Effects of Increasing Sodium Chloride Concentration on the Growth of Ankistrodemus falcatus

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Effects of Increasing Sodium Chloride Concentration on the Growth of Ankistrodesmus falcatus

The experiment was conducted to examine environmental pollution in the perspective of water pollution to be specific. Water pollution may come in different forms. Variation in sodium concentration is synonymous with changes in salinity in water. General characteristics of Ankistrodesmus falcatus halotolerance was studied by the experiments of growth and the follow-up analysis conducted on a weekly basis. The rate of growth and other growth responses of algae significantly depends on the concentration of different elements in the particular environment. Variation in the concentration of sodium chloride is therefore expected to induce different responses in the growth process of algae. Different nutrients play independent roles as nutrients elements for the particular species of algae. Algae are extremely tolerant to changes in salinity. The concentration of sodium chloride, therefore, has a role to play in altering the growth process of algae (Laws, 2017).

Living organisms, in general, regulate the concentrations of some ions to maintain the potential of the cell membrane. Salts and ions have the role of controlling the movement of water through osmosis. The halotolerance of a given living organism is a perfect reflection of the range of the concentrations of sodium that are suitable in which the organism can comfortably grow and survive. The requirements of sodium in living organisms vary significantly with different species. Different species of phylum Chlorophyta contains many species which survive in diverse environments. They, therefore, tolerate a high degree of halotolerance. However, there are some species which may behave differently. A. falcatus may be constrained to narrower ranges of sodium concentrations (Wong et al, 2016).

We conducted a lab experiment where we sought to investigate the effect of growing Ankistrodesmus falcatus in different saline conditions. This was to find out the relationship between sodium concentration and the growth response pattern of the organism at different concentrations. We hypothesized that the growth of a freshwater strain of Ankistrodesmus falcatus is directly affected by the addition of sodium chloride, with increasing the concentration corresponding to reduced algal growth in a one on one relationship.

Method

A.Falcatus, a species of algae was selected to find out the effect of different salinity concentrations on algal growth activity. Ankistrodesmus culture solution was obtained locally. The pollutant used in the experiment was salt. 5OOmM of Sodium chloride was used as the pollutant. Consequently, this solution was treated as a 100% pollutant solution.

Calculations to determine the volumetric requirements were perfomed as soon as the the preparation for the lab experiment began.4 tubes were used in the experiment. The first tube was used as a negative control tube while the remaining three tubes were for the experiment. 5ml of Ankistrodesmus culture solution was used in the main experiment under investigation. The culture solution was placed in tubes with a maximum capacity of 10ml. The volume of Alga-gro used in the experiment continuously decreased from one tube to the other by a difference of one. The pollutant, Sodium chloride solution was added in proportions of upto 4ml being the maximum value. No pollutant was added to the negative control tube. Addition of the volumes of Ankistrodesmus culture solution, the Alga-gro and the pollutant brought a maximum value of 10ml. Caps were used to tighly seal the tubes. In order to enhance homogeneity, the samples were turned over several times after which the tightened caps were loosened to maintain an equilibrium with the atmosphere. Incubation of the culture solutions took one week at a constant temperature. The table looked like this.

Negative control Tube Tube 1 Tube 2 Tube 3

Ankistrodesmus culture Solution 5ml 5ml 5ml 5ml

Alga-gro 5ml 4ml 3ml 1ml

Pollutant 0ml 1ml 2ml 4ml

Total Volume 10ml 10ml 10ml 10ml

Final % Pollutant 0% 10% 20% 40%

Before setting up the blanks another table was set up. The purpose of these second tubes was to act as a control experiment.

Negative Control Tube Blank Tube 1 Blank Tube 2 Blank Tube 3 Blank

Alga-gro 10ml 9ml 8ml 6ml

Pollutant(At stock concentration) 0ml 1ml 2ml 4ml

Total Volume 10ml 10ml 10ml 10ml

Final % Pollutant 0 10% 20% 40%

Additionally, absorbance of a pure, undiluted Ankistrodesmus culture was measured at different wavelengths. It was ensured that, the instrument was blanked before each reading. One optical density was defined as the number of cells associated with one unit of absorption at 450nm nm. This value was determined via the spectrophotometric analysis. Before taking further reading, it was ensured that the spectrophotometer was set to the 450nm wavelength that was determined to be the optimum. Here is the table for the absorbance

400nm 450nm 500nm 550nm 600nm 650nm 700nm

Absorbance For each of the tube samples, the absorption was measured and the value obtained multiplied by 1 optical density unit in order to determine the density of the sample cells. Statistical analysis was conducted on the results and the relationship between the cell density and the sodium chloride concentration determined. The table for the wavelengths is given below.

Day 0 O.D Day 1 O.D Day 2 O.D Net Gain/Loss O.D Average Gain/Loss O.DControl A Control B Tube 1A Tube 1B Tube 2A Tube 2B Tube 3A Tube 3B Results

The result table for turbulence is as shown below

400nm 450nm 500nm 550nm 600nm 650nm 700nm

Absorbance 0.069 0.092 0.065 0.038 0.038 0.045 0.050

On the other hand, the table for the wavelengths determined on the tube samples on the three days is provided below. Additionally, the net gain loss is provided in the table. From the net gain or loss, the average gain or loss is also provided.

Day 0 O.D Day 1 O.D Day 2 O.D Net Gain/Loss O.D Average Gain/Loss O.D

Control A 0.031 0.067 0.040 0.009 -0.029

Control B 0.079 0.051 0.012 -0.067 Tube 1A 0.031 0.061 0.057 0.024 0.0135

Tube 1B 0.047 0.084 0.048 0.001 Tube 2A 0.057 0.071 0.081 -0.026 0.016

Tube 2B 0.041 0.057 0.035 -0.006 Tube 3A 0.116 0.023 0.015 -0.101 -0.0665

Tube 3B 0.043 0.011 0.011 -0.032 The graph below shows the relationship between the wavelength and the absorbance.

The graph below shows the concentration gradient curve of the pollutant versus the O.D at different days.

Discussion

In this experiment, sodium chloride was found to inhibit the growth of Ankistrodesmus falcatus. Significant inhibition was observed in Tube 3A as indicated by the net loss in biomass activity at a high concentration of the sodium chloride. Although the difference between the densities in the freshwater and saline water was not very strong, the data collected at the lab demonstrated that there was a strong inverse relationship between the absorbance and the wavelength in conjunction with the sodium chloride concentration.

We hypothesized that the high concentration of sodium chloride would inhibit the growth of Ankistrodesmus falcatus in a linear relationship. For every molar increase in the concentration of sodium chloride, the cell growth inhibition increased by a factor of five. The differences in the optical densities imply that the growth as observed in the cell densities was directly proportional to the concentration of the sodium chloride solution.

In conclusion, the growth of the algae was greatly hindered by increasing the concentration of sodium chloride concentration. This, therefore, suggests that there was a strong negative correlation between the concentration of sodium chloride and growth of Ankistrodesmus falcatus. The relationship between the absorbance and the wavelength was not conclusive enough to give definite results. This is because it was not linear in a low-saline environment. Further studies should investigate the effect of the concentration of other elements in the environment to the growth of different algal strains.

References

Laws, E. A. (2017). Aquatic pollution: an introductory text. John Wiley & Sons.

Wang, D., Wang, W., Xu, N., & Sun, X. (2016). Changes in growth, carbon and nitrogen enzyme activity and mRNA accumulation in the halophilic microalga Dunaliella viridis in response to NaCl stress. Journal of Ocean University of China, 15(6), 1094-1100.