As technologies advance the study of ocean dynamics, new approaches to vexing problems of scale and process are becoming more widely available. Originally conceived as a tool primarily for indexing the abundance of near-bottom fishes, the Camera-based Assessment and Survey System (C-BASS) may also be an effective tool for monitoring benthic invertebrate resources vulnerable to natural and anthropogenic perturbations, and for characterizing the composition of benthic communities to inform spatial management. Using still images derived from the C-BASS video of benthic transects within the Florida Middle Grounds, I documented the abundance of benthic habitat-forming functional groups—sponges, algae, and corals—and noted taxa that were present in a SCUBA and ROV study conducted a decade earlier. Images were pre-processed using MATLAB computer programming language to correct for light attenuation and scattering in seawater at depth, and examined using ImageJ software and Coral Point Count software or rapid visual assessment methodology to assess image quality and percent cover, respectively. Exploratory data analysis (dissimilarity profile) delineated five habitat types in the northern Florida Middle Grounds, and discriminating benthic cover was identified using similarity percentage analysis: soft corals, fleshy macroalgae, low-relief algae, encrusted rubble, and sand. Hard corals and sponges represented relatively low area cover. A canonical analysis of principle components of in situ environmental measurements, chlorophyll a, turbidity, salinity, slope, and depth highlighted the association of the sand habitat type with greater depths and least amount of slope. Fleshy macroalgae were associated with greater slope, which reflected its presence in transitional areas between sand and reef. Soft coral habitat type was correlated with shallower depths, but also to lower temperature and lower salinity, highlighting the limitations of one-time environmental measurements to the condition of that time and space. A distance-based redundancy analysis of fish species abundance revealed that sponges, soft corals, and hard corals explained some of the variation of Holocentridae spp., angelfishes, and porgy, and that gray snapper appeared to associate with higher measurements of chlorophyll a. A comparison of C-BASS measurements with a coincidental stationary camera survey revealed that a slight shift in view, either from the seafloor to the water column, or from two slightly different positions in the water column, can obscure or reveal benthic cover to varying degrees, suggesting that more imaging could provide more complete representations of the benthic cover. Continued surveys of the benthic composition of the west Florida shelf could elucidate the range of environmental conditions and facilitate further investigations into the fish species associations with biotic cover in these benthic communities.

Headwater streams are extremely vulnerable to the consequences of land-use change as they are tightly coupled with the surrounding landscape. Understanding the natural processes that influence the structure and function of these ecosystems will improve our understanding of how land-use change affects them. Benthic substratum habitat was investigated in a sub-tropical headwater stream by quantifying temporal change to sediment texture of surface sediments (less than 10cm), over four years. Hydrological characteristics were also surveyed in detail, as hydrological regime is a primary determinant of sediment transportation. Additionally, measures of hydro-geological features - hydraulic conductivity and groundwater depth were made in order to explore features of sediment habitat that extend beyond the sediment-water interface. Whilst the typical discharge pattern was one of intermittent base flows and infrequent, yet extreme flood events associated with monsoonal rain patterns, the study period also encompassed a drought and a one in hundred year flood. Rainfall and discharge did not necessarily reflect the actual conditions in the stream. Surface waters were persistent long after discharge ceased. On several occasions the stream bed was completely dry. Shallow groundwater was present at variable depths throughout the study period, being absent only at the height of the drought. The sediments were mainly gravels, sand and clay. Changes in sediment composition were observed for fine particulates (size categories less than 2mm). The grain size change in the finer sediment fractions was marked over time, although bedload movement was limited to a single high discharge event. In response to a low discharge regimen (drought), sediments characteristically showed non-normal distributions and were dominated by finer materials. High-energy discharge regimes (flood) were characterised by coarsening of sands and a diminished clay fraction. Particulate organic matter from sediments showed trends of build-up and decline with the high and low discharge regimes, respectively. Benthic habitats were described according to prevailing hydro-geological parameters. Faunas from sediment substratum samples were associated with identified habitat categories. The fauna reflected the habitat variability in terms of hydrological disturbance of the substratum structure and intermittency of discharge. An applied multivariate procedure was used to correlate temporally changing environmental parameters and faunal abundance data. Faunas were correlated with a group of variables dominated by either discharge variables or sediment textural parameters. Sediment characteristics that affect substratum quality and substratum preference at the micro-scale were investigated via hypotheses testing. A model of carbon loss was used to determine how long particulate organic matter could potentially sustain microbial activity under experimental conditions. An estimate of up to 200 days was determined from this laboratory experiment. Secondly, enriched carbon isotopes were used in a field-based experiment to establish a link between sediments and macrofauna. Enrichment via organic sediments was found for various detritivorous and carnivorous taxa. In the 'third' experiment, artificial treatments were applied to elucidate substratum preference. Fauna was offered the choice of variable quantities of clay and/or quality of organic matter. There were no significant preferences found for the different substratum treatments, although further investigation is needed and a different outcome from this method may be achieved under more benign field conditions than those encountered during this experiment. Finally, the study was set within a context of the primary features of scale. Climate and hydrological features, including linkages with the alluvial aquifer and terrestrial ecosystem, and their potential to change within 'ecological time' are perceived as critical to understanding the role of benthic sediment substratum.

