THE CYCLE OF ORGANIC PHOSPHORUS IN THE GULF OF MAINE

¹ From the Woods Hole Oceanographic Institution and the Biological Laboratories Harvard University

1. Methods are described for the determination of the phosphorus present in particulate form and of the total phosphorus in a sample of sea water.

2. The distribution of phosphorus present as inorganic phosphate, as dissolved organic compounds, and as particulate matter (detritus and microörganisms) has been determined at all depths throughout the year at a station in the western part of the Gulf of Maine.

3. In late winter over 90 percent of the phosphorus is in inorganic form and three-quarters of the remainder is present as soluble organic compounds.

4. In the spring—February to May, inorganic phosphorus is converted to organic form by photosynthesis in the upper layer of water. Most of this fraction sinks to considerable depths before undergoing decomposition.

5. During the summer—May to November, large quantities of dissolved organic phosphorus appear at all depths, indicating a very considerable transport of inorganic phosphate from deep water to the surface and the sinking of an equivalent amount of phosphorus in particulate form to the depths in which organic compounds are liberated by decomposition. Decomposition appears to take place throughout the water column.

6. During the winter—November to February, the organic phosphorus compounds are converted to inorganic phosphate. This and vertical mixing of preformed phosphate are about equally important in bringing about the equalization of phosphate concentrations throughout the depth of water.

7. A method is described for analyzing quantitatively the factors producing a seasonal change in the distribution of a compound such as phosphorus. It is shown that the vertical transport of material within the water mass demanded by such an analysis may be accounted for reasonably by the hydrographic conditions obtaining.

8. Values of the coefficient of eddy conductivity at several depths are obtained.