A diatom chain by Charles Krebbs . Diatoms have always been important producers in the ocean. . They need a high concentration of nutrients so they do well where nutrient levels are high. The waters they proliferate in tend to be better mixed and the mixing is important in keeping the diatoms higher in the water where the sun is shining. In order to increase their surface to volume ratio and float better, they often group together in chains which are less prone to sinking .