The aim of the project was to determine factors which explain the distribution of macroinvertebrates in two Melbourne streams both drastically affected by urbanisation. A detailed description is given of Dandenong Creek, flowing through the south-eastern suburbs, and Darebin Creek, in the northern suburbs, emphasising stream features likely, or known, to influence the drift and benthic fauna. Faunal sampling was carried out in Dandenong Creek from June 1992 until July 1993, and in Darebin Creek from February 1995 until March 1998. Physicochemical parameters were also recorded. The collected data, together with previously existing data, were analysed using multivariate analyses: non-metric multi-dimensional scaling (NMDS); analysis of similarities (ANOSIM); matching biotic and abiotic variables using BIOENV, and principal component analysis (PCA). Various biotic and diversity indices were calculated in an attempt to identify the major factors responsible for the failure of the fauna to recover from previously more seriously degraded water quality. The contribution of drift to the colonisation potential in Dandenong Creek appeared to be impacted by retarding basins, underground barrel-draining and channelization. Results also indicated that increased conductivity adversely affected the fauna in the lower reaches of Dandenong Creek. It was concluded that in Darebin Creek, high nutrient levels, as well as other pollutants, had resulted in low macroinvertebrate diversity in both the drift and benthos. If, as this study suggests, faunal diversity is a valid measure of stream health, the following factors need to be addressed for catchment-wide, stream management: lack of riparian zone vegetation (increasing bank erosion and making the benthic habitat unstable, with greater temperature variability); control of stormwater runoff (flow variability, increased conductivity, nutrient levels, sediment loads, sewage effluent, industrial discharges and heavy metals), and to modify retarding basins to increase stream continuity.

Estuarine benthic assemblages are often numerically dominated by polychaetes. The limits of these populations are determined by larval, and probably to a lesser extent adult movement. A previous study (Newton 1996), indicated that planktonic polychaete larvae were very abundant over the summer months in the Hopkins River; however, the identification and source of these larvae was not known. Defining the extent of a population, and therefore the likelihood of that population recovering following a perturbation, is crucial for effective estuarine management. This study investigated both the likely source of the larvae, (i.e. estuarine or marine) and the extent of larval dispersal within and between estuaries by addressing the following questions: Which taxa produced the planktonic larvae? Are these taxa resident estuarine species? Are the larvae of different taxa evenly distributed within the estuary or do physicochemical parameters or other factors influence their abundance? Are the same larvae found in other estuaries along the coast? and Is there exchange of these larval taxa with the marine environment and other estuaries? Larvae were identified and described by culturing commonly occurring planktonic larvae until adult characteristics appeared. The spionids, Carazziella victoriensis and Prionospio Tatura, numerically dominated the plankton in the Hopkins and the spionid, Orthoprionospio cirriformia was recorded from the Hopkins, Curdies and Gellibrand estuaries. Two spionids, Carazziella sp. and Polydora sp. were identified from tidal waters. Mouth status and physicochemical conditions (salinity, temperature and dissolved oxygen) were monitored in each estuary. Whereas the Merri and Gellibrand estuaries were predominantly stratified over the sampling period, the Curdies was more often well mixed and the Hopkins varied from well mixed to stratified. The duration of mouth opening and hence the opportunity for larval exchange also varied in each estuary. The Merri River was closed for 13.5% of days over the study period, the Gellibrand River for 18.4%, the Hopkins River for 49% and the Curdies River for 71.0%. The distributions of larvae at spatial scales of metres, 100s of metres and kilometres were investigated within a single estuary. While the same larvae, C. victoriensis, P. Tatura and bivalve larvae, were found along the length of the Hopkins estuary the abundances varied at different spatial scales suggesting different processes were influencing the distribution of P. Tatura larvae, and C. victoriensis and bivalve larvae. The distribution of larvae between several estuaries was investigated by monitoring meroplankton at two sites at the mouth of each of the four estuaries approximately monthly (except for winter months). Different meroplanktonic assemblages were found to distinguish each estuary. Further, C. victoriensis and P. Tatura larvae were only recorded in the Hopkins but larvae of the spionid, Orthoprionopio cirriformia were detected in the Hopkins, Curdies and Gellibrand estuaries. The extent of larval exchange with other estuaries and the marine environment was determined by monitoring tidal waters. Settlement trays were also deployed to determine if larvae were moving into estuaries and settling but not recruiting. P. tatura larvae were not detected in the tidal waters of any estuary and while C. victoriensis and O. cirriformia were found in both flood and ebb tides there was no evidence of movement of theses taxa to other estuaries. Larvae of the spionids, Carazziella sp. and Polydora sp., were found in tidal waters of each estuary but were rarely detected in the plankton within the estuaries. Neither species was found as an