Photic Zone process.

Photic Zone process.

• A. Photosynthesis by phytoplankton
• B. Disintegration of sediments
• C. Chemosynthesis near vents
• D. Sedimentation

Answer: (A)

In the photic zone, light reaches enough to power photosynthesis, so the dominant process is photosynthesis by phytoplankton. These microscopic plants and algae use sunlight to convert carbon dioxide and water into organic matter, releasing oxygen in the process. Because light fades with depth, only the upper layers receive enough energy for this production to occur, making phytoplankton the primary producers that fuel the marine food web. The other options describe processes that don’t rely on light. Disintegration of sediments is a physical/biogeochemical breakdown on or near the seabed, not driven by light in the upper ocean. Chemosynthesis near vents uses chemical energy from the environment, not sunlight, and occurs in deep, dark regions. Sedimentation is the sinking of particles through the water column, a physical process that happens throughout the ocean, not specifically a photic-zone biological process.

In the photic zone, light reaches enough to power photosynthesis, so the dominant process is photosynthesis by phytoplankton. These microscopic plants and algae use sunlight to convert carbon dioxide and water into organic matter, releasing oxygen in the process. Because light fades with depth, only the upper layers receive enough energy for this production to occur, making phytoplankton the primary producers that fuel the marine food web.

The other options describe processes that don’t rely on light. Disintegration of sediments is a physical/biogeochemical breakdown on or near the seabed, not driven by light in the upper ocean. Chemosynthesis near vents uses chemical energy from the environment, not sunlight, and occurs in deep, dark regions. Sedimentation is the sinking of particles through the water column, a physical process that happens throughout the ocean, not specifically a photic-zone biological process.