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Table 7. (Continued) Ecosystem, and other information Application rate and other variables Effects and reference Freshwater ponds Salt marsh, 202 ha (500 acres), Florida Salt marsh, 78 ha plot Salt marsh estuary, Bay St. louis, Mississippi, 408 ha site (1,008 acres) Freshwater pond Single dose of ch1or- pyrifos, equivalent to 4, 10, or 1,000 ugjl. 0.56 kgjha (0.5 lbsjacre), single application applied as aerial spray, to kill mosquito larvae 0.56 kg/ha, emulsifiable concentrate, once, aeri- ally 0.56 kgjha (0.5 lbsj acre), granular, single aerial application, for mosquito control Single application of pelletized 10.6% chlorpy- rifos to obtain theoreti- cal water concentrations of 250 ug/l and higher 21 Increased algal bloom duration in treated ponds, possibly due to loss of grazing fauna (Butcher et al. 1977). Killed significant num- bers of fishes and crustaceans (FWS 1968). After 48 hours, mortality was 35% in caged fish and 84% in caged shrimp; no other adverse effects were noted during the next 27 days (Wall and Marganian 1971) . After spraying, all. caged fiddler crabs died, white shrimp (Penaeus setiferus) populations were reduced, and large numbers of blue crabs were found dead. No observable effects on terrestrial organisms, including insects. One month after spraying, shrimp and blue crab populations seemed normal, although fiddler crabs were absent (FWS 1967) . Species diversity of dia- toms reduced >50% in 6 weeks, vs. 12% increase in controls (Nelson et al. 1976).