The formation, structure and utilization of stone surface organic layers in two New Zealand streams

Abstract

1. The development of stone surface organie layers was investigated in dark and light experimental channels at two field sites. Layer formation was monitored by measuring organic carbon, chlorophylla, ATP and rates of oxygen consumption, and using scanning electron microscopy.2. In the darkened forest stream channel an organic layer consisting of slime, fine particles, bacteria and fungi developed and attained maximum biomass ( -0.08 mg cm -) in about 2 months. At the second site, channels were fed by spring water low in dissolved and particulate organic matter (DOC <0.5 g m"-') and no organic layer developed on stones in the dark. Organic layers grown in channels subject to natural light intensities and photoperiods were dominated by diatoms and/or filamentous algae at both sites.3. Laboratory experiments carried out in enclosed, recirculating stream channels demonstrated the importance of dissolved organic matter (DOM) as a prerequisite for layer formation. Also. DOM additions in the form of leaf leachates stimulated oxygen consumption by preformed layers. Uptake by microorganisms accounted for most of the reduction in watercolumn DOM. 4. Radiotracer experiments ("C and '"Ce) showed that several common stream invertebrates could feed on 'heterotrophic' layers. Calculated assimilation efficiencies ranged from 18% to 74% and imply that non autotrophic components of stone surface organic layers are likely to play a significant role in carbon transfer to the benthos, particularly in small, shaded streams.

Macroinvertebrate colonisation of perspex artificial substrates for use in biomonitoring studies

“…In this way, individuals of most species will always be available for colonisation. Similarly, the build-up of an organic layer and associated fine paniculate matter on the substrates is an important source of food and refuge for macroinvertebrates (Winterboum et al 1981(Winterboum et al , 1984Rounick & Winterboum 1983), and is important in shaping the community structure. As many of the New Zealand insects have been shown to be opportunistic in their feeding habitats, sufficient time must be allowed for such a layer to establish.…”

Processing of willow leaves in two suburban streams in Chrisrtchurch, New Zealand

“…Sections of leaf were excised 1-2 hours after bags were removed from the stream and stored in a solution of 3% glutaraldehyde in phosphate buffer. Later they were dehydrated by passing them through an alcohol series as described by Rounick & Winterbourn (1983), air dried, and mounted on SEM stubs. Before viewing with a Cambridge Stereoscan MK II SEM, leaves were vacuum-coated with 50 nm of gold palladium.…”

Crenic habitats, hotspots for freshwater biodiversity conservation: toward an understanding of their ecology

“…During the next 20 years, there were no studies characterising biological communities or spring habitats, although the origin of some springs of the east coast of the North Island was studied (Hunt & Glover 1995) and some ecological studies compared springbrook biota with invertebrate communities of unstable streams fed by run-off (e.g. Death & Winterbourn 1994;Death 1995) or included them as sites in experimental work (Rounick & Winterbourn 1983;Rounick & James 1984;Winterbourn & Fegley 1989;Suren 1991). …”