Marine algae perform photosynthesis, a process by which they produce oxygen by absorbing carbon dioxide and using sunlight. This is why they are an important source of oxygen in the ocean.
Marine algae function exactly like land plants: they use solar energy to transform carbon dioxide (CO₂) into oxygen and nutrients. In the ocean, most of the sun's energy is captured by these algae, which primarily populate the waters near the surface. By absorbing the CO₂ present in the water, they release a significant amount of oxygen, essential for the survival of many aquatic organisms. These tiny or larger organisms provide a substantial dose of fresh air: nearly half of the oxygen we breathe comes directly or indirectly from the discreet but effective work of marine algae. Without these small invisible workers, marine life (and even terrestrial life!) would be seriously compromised.
Marine algae alone produce about 50 to 80% of the oxygen on Earth. This means that more than half of the air we breathe outside of water actually comes from these microscopic or giant aquatic plants, quietly floating in the oceans. Their secret? They perform photosynthesis, absorbing carbon dioxide (CO₂) to release oxygen (O₂) in return. Even though we directly think of terrestrial forests when it comes to oxygen, it is the oceans and their algae that do the vast majority of the work, and have been doing so for millions of years. So yes, they may not be the most glamorous plants, but without their discreet and constant contribution, it's uncertain that we would all be here breathing easily.
Marine algae are generally classified into several types according to their color: green algae, red algae, and brown algae. Green algae, which are close to land plants, primarily grow in shallow water where light is abundant, allowing them to be very efficient in photosynthesis. Red algae can live deeper due to their red pigment, phycoerythrin, which effectively captures the blue light filtered underwater. They are slightly less productive but essential in areas where few plants grow easily. As for brown algae, such as large kelps, they are the champions: their large size and high chlorophyll density enable them to absorb a lot of light and produce a significant amount of oxygen. Each type thus has its specialty depending on where it grows and how it utilizes the available light.
Environmental conditions greatly influence the ability of algae to produce oxygen. For example, the quantity and quality of sunlight are essential: the less light there is, the less photosynthesis occurs, resulting in less oxygen produced. Temperature also plays a role: if it's too cold, algae growth slows down; if it's too hot, their metabolism speeds up, but their efficiency decreases after a certain threshold. Algae also need nutrients, primarily nitrogen and phosphorus. When these nutrients are lacking or become too abundant (due to human activities, notably), their growth is disrupted, which reduces their ability to efficiently produce oxygen. Finally, water quality comes into play: polluted or overly particle-laden water limits light penetration and hinders photosynthesis.
Marine algae act as the true lungs of the ocean: through photosynthesis, they absorb large amounts of carbon dioxide (CO₂) and release oxygen. This process reduces the acidity of the oceans and provides a healthier living space for fish and other marine organisms. Without these algae, the oceans would quickly become saturated with CO₂, threatening the entire marine and even terrestrial biodiversity. By capturing excess carbon, algae help combat climate change and maintain the essential balance between oxygen and CO₂ in the sea.
Some algae, such as spirulina, are not only valuable for their oxygen supply but also for their exceptional nutritional benefits, being rich in proteins and essential nutrients.
The 'blooms' (rapid proliferations) of algae can sometimes be visible from space thanks to satellites, revealing how variable their abundance is, but also crucial for the health of the oceans.
Marine algae produce nearly 50% of the oxygen found in our terrestrial atmosphere, which is almost as much as all the forests combined on the continents.
Only one species of microscopic algae, phytoplankton, forms the foundation of the marine food chain and alone generates a significant portion of the oxygen we breathe every day.
Although terrestrial forests are crucial, marine algae and oceanic phytoplankton produce nearly half of the world's oxygen. Oceans cover about 70% of the Earth's surface, providing a vast area for photosynthesis. Furthermore, marine algae reproduce quickly and offer an efficient conversion of CO₂ into oxygen.
Yes, marine algae are sensitive to climate change. The increase in ocean temperatures, changes in water acidity (ocean acidification), and alterations in ocean currents can negatively impact their growth, geographic distribution, and consequently reduce their ability to produce oxygen.
Marine algae play a crucial role in purifying ocean waters. By absorbing CO₂, they reduce water acidity and release oxygen, which is beneficial for marine life. Additionally, they can absorb and store various pollutants and excess nutrients, thereby helping to maintain better water quality.
Yes, seaweed has a great potential to mitigate the effects of climate change. Due to their ability to absorb CO₂ during photosynthesis, they directly contribute to the reduction of greenhouse gases. Numerous current research efforts are exploring how to enhance this capacity to better combat global warming.
All oceans contribute to oxygen production through algae, but particularly nutrient-rich waters, such as those in temperate and cold regions, are generally the most productive. The North Pacific and the North Atlantic are among the most active oceanic regions in terms of oxygen generation by marine algae.
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