Aquatic ecology and Biodiversity

Unit 5- Productivity

5.2.7. Nutrients
Productivity represents the amount of carbon fixed per unit time. Also productivity can be represented by the assimilation index in which growth is expressed as mg of carbon produced per mg chlorophyll ‘a’ per hour. Growth rates phytoplankton is as an increase in cell numbers. Phosphate and Nitrates are the two major nutrients recognized as one of the major factors limiting primary productivity. Phytoplankton absorbs nutrients from the solution during photosynthesis for the formation of particulate organic matter. Sometimes nutrient are absorbed for the synthesis of RNA, DNA, cell wall, spines etc. The effect of nutrients conservation on the growth of plankton can be described by

Growth rates - Nutrient uptake velocity
1. Growth and nutrient uptake curves generally follow the same pattern 2. Generally follows Michaelis-Menton uptake curve

Where a. = growth rate (or nutrient uptake rate)

b. S = substrate concentration

c. Ks = substrate concentration where growth rate is half of maximum