Most of the microalgae present in aquatic systems competed for the same available inorganic nutrients. The successful competitors would eventually dominate the rest because of their adaptive advantageous. Based on this premise, it was important to understand the effect of nutrients input rate on microalgal species-diversity and population. This was investigated in batch experiments of 14 days with pond water samples having natural ecosystem by varying nutrients dosing pattern under natural day light. Nutrients were supplied as single dose and multiple doses to the fresh water microalgal culture of fresh water. Prominent growth of many microalgal species was the key result of multiple dosing of nutrients compared to single or concentrated dosing of nutrients. Simulation towards oligotrophic condition was supporting the diverse population of microalgae. Whereas in the experiments with higher dosing of nutrients in one or two times had dominant growth of two or three microalgae and higher growth of heterotrophic bacteria. This condition resembled the eutrophic or hyper-eutrophic condition of water. This study thus showed the influence of the nutrients supply pattern on the growth and diversity of microalgae in freshwater and the nutrients added on eight, ten and twelve consecutive days from first day were considered as the effective nutrient addition pattern to promote maximum microalgal population present in a freshwater system.
Microalgae occur in all natural waters such as ponds, lakes, rivers and oceans, and are recognized as the primary producers of these ecosystems. The growth of microalgae depends on the changes in environmental parameters particularly temperature, light, nutrients availability and mortality factors such as grazing and parasitism [
Among the environmental disturbances in aquatic systems, nutrients additions from various sources by natural and anthropogenic processes have an important role in the microalgal community composition, species diversity and growth. Most of the microalgae compete for the available inorganic nutrients and the successful competitors will eventually dominate the rests [
However, the impact of nutrients supply in varied pattern on the growth of microalgae, population and species diversity under natural daylight is yet to be revealed clearly. Information in this aspect will be useful for promoting the growth of natural spectra of microalgae in aquaculture system. Current study demonstrates the growth of individual species of microalgae in pond water with varied pattern of nutrients supply. The results are discussed to find out the role of nutrients supply pattern on species diversity and population.
The present investigation was carried out with fresh water sample collected from Padmatheertha pond maintained by Padmanabha Swami Temple Trust, located at the latitude N8˚28'59.829" and longitude E76˚56'44.7432'' in Thiruvananthapuram city, Kerala, India. Temperature and pH of the water were measured at the sampling site using a calibrated Celsius thermometer and transportable pH meter by the method of Bakes model [
Dissolved oxygen was determined by following Winkler’s method [
The pond water samples of 1 L each was taken in seven sets of transparent plastic conical flasks having capacity of 2 L. The experimental flasks were kept on magnetic stirrers for gentle mixing under sunlight. Nutrients solution supplied in the experiments had NH4Cl―0.1 g (a final concentration of NH3―31.8 mg/L), KH2PO4―0.025 g (a final concentration of
Experiment Setup | Pond Water | Dosing Pattern of Nutrients Solution in mL | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6 | Day 7 | Day 8 | Day 9 | Day 10 | Day 11 | Day 12 | ||
All nutrient dosage (50 mL) | - | - | - | - | - | - | - | - | - | - | - | ||
1000 mL | 50 mL | ||||||||||||
- | - | - | - | - | - | - | - | - | - | ||||
1000 mL | 25 mL | 25 mL | |||||||||||
- | - | - | - | - | - | - | - | ||||||
1000 mL | 12.5 mL | 12.5 mL | 12.5 mL | 12.5 mL | |||||||||
