09.08. – 13.08.
Day 15: After 14 days of experiments we started to measure our organisms in closed incubations on the 9th of August. These measurements involved 104 incubations per day and lasted 3 days until all organisms will be measured.
During the whole course of the experiment we didn’t encounter any difficulties and due to good coordinated teamwork we managed to keep up with the daily and bi-weekly measurements as well as the work intensive regular cleaning of all tanks. We observed growth of all organisms in all our tanks and fortunately didn’t lose any organisms. During our measurements of the maximum quantum yield as well as the calcification measurements we could already see first effects of our light treatment as well as the increased organic matter availability.
Further analysis will now be performed in our home institutes. In addition we also took samples of coral and algae tissue for pigment analysis as well as the skeleton for the analysis of mineral structure.
Overall it was a successful experiment and we are looking forward to analyze our data. We are now very interested to see which impacts the treatments had on the different physiological levels of our organisms.
24.07. – 08.08.
Day 0: We started the experiment at the 24th of July and from now on measured the maximum quantum yield as indicator of photosynthetic efficiency on a daily basis as well as the calcification as an increase of buoyant weight every four days.
For our initial measurements we used closed incubation chambers which we specially prepared for our species and equipped with fiber optic cables to measure oxygen evolution parallel during the incubations via and multi-channel optode system. In order to control for equal light conditions in all incubations chamber we also had to set up a LED light system that allowed for the light adjustment above every single of in total 12 incubation chambers. This setup was also used for the final incubations after 14 days of experiments were we measured the same parameters as mentioned above from all individuals of our experiments.
During the course of the experiment we cleaned all aquaria on a regular basis to control for epiphytes and in addition we took multiple water samples to determine our carbonate system as well as the organic and inorganic nutrient regime our organisms were exposed to during the experiment.
19.7. – 23.7.
Just after attending the International Coral Reef Symposium (ICRS) and visiting the corals sea, offshore off Cairns I traveled with the Greyhound bus from Cairns straight to Townsville where I arrived on the night to the 19th of July.
Here I stayed nearly four weeks at the Australian Institute of Marine Science (AIMS) to do a joined experiment with the PhD student Nikolas Vogel. We investigate the combined effects of ocean acidification, increased organic nutrient availability and low light conditions on three model calcifying organisms from the Great Barrier Reef.
Our experiment consisted of a lab experiment where we exposed three reef organisms to different environmental conditions in separate aquaria while monitoring water parameters throughout the experiment.
Right after my arrival we started to setup the experiment, calibrated electrodes and measured the maximum quantum yield as indicator of photosynthetic efficiency of our organisms.
The organisms we used are the two calcifying green algae: Halimeda opuntia and Halimeda macroloba as well as the staghorn coral Acropora millepora. At the 23rd of July we measured the initial rates of photosynthesis, respiration, calcification and nutrient fluxes before we started the experiment.
Friedrich Meyer, WG Coral Reef Ecology