DIADEMA-project

Dear followers!

From now on we won’t use the Diadema and AROSSTA pages anymore. We have made one page dedicated to all our work regarding reef restoration projects:

https://www.facebook.com/reefrestorationVHL/

The MOREEF page will be the only remaining page next to reef restoration VHL, as this is a combined initiative from VHL and Wortel product design:

https://www.facebook.com/moreefmorelife/

We hope to see you there!

Moreef Moreef is a new design of artificial reef. It is easy to make, transport and to deploy. The modules

Fantastic news: this little sea urchin developed well!

Great news from the ARROSTA project!

Design of the optimal artificial reef tested on Saba A new study compared the effectiveness of three popular artificial reefs to increase fish densities around Saba and St Eustatius. The researchers found that a complex internal structure, providing …

A cloudy day in Leeuwarden...
We take great care in maintaining the tanks with our adult sea urchins (the brood stock), only the best water quality for our animals! Unfortunately the tank that contained our Diadema setosum, an Asian family member of our antillarum urchins, was very cloudy. We measured the water, everything fine, we changed a large part of the water, next week it was cloudy again. The animals were still doing fine but we didn’t know what was causing the cloudiness, until last week… While feeding the animals we noticed on of the urchins started spawning, and as soon as the first one started all animals in the tank were spawning simultaneously! At least now we know what is causing the clouds.

In the meantime our Diadema antillarum larvae are doing fine, more results on this in the next update from Leeuwarden.

A lot of new eggs and metamorphosed larvae!

We collected a lot of new eggs during our last spawning event from just 6 of our 11 brood stock Diadema. The first run (6th of May) we collected 10000 eggs, the second run (27th of May) we already collected 40000 eggs but that is still nothing compared to the 6 million eggs we collected the 16th of June! Some of the larvae from the last run already show signs of competency at day 16, very comparable to the larvae of run 1 and 2.

We were also able to let all of the remaining larvae from the first run to settle and go through metamorphosis, turning them in to very small sea urchins of only about 1 millimeter in size.

Invitation link to the webinar!

A very interesting webinar on the first of july!

After only 28 days the first larvae metamorphosed in a small sea urchin of less than one millimeter in size! On the video in the comment section, you can see the urchin already walking on its tube feet.

It is amazing to see well developed urchins during our first trial. We have a second batch of larvae that are also developing well, three weeks behind the first run. This is very promising for the future of our laboratory experiments in Leeuwarden but also the culture of Diadema antillarum in general.

Lecturer-researcher Alwin Hylkema working on Saba and teaching children about the DIADEMA project!

Did you know Diadema have a pelagic larval phase of around 30 days? They start their life as tiny larvae, floating around in the ocean, and currents will determine where they end up. If the larvae are ready for it, they go through metamorphosis and settle on a suitable substrate.

Last year, we studied Diadema settlement around Saba, together with the Saba Conservation Foundation. One location, which is called Ladder Bay, had 2-100 times more settlement than the other locations. On St. Eustatius, we compared different settlement materials, together with Caribbean Netherlands Science Institute at St Eustatius - CNSI and Stenapa St Eustatius. It turned out that bio balls (see previous post) were the most suitable substrate to collect settlers.

This year, we combined the knowledge from Saba and St. Eustatius and we used bio balls at the Ladder bay location. In one month, we will know how many Diadema chose to settle on these new collectors!

Diadema larvae at last! Last week we had our third spawning attempt and it was very successful. Of our 11 brood stock sea urchins 3 males and 2 females spawned, resulting in fertilized eggs.

We are now testing which culturing method is best suitable for larval survival. It takes about 30-50 days of feeding the larvae with microalgae before larvae become competent. This mean that they are able to transform from a free floating larval to a little sea urchin attached to solid substrate like rock.