Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Subject: search.filters.subject.Freshwater invertebrates

Search Results

Now showing 1 - 10 of 21
  • Thumbnail Image
    Item
    Effects of disturbance and nutrient regimes on freshwater invertebrate community structure : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Manawatū, New Zealand
    (Massey University, 2018) Taylor, Joanna Marie
    Freshwater ecosystems globally are under threat from anthropogenically driven impacts including water abstraction for drinking and agriculture, exotic species invasion, eutrophication, channelization and destruction or modification of habitat. In New Zealand, eutrophication from nutrient enrichment is one of the most pervasive and detrimental impacts. High nutrient levels in waterways is detrimental not only to the species that inhabit them, but can also affect drinking and irrigation water for humans and result in loss of recreational and aesthetic values. Excess nitrogen and phosphorus can cause large amounts of periphyton to grow which in turn can impact water quality and the community composition of stream macroinvertebrates. Macroinvertebrate communities are also strongly affected by floods. More or less frequent flooding can cause changes in composition of stream invertebrate communities. Streams are usually affected by multiple stressors but the effect of those stressors are often considered in isolation for management. As macroinvertebrates are often used as indicators of ecosystem health, it is important to assess how different stressors interact and how these impacts those communities. In this study, macroinvertebrate communities in four Taranaki streams were sampled to assess the interactive effects of nutrient enrichment and flood regime. Nutrient enrichment resulted in invertebrate communities changing markedly between upstream and downstream sites. All four streams had a similar composition at the upstream sites whereas downstream sites in most streams were very different. In two of the streams with lower disturbance regimes, nutrients were the most important driver of invertebrate community composition. In the two streams with a higher disturbance regime, the invertebrate communities were more similar between upstream and downstream sites indicating that flooding was overriding the effects of nutrient enrichment as the most important driver of community composition.
  • Thumbnail Image
    Item
    Seasonal and year to year variation in the macroinvertebrate communities of New Zealand forest streams : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 2002) Minchin, Stephen Mark
    The bed movement of 42 streams in the Ruahine Forest Park, Urewera National Park, and Cass-Craigiebum region was predicted from each stream's channel and catchment characteristics. While a stepwise regression was relatively unsuccessful in predicting tracer particle movement, an artificial neural network analysis achieved strong correlations with measured tracer particle data. Forty-three streams in the Ruahine and Tararua Forest Parks were sampled in the summers of 1996 and 2001, and the macroinvertebrate communities compared. Changes in community structure between the two surveys did not correlate with any measured environmental characteristics including stream bed movement and change in periphyton biomass. MCI scores changed by a mean of 12.8 points between the two surveys, and the number of sites attaining an MCI score indicative of a 'pristine' stream dropped from 40 to 29. This appears to be related to a change in stream temperature, with streams that were cooler in 2001 than in 1996 showing an increase in MCI, while those which were warmer showed a decrease. Changes such as these could have a marked effect on biomonitoring programmes that use reference sites similar to these streams. In both 1996 and 2001, a greater number of taxa were collected from sites with more periphyton - taxon richness appears to asymptote at chlorophyll a concentrations greater than 5 μg/cm² Twelve streams within the Ruahine Forest Park were sampled every three months between June 2000 and May 2001. Both periphyton biomass and macroinvertebrate taxon richness tended to decrease with bed movement. While macroinvertebrate community structure showed marked changes over the study period, these changes were not linked to bed movement or variation in periphyton level. The seasonal changes observed in these streams are not significantly different to the changes seen between the summers of 1996 and 2001 - community structure was no more stable between two summers separated by five years than it was between the seasons of a single year. Eight artificial channels were laid on the bed of the Turitea Stream. At the onset of the experiment, half of the channels contained neither invertebrates nor periphyton cover, while the other half had no invertebrates but an initial periphyton layer. Drift samples indicate that approximately one in four drifting invertebrates colonised the channels during the 14 day study period, with benthic taxon richness reaching a peak after only four days. Colonisation was not affected by periphyton biomass. Some of the less common taxa that were present in the water column did not colonise the channels within 14 days.
