Este trabalho teve como objetivo investigar a hipótese de que a decoada (alteração dos parâmetros físicos e químicos da água) é um fenômeno natural importante na estruturação da comunidade de invertebrados bentônicos do Pantanal do rio Paraguai, bem como a caracterizar a comunidade de macroinvertebrados bentônicos quanto à composição, abundância de organismos e riqueza em função das alterações ambientais provocadas pela decoada. Além disso, pretendeu-se contribuir para o conhecimento da biota do pantanal de Mato Grosso do Sul com o intuito de subsidiar ações de prevenção e/ou mitigação de possíveis impactos ambientais. Os ambientes escolhidos foram dois corpos de água adjacentes ao rio Paraguai, sendo um com características lênticas (Baía Tuiuiú) e outro, semi-lóticas (Bracinho), Corumbá/MS, ambos sob o efeito do pulso de inundação. O capítulo um realizou uma caracterização limnológica dos dois corpos de água ao longo de um ciclo hidrológico, enfatizando as alterações provocadas pela decoada, por ocasião da subida das águas. O capítulo 2 objetivou estudar a composição e a distribuição da fauna de Chironomidae relacionando-as com as alterações limnológicas ao longo de um ciclo hidrológico (abril/2008 a fevereiro/2009), enfatizando a influência da decoada. O capítulo 3 pretendeu conhecer a composição de Oligochaeta, considerando as relações com fatores abióticos, no intuito de contribuir para o entendimento do fenômeno da decoada bem como subsidiar posteriores trabalhos e ações relacionados à gestão da planície pantaneira, objetivando sua manutenção e conservação. A decoada é um evento que potencializa a desestruturação do ambiente, agindo significativamente sobre as populações de invertebrados bentônicos. O fato de não ter sido encontrado nenhum organismo vivo durante a ocorrência do fenômeno destaca a sua importância enquanto fator ecológico essencial na dinâmica das populações biológicas dos ecossistemas pantaneiros. / This study aimed to investigate the hypothesis that the decoada(change in physical and chemical parameters of water) is an important natural phenomenon in the community structure of benthic invertebrates in the Pantanal of the Paraguay River, and to characterize the benthic macroinvertebrate community regarding the composition, richness and abundance of organisms as a function of environmental changes caused by the \'decoada\'. In addition, soughted to contribute to the knowledge of the biota of wetland of Mato Grosso do Sul in order to support programs to prevent and / or mitigate potential environmental impacts. The areas chosen were two bodies of water adjacent to the Paraguay River, one with lentic feature (Tuiuiú Bay) and another, semi-lotic (\'Bracinho\'), Corumbá / MS, both of them suffering the effect of pulse flood. The chapter 1 conducted a limnological characterization of the two water bodies along a hydrological cycle, emphasizing the changes caused by the \'decoada\', when the water level rises. Chapter 2 aimed to study the composition and distribution of Chironomidae fauna relating them to limnologicals changes over a hydrological cycle (the april/2008 to february/2009), emphasizing the influence of the decoada. Chapter 3 intended know the composition of Oligochaeta, considering the relationships with environmental factors in order to contribute to the understanding of the phenomenon of \'decoada\' and support further work and actions related to the management of the Pantanal, aiming to maintain the ecosystem and related services. The decoada is an event that enhances the disintegration of the environment, acting significantly on populations of benthic invertebrates. The fact that no organism had been found alive during the occurrence of the phenomenon underscores its importance as an essential ecological factor in the dynamics of biological populations of wetland ecosystems.

O método de Caracterização Fisionômica de Comunidades Marinhas Bentônicas propõe o uso da unidade operacional chamada Povoamento aliada à amostragem fotográfica. Dentre as 4 abordagens do método, o objetivo do Capítulo 2 foi testar a precisão da abordagem quantitativa quando submetida a: a) diferentes pesquisadores e b) diferentes análises realizadas pelo mesmo pesquisador. A análise de correspondência (CA), baseada no recobrimento percentual obtido em cada situação, não mostrou diferenças significativas entre os valores encontrados para os Eixos I, II, III e IV (correspondentes a 42.8% da variabilidade dos dados) quando comparados por ANOVA (p= 0.963; 0,975; 0.867; 0.894, respectivamente). Os resultados apresentados no Capítulo 2 indicam que a etapa quantitativa do Método de Caracterização Fisionômica de Comunidades Marinhas Bentônicas é pouco subjetiva. No Capítulo 3, as posições geográficas de cada povoamento foram registradas com um GPS durante duas coletas (julho/2005 e janeiro/2006). Essas posições foram inseridas na base de mapas do Google Earth com auxílio do programa GPS Track Maker. Foram registrados 41 povoamentos, sendo a maior fração (36,6%) representada por povoamentos que possuem organismos do Filo Rhodophyta como espécies dominantes. Em seguida, cada um dos Filos Chlorophyta e Ochrophyta representou 17,1% dos povoamentos. Os povoamentos cujas espécies dominantes pertencem ao grupo dos animais compuseram 29,3%; com o Filo Cnidaria apresentando a maior fração de povoamentos (12,2%) e Porifera a menor (2,4%). A posição de todos os povoamentos é apresentada em um mapa integral das comunidades marinhas bentônicas de substrato consolidado da região entre-marés da Ilha do Francês, Espírito Santo. O Capítulo 4 teve como propósito descrever quantitativamente as comunidades marinhas bentônicas do médio-litoral da Ilha do Francês. A partir de observações realizadas durante o Capítulo 3, foram selecionadas três áreas que mostraram as