(Note: our usual Tuesday feature, Seed of the Week, will be back next week. Today we are going to visit the ocean. )

Algae and oceans go hand in hand, but what exactly are algae anyway? Are they plants? What are seaweeds and are they related to algae?

(Public domain photograph of seaweeds by Axel Kuhlmann)

Although algae may be large and appear plant-like, they are actually protists (belong to the Kingdom Protista). They have chlorophyll like plants so they can make their own food from the energy of sunlight, but they lack common plant structures like roots or leaves. Seaweeds, like that shown in the foreground of photograph above, are large forms of algae, also called “macroalgae.” The small forms that float around in the water are often called “microalgae” or “phytoplankton.”

You may be wondering why anyone would care about algae. Turns out, algae are important in a lot of ways. First of all, algae are the basis for aquatic food chains in both seawater and freshwater. They are also used for food, as fertilizer, and as a source of products such as agar and carrageenan. Algae are being studied as a potential source of biofuel. Let’s not forget, they make a significant amount of oxygen. In fact, it is not too farfetched to think that algae might be the most important organisms on the planet!

Activities for kids:

1. Investigate seawater under a microscope

If you have access to a microscope, obtain a sample of seawater (or pondwater) and take a look at what is in it. Look for green, blue-green or even brown or red organisms that are algae. Examining samples under a microscope is fun because it often leads to surprises.

2. Make an algal collection

You can make a collection of pieces of algae or seaweed you find at the beach, similar to the way you make a plant collection. Some of them can have beautiful shapes and colors.

(Illustration Adolphe Millot algues public domain from Wikimedia)

Gather pieces of algae on the beach and keep it moist in seawater. Once you are home, float the seaweed/algae onto a piece of heavy paper. Press the paper between layers of felt to remove the water and allow it to dry. The Hawaii Botany Department has step-by-step instructions on how to make an algal herbarium.

(Figure 3 – Seaweeds are pressed on herbarium sheets for further study and repository in botanical Herbaria. The species that Dr. Suzanne Fredericq is pressing was found at about 66 m depth (200 ft) in the West Flower Garden Banks, and represents a new record for the Gulf of Mexico. –From NOAA)

If you don’t want to disturb nature, which is a good idea, you can take close up photographs of what you find instead. You can share what you discover via blogs, websites or photo streams.

Once you have a collection, visit some of these websites to help you identify what you have. Seaweeds are not too easy to identify, but you might at least figure out which group your sample belongs to.

• The Seaweed Site
• Life on the Australian Shores

Biomara has an extensive booklet of activities/lessons about algae to download (30.3 MB). The link for the “entire teaching resource” is right above the “Information for Teachers” bold header. It contains large color photographs of many common “macroalgae.”

Who knows where studying algae might lead you. Perhaps you will be inspired to become a marine botanist, like Sylvia Earle (previous post).

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This post is part of our ocean science series. Visit the landing page for links to all the related posts.