records of bioavailable metal fractions over the life of the oyster. Significant differences in oyster accumulated concentrations (and hence bioavailabilities) of Fe, Zn, Cu, Cr, Pb, Cd, Ni and Ag (but not Mn) were found between stations, and attributed to anthropogenic inputs including discharges of sewage and industrial effluent. The oysters are also a local food source, and concentrations of zinc, copper and lead in some of the oysters are above typical public health recommended limits.

Biomonitoring of trace metal contamination in mangrove-lined Brazilian coastal systems using the oyster Crassostrea rhizophorae: comparative study of regions affected by oil, salt pond and shrimp farming activities

The oyster Crassostrea rhizophorae has been used as a biomonitor of trace metal contamination in two Brazilian coastal systems. C. rhizophorae were collected in January 1998 from 15 stations (from 4 coastal inlets (including 1 estuary) and 1 coastal beach) near Macau, Rio Grande do Norte (RN), Brazil, a region affected by the activities of the oil industry and salt manufacture in coastal salt ponds; oysters were also collected in September 1999 from 8 stations in the Curimatau estuary (RN), an estuary becoming increasingly affected by shrimp farming activities. C. rhizophorae is a net accumulator of trace metals and can be used as a biomonitor, the accumulated soft tissue concentrations representing integrated records of bioavailable metal over the life of the oyster. At Macau, significant differences in oyster accumulated concentrations (and hence bioavailabilities to the oyster) of Fe, Zn, Cu, and Mn were found between stations; raised zinc availabilities at the coastal site are in close proximity to oil industry activities but the very high availabilities of Fe, Cu and Mn in the Rio dos Cavalos estuary originate from an unknown source. In the Curimatau estuary, bioavailabilities of Mn, Pb and Cd, but particularly of Cu and Zn, to the oysters are raised at the two most downstream sites, the only sites below the effluent of a large shrimp farming enterprise. The oysters also act as a local food source, and concentrations of Zn, Cu and Pb of some of the oysters are above typical public health recommended limits.

Nature of POC transport in a mangrove ecosystem: A carbon stable isotopic study

Abstract The isotopic composition of particulate organic carbon (POC) was studied during five tidal cycles in a mangrove creek of Sepetiba Bay, Rio de Janeiro, Brazil. The results show that a mixture of organic carbon from mangrove and marine origins is always present in the creek. Mean mangrove contribution to the POC varied from 16% to 100% and was dependent on tidal amplitude. The results suggest that oceanic carbon can be an important component of carbon balance in mangrove ecosystems. Therefore, earlier carbon balance studies from mangroves which did not include measurements of carbon isotopic composition should be interpreted with care.

Solubility of Siderite (FeCO3) in NaCl Solutions

AbstractThe solubility of siderite (FeCO3) at 25°C under constant CO2 partial pressure [p(CO2)] was determined in NaCl solutions as a function of ionic strength. The dissolution of FeCO3(s) for the reaction

Distribution and fluxes as macrodetritus of phosphorus in red mangroves, Sepetiba Bay, Brazil

\begin{gathered}{FeCO}_{3} ({s}) + 2{\text{H}}^+ = {Fe}^{2 + } + {CO}_{2} ({g}) + {H}_{2}{O} \hfill \\ K{so}^{*} = [{Fe}^{2 + } ]\;p{CO}_{2} /[{H}^{ + } ]^2 \hfill \\ \end{gathered}

Relative importance of nitrogen and phosphorus emissions from shrimp farming and other anthropogenic sources for six estuaries along the NE Brazilian coast

has been determined as a function of pH = − log[H+]. From these values we have determined the equilibrium constant for the stoichiometric solubility to FeCO3(s) in NaCl