  • Thumbnail Image
    Item
    Are aquatic invertebrates useful for assessing wetland condition? : a thesis presented in partial fulfilment of the requirements for the degree of Master of Environmental Management at Massey University, Manawatu, New Zealand
    (Massey University, 2017) Ekelund, Lovisa
    Freshwater wetlands are one of the most biodiverse ecosystems and at the same time of the most threatened globally. New Zealand has lost 90% of its wetlands and of those remaining, 60% are considered degraded. Establishing accurate wetland inventories and assessing wetland condition are priorities for the management and conservation of these important ecosystems. Aquatic invertebrates are used worldwide to assess the condition of other aquatic ecosystems such as rivers and lakes; however, their use for assessing wetland condition has not been extensive. A wetland’s hydroperiod is considered one of the most important environmental variables affecting wetland biota and one that has also been most altered by anthropogenic stresses. The second chapter of this thesis analyses the effect of hydroperiod on the macroinvertebrate communities of the Ō Tū Wharekai (Ashburton lakes) wetland system in New Zealand. A total of 40 taxa from 11 orders were recorded from 4 permanent lakes, 3 semi-permanent ponds, and 7 temporary ponds in September 2016. The macroinvertebrate assemblages in lakes were distinct to those in semi-permanent and temporary ponds. Overall, temporary ponds were slightly more diverse than the semipermanent ponds and lakes. Semi-permanent and temporary ponds were most similar to each other in macroinvertebrate composition. They host more species of small crustaceans such as cladocerans and ostracods, while species belonging to the Trichoptera, Odonata and Hirudinea orders were only present at permanent sites. The results emphasize the need to include small and seasonal wetlands in freshwater conservation efforts since they often hold unique biotic communities. In the third chapter, the potential to use macroinvertebrate communities in wetland assessment is evaluated. The macroinvertebrate communities of 14 freshwater wetlands in the lower North Island were sampled. The sites represent a gradient of wetland condition and include urban lagoons, agricultural swamps and lacustrine wetlands with recognized ecological value. A total of 63 invertebrate taxa were identified, of which crustaceans were the most abundant. There appeared to be no link between the composition and diversity of macroinvertebrate communities and wetland condition. However, of the habitat characteristics measured at each site, nutrient enrichment appeared to be the most important variable in determining macroinvertebrate assemblages. On the other hand, macrophyte communities appear to be more reflective of wetland condition. There are considerable knowledge gaps regarding invertebrate response to environmental change in freshwater wetlands and this limits their suitability as a biomonitoring tool. Assessing wetland condition accurately is one of the greatest challenges for the management and conservation of these threatened ecosystems. Aquatic invertebrates are used as biomonitoring tool for many freshwater ecosystems but not wetlands. This is because the way wetland invertebrates respond to environmental change remains unclear. So far, in New Zealand, there appears to be no link between wetland condition scores and invertebrate communities. Thus, the final section of this thesis proposes a simple dichotomous wetland condition scoring system exemplified with information from the 14 freshwater wetland sampled in the North Island. The method has limitations, but allows the integration of biotic data into wetland condition assessment.
  • Thumbnail Image
    Item
    Multiple scales of biological variability in New Zealand streams : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatū, New Zealand
    (Massey University, 2016) Jayasuriya
    Stream fish communities in Taranaki, New Zealand, were studied for the patterns and drivers of their spatial ecology. The study was focused on three main themes: a) complementarity between geography and landuse in driving regional distribution patterns of stream fish, b) the impact of agriculture on community composition, structure and variability of fish and invertebrates, and c) concordance among environmental distance and community dissimilarities of stream fish and invertebrates. Stream sampling and data collection for fish was conducted at regional scale using 96 sites distributed in the protected forest (44 sites) of Egmont National Park in Taranaki, and in surrounding farmlands (52 sites). Local scale sampling for fish and invertebrates was carried out at 15 stream sites in pasture (8 sites) and in adjacent forest (7 sites). Environmental data of geography, landuse and local habitat description were also gathered concurrently to biological sampling. The regional scale survey reported fifteen fish species, dominated by longfin eels (Anguilla dieffenbachia), redfin bullies (Gobiomorphus huttoni) and koaro (Galaxias brevipinnis), while 12 fish species and 69 different invertebrate taxa were recorded from the 15 sites at local scale. Regional scale spatial patterns of fish were mainly driven by landuse pattern. Catchment landuse (characterised by percentage cover of farming/native forest) effectively partitioned the stream fish community structure in Taranaki. Within each level of catchment landuse (farming), abundance and richness of fish species were negatively correlated with the altitude. Moreover, the upstream slope in high elevations and intensive farming downstream limited the distribution of stream fish across the region. Fish community composition differed significantly but weakly between forest and pasture in the immediate proximity. The dissimilarity of fish communities between forest and pasture increased from regional to local scale, and a similar result was found with stream invertebrate dissimilarity at the local scale. Stream communities (fish and invertebrates) were equally