TOXICITY OF METHYL MERCURY AND MERCURY(II) CHLORIDE TO A BROWN ALGA CYSTOSEIRA-BARBATA (FUCALES) UNDER LABORATORY CULTURE CONDITIONS - DETOXIFYING ROLE OF CALCIUM

The effects of organic (CH3HgCl) and inorganic (HgCl2) mercury have be en investigated on the growth, pigment content, and metal accumulation of the brown alga Cystoseira barbata forma hoppii. The element concen tration factor for the alga was also studied. The experimental design allowed simultaneous investigations of the toxicity and the exposure t ime of both mercury compounds, the role of calcium ion concentration, and the interactions between these three experimental factors. These p hysiological results have been supplemented with ultrastructural obser vations in order to detect changes caused either by mercury chloride o r methylmercury. Cystoseira barbata forma hoppii shows an important ab ility to accumulate mercury and a great resistance to the action of me rcuric chloride. Methylmercury appears more harmful than mercuric chlo ride, but the addition of calcium (250 mg L-1) to the culture media re duces the toxicity.