When microbial action during decomposition in aquatic ecosystems removes too much oxygen, the body of water experiences

N and P limitation is strongest in aquatic ecosystems (because light and water isn't) governed by same principles as terrestrial ecosystems radically different environmental controls streams have been treated as "sewers of terrestrial ecosystems" yet stream ecosystems have their own characteristics generated by the interaction of biota with the physical and chemical properties of the system unlike terrestrial ecosystems, nutrients "spiral" rather than cycle. The more limiting the nutrient, the tighter the spiral. Detritus/heterotrophs <---> autotrophs. 

its probably to later but whats the question