Team:UCL Academy/Algae Experiments


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Algae experiments!

School Algae experiment:


We carried out an investigation in order to determine the optimum concentrations of nitrates and phosphates for the highest growth of algae in distilled water. These nutrients have been identified as substances that increase algal growth in water columns, and are therefore responsible for the increasing occurrence of algal blooms. Therefore, we aimed to prove that nitrates and phosphates were in fact responsible for an increase in algal growth, as well as determining the optimum concentrations of nitrates and phosphates that produced the highest growth of algae.

Why did we carry out this investigation?

We made the decision to carry out this investigation as a result of our findings in Hampstead Heath in London as part of our human practice work. We discovered that fertilisers were added to water columns containing prominent algal blooms, and therefore decided to investigate the effect of different concentrations of nutrients found in fertilisers, namely nitrates and phosphates, on algal growth.


We predicted that the addition of nitrates and phosphates to distilled water resulted in an increase in algal growth, as demonstrated by a higher reading on the colorimeter. Moreover, we predicted that the highest concentration of nitrate and phosphate used, specifically 0.05g/dm³, would produce the highest growth of algae.

Scenedesmus quadricauda:

We used a strain of algae called Scenedesmus quadricauda, which is a good example of typical planktonic algae: -Contains between four to eight cells, -Remains buoyant (keeps afloat) because of its spines.


Our results demonstrate that:

The addition of phosphate and nitrate to distilled water increases algae growth as the control beaker had the lowest reading on the colorimeter. As the concentration of phosphate increases, the reading on the colorimeter and therefore the amount of algae growth increase. The optimum concentration of phosphate for the highest algae growth is 0.05 g/dm³. There is no distinct trend relating to an increase in the concentration of nitrate and algae growth. The optimum concentration of nitrate for the highest algae growth is 0.04 g/dm³, which is lower than the expected concentration of 0.05 g/dm³.

Bioreactor experiments

Why did we decide to use a bioreactor to upscale algae growth?

We aimed to determine the best way to simulate algae bloom growth in a larger scale, and hence we discovered that use of bioreactor offers this.


To upscale the growth of Chlorella sorokiniana and compare its growth in 500 ml flask with 100 ml of media volume with 7.5 L bioreactor with 5 L of media.

Information about the strain

Our strain of interest, Chlorella sorokiniana, is widely found in UK. We chose this strain as its growth is similar to that of Cyanobacteria which produces the Microcystin toxin. Chlorella is a genus of single-cell green algae which belongs to the phylum Chlorophyta. It has a spherical shape, about 2 to 10 μm in diameter, and it does not have flagella is without flagella. Chlorella contains the green photosynthetic pigments chlorophyll-a and -b in its chloroplast. Through photosynthesis, it multiplies rapidly, requiring only carbon dioxide, water, sunlight, and a small amount of minerals to reproduce.

Results and Discussion

Our results showed similar algae growth in the flask as well as bioreactor. The levels of OD increased similarly for both; pH dropped at the similar rate in both cases as well. The levels of glucose in the bioreactor started dropping down faster after 48 hours in in comparison to the algae growth in the flask. The levels of ammonia dropped down at the similar rate for bot bioreactor and conical flask algae cells. As bioreactor is a standard technique in biochemical engineering we showed that biochemical engineering techniques complement synthetic biology. This algae bloom simulation will aid our future work when testing the degradation of microcystin.