de Baar¹ , H., and J. La Roche²

¹Royal Netherlands Institute for Sea Research, Texel, The Netherlands, Email: debaar@nioz.nl and ²Institut fuer Meereskunde, Kiel, Germany

Trace metals in the oceans: evolution, biology and global change

During evolution of prokaryotes and later on eukaryotes several metals became incorporated as essential factors in many biochemical functions in accordance with the abundance of these metals on the planet. The biological role of first row metals can be ranked Fe, Zn, Cu, Mn, Co, Ni. Second row metals Ag and Cd or third row metals like Hg and Pb appear to have no biological function, except possibly for Cd. Iron (Fe) being the fourth most abundant element of the planet has also played a role to temper the evolution of biogenic oxygen in the atmosphere and oceans. Yet eventually O₂ has taken over the biosphere where now both atmosphere and ocean are strongly oxidizing. Inside the cell primordial reducing niches have remained however. Therefore enzyme systems based on metal couples Fe-Mn and Cu-Zn are required to protect the cell interior from damage by reactive oxygen species. The key role of metals in these and many other enzymes as well as in protein folding is one of the major vectors in biological diversity at both the molecular and the species level. Plankton ecosystems are governed by colimitation of several metals. Co-limitation of plankton growth is consistent also with observed interactions between metals. The supply of Fe to ocean waters is one of the major controls of plankton ecosystems and ocean element cycling (C, Si, N, P). Understanding the role of metals in the oceans is crucial for understanding global change of past, present and future.