ABSTRACT
Marine phytoplankton require certain trace elements for growth. These nutrients are used until they become limiting and further growth is inhibited. A crude way of assessing the availability and need of marine plants for various elements can be made by examining the composition of phytoplankton compared to the concentration in average seawater. Such a comparison is shown in Table 8.1. The most important micronutrients are nitrogen and phosphorus. Some organisms (diatoms) have siliceous frustules and require silica. Although other elements such as Fe, Mn, Cu, Zn, Co, and Mo are also essential for growth, it is generally thought that growth is not inhibited or limited by the concentration of these metals. An exception for certain waters may be Fe and Mn. In addition, certain organic compounds, such as vitamins, are necessary for growth. This chapter discusses the major micronutrients P, N, and Si.
