Bioaccumulation and formation of arsenicals in tropical shallow reef organisms

A project undertaken at the Institute of Applied Ecology, University of Canberra, and supervised by Bill Maher

Arsenic in marine macro algae (food source for hebivorous animals), is present as dimethyl-arsenoribosides while in animals arsenobetaine (AB)is the most abundant arsenical. A major pathway has been proposed for the biosynthesis of AB in marine animals based on the bioconversion from arsenoribosides. Based on recent work in our laboratory we proposed two  metabolic pathways that accounts for AB  by (I) formation of  trimethyl-arsenoribosides from dimethyl-arsenoribosides and  catabolism  via arsenocholine to AB; (II) production of  of AB via 2-dimethylarsinothioyl ethanol. In this study we found that phytoplankton, the basis of many marine food chains,  produce dimethyl-arsenoribosides and that on degradation both phytoplankton and macroalgae produce 2-dimethylarsinothioyl ethanol, the precursor to the formation of AB. Trimethyl-arsenoribosides were successfully isolated form many marine animals, but conversion to AB  awaits confirmation


Figure 1. Algae being feed to organisms


Figure 2. Naturally decaying macroalgae


Figure 3. Macroalgae degradation experiments


Figure 4. Phytoplankton continuous cultures