Mussels are not only delicious and nutritious, but also resilient and adaptable. They can survive in harsh and changing environments, such as marine heat waves.
Marine heat waves are episodes of unusually high sea surface temperatures that can last from days to months and have harmful effects on marine ecosystems.
They are expected to become more intense, frequent, and long-lasting due to climate change.
How do mussels manage to endure these extreme events? A new study reveals that they can modify their heart rate and other body functions to deal with heat stress.
How Mussels Change Their Body Functions Under Heat Stress
Scientists from the Chinese University of Hong Kong and the University of South Australia examined the vital signs of Asian green mussels (Perna viridis) exposed to three weeks of very warm ocean temperatures.
This species is widespread in the Indo-Pacific region, which is likely to experience a higher increase in marine heat waves in the next decades, compared to other latitudes.
The scientists collected large and small mussels from Tolo Harbor in Hong Kong, kept them in laboratory conditions in tanks filled with seawater, and fed them a phytoplankton diet.
Half of the tanks were controls and the other half were experimental tanks, where the temperature was raised by 1°C each day until it reached almost 27°C.
The high temperatures were maintained for three weeks, and the biological responses of the mussels were measured in the last two days.
The temperatures of the heat wave tanks were then lowered to the control temperature and the mussels monitored over the next week.
The scientists found that both large and small mussels raised their heart rate and clearance rate (the rate at which a certain volume of water is cleared from all particles) with high temperatures.
These changes indicate that the mussels were trying to keep their oxygen uptake and food intake under heat stress.
However, these changes also have a downside, as they increase the metabolic demand and energy expenditure of the mussels.
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How Mussels Recover After Heat Stress
The scientists also found that after the heat wave recovery period, all physiological traits-including heart rate, temperature, and clearance rate-went back to normal levels, showing that the mussels' long-term functioning was not affected by heatwave conditions.
This suggested that the mussels have a remarkable capacity to cope with environmental stress, despite short-term physiological changes.
"They persisted through-and recovered after-the marine heat wave," says UniSA environmental lecturer Dr. Laura Falkenberg, who was involved in the study.
"We expected to see some significant impacts of increased ocean temperature on their vital signs, including survival, heart, and respiratory rates, but they were surprisingly resilient."
The Importance and Benefits of Mussels for Ecosystems and Humans
Mussels are essential to marine ecosystems, playing important roles in recycling nutrients and improving water quality in coastal systems by filtering large volumes of water while feeding, which helps to keep the water clean.
They also provide habitat and food for other marine organisms, such as fish, crabs, and birds.
Mussels are also a valuable source of protein for humans, especially iron, B-12, and omega-3, containing more than nine times the amount of B-12 than beef and five times more than salmon.
They are also low in fat and calories, making them a healthy choice for a balanced diet.
Moreover, mussels are among the most widely cultivated shellfish in the world, with a global production of over 2 million tonnes per year.
They are also harvested from wild populations by fishers and collectors.
Therefore, understanding how mussels respond to marine heat waves is important for ensuring their sustainability and conservation.
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