Monday, May 7, 2007

Seaweeds: Salads of the Sea

Seaweeds are a tour-saver. If there is absolutely NOTHING else on a shore, there is usually some seaweed. But please do NOT talk ONLY about seaweed. Or discuss each and EVERY kind of seaweed that you see! Unless that is what your visitors ask for.

Three NAKED facts

Interactive activity: Feel this. What do you think this is? (You might want to give them a variety of seaweeds to feel and look at)

NF#1: Seaweeds are algae ('el-gay'). Algae is the scummy green stuff that grows on your bathroom if you don't clean it. Also inside your aquarium. Algae can grow in almost any dark, damp place.

Corny joke: If you don't bathe often, algae will probably grow on you too! (and if the visitors look like they can take a corny dirty joke..."In your dark damp places too!")

In the sea, algae can be very large. And comes in a wide range of shapes, colours and textures.

NF#2: Everyone loves to eat seaweeds. Fish, crabs, snails, slugs, sea urchins eat seaweeds. Even YOU love to eat seaweed!

Thoughtful question: Can you think of seaweeds that you eat? I can bet that you have eaten some seaweed today! Or will eat it today.

Sushi usually comes immediately to mind.

Extracts of seaweeds are widely used to colour, stabilise and thicken commercial food products. If you eat ice-cream or canned food or commercially prepared food, you would have eaten seaweed.

Agar-agar and jelly are also made from seaweed extracts.

NF#3: Seaweeds are slippery and slimy!

Interactive activity: Feel the seaweed!

The slimy coating reduces water loss when exposed at low tide. Being leathery also helps. Seaweeds also protect themselves from being eaten by containing unpleasant tasting chemicals such as iodine.

Weedy Hints for Naked Hermit Crabs

It's probably best NOT to let visitors eat seaweed. Some seaweeds produce natural toxins at certain times of the year. Seaweeds may also concentrate pollutants. Not to mention seaweed gets trampled on by people. And who knows where they have been beforehand.

Snippets of Weeds
Here are snippets on various seaweeds commonly seen on our shores.

Green Seaweed
Hairy green seaweed (Bryopsis sp.)
It can be seasonally abundant. On the Southern shores, it sometimes covers the entire shore in a fluffy green carpet. The carpet may completely disappear in a few weeks, not appearing again for several months.

Various slugs are often found among this seaweed.

Interactive activity: Let's see what animals we can find living in this seaweed.

Green coin seaweed (Halimeda sp.)

Interactive activity: feel the seaweed!

It is made up of little hard coin-like shapes, joined to one another. It is hard because it incorporates calcium carbonate in its structure. When the seaweed dies, the calcium carbonate particles become part of the sandy shore.

In some parts of the world, this seaweed contributes to a large percentage of the sand on the shore!

Sea lettuce (Ulva sp.) ("Ool-va or "Aul-va") It can be seasonally abundant. On the Northern shores it sometimes gathers at the low-water mark forming a thick green carpet. The carpet may completely disappear in a few weeks, not appearing again for several months.

Corny joke: To the question "Can eat or not?", the answer is yes! You can eat it if you are a pig. This seaweed is fed to pigs and other livestock in other parts of the world.

These are green seaweeds! Bubble green seaweed (Boergensenia sp.) on the left, and what I like to call Sea sausage (Neomeris sp.) on the right. But you can give them other common names if you like. Neomeris incorporates calcium.

These feathery stuff are seaweeds and not seagrasses. There are several different species of these feathery green seaweeds, these Caulerpa sertularioides on the left and Caulerpa taxifolia on the right. ("Kah-ler-pah")

Sea grapes are also green seaweeds. Two kinds are commonly seen: Caulerpa lentillifera on the left and Caulerpa racemosa on the right.

Brown Seaweed
Sargassum (Sargassum sp.)
The longest brown seaweed seen on our shores. They are more commonly seen on our Southern shores.

The little 'balloons' are NOT fruits. They help to keep the seaweed afloat. Smaller seaweeds grow on it or among the 'branches'. Sometimes, small animals can be found hiding among the tangles.

Interactive activity: Let's see what we can find on this seaweed!

Mermaid's fan (Padina sp.) ("Peh-die-nah") on the left is more commonly seen on our Southern shores. It incorporates a bit of calcium, forming concentric rings on the seaweed. Some people call it Mermaid's Ear, but I think that's so gross. The lumpy seaweed on the right is Colpomenia sp. which you can call Bubble brown seaweed if you like :-)

Red Seaweed

The prickly red seaweed (Acanthophora sp.) on the left is more commonly seen on our Northern shores. The seaweed that looks like big flat red sheets (Halymenia sp.) on the right is sometimes mistaken for plastic bags.

The pink stuff that grows over coral rubble (on the left) is a red algae! It incorporates calcium and is quite hard. It is called coralline or encrusting algae. Like living cement, by growing over rubble and bits and pieces on the shore, the algae helps to consolidate the reef. The pink stuff grows everywhere, even on shells of living snails. Some coralline algae grow into delicate branching forms that look like a pom-pom! (on the right).