Final answer:
Plankton avoid sinking to the bottom by using various mechanisms such as having a low density and appendages that increase surface area. These adaptations help them stay afloat in the upper layers of the water where sunlight and nutrients are more abundant.
Step-by-step explanation:
Plankton avoid sinking to the bottom by using various mechanisms that help them stay afloat in the water column. One common adaptation is having a low density, which allows them to float. They may have gas-filled structures, such as air sacs or oil droplets, that provide buoyancy. Another adaptation is having appendages or structures that increase their surface area, which helps them stay suspended in the water. Some plankton also have flagella or cilia that enable them to move and stay afloat. Overall, these adaptations help plankton remain in the upper layers of the water where sunlight and nutrients are more abundant.