What is the primary succession in freshwater called?

The primary succession in a sere is

Which of the following statements is incorrect regarding the phosphorus cycle?

Fill in the blanks.
$(a)$ Plants are called as . . . . . . because they fix carbon dioxide.
$(b)$ In an ecosystem dominated by trees,the pyramid (of numbers) is . . . . . . type.
$(c)$ In aquatic ecosystems,the limiting factor for the productivity is . . . . . . .
$(d)$ Common detritivores in our ecosystem are . . . . . . .
$(e)$ The major reservoir of carbon on earth is . . . . . . .

In a food chain of a grassland ecosystem,the top consumers are

Give scientific reasons: Coral reefs are not found in the regions from West Bengal to Andhra Pradesh,but are found in Tamil Nadu and on the east coast of India.