Temephos distribution and persistence in a southwest Florida salt marsh community

The distribution and persistence of the mosquito larvicide temephos was monitored throughout an intertidal salt marsh community in southwest Florida following routine aerial applications of Abate 4-E (43% temephos) from 1988 through 1993. Temephos was found to be more highly concentrated in the surface water microlayer than in mid-depth water, exhibiting a mean of 330 micrograms/liter at the surface and 12 micrograms/liter at mid-depth from 1 fl. oz./acre applications and 120 micrograms/liter in the surface and 4.5 micrograms/liter in mid-depth water for 0.5 fl. oz./acre applications. Concentrations at both surface and mid-depth diminished rapidly within the first 24 hours. Mangrove leaves provided the most persistent reservoir for temephos, remaining more than 7 days. Temephos residues also were observed in select salt marsh organisms, including the sheepshead minnow (Cyprinodon variegatus), adult fiddler crabs (Uca rapax) and the ribbed mussel (Geukensia sp.).