TRIPHENYLTIN INHIBITS PHOTOSYNTHESIS AND RESPIRATION IN MARINE MICROALGAE

The effects of diphenyltin and triphenyltin (TPhT) on gross photosynth esis and respiration by the diatom Skeletonema costatum (Greville) Cle ve and the chlorophyte Dunaliella tertiolecta (Butcher) were investiga ted by measuring the rates of change of oxygen concentration in sample s which were alternately illuminated and unilluminated. Measurements w ere carried out for 90 min after organotin addition. Triphenyltin at c oncentrations in the nM to mu M range inhibited photosynthesis and res piration in both ogranisms. Levels of TPhT inhibiting these processes were two to three orders of magnitude higher for D. tertiolecta than f or S. costatum. Photosynthesis and respiration by D. tertiolecta were resistant to diphenyltin at concentrations up to its limit of solubili ty (0.84 mM). With S. costatum, inhibitory levels of diphemyltin were one to two orders of magnitude higher than those for triphenyltin. Inh ibition was often progressive over the period after organotin addition . This effect varied in intensity and was more noticeable with the mor e resistant D. tertiolecta. Comparison of our results with levels of o rganotins which have been observed by others in Mediterranean coastal waters indicate that environmental levels of TPhT could influence phyt oplankton composition and dynamics.