ACUTE TOXICITY OF AMMONIA TO 4 SPECIES OF MARINE AMPHIPOD

Ammonia has been found to be toxic to many species of marine organisms , but little data address the toxicity of ammonia to benthic infaunal species such as amphipods. Organisms closely associated with marine or estuarine sediments may be exposed to higher ammonia concentrations t han are found in the water column, especially when sediments are distu rbed. In this study, four species of marine or estuarine amphipods (Rh epoxynius abronius, Eohaustorius estuarius, Ampelisca abdita and Grand idierella japonica) were exposed to ammonia in seawater, in the absenc e of sediment, under controlled laboratory conditions, to determine th e concentrations of ammonia that would be acutely toxic to those speci es. A. abdita was found to be the most sensitive to ammonia, with a me dian lethal concentration (LC50) of 49.8 mg/liter total ammonia (0.83 mg/liter as un-ionized ammonia). R. abronius was also relatively sensi tive: LC50 = 78.7 mg/liter total ammonia (1.59 mg/liter un-ionized amm onia). E. estuarius and G. japonica were less sensitive, with estimate d LC50 values of 125.5 mg/liter and 148.3 mg/liter total ammonia, resp ectively (2.49 mg/liter and 3.35 mg/liter un-ionized ammonia). The abs ence of sediment did not appear to influence the response of the amphi pods over the 96-h exposure period.