The seasonal distribution of trace metals was made on surface waters in Florida Bay and adjacent waters, and additionally surface sediments were also collected at 40 stations across Florida Bay. Florida Bay is the largest estuary in Florida with nearly pristine conditions and it is a shallow carbonate estuary. The measurements in Bay seawater were made from May 2000 to May 2001, and the adjacent waters were sampled in September 2000 and May 2002. The sediments were collected in June, November and February 2000-2001. Concentrations of Sc, V, Ba, Cd, Cr, Co, Cu, Pb, Mn, Ni, Zn, Al and Mg were determined by ICP-MS, and the total Fe was determined by spectrophotometry. Organic carbon (OC), nitrogen (N), and calcium carbonate in sediments were also measured by a LECO CN 2000.

Most of the dissolved trace metals exhibited their maximum concentrations in summer. The exceptions were Al and Pb which did not show any seasonal variation. The high concentrations in the northwestern part of the Bay were influenced by the Shark River. High concentrations were also found near Flamingo and the input of Taylor Slough waters from the Everglades. In some surveys, high concentrations of Cr, Cu and Pb were found near the Tavernier Marina. The minimum concentrations for most of the metals were found in areas near the Key channels that exchange waters between Florida Bay and the Atlantic Ocean (Gulf Stream). The adjacent waters in the Atlantic side including the Gulf Stream waters showed very low concentrations for all the metals. The variations of the metals over the year are related to the influx of fresh water from rainfall. The lowest concentrations are found during the dry season in the winter and the highest during the wet season in the summer.

Eleven of 13 metals measured in Florida Bay sediments showed a similar distribution pattern for the various months studied. Maximum concentrations of metals were lower than those found in most estuarine systems and were concentrated in the north-central and western zones of the Bay. The Mn and Fe concentrations, unlike the other metals, gradually decreased from north (Everglades) to south (Florida Keys). Some metals (Ni, Zn, Cu, Cr, Pb and Ba) associated with petroleum use showed high concentrations at stations near the Tavernier marina. Florida Bay sediments are predominately CaCO3 (65.9% - 92.5%). The greatest value for OC (5.5%) and the lowest value of CaCO3 (65.9%) were found in the western zone. Trace metal distribution patterns are similar to the OC and N in the sediments. There was a strong correlation between most metals (V > Cu > Ni> Cr > Al > Co > Ba > Zn > Pb >Mg) and the percentage of OC. The maximum C/N values (9-12) were observed at the stations with the highest OC, where dense colonies of seagrass are found and most of the metals are concentrated. All metals except Mg, Mn and Co showed a strong correlation with Al and the fine fraction of the sediments (aluminosilicates) associated with continental input and river runoff.