Marine algae are simple, plant-like organisms that grow in oceans and other saltwater environments. They play a crucial role in the ecosystem by producing oxygen through photosynthesis and serving as a primary food source for many marine animals. There are various types of marine algae, including seaweeds, which can be classified into three main groups: green algae, brown algae, and red algae. These organisms can vary in size from microscopic phytoplankton to large kelp forests. Marine algae are also important for humans, as they are used in food products, cosmetics, and even as biofuels. Their ability to absorb carbon dioxide makes them significant in efforts to combat climate change.