variable among streams between the two land use classes both at regional and local scales. Although the land use difference did not affect within-stream variability of fish, invertebrate communities were less variable within a pasture stream. Trends in in-stream variability of invertebrates were influenced mainly by altitude, stream morphology, pH, and riparian native cover. In concordance analysis, Mantel and Procrustes tests were used to compare community matrices of fish and invertebrates and the environmental distance between stream sites. The spatial patterns of fish and invertebrates were significantly concordant with each other among the 15 streams at the local scale. Nevertheless, community concordance decreased with lower spatial scales, and the two communities were not concordant at local sites within a given stream. Agriculture had a negative impact on the concordance between fish and invertebrates among streams, and none of the communities correlated with the overall environmental distance between agricultural streams. Community concordance between fish and invertebrates was consistently higher than the community-environment links, and lower trophic level (invertebrates) linked to their environment more closely than the upper trophic level (fish). The overall results suggest a bottom-up control of the communities through the stream food web. Finally, to inform the regional management and conservation decision, stream sites were partitioned according to the most important bioenvironmental constraints. The ecological similarity was measured by geography, land use pattern and the abundances of influential native fish species within the region, and the streams were clustered into seven distinct zones, using the method of affinity propagation. Interestingly, the dichotomy in proximal land use was not generally represented between zones, and the species diversity gradients were not significantly different across the zonal stream clusters. The average elevation of a given zone did not influence the community variability, while upstream pasture significantly homogenised fish communities between streams within a zone. Nonetheless the zones were based on river-system connectivity and geographical proximity. This study showed separate effects of confounding geography (altitude) and landuse on stream fish community structure, which has not explicitly been explored by previous studies. Studies with a simultaneous focus on multiple biological (e.g. fish and invertebrates) and environmental (e.g. geography, landuse, stream morphology) scales in varying spatial scales are not common in freshwater ecology. Therefore, this study has a great contribution to the understanding of the spatial ecology of stream communities linked with the control of geography, landuse, environment and likely biological interactions between fish and invertebrates.
  • Thumbnail Image
    Item
    Leaf litter decomposition and stream macroinvertebrate communities of the Central Volcanic Plateau : the effects of landuse : a thesis presented in fulfilment for the degree of Masters of Science in Ecology at Massey University
    (Massey University, 2000) Tubby, Christopher Jon
    The effects of landuse on benthic macroinvertebrate community structure was assessed in 35 streams draining four different landuse activities (native (Beech and Broadleaf/Podocarp) forest, exotic (Pinus radiata) forest, hill country pasture and scrubland) around Lake Taupo, North Island, New Zealand, between January and March 1997. Ephemerotera (mainly Deleatidium sp.) were abundant in all landuse types. Diptera (Chironomidae), Coleoptera (Elmidae) and Trichoptera (Pycnocentrodes aureola) dominated invertebrate communities in open canopy pasture streams, where higher algal biomass existed. Native forest and exotic forest stream communities were considerably different. Native forest streams had higher water velocities, substrate stability and overhead cover, whereas exotic forest streams had low bed stability and high sand levels. In response to the higher sand levels in exotic streams, invertebrate communities had higher abundance of molluscs (Potamopyrgus antipodarum) and Coleoptera (Elmidae). Native stream communities were dominated by Ephemeroptera (Deleatidium sp. and Colorburiscus humeralis), Coleoptera (Elmidae) and Trichoptera (Aoteapsyche colonica). Landuse effects on invertebrates are different throughout New Zealand and will depend on local conditions, especially geology. In December 1997 and January 1998, leaf litter decomposition and invertebrate colonisation were examined in 12 streams draining four different landuse activities around Lake Taupo. Mesh leaf tubes (0.2mm) and mesh leaf bags (3mm) containing dried Rangiora (Brachyglottis repanda) leaves were immersed into streams draining the four landuse types. Leaf tubes and bags were removed from streams after 14 days, 28 days and 42 days to measure the percentage of leaf weight lost from each leaf tube and bag and to assess the invertebrate colonisation of the leaf litter bags. Open canopy streams processed leaf litter in the tubes faster than closed canopy streams and it is likely that the increased temperatures and nutrient levels in open streams contributed to this phenomenon. Leaf bags were decomposed more rapidly in exotic streams where invertebrate densities in bags were highest among the landuse types. The low abundance of quality food available in exotic sites is likely to have contributed to the higher numbers of invertebrates feeding on the limited food resource. Invertebrate communities in all landuse types were distinctly different from each other, in contrast to benthic communities which were more similar. It appears that landuse does affect invertebrate communities in leaf bags, and this in turn influences leaf litter decomposition rates. Keywords: abundance, algal biomass, benthic communities, exotic forest, hill country pasture, invertebrate colonisation, leaf litter decomposition, macroinvertebrate community structure, mesh bags, mesh tubes, native forest, percentage weight loss, scrubland.
