Factors governing macrozoobenthic assemblages in perennial springs in north-western Switzerland

Springs are important freshwater habitats that provide refuge for many rare species. In this study, the fauna and abiotic parameters of 20 perennial springs in north-western Switzerland were investigated. Correlation of abiotic and macrozoobenthos data showed that physicochemical parameters had little impact on macrozoobenthic composition, whereas specific substrate parameters strongly influenced the composition of the macrofauna. Surprisingly, nonmetric multidimensional scaling did not reveal a grouping of springs with similar substrate composition or macrozoobenthic assemblages. However, discharge was identified as the factor significantly determining substrate and the composition of macroinvertebrate assemblages. This justifies the hypothesis that, variation in discharge is the disturbance factor governing the macrofaunal composition temporally and spatially within and between patche

A review of assessment methods for river hydromorphology

The work leading to this paper has received funding for the EU’s FP7 under Grant Agreement No. 282656 (REFORM

Leben an turbulenten Orten: Benthische Gemeinschaften im Litoral von Seen in Wechselwirkung mit abiotischen und biotischen Umweltbedingungen

The central issue of this doctoral thesis is an evaluation of abiotic and biotic constraints on benthic communities in lake littoral zones. The thesis concentrates on various aspects of hydrodynamics, i.e. wave exposure, as a major abiotic force within the upper eulittoral zone of a large lake and its potential influence on taxa occurrence and habitat parameters and further its interference with biotic interactions. The importance of another abiotic factor water level fluctuations for the benthic community within the upper eulittoral zone of unregulated pre-alpine lakes is also emphasised. The thesis summarises results from standardised field, enclosure and mesocosm experiments and from a field sampling at Lake Constance, a large pre-alpine lake.In order to understand the impact of abiotic disturbance processes, the colonisation abilities of macroinvertebrates were studied under field conditions. The effects of wave propagation and dissipation on behaviour and growth of the herbivorous snail Radix ovata were studied within an outdoor mesocosm deployed with a newly developed pneumatic wave machine. The determination of benthic variability was the central focus of a one-year field study at three representative sites. The understanding of the mechanism influencing the spatial and temporal patterns of benthic communities is an important background information on the system itself.The present work involves two studies with emphasis on predator prey interactions between benthivorous fish and their macroinvertebrate food source. The predation impact of the most abundant fish taxa in Lake Constance, perch (Perca fluviatilis) and ruffe (Gymnocephalus cernuus), as well as of juvenile cyprinids [dace (Leuciscus leuciscus), bream (Abramis brama, Blicca bjoerkna)] were studied in enclosure experiments. Despite the direct impact of fish on benthic variability, wave exposure was expected to interfere with such food web interactions

Complex spatial and temporal patterns of littoral benthic communities interacting with water level fluctuations and wind exposure in the littoral zone of a large lake

The spatial and temporal organisation of benthic invertebrate communities was studied in a large oligotrophic lake in central Europe. Three shallow littoral sites at 0.4 m depth were sampled monthly from May 2002 to April 2003. On a spatial scale, the benthic community composition at all sites and in all samplings significantly differed in both abundance and biomass. On a temporal scale, the benthic communities at all sites gradually changed each month; monthly samples always significantly differed, but samples from consecutive months were more similar to each other than to samples of non-consecutive months. The observed variability within benthic communities corresponded with changes in the abiotic parameters water level and wind exposure, but was best explained by short- and long-term fluctuations in the water level. Effects of wind exposure were most pronounced in the winter months, when high wind events most often occurred. However, wind effects were masked by stronger effects, such as water-level fluctuation within the shallow littoral zone, or diminished by parameters with opposite effects, e.g. slope vs. exposure. Wind-induced shear stress in the upper eulittoral zone directly influenced the abundance and biomass of the benthic community to a lesser extent. We conclude, however, that this stress alters habitats constantly(e.g. substrate composition, periphyton growth, resuspension vs. sedimentation) and is therefore the driving force for the reported permanent site differences. Furthermore, benthic communities were well adapted to frequent minor changes and also to regular major changes of their habitat, as bare substrates were rapidly recolonised within a month

Factors governing macrozoobenthic assemblages in perennial springs in north-western Switzerland

Fauna in 20 ausgewählten Quellen der Nordwestschweiz Springs are important freshwater habitats that provide refuge for many rare species. In this study, the fauna and abiotic parameters of 20 perennial springs in north-western Switzerland were investigated. Correlation of abiotic and macrozoobenthos data showed that physicochemical parameters had little impact on macrozoobenthic composition, whereas specific substrate parameters strongly influenced the composition of the macrofauna. Surprisingly, nonmetric multidimensional scaling did not reveal a grouping of springs with similar substrate composition or macrozoobenthic assemblages. However, discharge was identified as the factor significantly determining substrate and the composition of macroinvertebrate assemblages. This justifies the hypothesis that, variation in discharge is the disturbance factor governing the macrofaunal composition temporally and spatially within and between patches

An efficient in situ method for sampling periphyton in lakes and streams

Peters L, Scheifhacken N, Kahlert M, Rothhaupt K-O. An efficient in situ method for sampling periphyton in lakes and streams. Archiv für Hydrobiologie. 2005;163(1):133-141.We present an efficient in situ sampling device that allows a simple and quantitative sampling of natural periphyton communities. The Brush Sampler is based on a previously developed sampler, which was improved by the addition of an external water supply, ball valve closing mechanism, and special exchangeable stiff brushes to solve previously reported problems of biomass overestimation and underestimation. The Brush Sampler was tested under ambient conditions in the field at four different sampling sites in a lentic and a lotic system and compared to the old sampler and control samples. The tests revealed a high inaccuracy of the old sampler and showed that biomass estimates (ash-free dry mass and chlorophyll-a content) obtained with the improved Brush Sampler did not significantly differ from biomass values determined from scrapings of control samples collected at the same sites. Therefore, our modified sampling device can be used as a tool for quantitative and qualitative epilithon community analyses

Leaf litter degradation in the wave impact zone of a pre-alpine lake

Contrary to streams, decomposition processes of terrestrial leaf litter are still poorly understood in lakes. Here, we examined the decomposition of two leaf species, beech (Fagus sylvatica) and poplar (Populus nigra italica ) in the littoral zone of a large pre-alpine lake at a wave exposed site. We focussed on the shredding impact of benthic invertebrates in a field experiment and on the effects of wave-induced disturbances under field and mesocosm conditions. In contrast to our expectations, benthic shredders did not reveal an important role in leaf processing under the conditions of the field experiment (early spring time, wave impact zone). Strong wave turbulence during storm events significantly reduced leaf mass, FPOM and invertebrate densities at field conditions. Several reasons can explain the low importance of shredders in our field study: (a) phenology of the shredder species, (b) feeding preferences and alternative food sources for gammarids, (c) generally low abundance of the native gammarid species due to the recent occurrence of an invasive predator, (d) disturbance of shredder activity due to high wave impact and (e) relatively low food value of the offered leaves. We suggest that leaf litter decomposition in lakes occurs in specific process domains, which largely depend on the hydraulic characteristics and on water-level fluctuations