Statistical models for predicting the effects on algal biomass of eutrophication are much better developed lentic systems than lotic systems, partly because dynamic physical nature streams as controlled by flood regimes. I analyzed data from 30 sites in 25 runoff-fed and rivers to develop statistical mean monthly maximum chlorophyll a function soluble nutrient concentrations days accrual (reflecting frequency disturbance events). Variation stream-water nutrients explained 12–22.6% variation...

SUMMARY. 1. Periphyton chlorophyll a and ash free dry weight (AFDW) were monitored in nine rivers to examine the relative importance of flows nutrients for regulating periphyton biomass gravel bed rivers. 2. Mean annual ranged from 0.94 169 m 3 s −1 , mean dissolved reactive phophorus (DRP) 1.3 68 μ g 1 periphytic 4.6 73 mg −2 . AFDW 2.8 16 3. For eight NH 4 ‐N. DRP, total Kjeldahl nitrogen, phosphorus suspended solids correlated ( P <0.01) with flow, seven conductivity was inversely...

SUMMARY 1. Periphyton chlorophyll a (chl ), ash‐free dry mass, taxonomic composition, and cellular water‐column nutrients were analysed every 4 weeks for year at sixteen stream sites in New Zealand. The hypothesis was investigated that broad‐scale differences mean monthly periphyton development are defined primarily by the frequency of flood disturbances periphyton's interaction with nutrients. it us streams as determined catchment geology land use. 2. Overall, chl concentration declined...

ABSTRACT: River Environment Classification (REC) is a new system for classifying river environments that based on climate, topography, geology, and land cover factors control spatial patterns in ecosystems. REC builds existing principles environmental regionalization introduces three specific additions to the “ecoregion” approach. First, assumes ecological are dependent range of associated landscape scale processes, some which may show significant variation within an ecoregion. arranges...

In this paper we suggest a conceptual model for the evaluation of periphyton communities in unshaded temperate streams based on primary habitat variables flood disturbance, nutrient resource supply and invertebrate grazing. The core is classification 35 taxa into four main functional groups C-S-R life history strategies Grime. Possible successional trajectories following system-wide disturbances under different regimes are also discussed. interaction disturbance species membership,...

1. The objective of this study was to identify the most ecologically relevant hydrological indices for characterizing regimes in New Zealand streams. To do we related measures periphyton chlorophyll a , ash‐free dry mass (AFDM), species richness, and diversity invertebrate density, richness diversity, thirty‐four variables derived from daily flow records at eighty‐three sites. included some describing average conditions, variability, floods, low‐flow characteristics. 2. A principal...

Abstract Obtaining a better knowledge of how flow variability affects lotic biota is considerable importance to stream and river management. We contend that processes at different hierarchical levels organization in ecosystems are sensitive variation related temporal scales. Ecosystem disturbance caused by large‐scale events (i.e. infrequent, but high magnitude with recurrence interval years many days) tend determine high‐level characteristics ecosystem structure (e.g. determining species...

Macrophytes play a key role in many unshaded lotic ecosystems, but little is known of the factors controlling their presence, abundance, and composition. Macrophyte diversity, composition were studied 15 New Zealand streams to test hypotheses that presence development macrophytes systems primarily controlled by hydrologic regime (frequency high‐velocity flood events) interflood spatial distribution performance taxa more stable strongly influenced local hydraulic conditions...

Previous studies have shown major differences in the way biomass of stream periphyton is controlled by spatial variations velocity. We hypothesize that these may be result different growth forms within community. Some dense and coherent (e.g. mucilaginous diatom/cyanobacterial mats) resistant to diffusion also dislodgment shear stress. Higher velocities applied such communities could therefore expected enhance accrual increasing rates mass transfer, but without greatly losses through...

The random field approach for gravel‐bed roughness characterization, which is based on the presentation of bed elevations as a three‐dimensional field, justified an alternative to characteristic particle size approach. We first show that elevation distribution close Gaussian and then investigate using second‐order structure function. latter reveals two distinct regions: scaling region at small spatial lags saturation large scales. exponent H (a form Hurst exponent) appears be isotropic...

We sampled benthic algae monthly for 15 months in 12 New Zealand gravel‐bed streams to investigate amongstream differences algal taxonomic richness and how this might relate among‐stream flood disturbance nutrient resource regimes. The mean number of taxa per month ranged from 9.4 21.3 among streams. There were moderate month‐to‐month fluctuations richness, partly response disturbances. Flow perturbations generally reduced with unarmored bed sediments but had little or no effect on armored...

