Chronic effects of linear alkylbenzene sulfonate (LAS) and ammonia on rainbow trout (Oncorhynchus mykiss) fry at water criteria limits

Rainbow trout fry was chronically exposed (54 days) to 0.2 mg l−1 LAS(C11–12). Although this concentration is considered to be the NOEC (no observed effect concentration), lamellar gill epithelia hypertrophied and swimming capacity was reduced. Furthermore, the exposure of the fish to a secondary stressor (low salinity challenge test) caused increased mortality. Un-ionized ammonia did not affect the above-mentioned parameters when fish were treated with a NOEC of 24 μg 1−1. At 72 μg l−1, however, un-ionized ammonia caused distinct hypertrophy of gill epithelia. This effect was significantly enhanced when combined with LAS (additive effect). Only in this group, growth was reduced.