Analysis of particulate organic matter retention by benthic structural elements in a lowland river (River Spree, Germany)
Wanner, Susanne C.; Pusch, Martin
published: May 23, 2001
ArtNo. ESP141015103014, Price: 29.00 €
In a 6th-order section of the lowland River Spree, we analysed the retention of particulate organic matter (POM) by the following characteristic benthic structural elements: stable sands colonised by macrophytes or mussels, shallow sandy banks, and shifting sands. Our hypothesis was that the retention and storage of suspended particles and, therefore, the organic matter budget of a specific river reach is determined by the retentive properties of the various types of benthic structural elements in the channel. The relative storage capacity of each structural element for POM, chlorophyll-a, and protein was calculated. This storage capacity reflects the dynamics of processes that occur on the time scale of several months. Additionally, the relative trapping efficiencies of the structural elements were determined by means of tracer particles, which provide information about their retentive properties on shorter time scales. The investigated structural elements differed significantly with respect to the amount and composition of stored POM, and the time scale of retention. Biotic structures were the most effective retention features on longer time scales in the investigated lowland river. Macrophyte stands showed the highest relative storage capacity for organic matter, followed by stable sands that were colonised by mussels. On a shorter time scale during low discharge conditions, shallow sandy banks were similarly retentive. Shifting sands were least retentive, but the highest nutritional quality of the organic matter was found there. Those spatial patterns within a river reach are supposed to be an important factor controlling the microbial processing of POM in the benthic zone and the distribution of benthic invertebrates. Based on our results, it can be expected that changes in the size and composition of benthic structural elements within the channel (e.g. due to bank reinforcements, straightening measures, or impoundments) will influence the organic matter budget of a stream ecosystem considerably.