Question

how do chemical weathering, gas exchange, and limestone formation help marine organisms thrive? select all that apply.
ocean chemistry is regulated in part by the exchange of co₂ gas between the atmosphere and the ocean.
marine organisms break down caco₃ as they build their shells and exoskeletons. this process releases hco₃⁻ ions that make the ocean less acidic.
carbon from the shells and exoskeletons of marine organisms can be stored underground in limestone for millions of years. this prevents excessive buildup of co₂ in the atmosphere and ocean water.
ca²⁺ ions primarily enter the oceans via runoff from chemical weathering. they combine with co₃²⁻ ions as marine organisms build their shells and exoskeletons.

Explanation:

To determine the correct options, we analyze each:

1. Ocean chemistry & CO₂ exchange: Regulating ocean chemistry via atmospheric - oceanic CO₂ exchange is vital for marine life (e.g., pH balance for respiration, photosynthesis of organisms). So this is correct.
2. Marine organisms & CaCO₃ breakdown: Marine organisms (like mollusks, crustaceans) use CaCO₃ to build shells/exoskeletons. Breaking down CaCO₃ releases $HCO_3^-$ which acts as a buffer, reducing ocean acidity. A less acidic ocean is more hospitable for marine organisms (e.g., prevents shell dissolution in calcifying organisms). So this is correct.
3. Carbon storage in limestone: When marine organisms die, their CaCO₃ - based shells/exoskeletons can form limestone. Storing carbon in limestone removes CO₂ from the ocean - atmosphere system, preventing excessive CO₂ (which causes acidification). This stabilizes the environment for marine life. So this is correct.
4. Ca²⁺ from chemical weathering & shell building: Chemical weathering of rocks (e.g., limestone) releases Ca²⁺ into runoff, which enters the ocean. Marine organisms use Ca²⁺ and $CO_3^{2 - }$ to build CaCO₃ shells/exoskeletons, which is essential for their structure and survival. So this is correct.

Answer:

All the options are correct:

• Ocean chemistry is regulated in part by the exchange of $\ce{CO_{2}}$ gas between the atmosphere and the ocean.
• Marine organisms break down $\ce{CaCO_{3}}$ as they build their shells and exoskeletons. This process releases $\ce{HCO_{3}^{-}}$ ions that make the ocean less acidic.
• Carbon from the shells and exoskeletons of marine organisms can be stored underground in limestone for millions of years. This prevents excessive buildup of $\ce{CO_{2}}$ in the atmosphere and ocean water.
• $\ce{Ca^{2+}}$ ions primarily enter the oceans via runoff from chemical weathering. They combine with $\ce{CO_{3}^{2-}}$ ions as marine organisms build their shells and exoskeletons.