Effect of Chironomus plumosus on spatial distribution of pore-water phosphate concentration in lake sediments: a laboratory experiment

摘要

Chironomids influence their sediment environment by bioirrigation, bioturbation, sediment resuspen-sion, ingestion, digestion, excretion and secretion (Aller & Aller 1998). These different activities effect phosphorus (P) turnover and release in a complex manner (Lewandowski & Hupfer, subm.), and it is difficult to evaluate the importance of single processes for the distribution of pore-water phosphate (SRP) concentrations. Bioirrigation is the pumping of water by chironomids through their U-shaped burrows to extract dissolved oxygen for respiration and suspended phyto-plankton for food (Walshe 1947). We assume that bioirrigation is of great importance for P mobility in iron-rich sediments because it increases the redox potential in the sediment. To better evaluate the effect of bioirrigation on small scale pore-water distribution, a special experimental setup was developed using two-dimensional (2-D) peeper technique combined with a visualization of burrows. This is the first investigation that permits measurements of distribution of the SRP pore-water concentrations in relation to the course of the chironomids burrows.