EFFECTS OF CHRONIC SUBLETHAL AMMONIA AND A SIMULATED SUMMER GLOBAL WARMING SCENARIO - PROTEIN-SYNTHESIS IN JUVENILE RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Protein synthesis, net accretion, and degradation in liver, gill, and white muscle and ribosomal translational efficiency and protein synthe sis capacity in liver and gill were measured using a flooding dose of [H-3]phenylalanine in juvenile rainbow trout (Oncorhynchus mykiss). Th e fish were chronically exposed (90 days) in hardwater to the presence or absence of sublethal ammonia (70 mu mol total ammonia.L-1) alone o r in combination with a 2 degrees C elevation in the normal temperatur e profile over the months of June-September 1993 (ambient temperature range 13-22 degrees C). Chronic sublethal exposure to ammonia had litt le impact on gill protein synthesis and degradation (protein turnover) and even less in muscle. However, in the liver, both protein synthesi s and degradation were stimulated following 60 days of the sublethal a mmonia exposure. The 2 degrees C elevation in temperature resulted in a slight increase in protein turnover in both gills and liver. However , during the period of peak water temperature, the 2 degrees C elevati on in temperature inhibited protein dynamics in these tissues. Overall , elevated environmental ammonia in combination with a summer global w arming scenario would challenge the ability of fish to adapt to altera tions in the quality of their environment, most notably during periods of peak temperatures.