The negative effects of chemical contaminants on tropical marine ecosystems are of increasing concern as human populations expand adjacent to these communities. Watershed streams and ground water carry a variety of chemicals from agricultural, industrial, and domestic activities, while winds and currents transport pollutants from atmospheric and oceanic sources to these coastal ecosystems. The implications of the limited information available on impacts of chemical stressors on mangrove forests, seagrass meadows, and coral reefs are discussed in the context of ecosystem management and ecological risk assessment. Three classes of pollutants have received attention: heavy metals, petroleum, and synthetic organics. Heavy metals have been detected in all three ecosystems, causing physiological stress, reduced reproductive success, and outright mortality in associated invertebrates and fishes. Oil spills have been responsible for the destruction of entire coastal shallow-water communities, with recovery requiring years. Herbicides are particularly detrimental to mangroves and seagrasses and adversely affect the animal-algal symbioses in corals. Pesticides interfere with chemical cues responsible for key biological processes, including reproduction and recruitment of a variety of organisms. Information is lacking with regard to long-term recovery, indicator species, and biomarkers for tropical communities. Critical areas that are beginning to be addressed include the development ofmore » appropriate benchmarks for risk assessment, baseline monitoring criteria, and effective management strategies to protect tropical marine ecosystems in the face of mounting anthropogenic disturbance.« less

https://setac.onlinelibrary.wiley.com/doi/pdf/10.1002/etc.5620160103

Ecotoxicology of tropical marine ecosystems

https://hal-insu.archives-ouvertes.fr/hal-00022511/document

Heavy metals distribution in mangrove sediments along the mobile coastline of French Guiana

https://hal-insu.archives-ouvertes.fr/insu-00536395/document

Relationships between heavy metals distribution and organic matter cycling in mangrove sediments (Conception Bay, New Caledonia)

Soils and porewater of the rhizosphere of mangrove trees, Rhizophora mangle L. and Avicennia schaueriana Stapf & Leech., of the salt marsh grass Spartina alterniflora Loisel, and of unvegetated mud flats, were analyzed for pH, salinity, platinum electrode redox potential, organic matter content, sulfide concentrations, and the total and exchangeable concentrations of trace metals (Fe, Zn, Cu, Pb and Cd). The study was conducted in a fringe mangrove forest in Sepetiba Bay, Rio de Janeiro, Brazil. The rhizospheres differed in their biogeochemistry. Mud flats and Rhizophora soils were very reducing, with highest concentrations of sulfide. Avicennia soils showed the highest variability of the variables measured, with the rhizosphere changing from oxic to anoxic conditions. Spartina soils, on the other hand, were generally oxic, with very low sulfide concentration. The distribution of trace metals in these soils varied with the major physical and chemical characteristics. Mud flat soils presented the highest total trace metal concentrations followed by mangrove soils and Spartina soils. However, exchangeable trace metals were similar among the different soils with the exception of Avicennia soils, which due to their characteristic instability of redox conditions, presented much higher exchangeable trace metals concentrations.

https://www.jstor.org/stable/info/2388783

The biogeochemistry and trace metals distribution of mangrove rhizospheres

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.

F.M.B Nogueira

Papers

The fate of trace metals in suspended matter in a mangrove creek during a tidal cycle

C3 and c4 grasses distribution along soil moisture gradient in surrounding areas of the lobo dam (sao paulo, brazil)