Longitudinal changes in macroinvertebrate assemblages along a glacial river system in central Iceland

Abstract

1. Macroinvertebrate assemblages were studied in the glacial river West‐Jökulsá, originating from the Hofsjökull Ice Cap in central Iceland at an altitude of 860 m. Sampling sites were distributed from the source to 45 km downstream at 160 m a.s.l. Comparative studies were carried out on non‐glacial rivers and tributaries in the area, at similar altitudes and distances from the glacial source. 2. Detrended correspondence analysis (DCA) demonstrated that species composition of benthic macroinvertebrates was related to the distance from the glacier. Assemblages at sampling sites furthest from the glacier were similar in species composition to sites in non‐glacial rivers. Temporal variation was small compared with longitudinal zonation. 3. Based on canonical correspondence analysis (CCA) of data from the main glacial river, distance from the glacier, altitude, bryophyte biomass and the Pfankuch Index of channel stability were the measured explanatory variables having a significant effect on the structure of macroinvertebrate assemblages, accounting for 31% of the total variation in the data set. When data from all the rivers were analysed, altitude, bryophyte biomass, channel slope, suspended sediment concentration and maximum water temperature explained 21% of the variance. 4. Macroinvertebrate communities were in general agreement with the predictions of the conceptual model of Milner & Petts (1994) for the upstream reaches. The assemblages consisted mainly of Orthocladiinae and Diamesinae (Chironomidae), although other taxa such as Simuliidae, Plecoptera and Trichoptera were also found in low numbers. Shredders were lacking from the benthic communities, apparently because of continued glacial influence in the river even 45 km downstream from the glacier and lack of allochthononus inputs from riparian vegetation.

Microdistribution of chironomids (Diptera: Chironomidae) in Alpine streams: an autoecological perspective

“…Algal mats such as thalli of H. foetidus trap organic particles that act as food supply for invertebrates. Furthermore, these thalli contribute to the development of stable microhabitats where current velocity is reduced, and constitute a valid substrate for epiphytic diatoms, thus playing an important indirect role for the diet of invertebrates (Nolte, 1989;Gı´slason et al, 2001). Algal and moss mats have also been emphasized as oviposition habitats (Nolte, 1989).…”

The physico-chemical habitat template for periphyton in alpine glacial streams under a changing climate

“…Therefore, the hypothesis that grazing influences annual patterns of periphyton biomass in glacial streams, apart from abiotic factors, should be considered. Invertebrate densities in glacial streams are likely to be low during summer high flow and high between autumn and spring (Kowanacki, 1991;Gíslason et al, 2001Schütz et al, 2001;Burgherr et al, 2002), although deviations from this overall pattern can be substantial. For example, annual patterns of benthic grazers were quite different in some of the streams investigated in this study (Fig.…”

Physical integrity: the missing link in biological monitoring and TMDLs

“…The PSI is a tool used in the USEPA WARSSS procedure (Rosgen 2006) to assess stream channel condition and stability for watershed assessment and TMDL problem investigations. The PSI has also been used extensively in international research investigating relationships between channel stability and biota (Rounick and Winterbourn 1982;Death andWinterbourn 1994, 1995;Townsend et al 1997b;Duncan et al 1999;Robertson and Milner 1999;McIntosh 2000;Gislason et al 2001;Lods-Crozet et al 2001a, b;Maiolini and Lencioni 2001;Heiber et al 2002). The PSI has also been used to evaluate streambanks for restoration by the Izaak Walton League of America (IWLA 2006).…”