(i) Productivity - conversion of inorganic into organic material with the help of solar energy by the autotrophs
(ii) Energy flow - unidirectional movement of energy towards higher trophic level (and its dissipation and loss as heat to the environment)
(iii) Decomposition - fragmentation, leaching, catabolism, humification, mineralization by bacteria, fungi and flagellates (abundant at the bottom of lake)
(iv) Nutrient cycling - decomposition of **** matter to release the nutrients back to be re-used by the autotrophs
Food chain in aquatic ecosystem (lake)
Phytoplanktons → Zooplanktons → Small fish → Big fish
