52 



O 



- 



10 - 



20 - 



Figure 4. Organism-sediment relationships along a hypothetical enrichment gradient. Zone 1: Azoic, 

 bioturbation is absent, high sediment oxygen demand (SOD) and release of anaerobic metabolites. 

 Zone 2: High densities (low species richness and productivity of polychaete opportunists, bioturbation 

 depth is surficial, SOD is high. Zone 3: Area of enhanced carrying capacity, peak species richness 

 and deep bioturbation, reduced SOD. Zone 4: Ambient community living in relatively oligotrophy 

 sediment, reduced diversity and biomass relative to Zone 3, very low SOD, deep bioturbation. 



