A Role for Vanadium in Ascidians and in Marine Algae

Vanadium is – next to molybdenum – the second-to-most abundant transition metal in sea water. Oxygenated sea water commonly contains 24-45 μM of vanadate H 2 VO 4 ˉ (and is thus – next to molybdenum – the second-to-most abundant transition metal in sea water) with the levels mainly fluctuating with the season. Depletion by about 60% can occur as reduction to VO takes place which forms a sparingly soluble hydroxide, VO(OH) 2 , that is readily absorbed by particulate organic matter [1]. Consequently, the factors influencing the occurrence of vanadium are redox conditions (such as dissolved O 2 and Fe, the presence of NH 3 and S , and – of course – its uptake by marine organisms. Vanadate is mainly taken up by marine algae, the most prominent one being knotted wrack (also known as rockweed) Ascophyllum nodosum, (Figure 1), by ascidians and, to some extent, also by some Polychaeta fan worms [2]. The significance of vanadium as an essential element in these organisms will be addressed.