Unit 1

• Stratification of Facultative Ponds:
• Upper Aerobic Zone: Abundant sunlight and oxygen produced by photosynthetic algae supporting aerobic heterotrophic bacteria.
• Intermediate Facultative Zone: Inhabited by facultative bacteria that metabolize soluble organics oxidatively when dissolved oxygen is present or anaerobically via fermentation when oxygen is depleted.
• Bottom Anaerobic Zone: Devoid of oxygen, where anaerobic methanogens digest settled organic sludge.

Correct option: (3) Facultative bacteria

• Chlorella vulgaris $\rightarrow$ (I) Food supplement: Chlorella is a unicellular green alga rich in high-quality protein (50–60%), carotenoids, and B-vitamins, globally mass-cultivated as a human food supplement and single-cell protein (SCP).
• Lyngbya majuscula $\rightarrow$ (III) Pharmaceuticals: Lyngbya majuscula (cyanobacterium) is famous for synthesizing bioactive secondary metabolites, including apratoxins, curacin A, and other potent anticancer, antiviral, and antimicrobial drug candidates.
• Odontella aurita $\rightarrow$ (II) Cosmetics: Odontella aurita is an authorized marine diatom rich in EPA and fucoxanthin, extensively utilized in luxury cosmetic formulation for skin hydration, barrier repair, and anti-aging antioxidants.
• Scenedesmus $\rightarrow$ (IV) Biofuel: Scenedesmus species feature rapid growth rates, high lipid accumulation (triacylglycerols), and high biomass yield, making them primary candidates for commercial biodiesel and bioethanol production.

Correct option: (1) (A) - (1), (B) - (HI), (C) - (II), (D) - (IV).