Regional assessment of the historical trends of mercury in sediment cores from Wider Caribbean coastal environments.

Spatial and temporal variations of mercury (Hg) concentrations, enrichment, and potential ecological risks were studied in a suite of lead-210 (210Pb) dated sediment cores from 13 Wider Caribbean Region coastal environments. Broad variability of Hg concentrations (19-18761 ng g-1) was observed, encompassing even background levels (38-100 ng g-1). Most Hg concentration profiles exhibited a characteristic upward trend, reaching their peak values in the past two decades. Most of the sediment sections, showing from moderately to very severe Hg enrichment, were found in cores from Havana Bay and Sagua River Estuary (Cuba), Port-au-Prince Bay (Haiti), and Cartagena Bay (Colombia). These were also the most seriously contaminated sites, which can be considered regional Hg 'hotspots'. Both Havana Bay and Port-au-Prince Bay reportedly receive waste from large cities with populations exceeding 2 million inhabitants, and watersheds affected by high erosion rates. The records from the Sagua River Estuary and Cartagena Bay reflected historical Hg contamination associated with chloralkali plants, and these sites are of very high ecological risk. These results constitute a major contribution to the scarce regional data on contaminants in the Wider Caribbean Region and provide reference information to support the evaluation of the effectiveness of the Minamata Convention.

Metal and metalloid bioconcentration capacity of two tropical bivalves for monitoring the impact of land-based mining activities in the New Caledonia lagoon.

The clam Gafrarium tumidum and the oyster Isognomon isognomon have been proposed as potential biomonitor species of metal contamination in the New Caledonia lagoon. The influence of dissolved concentrations of As, Cd, Co, Cr, Mn, and Zn on uptake and depuration kinetics, tissue and subcellular distribution of these elements was investigated in both species. Results indicate that both bivalves take up elements proportionally to the dissolved concentration for Cd, Cr and Mn in the surrounding water over the entire range of concentrations tested (three orders of magnitude), and up to the second and third highest added metal concentration tested for Co (23 ng l(-1)) and Zn (700 ng l(-1)), respectively. All elements were efficiently retained in bivalve tissues (estimated T(b1/2) ranging from 16d to infinity), suggesting that both species should be able to preserve a record of contamination events over a long period of time. Considering the specific range of concentrations examined here, G. tumidum and I. isognomon would therefore serve as adequate biomonitor species to monitor dissolved metal contamination in the New Caledonia lagoon waters.