- | - | - | - | - | - | ||||||||
1000 mL | 8.33 mL | 8.33 mL | 8.33 mL | 8.33 mL | 8.33 mL | 8.33 mL | |||||||
- | - | - | - | ||||||||||
1000 mL | 6.25 mL | 6.25 mL | 6.25 mL | 6.25 mL | 6.25 mL | 6.25 mL | 6.25 mL | 6.25 mL | |||||
- | - | ||||||||||||
1000 mL | 5 mL | 5 mL | 5 mL | 5 mL | 5 mL | 5 mL | 5 mL | 5 mL | 5 mL | 5 mL | |||
1000 mL | 4.17 mL | 4.17 mL | 4.17 mL | 4.17 mL | 4.17 mL | 4.17 mL | 4.17 mL | 4.17 mL | 4.17 mL | 4.17 mL | 4.17 mL | 4.17 mL |
CaCl2―5 g, SrCl2―5 g, CdCl2∙2H2O―2.5 g, Na2SO4―0.02 g, MgSO4∙7H2O―0.001 g) and trace elements―1.5 mL (from a stock solution of 1000 mL having MnCl2∙2H2O―0.55 g, ZnCl2―0.05 g, NH4Mo7O24∙4H2O―0.05 g, FeCl3―0.01 g, CoCl2∙6H2O―0.05 g, CuCl2∙2H2O―0.05 g, NaSeO3―0.1 g, H3BO3―0.05 g, AlCl3―0.05 g, conc. HCl―1 mL and EDTA―0.5 mg). Composition of nutrients was constituted based on the stoichiometric equation formulated by Ho et al. [
Water sample collected from the Padmatheertha pond was analysed for physico-chemical and biological parameters, and the results are presented in
Analytical Parameters | Measured Value |
---|---|
pH | 8.3 |
Dissolved Oxygen (mg/L) | 7.6 |
TSS (mg/L) | 25 |
Ammoniacal Nitrogen (mg/L) | 0.26 |
Phosphate (mg/L) | 0.03 |
Chlorophyll a (mg/m3) | 1.8 |
In the water sample collected from Padmatheertha pond, Scenedesmus, Spirulina and Chlorella were the dominant microalgae in the community, but Microcystis also had a prominence with its total population of 8% (Fig- ure 1). When the nutrients were added in a single dose, Scenedesmus became the dominant microalgae through- out the experimental period and diatoms were the second largest. The growth of Spirulina and Chlorella were declined from the initial level with this one-time addition of nutrients. The population of certain species such as Volvox, Pediastrum, Tetraedron, Merismopedia and Anabena were decreased significantly or vanished from the initial level under this experimental condition. Closterium and Micractinium were not observed during the first day of the experiment, but began to appear in the system during the experiment period (
The supply of nutrients distributed in two successive days was resulted in the dominant growth of Scenedesmus followed by diatoms (
Leading growth of Scenedesmus and diatoms was continued as significant on the supply of nutrients in four days consecutively, and observed that the population of diatom was larger than the Scenedesmus towards the end of the experiment. The growth of Chlorella and Spirulina were observed decreasing from the first day (
While supplying the nutrients to six equal doses, a steady increase of growth was observed for Scenedesmus, Chlorella, diatoms and for Ankistrodesmus unlike nutrients supplied in one or two doses. The growth of Spirulina was in the decreasing trend throughout the period of experiment. Certain species like Merismopedia, Anabena and Volvox were not found in the experimental system after two days (
When the nutrients were divided and supplied in eight consecutive days, six microalgae namely Scenedesmus, Spirulina, Pediastrum, Chlorella, diatoms and Ankistrodesmus were found dominating in the community. In this experimental system the growth of Microcystis was not altered much during the experimental period, however, Volvox, Golenkinia, Merismopedia and Anabena were disappeared during the period (
Prominent growth of Scenedesmus, Spirulina, Pediastrum, Chlorella, Closterium, Microcystis, Ankistrodesmus, diatoms and Micractinium was observed when the supply of nutrients in ten consecutive days. Volvox was continuously absent in this system like in previous cases (
By the supply of nutrients in twelve days, the originally present microalgae, Scenedesmus, Spirulina, Microcystis, Pediastrum, Chlorella, Closterium, Ankistrodesmus and diatoms were grown in more or less similar proportion, except Volvox, Closterium, Anabena and Micractinium (
