Bryophytes as invertebrate habitat in two New Zealand alpine streams

Abstract

1. Quantitative samples of lotic benthic invertebrates and associated organic material were taken monthly for 18 months from bryophyte and gravel habitats in two New Zealand alpine streams in Arthur's Pass National Park, South Island; an unshaded site above the tree-line and a shaded stream flowing through mountain beeeh forest. This was to assess the ecological role of bryophytes in these habitats and to determine the relative effects on the fauna of algal and detrital resources.2. Bryophytes were confined to stable bedrock substrata in shallow (mean depth of 4.5 and 10.5cm), fast water (mean velocity of 0.21ms"' and O.SOms"'') at the unshaded and shaded sites. Mean ash-free dry weight (AFDW) of organic material from bryophyte areas was similar at the unshaded and shaded sites (335.6 and 272.4 gm"^). Low stream-bed stability of the gravel areas resulted in poor retention of organic matter, with average AFDW of 59.1 and 77.9gm"^ at the unshaded and shaded sites, respectively. Periphyton biomass, however, was much higher at the unshaded site.3. Within bryophytes, water velodty is redueed and large quantities of periphyton and detritus accumulate. This explains the greatly enhanced invertebrate densities within bryophytes (218400 and 53500 individuals m"^), compared with gravel areas (20900 and 7400 individuals m •^) in the unshaded and shaded sites, respectively. The higher invertebrate densities at the unshaded site reflect greater periphyton biomass there. 4. Invertebrate densities followed clear seasonal patterns, attributable to changes in chironomid densities. These reflected larval ehironomid hatching following adult oviposition. This illustrates the importance of these plants as oviposition sites, and as protective nurseries for small larvae where they can obtain shelter during floods and consume the abundant food sources available to them. 5. DECORANA ordination revealed taxonomically distinct invertebrate communities in each stream, and in bryophytes and gravels. Several taxa appeared restricted to either the unshaded site (e.g. Acroperla spiniger and Hydrobiosis sHvicola) or the shaded site (e.g. Zelolessica 399 400 A.M. Suren cheira, Orchymontia calcarata, Auslrosimulium ungulatum., Austroperla cyrene and a species of Empididae), reflecting the differences in energy input into each stream and the foods these animals consume.6. Repeated associations of certain taxa with bryophytes (e.g. Nematodes, Limonia hudsoni and Zelandoperla sp.) are postulated to reflect enhanced food availability, shelter from currents, and protection during pupation. Absence of certain common New Zealand stream taxa from bryophytes (e.g. the mayflies Nesameletus sp. and Deleatidium sp., and the stonefly Stenoperla prasina) is thought to be due to their inability to either move through tightly interwoven bryophyte stems or to utilize the available food sources.

Life histories and production of two trichopteran shredders in New Zealand streams with different riparian vegetation

“…Annual production calculated for O. maori (7.5 g D W m~2) was greater than the maximum value given by Perry et al (1987) for a trichopteran shredder, but still substantially lower than several estimates they provide for stonefly shredders (up to 23gDWrrr 2 y-1 ). Because they possessed large shredder populations, the Hinewai streams differed from most other small, South Island streams where faunistic studies have been conducted previously (e.g., Rounick & Winterboum 1982;Cowie 1985;Collier & Winterboum 1987;Winterboum & Collier 1987;Graesser 1988;Ryder & Scott 1988;Death 1991;Suren 1991). A major reason for the presence of large shredder populations, particularly in Mahoe and Fuchsia Streams, appeared to be their highly retentive nature (a consequence of their small size), shallow channels, and slow flow.…”

Bryophyte communities and seston in a karst stream (Jankovac Stream, Papuk Nature Park, Croatia)

“…Most investigations on aquatic bryophytes have dealt with macrofauna (Suren, 1991;Habdija et al, 2004;Milisˇa et al, 2006b), while protozoa and metazoan meiofauna (i.e., pass through a 500 mm sieve, Fenchel, 1978) have been neglected. There are many studies on protozoa/ meiofauna in macrophyte stands (Sleight et al, 1992;Duggan, 2001;Bogut et al, 2010), but there are only few papers concerning these communities in bryophytes (Madalin´ski, 1961;Donner, 1972;Linhart et al, 2002).…”

“…Conveniently, light conditions, together with detritus deposition, ensure a broad range of food resources (algae, bacteria and detritus) and provide suitable areas for invertebrate colonization (Linhart et al, 2002). Thus, bryophytic communities comprise a complex three-dimensional structure of microhabitats that are suitable for colonization by an array of algae, protists and invertebrates (Suren, 1991;Bowden et al, 2006).…”

Local Variation in Bryophyte and Macro-lichen Cover and Diversity in Montane Forests of Western Canada

“…Invertebrates living on stream bryophytes usually have similar or higher species richness and density than on bare substrata (Suren E-mail 1991), and certain invertebrate species are more common on bryophytes than in other habitats (Egglishaw 1969). For these reasons, bryophytes may provide a more diverse and stable ecological habitat than other substrata within headwater environments (Glime and Clemons 1972, Suren 1991, 1992. The importance of bryophytes in streams and the paucity of studies on them led a group of aquatic ecologists (Stream Bryophyte Group 1999) to review the state of this research and to propose several focal areas for future study.…”