Fossil fuels are running out, which means we need to find new sources of energy! But what has this got to do with algae? Algae use the sun’s energy for photosynthesis and growth. We can exploit this process, and use algae to produce electricity. But this is not all: algae can also make hydrocarbons - similar molecules to those found in fossil fuels - which can be used directly as a source of biofuel.
The science behind the scenes
Algae are an amazingly varied group of photosynthetic organisms, and not all of them are green! Algae can be red, brown, green or even gold. Some are very small - a single cell, and others are multicellular organisms, like seaweeds. You might have seen algae grow on top of ponds (the green goo!) very close to home, but algae are found all over the world, living in habitats as different as ice-cold glaciers and steaming hot springs.
Even though algae photosynthesise they are not the same as plants on land. They do not have proper roots, leaves, stems or complex reproductive structures - they are much simpler organisms. Through photosynthesis, in the same way that land plants do, algae use water, CO2 and the energy from sunlight to make their food, in the form of starches or oils. They can even make vitamins and coloured pigments, which can be harvested and used by humans.
Although algae make vitamins for us, they also need vitamins of their own. Some species require the vitamin B12. This is present in sea water, but in levels lower than the algae require. So the algae use bacteria to help them get all the vitamin B12 they need. In return for the vitamin, algae can supply the bacteria with food and energy. This is known as a symbiotic relationship. Scientists are currently studying what mechanisms algae use to get the vitamin from the bacteria. This information will help them to grow algae better in artificial conditions.
Some algae, like seaweeds, attach themselves to rocks, and so don't move very much. Others might be carried about in moving water. Some single-celled algae have a structure called a flagellum, a structure like a tail that whips around and propels them forwards. Another way that algae can move is by making themselves more or less dense. This allows them to float up and down in a body of water. When they have used up most of their stored food, they become less dense, so they will float upwards. This means they are closer to the light, which is what they need in order to photosynthesise and replenish their energy store.