Non-Living Detritus

• Trapped fine sediment and mud make up most non-living detritus in an estuary ecosystem, but dead microorganisms, vegetation and animal waste are also major components. Microorganisms, both plant and animal, live on and in the mud and silt, so larger animals that feed on the detritus usually eat mouthfuls of the detritus and filter out the silt and mud as part of their waste. In that way, the non-living detritus is filtered and cleaned.
  
  

Living Detritus

• Living plants or microorganisms make up most of the living material in detritus. Living vegetation includes submersed aquatic plants, partially immersed terrestrial plants, seaweed, marsh plants such as rushes and seagrass and macroalgae. Microscopic plants such as benthic microalgae and phytoplankton also live in the detritus. The microscopic, underwater vegetation absorbs phosphorus and nitrogen from the water to grow. Microscopic animals called zooplankton feed on the plankton and live within the detritus.
  
  

Detritus as Food

• Animals that live on the muddy bottom of the estuary, also called benthos, often take at least some of their nutrition from the detritus. These animals include worms, shellfish, snails and small or young fish. They often eat the detritus and allow their bodies to filter out the mud and silt. These animals are filter or suspension feeders, and they use a variety of species-specific organs to do the filtering: For example, shellfish might use cilia or cockles, and worms use tentacles. Most detritus is made up of complex carbohydrates that decompose relatively slowly and with difficulty. As the animals filter the detritus through their bodies, they both fertilize and clean it, just as the detritus nourishes the animals.
  
  

Production of Detritus

• The animals that use detritus as food produce waste that helps to fertilize and feed many of the microorganisms and vegetation within the detritus. Zooplankton that feed on the phytoplankton also produce waste, and when they or the phytoplankton die, they become part of the non-living detritus. Silt from the ocean and mud from the river may also be swept into the estuary and add to the detritus.