Epipelic

Epipelic refers to organisms that live on the surface of sediment, particularly in aquatic environments. These are organisms that are neither truly pelagic (living in the open water column) nor benthic (living within the sediment itself). Instead, they inhabit the very top layer of the sediment-water interface, often forming a thin biofilm.

The epipelic community typically includes a diverse array of microorganisms such as bacteria, diatoms, cyanobacteria, and protozoa. Small multicellular organisms, like certain types of nematodes and rotifers, can also be found in this zone. These organisms are adapted to fluctuating conditions of light, oxygen, and nutrient availability that characterize the surface of sediments.

Epipelic communities play a crucial role in aquatic ecosystems. They are primary producers, converting sunlight into energy through photosynthesis, and are a vital food source for larger organisms. Their metabolic activities also contribute to nutrient cycling within the sediment and the overlying water. The composition of epipelic communities can be indicative of environmental conditions, making them useful as bioindicators for water quality and sediment health. Studying epipelic organisms helps scientists understand the complex interactions at the sediment-water boundary.