Dissolved CO2 concentration is high near the ocean bottom due toGroup of answer choicesphotosynthesisdissolutiondecayrespirationdownwelling

The concentration of dissolved CO2 is high near the ocean bottom due to several factors:

1. Downwelling: This is a process where surface water gets pushed down into the deeper parts of the ocean. As this water contains CO2 absorbed from the atmosphere, it increases the concentration of CO2 at the ocean bottom.

2. Decay: Organic matter, such as dead plants and animals, sinks to the ocean floor where it decays. This process of decay releases CO2, increasing its concentration at the ocean bottom.

3. Respiration: Marine organisms, like fish and plankton, also contribute to the CO2 levels. They consume oxygen for their metabolic processes and produce CO2 as a by-product, which adds to the CO2 concentration.

4. Dissolution: The solubility of CO2 increases with pressure and decreases with temperature. Since the bottom of the ocean is cold and under high pressure, more CO2 can dissolve there than at the surface.

Photosynthesis, on the other hand, would decrease the concentration of CO2 near the ocean bottom as it involves the uptake of CO2 by plants and algae for the production of oxygen. However, photosynthesis is limited to the euphotic zone, the uppermost layer of the ocean where sunlight can penetrate, and thus doesn't significantly affect CO2 levels at the ocean bottom.