Seaweed

Seaweed is a name for thousands of different types of marine algae.

These living things are multicellular, which means they are made of many cells. Scientists group them into three main colors: red, brown, and green. While they might look like land plants, they are actually quite different. Some types, like eelgrass, are flowering plants that live under the sea. Most seaweed belongs to groups of algae that do not share a single common ancestor.

They are very important for our planet's health. Some algae produce at least 50% of the oxygen on Earth. Other types, like kelp, create huge forests that act as nurseries for many sea creatures.

To grow, most seaweed needs two main things: seawater and light. They use light to perform photosynthesis, which is how they make food. Many species need a solid place to stay attached, like a rocky shore. They use a part called a holdfast to grip onto the ground. Some seaweed has special parts called pneumatocysts, or air bladders, to help them float.

These gas-filled bubbles keep the seaweed near the sunlight. Other types, like Sargassum, do not attach to the floor at all. Instead, they float freely through the ocean currents. This allows them to travel long distances across the sea.

Humans have been using seaweed for a very long time. In the past, collecting seaweed was a popular hobby during the Victorian era. Today, seaweed farming is a massive global business. In 2019, the world produced over 35 million tonnes of seaweed.

Most of this comes from Asian countries. China is the largest producer, growing over 20 million tonnes each year. Indonesia and South Korea also grow huge amounts. This seaweed is used for many different jobs around the world. It can be used for food, medicine, or even to make paper.

We use seaweed in many unexpected ways in our daily lives. Many people in East Asia eat seaweed in foods like sushi or soup. In some places, like Wales, people make a special bread called laverbread. We also use seaweed to make thickeners called hydrocolloids. These include things like agar and carrageenan, which help make desserts and sauces.

Even your toothpaste or cosmetics might have seaweed in them. Some scientists are even looking at seaweed to help fight climate change. Because seaweed absorbs carbon dioxide, growing more of it might help the planet. It can also help reduce pollution in the water.

However, seaweed ecosystems can face many hard jobs. Human activities, like mechanical dredging, can destroy kelp forests. There are also natural threats, like diseases that affect seaweed crops. In California, a disease killed the predators of purple urchins. Without those predators, the urchin population grew too large and ate the kelp.

Some seaweed can also be dangerous to touch. A type of blue-green algae called Microcoleus lyngbyaceus can cause painful skin rashes. It is important to learn about these plants to protect them and ourselves. Understanding seaweed helps us understand how the whole ocean works.