Which one of the following is the correct sequence of ecosystems in the order of decreasing productivity?

The correct answer is C) Mangroves, grasslands, lakes, oceans. Here's a detailed explanation:

Mangroves are highly productive ecosystems due to high nutrient availability, sunlight, and decomposition rates. They support a rich biodiversity and have a high rate of primary production.

Grasslands are also highly productive, though generally less so than mangroves. They have a significant amount of biomass production, supporting large grazing animals.

Lakes have moderate productivity. Productivity varies depending on nutrient levels (oligotrophic vs. eutrophic), but generally, they are less productive than mangroves and grasslands.

Oceans, despite their vast size, have relatively low productivity overall. While certain areas (upwelling zones) are highly productive, the average productivity across the entire ocean is the lowest among these options. This is due to factors like limited nutrient availability in many areas and light penetration.

Let's analyze why other options are incorrect:

A) Oceans, lakes, grasslands, mangroves - Incorrect because oceans are the least productive, and mangroves are the most.

B) Mangroves, oceans, grasslands, lakes - Incorrect because oceans are generally less productive than grasslands.

D) Oceans, mangroves, lakes, grasslands - Incorrect because oceans are the least productive and grasslands are more productive than lakes.