adult in background cores from any estuary, nor with the exception of a few individuals in the Merri, were they detected in settlement trays in any estuary. I conclude that the source of the larvae of C. victoriensis, P. Tatura and O. cirriformia is estuarine and while C. victoriensis, and O. cirriformia move in and outh of the source estuary in tidal waters there was no evidence for movement to other estuaries. The spionids, Carazziella sp. and Polydora sp were considered to be marine and while they moved in and out of estuaries in tidal waters they did not usually settle in the estuaries. The results of this study are a crucial first step in the development of ecological models to better understand dispersal in seasonally closed estuaries that are typical of southern Australia. This study emphasises the unique physicochemical characteristics and biological assemblages within these estuaries and the need for estuarine management to reflect these differences.

The study aimed to gain understanding about diversity, patterns and processes in natural temperate grassland sites in the ACT. Thirty natural grassland sites were surveyed for plant composition, soil invertebrate abundance and site attributes. Floristic associations were identified using multivariate analysis. These were compared to the other site attributes to determine related characteristics. Total plant species richness was 191 species, of which 41% were exotics. Forbs comprised 56% of the total species, with 69 native forb species. There were 10 native grass species and 12 sub-shrubs recorded. The number of species found within ten 1 m2 quadrats measured in each site ranged from 23 to 56 species. Three floristic associations were identified through classification analysis using frequency data. The Danthonia association occurred in well drained sites on soils with high clay content and low nutrient levels and a greater percentage of bare ground. The sites were assessed as having been subject to moderate to high disturbance in the past and 46% were grazed and 46% mown. Species richness of both natives and exotics was high (quadrat richness averaged 37 species, with 32.8% exotic cover in spring). The Wet Themeda association occurred in poorly drained sites and had also been subject to moderate to high disturbance; 67% of sites were grazed and 25% mown. Phosphorus levels were higher in these sites and the acidity of the soil was also greater. Quadrat richness averaged 39 species, with 35.5% exotic cover in spring. The Dry Themeda association was well drained. These sites had a lower native and exotic diversity, with a mean quadrat richness of 30 species, and 11.1% exotic species cover in spring, but a high species richness in the sites (mean 65.4 species) and a high litter cover of 39.9%. All have been subject to low disturbance and none were grazed. Phosphorus levels were low (7.9 ppm). Wet Themeda grassland sites were more similar to Danthonia grassland sites in terms of species occurrence and frequency than Dry Themeda grasslands, despite both associations being dominated by Themeda australis. While trends emerged regarding management and disturbance levels in the three associations, these were not major differentiating attributes. Invertebrates were collected from soil samples from the sites and identified to order level. Twenty two orders were found, but only three orders, Acarina, Collembola and Coleoptera, were sufficiently abundant to enable statistical tests to be undertaken. Invertebrate order richness and abundance showed strong relationships with vegetation attributes that measured or reflected vegetation structure, with higher abundance in sites dominated by T. australis and where wet soil colour was darker. Both order richness and total abundance of invertebrates were highest in mown sites and lowest in grazed sites. The invertebrate order richness and abundance did not have significant relationships with the floristic associations. A field experiment was conducted in which above- and below-ground gaps were created using the herbicide, Glyphosate, to remove interspecific competition and comparing responses between the Dry Themeda and Danthonia associations. Litter load and soil disturbance were also manipulated. The subsequent establishment of species was studied over two growing seasons, a period of 18 months. Both native and exotic forb richness and cover increased as a result of gap formation. Exotic grass cover and richness showed a strong increase in the first season, but after 18 months had decreased to levels similar to those prior to the application of treatments. Native grasses had not recovered to pre-treatment levels after 18 months. Native forb richness and cover were not inhibited by litter retention, but exotic forb richness and cover were higher in treatments with litter removal. Soil disturbance to a depth of 20 mm had no significant effect on the recruitment of the species. Recommendations for protection and management of the sites were developed from the study. Conservation recommendations are based on the aim of maintaining or enhancing native species diversity and habitat, while protecting threatened species and their habitat. Management plans should recognise requirements based on the floristic associations, diversity of native species, drainage conditions and retention of invertebrate habitat, including structural requirements. Grazing should be retained as a viable management regime, particularly in sites where small species occur. Future research should aim towards a greater understanding of the effects of management on species diversity, including invertebrates, and include a monitoring component with which to determine if management actions should be modified.

