Particulate organic matter (POM) in water bodies is primarily formed or derived from a diverse range of sources, including materials from land, aquatic plants, and microscopic algae.
The Origins of Particulate Organic Matter in Aquatic Environments
The formation of particulate organic matter is a continuous process driven by the input of organic materials from both terrestrial and aquatic ecosystems. These diverse origins contribute to POM's varied chemical compositions, which in turn affect its "lability" – its accessibility and usefulness within the aquatic food web. Understanding these sources is crucial for comprehending the dynamics of carbon cycling and ecosystem health.
Below are the main ways particulate organic matter is formed:
1. Terrestrial Inputs
One significant source of POM in water bodies comes from terrestrial inputs. These are organic materials that originate from land and are subsequently transported into aquatic systems, often through runoff or wind.
- Soil Organic Matter: Fine particles of organic matter from soil can be eroded and washed into rivers, lakes, and oceans during rainfall events.
- Leaf Litterfall: Decaying leaves, twigs, and other plant debris from surrounding land areas fall into water bodies, breaking down into particulate forms over time.
2. Aquatic Vegetation
Within the water bodies themselves, submerged or floating aquatic vegetation also contributes substantially to the formation of POM. As these plants grow, senesce, and decompose, their organic matter becomes part of the particulate pool.
- Submerged Plants: Plants that grow entirely underwater contribute their biomass upon death and decomposition.
- Floating Plants: Plants like water lilies or duckweed, which float on the surface, also release organic matter as they break down.
3. Autochthonous Production of Algae
A vital process for POM formation, especially in lakes and oceans, is the autochthonous production of algae. "Autochthonous" means it originates from within the system itself.
- Living Algae: Actively growing phytoplankton and other microalgae are a direct form of living POM.
- Detrital Algae: When algae die, their cellular material contributes to the detrital (dead organic matter) component of POM. This detritus can range from whole dead cells to fragmented organic compounds.
Summary of POM Sources
To illustrate the primary origins of particulate organic matter, consider the following breakdown:
| Source Category | Description | Examples |
|---|---|---|
| Terrestrial Inputs | Organic material originating from land, transported into water bodies. | Soil organic matter, leaf litterfall |
| Aquatic Vegetation | Organic matter derived from plants growing within the water body. | Submerged aquatic plants, floating aquatic plants |
| Autochthonous Algae | Organic matter produced by photosynthetic organisms within the water body. | Living algae, detrital (dead) algae |
Each of these sources contributes POM with unique characteristics, influencing its ultimate fate and role within the aquatic ecosystem.
