Which sequence correctly describes the eutrophication process as presented?

Which sequence correctly describes the eutrophication process as presented?

• A. Increased plankton (algae) - GPP - algal blooms blanket water surface - increase in total biomass - increase in dead organic matter - increase in BOD - decline in O2 levels
• B. Increased plankton (algae) - algal blooms blanket water surface - GPP - increase in total biomass - increase in dead organic matter - increase in BOD - decline in O2 levels
• C. Increased plankton (algae) - GPP - algal blooms blanket water surface - increase in dead organic matter - increase in total biomass - increase in BOD - decline in O2 levels
• D. Nutrients enter water - algal blooms - increase in plankton - drop in BOD - increase in O2

Answer: (A)

Nutrient input fuels rapid growth of algae, so the first effect is more plankton. That uptick in plant production means gross primary production increases as more algae photosynthesize. Algal blooms then spread across the surface, forming a blanket that reflects the surge in living biomass. As the bloom runs its course, a lot of that biomass dies, adding dead organic matter to the water. Microbes break down this material, elevating the biological oxygen demand. The ongoing decomposition consumes more dissolved oxygen, causing O2 levels to fall. This sequence—nutrient input, increased plankton with higher GPP, surface algal bloom, rising total biomass, more dead organic matter, higher BOD, and declining oxygen—best fits the eutrophication progression.

Nutrient input fuels rapid growth of algae, so the first effect is more plankton. That uptick in plant production means gross primary production increases as more algae photosynthesize. Algal blooms then spread across the surface, forming a blanket that reflects the surge in living biomass. As the bloom runs its course, a lot of that biomass dies, adding dead organic matter to the water. Microbes break down this material, elevating the biological oxygen demand. The ongoing decomposition consumes more dissolved oxygen, causing O2 levels to fall. This sequence—nutrient input, increased plankton with higher GPP, surface algal bloom, rising total biomass, more dead organic matter, higher BOD, and declining oxygen—best fits the eutrophication progression.