Marine environmental resource managers and consultants require comprehensive, accurate and current data on the status of marine biodiversity in order to fully evaluate resource consent applications that involve development, impact or encroachment within the marine environment, and for identifying areas of coast appropriate for conservation. The role and efficacy of existing global, national and regional marine biodiversity databases in delivering these types of data are evaluated. Consultation with environmental consultants revealed that none regularly, if ever used any existing marine biodiversity database during their routine consulting activities. Moreover, no existing biodiversity database had appropriate data-mining tools, although each was determined to provide information of value to resource managers and environmental consultants operating at national and regional scales; none was deemed to provide the sort of information required to manage marine resources at a local scale. To achieve the objectives of this research programme, resource managers, data users and data compilers were consulted to determine their ideal data and database requirements. Existing biodiversity data sets that included New Zealand marine biodiversity then were searched or procured, and these data and that of a novel data set of species occurring at 296 intertidal and 25 fringe-saline (effectively freshwater) sites within and proximal to the Hauraki Gulf Marine Park (from Mimiwhangata Bay in the north to Tauranga Harbour in the south) were compared with species inventories from environmental consultants operating in this region. Biodiversity data from the 296 saline, comprising presence/absence data for 713 taxa recorded from the survey region were analysed in detail. Significantly different species assemblages were identified amongst these 296 sites, five intertidal habitats being recognised, each with characteristic species assemblages: marine-hard shores, marine-soft shores, brackish-hard shores, brackish-soft shores, and mangrove shores. Species richness and diversity were consistently higher in marine habitats, and greatest on hard substrata. Most sites host unique assemblages of species. A novel index of species richness is proposed, and although the spatial distribution of richness isn’t particularly revealing, as obvious patterns in the distribution of richness are not apparent, this index has value in that the richness of any shore can be compared and contrasted with that of others throughout the region. Augmenting this richness index is a novel index of species rarity. Based on the frequency of occurrence of taxa on shores throughout the survey region, very rare through to ubiquitous taxa are recognised to routinely occur on almost all shores, regardless of the total species richness. Moreover, very rare to uncommon taxa often comprise a disproportionately high percentage of the total species occurring on any given intertidal shore, in any habitat. Accordingly, alarm bells should ring for reviewers of resource consent applications wherein environmental consultants state that an area subject to development ‘hosts no rare, unique or otherwise remarkable species or ecology.’ Two applications of these novel biodiversity data are demonstrated: the relationship between species richness and regional council consented activities is described, with a negative correlation reported for the intensity of disturbance (using the number of consented activities as a proxy for disturbance) and species richness on marine hard shores; and an appraisal of four selection criteria for marine reserves (naturalness, representativeness, uniqueness and complementarities), wherein the intertidal fauna and flora of no existing or proposed marine reserve appears to be natural, unique or representative, and effort seems to have been spent duplicating certain assemblages of species in reserve networks. The former is intuitively obvious, but the latter is alarming, and the ramifications of it far reaching in terms of conservation of the marine environment. Protocols for conducting biodiversity surveys must be established and implemented to elevate the standards of environmental consultants, resulting value judgements on the composition of species, and the likely and actual effects of these developments on the marine environment to ensure that statements made in reports are based on current data rather than perceptions and client expectations. It is possible that resource consents have been issued based on spurious appraisals of the immediate and cumulative effect of discharge on the environment, or of the relative rarity (or appreciation of this) of species that occur within it. Prior to development of the novel Monalisa data set, no existing database or data set existed that provided the information routinely required by managers and consultants to make informed judgements that affect coastal development throughout the survey region. Recommendations for additional research to build on findings detailed herein are made.

