Bank profile and structure as determinants of macroinvertebrate assemblages—seasonal changes and management

Abstract

Management and restoration procedures in rivers frequently have a major influence on the bank and marginal zone, depending on the timing of disturbance and the eventual structure of the bank. This study examines changes in macroinvertebrate communities in four different bank types at 3-weekly intervals throughout a year. The banks differed in their profile and in their structure: shallow sloping and vegetated, stepped shallow profile, steep profile (eroded soil bank), and iron revetments. Velocity patterns over the year showed much variability, both between and within bank types ranging from standing water in the summer to velocities in excess of 0.9 m s − 1 in the winter. The shallow-sloping vegetated site supported a total of 115 taxa, in contrast to the artificial iron revetment, on which only 32 taxa were recorded. Total abundances were five to six times greater in the shallow vegetated sites compared with the steeply sloped and artificial banks. Highest abundances were recorded in the late spring (May/June) and most taxa were found in August and September. Fluctuations in both abundance and number of taxa were least on the reveted bank. Ordination of the fauna/site matrix revealed a seasonal separation with specific winter and summer communities. The results suggest that the bankside is a dynamic environment where communities change in relation to growth of bankside vegetation and its concomitant effect on flow. The implications of these findings to management activities and restoration procedures are discussed.

Interaction between macroinvertebrates, discharge and physical habitat in upland rivers

“…The importance of livestock poaching on LIFE score is also not surprising: its influence on invertebrates has been documented elsewhere (Naura and Robinson, 1998;Armitage et al, 2001). In lowland streams, the locations of poaching can be highly localized, although downstream impacts through increased silt loading would be evident.…”

Ditch communities: a major contributor to floodplain biodiversity

“…Although there are no specific data available on seasonal changes in faunal and floral diversity for ditches in the area, studies of emergent bankside communities on the Frome (Armitage et al, 2001) suggest that biodiversity is highest in the period August/September, an observation supported by work in ditches in the Netherlands . A total of 16 sites was therefore sampled along its length in September 1998.…”

“…The River Frome adjacent to the ditch has been the subject of some recent intensive work on freshwater macroinvertebrate communities (Armitage et al, 1995(Armitage et al, , 2001Cannan and Armitage, 1999) These studies undertaken at the same time of year (September/October) provide the opportunity to compare the contribution of instream, bankside and ditch communities with the biodiversity of the floodplain. In most cases, the sample unit is the 15 s sweep and after standardization for identification level (Chironomidae to sub-family and tribe level) the results are comparable.…”

Constructed marginal shallow water zones along a navigable canal: possibilities and constraints for helophyte and aquatic vegetation

“…Aquatic vegetation provides substratum for invertebrates and zooplankton (Carpenter and Lodge, 1986). In correspondence with this, Armitage et al (2001) observed a three times higher number of macroinvertebrate taxa and a five to six times higher total abundance of taxa in shallow vegetated riparian sites compared with the steeply sloped and artificial banks. Bats prefer bank side plants and avoid water bodies with no vegetation edge (Russ and Montgomery, 2002).…”