  • Thumbnail Image
    Item
    The influence of hydrology and landscape on stream invertebrate communities of the Whanganui Catchment, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Ecology at Massey University
    (Massey University, 2002) Lemke, Dawn
    This study examines the effect of the hydrological regime and landscape characteristics on benthic stream macroinvertebrate communities in the Whanganui Catchment, New Zealand, using a variety of statistical techniques. A total of 36 hydrological variables were considered. Thirteen of these were calculated from long-term flow and rainfall records, and interpolated using geographic information systems (GIS) to cover the area of interest. Ten hydrological variables were derived from topographical maps though GIS, with a further 13 hydrological variables determined from rainfall information relating to the timing since the last event. Catchment and riparian landscape variables (land cover, geology and soil type) were derived from New Zealand's land classification database and land resource inventory using GIS. Community structure was measured using an ordination, species richness, total number of animals and the densities of 22 common taxa. Biological data was also quantified with a variety of diversity and water quality indices including Simpson's, Margalef's and Macroinvertebrate Community Index. Individual links between biological and all environmental data were explored through Pearson's correlations. Multiple regression was used to examine the combination of the environmental variables that were best in determining individual characteristics of community structure. Canonical correlation was utilized to assess overall concurrent patterns between landscape and biotic data. Stepwise logistic regression and classification trees were used to explore occurrence of the 22 selected taxa in relation to environmental variables. Of the modelling techniques assessed for prediction of taxa occurrence classification trees gave as good or better predictions than the other models and tended to produce simpler models, suggesting that it is probably a better modelling technique for this data. Of the environmental variables, FRE3 (number of flood events per year over 3 times the medium flow) was the best individual predictor of community structure, showing the greatest number of links and strongest relationships with the biotic variables. The other hydrological variables of river size and specific discharge also had numerous individual correlations, and as they are easier to calculate they may be more appropriate for use in ecological studies. Time since the last event was another important component in determining invertebrate community structure. Hydrological characteristics dominated the explanatory variables in many of the models representing water quality and diversity indices, suggesting that indices that measure water quality and diversity may only be comparable over areas with similar hydrological regimes. Landscape variables, as measured by this study, were also shown to influence invertebrate community structure but to a lesser extent than hydrology. All indices and ordinations show significant multiple regressions with landscape variables with 12 out of the 22 taxa models being highly significant. Canonical correlations of landscape variables showed catchment scale variables to be more predictive of community structure than riparian scale variables. When separating landscape variables into land cover and geology no clear pattern of dominance was shown.
