Aragonite

Definition

Aragonite is a mineral form of calcium carbonate (CaCO₃) that crystallizes in the orthorhombic system, often found in marine environments. It serves as a significant component of coral reefs and mollusk shells, and its solubility plays a crucial role in the biogeochemical cycles of carbon and calcium in aquatic systems.

5 Must Know Facts For Your Next Test

1. Aragonite is less stable than calcite at surface conditions, which means it can dissolve more readily in certain environments.
2. The solubility of aragonite is affected by factors such as temperature, pressure, and the presence of dissolved ions in seawater.
3. Aragonite plays a vital role in the carbon cycle by providing a means for carbon storage through marine organisms' biological processes.
4. Coral reefs primarily consist of aragonite, making them sensitive to changes in ocean chemistry due to their dependence on calcium carbonate saturation states.
5. As ocean temperatures rise and acidification progresses, the availability of aragonite may decrease, threatening marine life that relies on it for shell and skeleton formation.

Review Questions

• How does the solubility of aragonite differ from that of calcite, and what implications does this have for marine ecosystems?
  • Aragonite is generally more soluble than calcite under most environmental conditions. This difference in solubility means that in areas where aragonite predominates, such as coral reefs, organisms may face challenges as water chemistry changes. Higher solubility can lead to greater dissolution rates, affecting the integrity of coral structures and the overall health of marine ecosystems that depend on these calcium carbonate forms.
• Discuss the impact of ocean acidification on aragonite saturation levels and its subsequent effects on marine life.
  • Ocean acidification decreases aragonite saturation levels by lowering pH and altering carbonate ion concentrations in seawater. This shift can inhibit the ability of marine organisms, like corals and mollusks, to successfully produce and maintain their calcium carbonate structures. As these organisms struggle to build their shells and skeletons, the health of entire ecosystems can be jeopardized, leading to declines in biodiversity and changes in community structure.
• Evaluate the role of aragonite in biogeochemical cycles and its significance for climate regulation.
  • Aragonite plays a critical role in biogeochemical cycles by acting as a major reservoir for carbon. Through biomineralization, marine organisms sequester carbon into aragonite structures, which can subsequently be stored in sediments upon death. This process contributes to long-term carbon storage and helps regulate atmospheric CO₂ levels. However, factors like ocean acidification threaten this mechanism, potentially reducing aragonite availability and disrupting its role in climate regulation.

Related terms

calcite: Calcite is another mineral form of calcium carbonate, which has a different crystal structure than aragonite, crystallizing in the trigonal system.

ocean acidification: Ocean acidification refers to the reduction in pH levels of ocean water due to increased CO₂ absorption, which can impact aragonite and other carbonate minerals.

biomineralization: Biomineralization is the process by which living organisms produce minerals, such as aragonite, for structural or protective purposes.