In the marine environment, relatively little is known about how the effects of climatic change will manifest into future patterns of biodiversity and community stability, with the exception of recent work on corals in tropical reef ecosystems. In this thesis, I examine quantitatively how patterns of coral reef biodiversity will respond to the impacts of climatic change and provide essential information (i) to address a critical knowledge gap in the understanding of coral reef biodiversity and (ii) predict how a wide range of sessile invertebrates from coral reef ecosystems will respond to a range of potential impacts of climatic change such as increased physical disturbance and rising sea level. An initial descriptive component of my thesis was required to determine the distribution and abundance of a diverse assemblages of sessile non-scleractinian invertebrates, found along gradients of increasing physical disturbance from wave action and increasing intertidal shore height. I also examined the source, intensity and frequency of disturbance along these environmental gradients. This information was used to derive testable hypotheses about the potential impacts of increasing physical disturbance and rising sea level associated with climatic change. I found that physical disturbance had a substantial influence on the types of species that are able to survive in these intertidal rubble habitats, with diversity decreasing at more exposed shores and further down the shore. Physical disturbance was more important for determining the composition of sessile assemblages than other biotic factors such as predation, which only had weak effects on these sessile assemblages. Increased frequency and intensity of waves and storms will increase rates of physical disturbances such as scraping and overturning of rubble plates, which will have a substantial negative impact on biodiversity in these tropical intertidal habitats. These effects may be more complicated that first thought when combined with the effects of rising sea level which will not only alter the extent of inundation, but may also allow wave energy to propagate further up the shore, which has the potential to modify interactions among species through changes to the supply and recruitment of larvae, predator-prey interactions, competition and survival in harsher environments. However, the magnitude of these impacts may depend on how increased physical disturbance and rising sea level affect established species, and whether they will have a substantial effect on larval mortality rates, which currently appears to be limited by physical disturbance. Declines in biodiversity as a result of climatic change over the next 100 years could have important implications for the future health and productivity of coral reef ecosystems, especially given the ecosystem services these organisms provide. A greater understanding of the processes that drive the distribution and abundance of many different types of organisms on coral reefs, and indeed in other ecosystems, will provide essential information that managers can use to better understand and maintain these important ecosystems for future generations.

Thesis (M.S.)--Baylor University, 2005. / Includes bibliographical references (p. 61-68).

Intermittent headwater streams serve important functions in semi-arid rangelands, both for humans and wildlife. However, few studies have assessed species-environment relationships for fish and benthic macroinvertebrate assemblages in these systems. Additionally, no published studies could be found that addressed the influence of juniper coverage in watersheds on assemblage structure of these taxa. Increased juniper coverage in recent decades is believed to be associated with decreased water yields in central Texas streams. During summer 2003 and spring 2004, I examined potential effects of juniper cover on aquatic ecology. Fishes, benthic macroinvertebrates, and the physicochemical habitat were investigated in spring-fed headwater tributaries of the Pedernales River. My objectives were to: 1) describe the typical fish and benthic macroinvertebrate assemblages in headwater creeks of the Pedernales River basin; 2) compare seasonal variability of fish and benthic macroinvertebrate assemblages; 3) identify species-environment relationships in this river basin; and 4) evaluate the influence of juniper coverage in the watershed, relative tolocal and landscape-level environmental factors, on the structure of fish and benthic macroinvertebrate assemblages. A total of 4,181 individual fish were collected in summer 2003 samples, 551 fish were collected in spring 2004, 59,555 macroinvertebrates were captured in summer 2003 samples, and 51,500 macroinvertebrates were collected in spring 2004. Assemblages were typical for the area and habitat conditions. Faunal richness was lower in spring than in summer, possibly due to a combination of sampling after a relatively dry period in the spring, and lack of winter refugia in the form of deep pools. Fish assemblages may structure based principally on abiotic factors in spring, the harsher season (less available water), whereas predation pressure may influence structure in summer. Another important environmental gradient for both fish and invertebrate assemblages contrasts pool and run mesohabitats. In general, juniper cover was weakly associated with fish and invertebrate assemblages, although it tended to be associated with relatively high quality habitat for sensitive taxa (flowing runs with coarse substrate; deep, connected pools). In these intermittent streams, local-scale environmental factors probably are the dominant influences on fish and benthic macroinvertebrate assemblages. Implications for future studies are discussed.