  • Thumbnail Image
    Item
    The effect of land use on benthic communities in Hawkes Bay streams of differing geology : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University
    (Massey University, 1999) Gibson, Jason Ross
    Benthic macroinvertebrate and periphyton communities of streams draining four different land use types within four distinct geological types were sampled between December 1996 and January 1997. Catchment land use comprised either standing mature or logged exotic forest, native forest, or hill country pasture. The geological types of these catchments were either Mesozoic sandstone-greywacke, Pleistocene-greywacke, Tertiary mudstone, or limestone in origin. Pastoral stream invertebrate community structure was significantly different from that found in forested streams, with no clear distinction separating communities from standing exotic, logged exotic, and native forest sites. Pastoral communities were dominated by dipterans and trichopterans. while in contrast, macroinvertebrate communities in streams draining sandstone-greywacke catchments were dominated by ephemeropterans and plecopterans, showing a clear influence of catchment geology on benthic macroinvertebrate communities. This sandstone-greywacke effect appeared to be independent of land use. Periphyton biomass was greatest in pastoral and exotic sites, particularly those draining limestone catchments. High nutrient and conductivity levels, both of which are characteristic of limestone streams, appeared to override the effect of light restrictions on periphyton growth in exotic forest sites. Overall, both geology and land use played major roles in determining the structure of stream benthic communities, with factors such as altitude and stream temperature also important influences on these communities. In November and December 1997, nutrient, shade, and disturbance effects were examined in periphyton communities colonising artificial substrates. These substrates were left in the 8 forested Hawkes Bay streams for 28 days with disturbance treatment substrates being physically abraded every 7 days. Nutrients (N + P) were added to nutrient treatment substrates and polythene cloth was used to create an artificially shaded environment for shade treatment substrates. Light availability and percentage canopy cover had the greatest effect upon periphyton, with light limitation being exhibited in closed canopy systems. Nutrient supply was also a factor determining periphyton biomass at both open and closed sites, although only up to a limit. Physical disturbance successfully removed organic matter from substrates as well as reducing chlorophyll a levels at open sites, however light and nutrient levels were more important determinants of chlorophyll a concentrations. In summary, both land use and geology play a considerable role in influencing both macroinvertebrate community structure and periphyton biomass. The geological influence was mediated through direct effects on nutrient inputs into the stream (as measured by conductivity), as well as by the indirect influence upon stream water temperatures. The influence of land use on benthic communities is predominantly as a result of shade levels created by vegetation types and enrichment levels derived from agriculturally influenced land. These results are of particular importance when comparing or analysing results from studies involving different land use types, particularly when these land uses cover a range of altitudes or are found in more than one geological type.
  • Thumbnail Image
    Item
    Effects of land use and point source discharges on macroinvertebrate and periphyton communities of the Taranaki ring plain : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science at Massey University
    (Massey University, 2000) Wells, A.G.
    Macroinvertebrate and periphyton communities were sampled from February 1998 to May 1998 in 83 stream and river sites throughout the Taranaki Ring Plain, New Zealand. Generally as streams descend the mountain, the catchment moves along a continuum ranging from pristine headwater streams with a high proportion of catchment in native forest, through to lowland streams with a high proportion of pasture catchment, draining intensive agricultural and industrial practices which put pressure on water resources. Ordination of sites indicated that the environmental continuum on the Ring Plain corresponds to a gradient of taxa along Axis 1 from clean water mayfly, caddisfly and stonefly taxa (i.e., Deleatidium spp., Coloburiscus) that prefer headwater streams, through to nutrient tolerant taxa (i.e. Oxyethira, Nemertea, Potomoprygus) that prefer lowland streams. This was emphasised by the positive correlation of Axis 1 with altitude and percent native forest and negative correlation with conductivity, chlorophyll a, temperature and BOD (Biological Oxygen Demand). A decline in invertebrate richness (number of taxa, Margarlef's index), and an increase in periphyton richness (number of taxa) and biomass (chlorophyll a) also occurred with distance downstream on the Ring Plain. Data collected in my study were compared to earlier studies (Taranaki Catchment Commission 1982,1984; Stark 1982; Hirsch 1958) to examine longer term temporal changes in macroinvertebrate communities. Significant differences in MCI and the SQMCI were found between my study and studies in the 1980's and 1958, as well as differences in percent EPT and the number of taxa between my study and 1980's studies. The decline in biotic indices in my study was also accompanied by a decrease in the abundance of mayfly and sensitive caddisfly taxa (i.e., Deleatidium spp., Coloburiscus) and an increase in the abundance of Diptera and the more tolerant caddisfly taxa (i.e. Oxyethira, Tanytarsini), since 1980's studies. Although invertebrate communities in my study that used to be below dairy factories and septic tank discharges were similar to the invertebrate communities in the 1980's studies, there was a general improvement since the 1958 study. This recovery was reflected in the smaller negative differences in MCI values between sites directly upstream and downstream of discharge points within my study compared to the 1958 study. Temporal changes in water quality were mostly attributed to the intensification of agricultural practices, point source discharges from dairy factories and industry, changes in the flow regime and sand movement.