ABSTRACT The resistance of stream periphyton to structural disturbance by increases in shear stress (simulating a spate) was investigated laboratory flow tank. We monitored loss biomass from filamentous community (dominated Melosira varians) under four different levels stress. In each case, any that going occur did so within 10 min for this community. second experiment, we tested the communities (two dominated nonfilamentous diatoms and two green algae/diatoms) Nine were used, ranging 1‐...

Plant development in unshaded streams is reviewed within the context of a conceptual habitat model. Resource factors (incorporating light, nutrients and temperature) predominantly govern processes biomass gain hydraulic separate temporal spatial scales) loss. It postulated that differences stability among over periods greater than year whether stream (or site) dominated by periphyton, bryophytes or macrophytes. Hydraulic less governs average periphyton biomass. During steady-state,...

Abstract Microhabitat preferences of 12 benthic invertebrate taxa were investigated in four New Zealand rivers. Most showed significant habitat preferences. Generally, more abundant water less than 0.75 m deep and gravel or coarser substrates, no a clear preference for fine substrate (sand gravel) water. Coloburiscus humeralis, Zelandoperla spp., Aoteapsyche spp. preferred coarse velocities s−1, whereas Nesa‐meletus Pycnocentrodes associated with similar but lower (0.2–0.8 s−1). Naididae low...

The loss of phosphorous (P) from the landscape is commonly viewed as deleterious for surface water quality. However, quantities lost and impact this can have on waters depends numerous mechanisms that occur whilst en route. aim review to give an outline these thus how sources P in agricultural are connected impairment Processes dealt with by examining potential its availability aquatic plants during flow overland subsurface once streamflow or a lake reservoir. By connectivity between...

Abstract River water quality in New Zealand is at great risk of impairment low elevation catchments because pervasive land‐use changes, yet there has been no nationwide assessment the state these rivers. Data from surface‐water monitoring programmes 15 regional councils and unitary authorities, National Water Quality Network were used to assess recent (1998–2002) trends (1996–2002) low‐elevation rivers across Zealand. Assessments made national level, within four land‐cover classes (native...

Photosynthesis‐irradiance (P‐I) characteristics of periphyton (microphytobenthos) have been considered primarily for entire assemblages. How P‐I responses vary with mat thickness and community composition has not in detail. We used a combined approach modeling, microscale determinations photosynthetic rate light attenuation, whole‐assemblage O 2 flux measurements to explore relationships. The modeling suggested that the onset saturation photoinhibition will occur at higher irradiance...

This study examined how the leptophlebiid mayfly Deleatidium spp., mudsnail Potamopyrgus antipodarum, and stony-cased caddisflies Pycnocentrodes aeris Hudsonema amabilis, each with different flow habitat preferences motilities, respond to elevated flows. Our aim was learn more about refuge-seeking behavior life-history traits affect species persistence along disturbance gradient. All taxa responded incrementally increased flows in a recirculating laboratory flume layered substrata by moving...

Abstract A programme of research to characterise, classify, and model New Zealand rivers according hydrological, water quality, biological properties is introduced. The results are detailed in the accompanying eight papers. These studies provide first national perspective on quality biology Zealand's using a consistent methodology. They also step toward providing managers with robust models for predicting effects aquatic biota changes flow regimes catchment land use. synthesis given this...

Abstract The composition of periphyton communities was assessed over an extensive range New Zealand river environments during late‐summer low flows. chemical, hydrological, and watershed characteristics the sites were determined broad associations developed between several key variables. Eight identified 91 classified into groups according to presence first seven these communities. Most dominated by filamentous taxa. A taxonomic‐biomass classification also condensing site three, more...

Summary 1. Blooms of the benthic, stalked diatom Didymosphenia geminata were first observed in New Zealand 2004. Since then, D. has spread to numerous catchments South Island and is also spreading its native range. The species a rare example an invasive alga lotic systems. 2. Ecosystem effects may be expected as attains unusually high biomass rivers. We examined data from three independent studies Island, Zealand, rivers for evidence on periphyton benthic invertebrate communities. 3....

Abstract New Zealand rivers were surveyed for filamentous algal proliferations following prolonged periods of low flows to define their extent, standing crop, and composition. Significant growths found at 167 the 423 sites surveyed. The geometric mean river bed cover algae was 26% in summer 22% winter. Proliferations >40% occurred 16% sites. crop 15.3 g/m2 (ash‐free dry weight) 1.87 >50 (AFDW) 8% A taxonomic classification analysis data identified nine main clusters which appeared correspond...