Mississippi River Flood Waters That Reached The Gulf Stream

Distributions of physical, biological, and chemical parameters in Florida Keys coastal waters seaward of the reef track were surveyed on September 9 to 13, 1993, as part of a coordinated multidisciplinary study of surface transport processes. A band of low-salinity water was observed along the shoreward side of the Florida Current over the downstream extent of the survey from Miami to Key West. Biological and chemical indicators within the band, together with its large volume, satellite imagery, and a surface drifter trajectory suggested the recent Mississippi River flood as the source

Sequential Photochemical and Microbial Degradation of Organic Molecules Bound to Humic Acid

We studied the effects of photochemical processes on the mineralization by soil microorganisms of [2-(14)C]glycine bound to soil humic acid. Microbial mineralization of these complexes in the dark increased inversely with the molecular weight of the complex molecules. Sunlight irradiation of glycine-humic acid complexes resulted in loss of absorbance in the UV range and an increase in the amount of (14)C-labeled low-molecular-weight photoproducts and the rate and extent of mineralization. More than half of the radioactivity in the low-molecular-weight photoproducts appears to be associated with carboxylic acids. Microbial mineralization of the organic carbon increased with solar flux and was proportional to the loss of A(330). Mineralization was proportional to the percentage of the original complex that was converted to low-molecular-weight photoproducts. Only light at wavelengths below 380 nm had an effect on the molecular weight distribution of the products formed from the glycine-humic acid complexes and on the subsequent microbial mineralization. Our results indicate that photochemical processes generate low-molecular-weight, readily biodegradable molecules from high-molecular-weight complexes of glycine with humic acid

The contribution of rainwater to variability in surface ocean hydrogen peroxide

Hydrogen peroxide concentrations have been determined in marine rain from the Gulf of Mexico, the western Atlantic Ocean, and one rain event off the Florida Keys. In several cases, simultaneous measurements of the concentration of H2O2 in the surface ocean were also determined. These measurements were made with the ship under way using a continuous flow sampling system with the intake at the bow. In shallow stratified layers, rain events can increase the existing hydrogen peroxide concentration by a factor greater than 10 and dramatically increase the mean H2O2 concentration of mixed depth layers of 50 m or more. Rain is a significant transient source of H2O2 in the surface ocean

Rivers in the Sea: Can We Quantify Pigments in the Amazon and the Orinoco River Plumes from Space?

Coastal Zone Color Scanner (CZCS) images of the western tropical Atlantic (1979-1982) were combined into monthly mean surface pigment fields. These suggest that Amazon River water flows along northeastern South America directly toward the Caribbean sea early in the year. After June, however, the North Brazil Current is shunted eastward, carrying a large fraction of Amazon water into the North Equatorial Countercurrent (NECC). This eastward flow causes diminished flow through the Caribbean, which permits northwestward dispersal of Orinoco River water due to local Ekman forcing. The Orinoco plume crosses the Caribbean, leading to seasonal variation in surface salinity near Puerto Rico. At least 50% of the pigment concentration estimated in these plumes seems due to viable phytoplankton