Gruvbrytnings- och anrikningsverksamheten av komplexa zink-och kopparsulfidmalmer orsakar på flera håll i Västerbottens län vattenföroreningsproblem. För att studera effekterna av utsläppen i recipienten, har undersökningar och utvärderingar gjorts av de fysikalisk-kemiska och biologiska förhållandena i Vormbäcken 1971 - 1975.Vattenmiljön förändras främst genom utsläppen av svavel, kalcium och tungmetaller. Förutom haltförhöjningarna av ett antal enskilda ämnen sker också en försurning som tydligast märks i de nedre delarna av bäcksystemet. pH-sänkfiingen är. störst under sommaren och hösten, då också metallhalterna är som högst. Flera av de fysikalisk-kemiska parametrarna är nära korrelerade. Mest tydligt är det positiva sambandet mellan konduktivitet och sulfat. Men även grumlighet, järn och färg samt i viss mån pH är på olika sätt relaterade till varandra. Detta betyder att ur översiktlig vattenkvalitetsbedömning ett överflöd av information finns i det omfattande materialet av mätdata. Inom ramen för det nuvarande kontrollprogrammet skulle därför ett noggrannare urval av parametrar och provtagningstidpunkter ge en betydligt bättre bild av de fysikalisk-kemiska effekterna.Bottenfaunan i bäckens forsar, som undersökts med en enkel håvmetodik, är kvalitativt förändrad i hela recipienten. De känsligaste evertebratgrupperna är musslor, dagsländor och bäcksländor. Av basresultaten framgår att antalet taxa både totalt och för dag-, bäck- och nattsländor hopslaget har mindre spridning och osäkerhet jämfört med totalindividtal och individtal för enskildataxa. Antalet taxa följer också de förändrade fysikalisk-kemiska förhållandena bättre än ett ofta använt diversitetsindex, Shannonindexet. Antalet bottenfaunataxa är i recipienten lägst under sommaren och hösten.Förändringarna av antalet bottenfaunataxa och Shannonindexen är tydligast relaterade till de ospecifika parametrarna färg, konduktivitet, pH och grumlighet. Det minskade antalet fors-faunataxa hänger också samman med minskningen av primärproduktionen i form av påväxtalger och mossor.Utifrån dessa resultat föreslås vissa förändringar av kontrollprogrammet. Som nödvändigt komplement till detta bör bottenfalanaundersökningar läggas in varje år under senhösten. Detta som indikator på de biologiska förändringar som gruv-utsläppen ger, och som hjälp att utforma reningsåtgärder som ger avsevärt mindre påverkan på Vormbäckens ekosystem. / The raining and milling of complex zinc and copper pyrite ore is the cause of water pollution in some districts of the county of Västerbotten. To determine the effects of the wastewater from the mining process in the stream Vorm-bäcken 1971 - 1975, physical, chemical and biological investigations have been performed and evaluated.The character of the stream is changed principally by the inflow of sulphur, calcium and heavy metals. In addition to higher concentrations of a number of substances an acidification occurs, which is most distinct in the lower reaches of the stream. The pH decrease is greatest during summer and autumn, when the metal concentrations also peak. Several of the physicochemical parameters are closely correlated. Most evident is the correlation between conductivity and sulphate. But turbidity, iron, colour and pH are also related to each other in different ways. This means that for a continuous survey of the physical and chemical conditions there is redundancy of data in this comprehensive material. Within the framework of the present control program, a more careful selection of parameters and sampling times should therefore provide a considerably better overall picture of the physicochemical effects.The bottom fauna in the riffles, sampled by a simple netting technique, are qualitatively changed. The effects are most accentuated on mussels, mayflies and stoneflies. The number of taxa for the total fauna and for the combined orders mayflies, stoneflies and caddisflies is the most reliable parameter compared to the total abundance and the number of specimens of each taxon. The number of taxa also follows the changing physicochemical conditions better than the commonly used diversity index (the Shannon-Weaver index). The number of riffle fauna taxa are lowest in summer and autumn.The changes in number of taxa and diversity indices are best related to colour, conductivity, pH and turbidity. The decrease in number of taxa is also associated with the decrease in primary production, such as perifyton and mosses. Based upon these results, some alterations of the existing physical and chemical control program are proposed. As an indicator of the changed biological conditions, it is suggested that bottom fauna investigations should be performed annually each autumn. / digitalisering@umu