Abstract
The previously undescribed dynamics of the heat shock protein HSP70 and subsequent lipid peroxidation products have been assessed alongside lactate dehydrogenase activity for Gammarus lacustris Sars, an amphipod species from the saltwater Lake Shira (Republic of Khakassia). Individuals were exposed to a gradual temperature increase of 1 °C/hour (total exposure duration of 26 hours) starting from the mean annual temperature of their habitat (7 °C) up to 33 °C. A complex of biochemical reactions occurred when saltwater G. lactustris was exposed to the gradual changes in temperature. This was characterized by a decrease in lactate dehydrogenase activity and the launching of lipid peroxidation. The HSP70 level did not change significantly during the entire experiment. In agreement with the concept of oxygen-limited thermal tolerance, an accumulation of the most toxic lipid peroxides (triene conjugates and Schiff bases) in phospholipids occurred at the same time and temperature as the accumulation of lactate. The main criterion overriding the temperature threshold was, therefore, the transition to anaerobiosis, confirmed by the elevated lactate levels as observed in our previous associated study, and by the development of cellular stress, which was expressed by an accumulation of lipid peroxidation products. An earlier hypothesis, based on freshwater individuals of the same species, has been confirmed whereby the increased thermotolerance of G. lacustris from the saltwater lake was caused by differences in energy metabolism and energy supply of nonspecific cellular stress-response mechanisms. With the development of global climate change, these reactions could be advantageous for saltwater G. lacustris. The studied biochemical reactions can be used as biomarkers for the stress status of aquatic organisms when their habitat temperature changes.
Highlights
Temperature is one of the factors that determines function and stability of ecosystems
We show that the HSP70 level did not change significantly during the entire exposure to gradual temperature increase from 7 ◦C to 33 ◦C (Fig. 1)
It is shown that the gradual temperature increase leads to lactate dehydrogenase activity decrease, an important component of anaerobic metabolism (Fig. 2)
Summary
Temperature is one of the factors that determines function and stability of ecosystems. Surface temperature of lakes throughout the world has grown significantly (about 0.34 ◦C within 10 years) (O’Reilly et al, 2015; Yasuhara & Danovaro, 2016). Such rapid warming is a drastic signal for the need to study comprehensively the impact of climate change on the status of water ecosystems to assess the fauna vulnerability and adaptive capacity. This induces the need to develop new methods and tools for environmental protection. Studying thermal tolerance mechanisms and energy metabolism components in aquatic organisms in changing ambient temperature is of essential interest and relevance
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