Why are algae an important part of the marine forest community? What are the different types of marine algae? Is ‘algae’ a Linnaean classification? 

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jgregerson eNotes educator| Certified Educator

Algae is important for a marine ecosystem because it serves as the main food source at the bottom of the food webs found in those communities. It provides the energy that will flow through the food chain as organisms are eaten. Algae are generally classified as part of the Kingdom Protista because they are more related to protists than to plants. Algae lack the vascular structures and roots, shoots and stems that plants have.

There are three different groups of marine algae: brown algae, green algae and red algae. You may hear about blue-green algae, but it is classified as a cyanobacteria since it is more closely related to bacteria than to other algae. 

Brown algae are generally multicellular organisms that can grow at deep depths and can grow very large. A common example of brown algae is kelp, which is a very important part of marine kelp forests. In a kelp forest, the kelp serves as an essential food source and form of shelter for many different organisms. Green algae can vary from unicellular to multicellular organisms that may look similar to plants. Since green algae need large amounts of sunlight for photosynthesis, they grow in shallower waters than brown algae. Red algae are also usually multicellular and grow more slowly than green algae. The red color comes from pigments called phycobiliproteins. 

In Linnaeus' original classification system, he included three kingdoms: plants, animals and minerals. The minerals were discarded early on, and the kingdoms have been modified and added to. Most scientists recognize five kingdoms, but there is growing use of the three domain system (bacteria, archaea and eukaryota). Algae falls into the Kingdom Protista as described earlier, and in the domain system it belongs to the Domain Eukaryota. These groups did not exist in the original Linneaen classification system.

Humans use algae for a wide variety of reasons, including food (the green seaweed wrapped around sushi is algae), ingredients in toothpaste, paint, cosmetics, and food additives, and in medical settings for wound dressings and the agar to make petri dishes in microbiology. Lastly, the oil and natural gas we use is made up mainly of the remains of algae that lived millions of years ago.

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