Suren - Bryophytes and invertebrates in alpine streams

New Zealand Journal of Marine and Freshwater Research abstracts

Bryophytes and associated invertebrates in first-order alpine streams of Arthur's Pass, New Zealand

ALASTAIR SUREN

NTWA - Freshwater National Institute of Water and Atmospheric Research Ltd P. O. Box 8602, Riccarton Christchurch, New Zealand

Abstract Tributary alpine streams in six sub-catchments in Arthur's Pass National Park (South Island, New Zealand) were surveyed to assess the frequency of streams supporting aquatic bryophytes. Relationships between streambed stability and bryophyte occurrence were examined. Invertebrate communities associated with bryophytes were characterised, and compared between streams flowing above the tree line, and below. Of 103 tributary streams encountered, 53 were above the tree line, and 50 were below. Aquatic bryophytes occurred in half these streams irrespective of riparian shading, but bryophyte distributions were strongly influenced by streambed stability. Invertebrate communities associated with bryophytes were dominated by Nematoda, Chironomidae, Oligochaeta, and Copepoda. This is fundamentally different from the bryofauna outside New Zealand, and may reflect the absence of certain bryophyte-dwelling families of Trichoptera, Plecoptera, and Ephemeroptera from New Zealand. Invertebrate densities within bryophytes were higher above the tree line, and the faunal composition also differed between streams. This may reflect differences in detrital and periphyton biomass associated with bryophytes in each stream type. Positive relationships existed between bryophyte biomass, and both invertebrate density and detrital/ periphyton biomass. Invertebrate densities were also higher within plants containing periphyton than plants containing detritus, suggesting periphyton's greater value as a food source to invertebrates.

Keywords aquatic bryophytes; invertebrate communities; periphyton; detritus; streambed stability; headwater streams; Arthur's Pass

New Zealand Journal of Marine and Freshwater Research, 1993: Vol. 27: The Royal Society of New Zealand 1993
Received 23 February 1993; accepted 30 September 1993

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