Effects of chronic environmental acidification and a summer global warming scenario: protein synthesis in juvenile rainbow trout (Oncorhynchus mykiss)

Protein synthesis (Ks), net accretion (Kg), and degradation (Kd) in liver, gills, and white muscle were measured using a flooding dose of [3H]phenylalanine in juvenile rainbow trout chronically exposed (90 days) to softwater in the presence or absence of sublethal acidity (H2SO4, pH 5.2) alone or in combination with a 2°C elevation in the normal temperature profile over the months of June-September 1993 (control temperature range 13-24°C). Chronic sublethal exposure to low pH reduced protein synthesis and degradation in both the gill and liver with little apparent impact on white muscle. As a result, protein was increased in the affected tissues. This suggested that both liver and gill have some capacity to compensate for the effects of acid exposure. The 2°C elevation in the normal temperature profile resulted in a slight increase in protein turnover in both gills and liver. However, during the period of peak water temperature, the 2°C elevation in temperature triggered a dramatic reduction in the protein turnover rates in these tissues. The exact mechanism by which these modifications in protein turnover occurred could not be clearly established. Overall, environmental acidification in combination with a summer global warming scenario would decrease fish growth and survival, most notably during periods of peak temperatures.