ACUTE TOXICITY OF HEAVY-METALS FOR BENTHIC EPIPHYTIC FORAMINIFERA PARAROTALIA-SPINIGERA (LECALVEZ) AND INFLUENCE OF SEAWEED-DERIVED DOC

The acute toxicity of cadmium, copper, and mercury to the benthic epip hytic foraminiferan Pararotalia spinigera (Le Calvez) was investigated using seven different vital cytophysiological and cytochemical method s. The ability to enzymatically hydrolyze the fluorogenic substrates f luorescein diacetate or fluorescein dibutyrate was the most sensitive method of LC50 value determination. The LC50 (24-h) values for cadmium , copper, and mercury determined by this assay with fluorescein diacet ate was 0.56, 1.4, and 0.07 mu M, respectively. The content of seaweed -derived dissolved organic carbon (DOC), measured by absorbance at 436 nm, produced a dramatic increase of LC50 values for the heavy metals in a dose-dependent manner. ''Intact'' epiphytic foraminifera attached to seaweeds are less sensitive to acute toxicity of cadmium, copper, and mercury than are ''detached'' foraminifera.