Question

Which one of the following exhibits the least productivity?
A. Salty marshes
B. Grasslands
C. Open oceans
D. Coral reefs

Answer 1

Hint: Productivity denotes the rate of production of biomass in an ecosystem. It is generally expressed in the terms of mass per unit surface. The primary factors affecting the productivity of any ecosystem are sunlight, carbon dioxide, water, and nutrients.

Complete answer: Salt marshes are the estuaries where both the brackish water and saltwater combine. Saltmarsh plants are also known as halophytes. These plants are tolerant of salt and are efficiently adapted to the fluctuating water levels with tides. Tides transfer the nutrients which stimulate plant growth in the marshes.
-Grasslands are one of the less productive ecosystems. They have an annual productivity of about 200−1000 gm/$$m^2$$.
-Oceans contain lots of nutrients but they have no sufficient sunlight reaching in the deep areas, therefore, oceans have the least productivity among all ecosystems. The average productivity of an ocean ecosystem is about 50 grams of carbon per square meter per year.
-The maximum productivity among all ecosystems is seen in the coral reefs followed by the estuaries.
So, the right answer is option C.
Additional Information:
Coral reefs are among the most biologically diverse ecosystems present on earth, followed by the tropical rain forests. Coral reefs are made up of hard and soft corals and organisms such as sponges, crustaceans, mollusks, fish, sea turtles, sharks, dolphins, etc. Primary production in coral reefs is closely coupled with the effective utilization and renewal of the organic and inorganic nutrients. This allows remarkably high productivity despite a nutrient-poor environment.

Note: The net primary productivity (NPP) of an ecosystem is the gross primary productivity without the rate of energy loss in the process of metabolism and maintenance. Alternatively, it is the rate at which the energy is stored by plants or other primary producers as biomass. This energy is then made available to the consumers in that ecosystem.