Microbial growth is a complex process that involves numerous anabolic and catabolic reactions and ultimately results in cell division.

Growth dynamics. This phase, during which little increase in cell density occurs, is relatively long when an algal culture is transferred from a plate to liquid culture. Cultures inoculated with exponentially growing algae have short lag phases, which can seriously reduce the time required for upscaling. Flow cytometry is a technique commonly used for cell enumeration in ecology, microbiology, and medical sciences because of its accuracy and speed.

Four distinct growth phases can be observed within a growth curve obtained from a batch culture.

1. The lag phase during which there is practically no growth, characterized by synthesis of cellular components for basal metabolism and adaptation to the new environment.

2. The log or exponential phase during which the population increase is exponential and the generation time is constant.

The stationary phase where the cells number does not change due to the equilibrium between cellular division and death induced by nutrient depletion and wastes accumulation; and

3. The phase of decline or death phase.

The study of the microbial population growth in batch culture is part of typical ecology, microbiology and plant physiology courses, and the demonstration of this growth curve is a classical experiment in microbiology practices.

Could you just measure the development in chlorophyll concentration with time using a standard water analysis method for field samples.

Hello,

First you need to ensure that no additional inputs of new populations of algae are introduced after the initial measurement. Because in a dynamic environment that is always the case as new additions can happen either as unidirectional current carried cells or upwelled cells. Hence quite difficult to monitor biomass growth unless you are monitoring it on hourly basis and then the mean value of a certain period can be compared with the next day, although fraught with errors.

In a stagnant body however, it is comparatively easy but still you have to be careful. Different part of the day yields different values of chlorophyll contents as it is dependent on the supply of element like carbon, magnesium and manganese and iron etc. And the biggest factors are the light intensity and ambient temperature. If your sampling pond/body is stagnant them you need to ascertain the time of sampling and measure the temperature and light flux at the surface and/or at the depth of your sampling and keep on monitoring the same parameters every day for a certain period at the same time and try to collect sample within the range of the parameters of the first sampling period to yield a comparable data. The comparison can be made as mean number of cells (when dealing with populations) per unit volume, mean surface area/biovolume of the cells collectively or for a specific specific or the amount of mean chlorophyll a concentration per unit volume.

I hope this helps you.

Dr. Abhishek Mukherjee