Triphenyltin inhibits photosynthesis and respiration in marine microalgae

Summary The effects of diphenyltin and triphenyltin (TPhT) on gross photosynthesis and respiration by the diatomSkeletonema costatum (Greville) Cleve and the chlorophyteDunaliella tertiolecta (Butscher) were investigated by measuring the rates of change of oxygen concentration in samples which were alternately illuminated unilluminated. Measurements were carried out for 90 min after organotin addition. Triphyltin at concentrations in the nM to M range inhibited photosynthesis and respiration in both ogranisms. Levels of TPhT inhibiting these processes were two to three orders of magnitude higher forD. tertiolecta than forS. costatum. Photosynthesis and respiration byD. tertiolecta were resistant to diphenyltin at concentrations up to its limit of solubility (0.84 mM). WithS. costatum, inhibitory levels of diphenyltin were one to two orders of magnitude higher than those for triphenyltin. Inhibition was often progressive over the period after organotin addition. This effect varied in intensity and was more noticeale with the more resistantD. tertiolecta. Comparison of our results with levels of organotins which have been obeserved by others in Mediterranean coastal waters indicate that environmental levels of TPhT could influence phytoplankton composition and dynamics.