Incorrect Statement about Cyanobacteria:

The incorrect statement about Cyanobacteria is option 'B': They lack heterocysts.

Explanation:

Cyanobacteria, also known as blue-green algae, are a group of photosynthetic prokaryotes that are capable of carrying out oxygenic photosynthesis. They are considered to be one of the oldest organisms on Earth and have played a significant role in shaping the planet's atmosphere and ecosystems.

1. Photoautotrophs:
Cyanobacteria are photoautotrophs, which means they can produce their own food through photosynthesis. They possess pigments like chlorophyll A, which is similar to green plants, as well as other accessory pigments that enable them to capture light energy from the sun.

2. Heterocysts:
Heterocysts are specialized cells found in some cyanobacteria that are involved in nitrogen fixation. Nitrogen fixation is the process by which atmospheric nitrogen is converted into a usable form (ammonia) by certain bacteria. This process is important because nitrogen is an essential nutrient for living organisms. Therefore, the statement that cyanobacteria lack heterocysts is incorrect.

3. Blooms in Polluted Water Bodies:
Cyanobacteria often form blooms in polluted water bodies. Excessive nutrient runoff, particularly phosphorus and nitrogen, from agricultural and urban areas can lead to the eutrophication of water bodies. This nutrient enrichment promotes the rapid growth of cyanobacteria, leading to the formation of dense algal blooms. These blooms can have harmful effects on aquatic ecosystems and human health due to the production of toxins.

4. Chlorophyll A:
Cyanobacteria possess chlorophyll A, which is the primary pigment involved in photosynthesis. Chlorophyll A absorbs light in the red and blue regions of the electromagnetic spectrum and plays a crucial role in capturing light energy for photosynthesis. This pigment gives cyanobacteria their characteristic blue-green color.

In conclusion, the statement that cyanobacteria lack heterocysts is incorrect. Heterocysts are specialized cells found in some cyanobacteria that are involved in nitrogen fixation. Cyanobacteria are photoautotrophs, often form blooms in polluted water bodies, and possess chlorophyll A similar to green plants.