Something is fishy with these fillets Free

Did you know that plants are the lungs of the earth? Just like your lungs provide oxygen and remove carbon dioxide (CO₂) from your body, plants create oxygen and remove CO₂ from the atmosphere by photosynthesis. As deforestation becomes increasingly common, more CO₂ is left in the atmosphere. Accumulating CO₂ may result in rising temperatures, a phenomenon to which fish are particularly vulnerable. Fish are unable to regulate their internal temperature, so their body temperature is determined by the environment. High temperatures directly increase the speed of their metabolism, increasing their demand for energy. When this energetic demand becomes greater than what can be fuelled by available oxygen, the mitochondria compensate, but create toxic byproducts in the process. These toxins can destroy cells. Cristiano Siqueira (Franciscan University, Brazil) and colleagues from the Federal University of Santa Maria, Franciscan University and the Brazilian National Institute for Research of the Amazon were interested in the physiological impacts of high CO₂ levels on an Amazonian fish: the pirarucu. The research team was curious whether high CO₂ levels would cause severe toxin-induced damage, or whether the fish's antioxidant system would overcome the effects.

After transferring the fish to tanks in a climate-controlled room, Siqueira and colleagues painstakingly recreated the atmospheric conditions that are predicted to occur in 2100 – 4.5°C above current temperatures and 800 ppm above present-day CO₂ – thereby increasing the fish's water temperature to 29.7°C and the CO₂ levels to 22.3 ppm for 4 days. Then, they collected muscle samples from the fish to quantify production of the toxic metabolic byproducts and the associated cellular damage experienced by the fish. The researchers also quantified the muscle's ability to defend against toxin-induced damage, by measuring activity of antioxidant enzymes, including glutathione peroxidase and superoxide dismutase, which break down the toxic metabolic byproducts.

The team saw that this extreme climate scenario induced an increase in the damage caused by the toxic metabolic byproducts, and the body's antioxidant system was unequipped to handle the damage. Over the 4-day exposure, the levels of toxic byproducts rose and the damage caused by these toxins was evident. Meanwhile, the body's defence system failed, showing a declining antioxidant response over time, with glutathione peroxidase activity falling by 45%. The most significant damage was seen in the muscle's fatty acids. Fatty acids make up the cell wall, which protects cells, buffering them against physical damage and guarding against harmful chemicals. The toxic byproducts produced by the body's metabolism attacked the fatty acids in the cell wall. The researchers suspect that high temperatures accelerate the fish's metabolism to an unstainable level, increasing production of toxic byproducts, which then induce significant damage to the cell wall, and render the mitochondria vulnerable, disabling the antioxidants that protect the cell from damage.

Interestingly, the pirarucu changed their muscle fatty acid composition, presumably in an attempt to maintain the integrity of their cell wall as toxic byproducts attack the fatty acid layer. Unfortunately, these compositional changes included reductions in the levels of healthy fatty acids, such as linoleic and arachidonic acid, which are essential nutrients in the human diet, while increasing the content of unhealthy fatty acids that contribute to high cholesterol and cardiovascular disease. The discovery of this reconfiguration within the fish's muscle adds an intriguing economical element to this study, as it appears that elevated CO₂ levels could degrade the nutritional quality of fish meat. So next time you go to cut down a tree, remember, you may be making your fillet the bad kind of fatty!