Trace Metals in the Oceans: Evolution, Biology and Global Change

Abstract

All living organisms require several essential trace metal elements. During biological evolution of prokaryotes and later on also eukaryotes several metals became incorporated as essential factors in many biochemical functions more or less in accordance with the abundance of these metals on the planet. As a result the biological importance of first row transition metals can be ranked roughly in the order Fe, Zn, Cu, Mn, Co, Ni. The 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 in the crust of the planet has also played a role to temper the evolution of biogenic oxygen (02) in the atmosphere and oceans. Yet eventually 02 has taken over the biosphere where now both atmosphere and ocean are strongly oxidizing. Inside every living cell the primordial reducing conditions 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. Abundance and biological role of metals in the oceans are being discovered only since 1976 and many questions remain. Until now many metals appear to be tightly linked with the large scale biological cycling. Recently the significance of very fine colloids as well as dissolved organic metal-complexes has been shown. Plankton ecosystems now appear to be governed by co-limitation of several essential metals, where the biological fractionation of their stable isotopes is expected to give rise to significant shifts in isotopic ratio for any given metal element. Co-limitation of plankton growth is consistent also with observed interactions between metals. Firstly substitution of for example Co or Cd for Zn is known for some but not all phytoplankton taxa. Secondly the cellular uptake of one metal, e.g. Cd, may respond to a complex matrix of other metals like Zn, Mn and possibly Fe. By mining and industrial use of metals, land use change and irrigation, mankind has greatly modified the abundances and mutual ratio's of metals in the biosphere. Biota can to some extent resist the ensuing external stress through cellular homeostasis. However at highly elevated levels or excessive metal ratio's several biological species cannot longer exist and major shifts of ecosystems and their diversity do occur. Likely such changes have already taken place for centuries and as such have largely gone unnoticed. The past decade was the onset of the iron age in oceanography. Nowadays Fe is known to be a severely limiting element in some 40 % of the world oceans. This limitation is sometimes relieved by aeolian supply of continental dust, but most Fe supply is actually from below emanating of reducing sediments. With adequate Fe there is a systematic response by the class of very large oceanic diatoms, the...

Effect of trace metal‐limited growth on the postmortem dissolution of the marine diatom Pseudo‐nitzschia delicatissima

“…During the last two decades, it has been convincingly shown that the subnanomolar oceanic concentrations of iron (Fe) are low enough to limit primary production in ~ 50% of the world's oceans, including the Southern Ocean where diatoms dominate the phytoplanktonic community [ Boyd and Ellwood , ]. Fe limitation also induces a decoupling in the use of major macronutrients by phytoplankton, which is likely to influence the cycling of the major biogeochemical cycles (C, N, P, and Si) over geological time scales [ de Baar and La Roche , ]. Fe‐limited diatoms generally increase their consumption of silicate relative to nitrate, which increases their Si:N and Si:C ratios [ Marchetti and Cassar , , and references therein].…”

Ordinary stoichiometry of extraordinary microorganisms

“…Indeed, phylogenomic analyses of protein structures reveal that biological utilization of transition metals likely varied with the availability of metals through the history of life on Earth (Zerkle et al ., ; Dupont et al ., ; see also Quigg et al ., ). For example, the presumed increased availability of Zn and decreased availability of Fe in Earth's oceans over time, due to a change in ocean chemistry from anoxic in the Archean and sulfidic in the Proterozoic (though perhaps only intermittently in continental margin settings; Poulton & Canfield, ) to modern oxic conditions, seems to have resulted in greater use of Zn in enzymes, reflecting the evolution of eukaryotic cells (Fraústo da Silva & Williams, ; de Baar & La Roche, ; Saito et al ., ), and in use of Fe in decreased amounts in the photosystem of eukaryotic phototrophs (Raven, ). In the late Archaean, limited supply of Ni from the Earth's mantle to the oceans may have curbed biological methane production (Konhauser et al ., ).…”

“…Selection for efficient element use appears to be embedded even in patterns of amino acid usage in the proteomes of micro-and macro-biota (Baudouin-Cornu et al, 2001;Elser et al, 2011). In modern aqueous environments, low trace metal concentrations limit phytoplankton growth (Morel et al, 1991;Saito et al, 2002Saito et al, , 2004de Baar & La Roche, 2003;Morel & Price, 2003;Morel, 2008); these scarce metals are accumulated via membrane transport systems involving the use of ligands (Hudson & Morel, 1993;Tortell et al, 1999;Saito et al, 2005). Metal scarcity drives selection pressures that can result in the use of substitute metals, such as Cd or Co instead of Zn (Lane et al, 2005;Xu et al, 2007;Morel, 2008;Yee & Morel, 2008), or even in the ability to decrease metalloenzyme production altogether (Saito et al, 2010).…”

REGENERASI RUMPUT LAUT Kappaphycus alvarezii HASIL TRANSFORMASI GEN Sitrat Sintase MENGGUNAKAN Agrobacterium tumefaciens SECARA IN VITRO

“…Hal ini didukung dengan ditemukan fakta bahwa penyakit iceice lebih menonjol pada lingkungan yang kualitas airnya rendah, pergantian air sedikit, salinitas rendah dan tinggi rendahnya suhu air serta kandungan logam berat yang tinggi di perairan (Mtolera et al, 1995). Cemaran logam yang sering dijumpai pada sedimen dan perairan pantai antara lain Bp, Cd, Cu, Zn, Mn, dan Al (Jickells, 1955;De Baar & La Roche, 2003, dan Rochyatun & Rozak, 2007.…”