Book on Irish Seaweed

There is a new book on seaweed around Ireland, written by Michael Guiry, well known authority on seaweeds with over 200 scientific publications (thats a lot, folks!), and founder of the fantastic seaweed database algaeBASE.

This book is a must-have for all seaweed people, especially since the 48th European Marine Biology Symposium is held in beautiful Galway on the west coast of Ireland this year in August.

To learn more about the marine flora of Ireland, visit The Seaweed Site, also created by Michael Guiry, where you can find a lot of information, books and other useful knowledge.

Baby Fucus and red algae on mussel shell

Baby Fucus and red algae on mussel shell

World Water Day March 22nd

2013 is the International Year of Water Cooperation.
Therefore, you can expect a lot of activities on World Water Day, coming up on March 22nd.

At Stockholm University, there will be a series of short, captivating lectures from scientists all working in, on and with water.

Seaweed expert professor Lena Kautsky will give a talk on the reproduction of bladderwrack and why it is important in relation to the management of our coastlines.

A programme in Swedish can be found here.

There will also be a startup to World Water Day at Aquaria Water Museum on the 21st, more information on this will follow.


Narrow wrack (Fucus radicans) and bladderwrack (Fucus vesiculosus) have separate male and female plants. The reproductive organs are called receptacles and are placed at the tips of the plant. They are easily recognised by their warty structure.

When we try to “sow” seaweed”, we start with collecting ripe plants from the field, determine which sex they have, and cut of the receptacles.

Cut receptacles of bladderwrack

Cut receptacles of bladderwrack

The picture to the left shows a bladderwrack ready to sow. Note that the pile of cut receptacles to the right in the photo is from three plants.

In order to separate between males and females, one has to cut a mm-thin slice of the receptacle and (with a little magnifying help from a loupe or similar) see if there are oogonia (8 eggs in a small sack) or antheridia (64 sperm in an even smaller sack). This can only be done on ripe receptacles, or else it is very hard to see.

Round oogonia contains 8 eggcells. Some are beginning to open up.

Round oogonia contains 8 eggcells. Some are beginning to open up.

Each receptacle consists of several small chambers, conceptacles. The opening pore of these conceptacles are what causes the warty structure of the receptacle. Each conceptacle openes onto the receptacle surface, and this is where oogonia and antheridia (eggs and sperm in bags) are ejected out into the water mass during fertilization. When the oogonia and antheridia have reached the water, the bag keeping them contained, begins to dissolve.

The female oogonia looks like a collection of small green peas, and can be seen with the naked eye if they are very ripe.

It's a girl! Lots of ripe, round oogonia in the receptacles.

It’s a girl! Lots of ripe, round oogonia in the receptacles.

A ripe male, packed full of orange sperm.

A ripe male, packed full of orange sperm.

Antheridia are too small to see, even with a loupe. You need a microscope for them. On a receptacle cut, they give an impression of orange balls along the inside of the receptacle edge (see picture). The colour comes from the eyespot of the sperm, which is orange. With this, the sperm can tell light from dark.

Reproduction occurs around full moon, when it is much darker down towards the bottom than up towards the surface. The sperm “knows” that it should swim towards darkness. The reason for this is that the heavy eggs are sinking in order to attach to the bottom once they become fertilized.