Experiment with fruit on mooring blocks

The real method to gain knowledge is the experiment

Nothing is more exciting than experimenting with one’s own ideas!

Concrete is often the material of choice when it comes to creating structures beneath the sea. For example, concrete blocks are frequently used as anchors to attach buoys and boating lines, so that boats may moor up, or as obstacles to prevent illegal fishing. Windmills and quay walls are also made of concrete. It is a well-known fact that after a number of years, concrete in the tropics become teaming with life, algae, coral, and fish find a home here. This process can take a number of years, and for us it is a challenge to find ways to speed up this process. Usually the surface of the concrete is relatively smooth, and so it therefore offers little shelter for smaller organisms.

Beton blok waar koraal op groeit
Anchor block overgrown with coral
Betonnen blokken worden geplaatst rond Koh Tao tegen illegaal vissen
Concrete blocks are placed around Koh To against illegal fishing
Koraal transplanteren op betonnen blokken
Transplanting coral on the concrete blocks

If a coral larva seeks to find a home after fertilization, they prefer a safe place where fish cannot immediately reach them, to ensure they are not eaten. This makes a flat concrete surface unsuitable for these small coral larvae. Small crabs and shrimp also prefer to have a hole to hide in, and so the question arises: “How can we make the surface of the concrete suitable for marine life to find a cozy spot to call home?”

Twelve Concrete blocks have been made for the new structure of Suara Pulau and are placed in the water on CoralDay. We decided to make different textures on the surface of the blocks in order to test which features make the most difference. We chose four different surfaces, and made three iterations of each in order to compare the effectiveness of the different variations.

The surface of the first 3 blocks is just concrete, in which we carved grooves in order to create a rough surface.

In the next set of 3 blocks we placed dead coral skeletons, and shells. This is a beautiful natural material to which the new corals can easily attach themselves.

Dood koraal in het betonnen blok
Dead coral in a concrete block

The third trio of blocks have been ingrained with a layer of icing sugar. We have heard rumors that the application of icing sugar onto wet concrete changes the composition of the top layer, so that coral might more easily grow upon it. Unfortunately we cannot find any scientific evidence to back this up, and so this is just a test to see if this method is effective and has any merit.

In the last three concrete blocks we have places fruit residues, skins and pits in the wet concrete. When the concrete has hardened we remove these objects, so that various intricate holes remain molded into the concrete. These holes are ideal for all sorts of small organisms, including crustaceans, coral larvae, and fish.

Fruit wordt in het beton geplaatst
Veran, Irvan and Endah are putting Fruit in the concrete blocks

This is not scientifically sound research, but it is a first step. Should we discover that that these methods are effective, we will further investigate how concrete surfaces can be designed and built in such a manner as to be more hospitable to marine life, while remaining efficient and cost-effective in their production.

Heremietkreeftjes eten het fruit uit het beton
Hermit crabs eat the fruit from the concrete

Do you have knowledge, experience, or ideas on how we can make the the surface of concrete more suited to foster healthy and happy marine life? Let us Know!

The real method to gain knowledge is the experiment. ”
William Blake – English poet and painter 1757-1827