October 1 2011
The last month has been one of the more interesting ones in terms of development. At the time of writing the refugium has been running for almost 7 weeks and is producing better than ever. After around 6 weeks the diatom bloom finally stopped. That was expected as I did not want diatoms this time and had not dosed silica. But as soon as the diatom bloom died out, green algae took over. Another positive thing is that the skimmer is performing very well now, removing large quantities every day. Only the highest concentrations of diatoms caused a little bit of coloring of the water (in the display). But the quality of the water is acceptable even then, because I feel that a little coloring of the water from time to time is a natural part of such an environment. The temperature outside and in the aquarium room has gone down a little. This may be the reason that the artemia stopped growing effectively. I simply never saw anything more than small numbers of tiny nauplii any more. The temperature is 22 degrees C now. I tried putting the light back on 24 hours. But it did not have much effect. Still, I am keeping the light on at all times because of the increased pH stability. But I decided to stop dosing artemia.
Since the artemia project failed with the current flow regime, I decided to start a new experiment with zooplankton. The idea was to catch rather large numbers of native zooplankton, and see if I could get any of them to surive and reproduce in the refugium. I did two seedings with animals caught with a fine meshed net in the surface layer. The first batch mostly contained small, lightly colored, presumably calanoid, copepods. There were also a few specimens that I assume must have been krill, and and some larger calanoid copepods that may have been Calanus finmarchicus. I caught this far west by the open ocean. This batch was not very successful. As usual, the copepods disappeared quickly. The next batch was caught in a more sheltered location, and close to seaweeds. In addition to the previously mentioned animals, this contained a large number of another type of copepods. These were darker in color and had a distinct, more active, behavior. I have seen single specimens of these in the refugium before. And they have sometimes survived for weeks. They are also calanoids. At the time of writing, a large number of them are still alive after one and a half week. Now it remains to see if they can successfully reproduce.
This is from the first batch of plankton. The red arrow points to a large copepod that may be Calanus finmarchicus. The red arrows mark what may be krills or some small type of mysid. Some of the krills/mysids have survived for more that a week in the refugium.
In the second batch of plankton I got many of a type of hardy and active copepods that you can see as small darks specs in the water.
Microscope pictures of the hardy type of copepods. I assume they are calanoid because of the long antennae.
One of the most interesting things that has ever happened to the refugium setup took place last month. The refugium walls and bottom quickly get covered by algae film. It is made from cyanobacteria or something that looks like it. This will normally build up noticably from a week and on. This time something very nice happened: It started to disappear again, and after about 5 weeks the refugium walls were quite white. It was like the refugium got self cleaning. When looking closely at one of the remaining spots I could see a great swarm of copepods covering it. They had multiplied to great numbers and were cleaning away all surface films. The only remaining algae were the Ulva strands that seem to have protection from the grazing. This was great in several ways, both because of the cleansing effect and the growth of food animals. The algae came back somewhat after the diatom bloom was over and the water get clearer. But the copepods may "bloom" again too. So it will be interesting to see the development over time. Logically, grazing resistant algae will eventually take over, but how long it will take before that happens is yet to be seen.
Notice how the wall is absolutely clear of detritus and algae below the water line.
These are the copepods that are doing the cleaning job. I am not sure if they are harpacticoids or cyclopoids.
Photo setup for taking pictures of the copepods. The key is to let the animals sit in a drop of water on top of a slide with the light coming from the sides. That way the background remains dark while the specimen is well lit. I used my DSLR with a photo adapter because it was better than the low quality Bresser microscope camera.
Finally I got to take some photos from my underwater adventures. This is from a trip to Øygarden west of Bergen. We were lucky and got great weather this day. My diving buddy had the harpoon with him and shot 3 fish, including a very nice cod. We also collected scallops for food. We swam over great kelp forests of Laminaria hyperborea all the way out where the great ocean waves meet land. In some places the kelp specimens were old and over two meters tall. A true forest, even with undergrowth. I was struck by the beauty. Fish were swimming everywhere, mainly small pollocks and wrasses. But we also saw Lump suckers (Cyclopterus lumpus), Garfish (Belone belone), cod and mackerel. I did not find any new animals for my tank though.
Arriving at the location after a walk in heavy terrain.
Sheltered bay aquascape.
Lump sucker (Cyclopterus lumpus)
Tidal zone at high tide.
Wrasses over the kelp forest.
A nice cod! We didn't have a weight with us, but we estimated it to between 3 and 4 kilos.
A ballan wrasse (Labrus bergylta), hiding on the bottom.
A clearing in the forest.
Old kelp forest with more than two meters tall stalks, and undergrowth.
Wrasses and pollocks in a forest clearing.