Climate change is causing the world's oceans and freshwater habitats to warm up, with profound consequences for the biochemistry and growth of fish.
Researchers show in a new study how warmer water than a fish is used to acts as an aggressor, affecting internal biochemical processes and forcing the fish to stop growing at a smaller size than it would normally do in optimal habitat conditions.
How warmer water affects fish biochemistry
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The study, published in the journal Sea Around Us, explains how a process called "protein denaturation" intensifies when the waters in which fish live heat up, as per Phys.org.
Protein denaturation occurs when proteins, which are essential components of the cells and tissues of living organisms, lose their original structure as a result of disruptions to the weak links that maintain their complex shapes - a common, spontaneous occurrence in most living organisms.
Heat is one of the causes of such disruptions because it increases the movement of water and protein molecules within cells, causing them to collide and causing the proteins to lose their shape.
The stronger the shocks and the more proteins lose their shapes, the warmer the surrounding environment.
This is known as the "denaturation" process.
Proteins that have lost their shape cannot perform their assigned function and must therefore be resynthesized so that the organism does not disintegrate.
The process of resynthesizing proteins speeds up fish metabolism, requiring more oxygen to maintain body functions. The production of ATP and new proteins requires the presence of oxygen.
The issue is that warmer waters have less oxygen. So, fish are gasping for "air" to be able to maintain their bodily functions but there is little oxygen available.
The study also shows how warmer water affects fish growth. As fish grow, more proteins are denatured. When the rates of denaturation and synthesis of new proteins become equal, then they stop growing, as per OECD.
The problem is that when the water around them is warmer than usual, the process of creating new proteins cannot keep up with the accelerated rate of denaturation caused by heat, so fish must stop growing at an earlier stage so that both processes can balance each other out.
The researchers said that this phenomenon has been observed in many fish species around the world, especially in temperate regions where water temperatures are expected to increase significantly due to climate change.
They say that this phenomenon has important implications for fish ecology and fisheries management, as it may affect fish population dynamics, trophic interactions, food webs, and catch potential.
Furthermore, they believe that this phenomenon may have evolutionary consequences for fish adaptation to changing environments.
However, the researchers believe that more research is needed to understand how different fish species cope with warmer waters and how they may adjust their physiology and behavior to mitigate the negative effects of climate change.
Other effects of climate change on fish
The study also highlights some other effects of climate change on fish that go beyond biochemistry and growth. Some of these effects are:
Climate change may alter the distribution and migration patterns of fish species as they seek optimal thermal habitats or follow changes in prey availability. This may result in shifts in species composition, range expansions or contractions, invasions, or extinctions.
It may affect the reproductive success and survival of fish species by influencing factors such as spawning timing, egg development, larval dispersal, recruitment, and mortality. This may result in changes in population size, age structure, and genetic diversity.
It may increase the exposure and susceptibility of fish species to diseases, parasites, and pathogens by affecting their immune system or creating favorable conditions for disease transmission. This may result in reduced fitness, increased mortality, or outbreaks of epidemics.
Climate change may exacerbate the impacts of other human-induced stressors on fish species such as overfishing, habitat degradation, pollution, and invasive species by reducing their resilience or adaptive capacity. This may result in cumulative or synergistic effects that threaten their survival or recovery.
