Particulate Iron in Offshore Waters of the Panama Bight and in the Gulf of Panama

Particulate iron is reported from replicate samples taken at two depths at several locations in the Panama Bight during November 1955, and in replicate samples taken at two depths at a single inshore location in the Gulf of Panama at bimonthly intervals from December 1954 through December 1955. In addition, a few samples were taken at other locations in the Gulf of Panama and from a river flowing into the Gulf. The content of particulate iron, both in the Panama Bight and in the Gulf, shows highly contagious distributions, necessitating a logarithmic transformation to make the data amenable to statistical analysis. All samples from the Panama Bight could have arisen from a single log‐normal distribution with a mean of 12.2 µg/L. In the Gulf of Panama, there is significantly higher iron in the surface (115.2 µg/L) than at 30 meters (62.1 µg/L) during the early part of the year when the standing crops of plankton organisms are high. Particulate iron content is higher inshore in the Gulf of Panama than offshore in the Panama Bight, and two samples from the Rio Escota, containing 692 and 863 µg/L, were much higher than in the Gulf, indicating that possibly the iron is being brought in by runoff. From comparison of iron content in inshore and offshore waters, in both of which biological production is high, it is inferred that particulate iron cannot be a limiting factor on phytoplankton growth in the inshore waters.