Initial level of supplied nutrients and its residual concentration after the experiment were measured and are given in
Nutrients Supply Pattern | Ammoniacal Nitrogen | Phosphate | ||
---|---|---|---|---|
Calculated Value Based on the Supplied Nitrogen (mg/L) | Final Concentration Obtained during the End of the Experiment (mg/L) | Calculated Value Based on the Supplied Phosphorus (mg/L) | Final Concentration Obtained during the End of the Experiment (mg/L) | |
Single Dose on First Day | 31.8 | 83.85 | 17.4 | 12.3 |
Two Consecutive Days | 31.8 | 46.45 | 17.4 | 5.6 |
Four Consecutive Days | 31.8 | 50.7 | 17.4 | 5.5 |
Six Consecutive Days | 31.8 | 58.4 | 17.4 | 7.95 |
Eight Consecutive Days | 31.8 | 59.35 | 17.4 | 12.55 |
Ten Consecutive Days | 31.8 | 37.1 | 17.4 | 5.5 |
Twelve Consecutive Days | 31.8 | 38.3 | 17.4 | 6.05 |
Increased heterotrophic bacterial growth to the level of 7 × 105 cells/mL from 2 × 103 cells/mL was observed with the supply of nutrients in a single dose (
A noticeable change in the growth and population of microalgae was the key result of the experiment to supply the nutrients in varied pattern. The domination of only two microalgae, Scenedesmus and diatoms was observed by the supply of nutrients in a single dose and similar trend was followed when nutrients were added within two and four consecutive days. While distributed supply of nutrients for six, eight, ten and twelve consecutive days was resulted in the prominent growth of many microalgae likes Spirulina, Microcystis, Pediastrum, Chlorella, Closterium, Ankistrodesmus, in addition to Scenedesmus and diatoms. All of them were found growing in more or less same ratio. With some exceptions, results of the experiments generally supported the view that nutrients input pattern influences the individual population of microalgae significantly. The change in individual population with respect to the nutrients input pattern can be explained as follows reasonably.
The nutrients are essential for the growth and primary production of microalgae or phytoplankton in general [
In this study supply of nutrients in a single dose appears to resemble the eutrophied state of an aquatic system which was resulted in the domination and abundance of mainly two microalgae such as Scenedesmus and diatoms. Obviously the Scenedesmus and diatoms are two ubiquitous common fresh water microalgae, which are known for their fast growth rate and nutrients uptake [
While the nutrients were supplied in distribution like six, eight, ten and twelve days there were the dominant growth of eight different microalgal species. In this case the overgrowth of few species is not supported with nutrients input and cannot outcompete for nutrients. This study shows that the condition of water towards oligo- trophism could favour greater species diversity in nature.
The growth of heterotrophic bacteria with higher input of inorganic nutrients was significantly greater than the lower and distributed supply dosing (
Nutrients are supplied to the culture within one day, two days and four days has an eutrophic effect on microalgal ecosystem where growth is limited to few fast growers such as Scenedesmus and diatoms. Supply of nutrients by distributing eight, ten and twelve consecutive days promotes the growth of many species of microalgae as in oligotrophic waters. In addition to the growth of few microalgae higher dosing of nutrients prompts heterotrophic bacterial growth to more than hundred times compare to the growth of lower supply of nutrients. Inter relations of nutrients level, heterotrophic bacterial growth and microalgal ecosystem are difficult to explain with this study, which require further investigations. Confirmation of the findings is however, recommended through onsite studies.
Chandrasekharan Nair Aneesh,Ajit Haridas,Vattackatt Balakrishnan Manilal, (2015) Role of Nutrients Input Pattern on the Growth Dynamics of Common Freshwater Microalgal Community. American Journal of Plant Sciences,06,2481-2491. doi: 10.4236/ajps.2015.615250