In 10 stimulating chapters, Volume 43 of Metal Ions in Biological Systems focuses on the vibrant research area related to the cycling of elements, metals, and nonmetals in biology and geology. It critically highlights the biogeochemistry of hydrogen, oxygen, nitrogen, sulfur, and phosphorus, examines the interrelations between the availability of iron, phytoplankton growth, and the carbon cycle, considers the biogeochemical cycling of mercury and lead, and includes a chapter devoted to cadmium, a highly toxic element that is also a micronutrient for phytoplankton. This volume contains more than 50 illustrations along with more than 1300 references for further research on the subject.