Absorption

Definition

Absorption is the process through which light is taken up by substances in water, such as dissolved organic matter, phytoplankton, and sediment. This phenomenon significantly affects the amount of light that penetrates aquatic environments, influencing photosynthesis, aquatic ecosystems, and overall water clarity. The degree of absorption varies with wavelength and the specific properties of the absorbing materials.

5 Must Know Facts For Your Next Test

1. Absorption is wavelength-dependent; different materials absorb light at different wavelengths, affecting which colors penetrate deeper into water bodies.
2. Dissolved organic matter can significantly increase light absorption in aquatic systems, leading to reduced light availability for photosynthetic organisms.
3. Phytoplankton play a crucial role in light absorption as they convert absorbed light into chemical energy through photosynthesis.
4. Sediment can contribute to light absorption; higher concentrations of suspended particles often result in lower light penetration in water bodies.
5. Understanding absorption is vital for modeling primary productivity and ecological health in aquatic ecosystems, as it directly influences the growth of photosynthetic organisms.

Review Questions

• How does absorption impact the photosynthetic activity of phytoplankton in aquatic environments?
  • Absorption significantly impacts photosynthesis by determining how much light is available for phytoplankton to convert into chemical energy. When light is absorbed by dissolved organic matter or sediments, less light reaches the phytoplankton, reducing their ability to perform photosynthesis. This can lead to lower primary productivity, affecting the entire food web and overall health of the aquatic ecosystem.
• In what ways does the composition of water affect light absorption and how does this relate to aquatic ecosystems?
  • The composition of water, including levels of dissolved organic matter, phytoplankton concentration, and sediment load, directly affects light absorption. For instance, high levels of colored dissolved organic matter can increase absorption and decrease light penetration, hindering photosynthetic processes. This relationship is crucial for maintaining balanced aquatic ecosystems since reduced photosynthesis impacts food availability for higher trophic levels.
• Evaluate how changes in land use could influence absorption rates and subsequently affect local aquatic ecosystems.
  • Changes in land use, such as urban development or agricultural expansion, can increase runoff that carries sediments and nutrients into nearby water bodies. This results in higher concentrations of suspended particles and dissolved organic matter, leading to increased absorption rates. Such changes may reduce light penetration, adversely impacting photosynthesis in aquatic plants and phytoplankton, thereby disrupting local food webs and decreasing biodiversity within those ecosystems.

Related terms

Light Attenuation: The reduction in intensity of light as it passes through water due to absorption and scattering by particles and dissolved substances.

Chlorophyll: A green pigment found in phytoplankton that absorbs light energy for photosynthesis, particularly in the blue and red wavelengths.

Scattering:

The redirection of light in different directions as it interacts with particles in water, affecting the overall light availability for photosynthesis.