RELATIONSHIP BETWEEN INORGANIC AND ORGANIC NUTRIENTS IN SEA-WATER

The seasonal variations of dissolved inorganic and organic N and P in the waters of the English Channel during an 11 yr study were discussed. The N results showed that as NO3 was utilized by phytoplankton there was an increase in the concentration of the dissolved organic N fraction and there were always significant amounts of dissolved N in some form in the water. Phytoplankton may be directly using organic N compounds, such as urea. The classical theory of inorganic nutrient limiting growth was discussed. The yearly succession of phytoplankton species that occurred in this area may be partly explained by the hypothesis that when NO3 is exhausted there may be a change in the phytoplankton population such that species capable of utilizing other forms of N become dominant. The ratio of the various forms of dissolved N and P were discussed. The T[total]N:TP ratio was relatively constant throughout the year.