  • Thumbnail Image
    Item
    The effect of substrate stability and canopy cover on macroinvertebrate communities in Taranaki ring plain streams : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University
    (Massey University, 2001) Zimmermann, Erna Maria
    The relative effect of substrate stability and canopy cover on macroinvertebrate communities, and their possible interaction, were investigated in 10 Taranaki ring plain streams between April 1999 and March 2000. Substrate stability was examined as it is postulated to be the major influencing factor on stream invertebrates and canopy cover as it will effect periphyton, a major invertebrate food source. Invertebrate communities, periphyton biomass and stone movement were monitored at 20 sites on these Streams of differing hydrological regime, a closed canopy site and an open canopy site on each stream. Macroinvertebrate species richness and periphyton grazer abundance were higher in open canopy sites than closed canopy sites and this was probably related to periphyton biomass which was higher at the open sites. Species richness displayed a strong quadratic relationship with periphyton biomass and overall macroinvertebrate community composition also appeared to be related to levels of periphyton as dictated by canopy cover. However this effect was overridden by substrate stability when disturbance levels were high. The effect of substrate stability and cover was also examined in an experiment, in one of the 10 streams; Cold Stream, where both factors could be independently manipulated. Wire mesh substrate baskets which were subjected to either artificial disturbance or left undisturbed were used under an artificial cover. Cover was found to influence invertebrate community composition, probably via its effect on periphyton biomass, while physical disturbance decreased both invertebrate abundance and diversity. Keywords: substrate stability; canopy cover; disturbance; productivity; macroinvertebrates; periphyton; community structure; diversity.
  • Thumbnail Image
    Item
    Effects of exotic forestry on stream macroinvertebrates : the influence of scale in North Island, New Zealand streams : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Ecology at Massey University
    (Massey University, 1998) Dunning, Kimberley Jane
    The effects of exotic forestry, particularly harvesting, on stream macroinvertebrate community structure was assessed in four regions, Lismore, Tawarau, Pirongia and Te Wera, of central North Island, New Zealand. A survey of 42 streams draining exotic forest (of different ages), native forest or pasture catchments was conducted in January and February 1997. Stream macroinvertebrate communities in 12 of these streams were further monitored every two months for 11 months, to assess changes in macroinvertebrate communities following harvesting and road construction. Recent forest harvesting (within six years) was associated with an increase in the abundance of pollution tolerant taxa (e.g., Oligochaeta, Crustacea and Mollusca) and a decrease in the abundance of Ephemeroptera and Plecoptera, indicating a shift in community structure. Diversity was not affected by harvesting however. Communities in streams draining mature exotic forest were similar to those in streams draining native forest, both being dominated by Ephemeroptera. Similarly, streams in harvested and pasture catchments were comparable. However, invertebrate response to forestry differed in the four regions, with Lismore and Te Wera forests showing distinct differences in community composition between streams in mature exotic forest and those in harvested exotic forest, while Pirongia and Tawarau showed little or no difference. Large scale factors such as geology were important in determining the response of communities to forest harvesting through their influence on substrate characteristics and susceptibility to erosion, and masked clear differences between land use types when compared between regions. Within regions however, communities differed more between land use types. Pre and post harvest monitoring revealed that changes in community composition were immediate from commencement of harvesting. Road construction had little effect on community composition but did lead to increased abundance of invertebrates. Physiochemical characteristics associated with differences in macroinvertebrate community structure between streams in harvested and mature exotic forest included sedimentation, stream stability and removal of riparian vegetation which altered light and water temperature regimes, and invertebrate food sources. The effect of sedimentation was tested experimentally for 21 days in three streams draining mature exotic forest catchments and two draining pasture catchments. Total abundance of macroinvertebrates decreased significantly with light and heavy sedimentation, and community composition showed a change from Ephemeroptera to Coleoptera dominated. Taxa most affected by sedimentation were Ephemeroptera and Plecoptera. Stream communities in exotic forest showed different responses to sedimentation than those in pasture, indicating that if pollution or sediment tolerant taxa are already present, sedimentation may not change the community significantly. Keywords: community composition, exotic forestry, harvesting, land use, macroinvertebrates, riparian vegetation, sedimentation, spatial scale, temporal scale, water quality.