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Production and Decomposition in Aquatic Systems

Production and decomposition in aquatic systems are processes which are involved with the transformation, movement and recycling of nutrients. Some of the major elements involved with this nutrient cycling include carbon, nitrogen, potassium, and phosphorus.

Production in aquatic systems, which is similar to that of terrestrial systems, can be split into two major categories: primary and secondary production. Primary production is conducted by autotrophs, which are photosynthetic or chemosynthetic organisms. Photosynthetic organisms, such as algae, are capable of harvesting light from the sun to produce carbohydrates. Chemosynthetic organisms, such as methanogenic archaea, are found on the ocean floor and are able to convert inorganic compounds through oxidation into organic molecules in the absence of light. A general trend in lakes is that as algal biomass accumulates the rate of primary production increases linearly. Furthermore, in aquatic ecosystems the highest rates of primary production take place at continental margins where the nutrient content in the water is highest.

Secondary production is done by heterotrophs. Heterotrophs are unable to create organic compounds and instead feed on autotrophs or other heterotrophs. Fish species are an example in aquatic systems.

Decomposition, just like production, is required for nutrients to be cycled between different organisms within aquatic ecosystems. However, in contrast to production, decomposition involves the breakdown of organic compounds. In a study from 2004, comparing detritus, non-living organic matter, it was found that detritus in aquatic systems was of higher nutrient value than that in terrestrial ecosystems1. This is the material that decomposing organisms, such as invertebrate detritivores and microbial decomposers consume. Furthermore, this study found that in aquatic systems, more detrital matter was decomposed per unit time, leading to faster rates of nutrient recycling1.

Production and decomposition in aquatic systems are continuous and essential processes. Without these two processes, aquatic life would cease to exist. Therefore, a complete understanding of aquatic life requires an understanding of these two ecological processes. 




1. Cebrian, J. and Lartigue, J. (2004). Patterns of herbivory and decomposition in aquatic and terrestrial ecosystems. Ecological Monographs, 74(2): 237 - 259. 

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