Bacterial and phosphorus dynamics in profundal Lake Erken sediments following the deposition of diatoms: a laboratory study

The benthic microbial response to the deposition of naturalseston and the microbial impact on nutrient dynamics wasstudied in an experimental system using whole sediment coresequipped with flow-through systems for the overlying water. For20 days, changes in sediment bacterial activity, totalmetabolic activity (heat production), bacterial biomass,phosphorus fractions and basic chemistry were followed, as wellas the exchange of nutrients between sediment and water.Microbial activity and biomass increased immediately inresponse to the deposition of seston, peaked after seven daysand then decreased linearly over the remaining time of theexperiment. Co-settled bacteria were suggested to play animportant role in the microbial response. Changes in bacterialbiomass production, bacterial biomass and the NaOH-nrPextractable phosphorus fraction were concurrent in response toseston additions. The sediment acted as a trap for SRP from theoverlying water when bacterial activity was high and as asource when the bacterial activity decreased. Altogether, theresults suggest an important role of bacteria in theregeneration of seston P. Mineralization rates estimated fromsediment heat production showed that ca. 11% of the addedseston carbon was oxidized in the sediments during theexperiment. This revised version was published online in July 2006 with corrections to the Cover Date.