Answer:
D. Increased sunlight and increased nutrients will increase phytoplankton populations.
Explanation:
Both sunlight and nutrients are required by phytoplankton communities. We know that phytoplanktons are primary producers and they produce food via photosynthetic activities. To carry out photosynthesis, presence of (inorganic) nutrients and sunlight is highly important. In this process, energy is fixed in energy rich molecules such as glucose and organism multiply and/or gain biomass. A decrease in any of them will result into reduced photosynthesis and hence reduced phytoplankton population growth.