principais variações não biológicas (exposição aos ventos predominantes, exposição ao batimento de ondas, inclinação e a orientação). Uma coleta preliminar (julho de 2005) revelou que as comunidades do médio-litoral da Ilha do Francês podem ser divididas em duas grandes faixas. Em uma das faixas, o povoamento dominante foi Banco de Chthamalus (78,6%) enquanto na outra os povoamentos dominantes foram Tapete de Amphiroa e Jania (32,8%), Banco de Dictyota (16,5%) e Banco de Perna (16,7%). Nas coletas seguintes (Janeiro e Julho de 2006) a estratégia de distribuição dos elementos amostrais foi aleatória estratificada. Na faixa de algas, tanto no verão quanto no inverno, Tapete de Jania e Amphiroa foi o povoamento que apresentou os maiores recobrimentos percentuais médios na Área 1 (39% e 66,2%, respectivamente). Na Área 2 os povoamentos Banco de Dictyota (27,8%) e Tapete de Centroceras e Ceramium (28,7%) obtiveram os maiores recobrimentos médios durante o verão, enquanto no inverno o maior valor obtido foi o de Tapete de Amphiroa e Jania (55%). Na Área 4 Banco de Perna apresentou maior recobrimento médio durante o verão (43,2%) e Banco de Dictyota na coleta de inverno (29,4%). Na faixa de cracas Banco de Chthamalus apresentou maior recobrimento percentual médio em todas as áreas e épocas amostradas. Nas Áreas 1 e 2 a média do recobrimento desse povoamento apresentou maiores valores durante o inverno (87,9% e 64,6% respectivamente), enquanto na Área 4 no verão (80,7%). Espera-se que os Capítulos 3 e 4 juntos possam subsidiar acompanhamentos das condições das comunidades da Ilha do Francês, estudos de outros aspectos dessas comunidades e também o trabalho de órgãos ambientais. O Capítulo 5 tem como foco avaliar a precisão relativa de três variações (20, 50 e 100 pontos) das técnicas de pontos aleatórios aplicada à análise de imagens para comunidades marinhas bentônicas. Diferenças estatísticas entre valores de porcentagem de cobertura das diferentes técnicas foram verificadas por análise de correspondência (CA) e os valores obtidos para os dois eixos de maior variabilidade, foram testados por ANOVA. Os testes estatísticos não demonstraram diferenças quantitativa e qualitativa comparando 50 e 100 pontos aleatórios à Segmentação Manual. É possível concluir aqui que 50 ou mais pontos para análise de comunidades marinhas bentônicas fornecem dados qualitativos e quantitativos precisos. Este trabalho, além de demonstrar que o uso dos povoamentos é preciso, descreve as comunidades do médio-litoral da Ilha do Francês qualitativamente e quantitativamente. Essa descrição poderá, a partir de agora, constituir o ponto de partida para o monitoramento e o gerenciamento desse ambiente frente ao crescimento econômico esperado nos próximos anos para a região. O mapeamento dessas comunidades pode, ainda, subsidiar outros aspectos de pesquisa como, por exemplo, os experimentais. Entretanto, é fundamental ainda o estudo do infralitoral do local. A inclusão desses dados complementará e poderá alterar as conclusões que obtivemos neste trabalho acerca da diversidade e dos grupos dominantes, permitindo uma visão global das comunidades bentônicas da Ilha do Francês. / The method Physiognomic Assessment of Hard Bottom Marine Benthic Communities proposes the use of operational units called settlements, allied to photographic sampling. Among the 4 approaches of this method, the Chapter 2 aimed to test the precision of the quantitative one when submitted to: a) different researchers and b) different time analysis carried out by the same researcher. The correspondence analysis (CA) based on the percent cover showed no significant differences between values found for the Axes I, II, III and IV (corresponding to 42.8 % of data variability) when compared by ANOVA (p = 0.963; 0,975; 0.867; 0.894, respectively). The results presented on Chapter 2 indicate that the quantitative approach of the Physiognomic Assessment Method of Hard Bottom Marine Benthic Communities, is little researcherdependent. On Chapter 3 the geographic position of each settlement was taken with the use of a GPS during two samples (july/2005 and january/2006). These positions were inserted into Google Earth databases with the GPS Track Maker software (version 13.2). Forty one settlements were observed. The largest fraction (36,6%) was represented by Rhodophyta; followed by Chlorophyta and Ochrophyta; The last two represented 17.1% of the total. The settlements dominated by animals represented 29,3% where Cnidaria was the most common group (12,2%) and Porifera the most uncommon one (2,4%). The location of each settlement is presented on a map of the whole hard bottom marine communities located in the intertidal zone of the Francês Island, Espírito Santo state. The Chapter 4 described the hard bottom marine communities from the tidal zone of Francês Island. Using the data mapping presented in Chapter 3, three areas that showed the main non biological variations (predominant winds exposition, waves exposition, slope and orientation) were selected. The preliminary sample (July of 2005) showed that the hard bottom communities from Francês Island can be divided in two great zones. In one zone the dominant settlement is Chthamalus Bed (78.6%) while in the other one the dominants are Amphiroa and Jania Turf (32.8%), Dictyota Bed (16.5%) and Perna Bed (16.7%). For the following samples (2006 January and July) the stratified random sample strategy was chosen. On the seaweed zone, for the area 1, both during summer and winter the Jania and Amphiroa Bed was the settlement with the highest average percent cover (39% and 66.2%, respectively). On area 2, Dictyota Bed (27.8%) and Centroceras and Ceramium Turf (28.7%) showed the highest percent cover during summer while Amphiroa and Jania were predominant (55%) on winter. On area 4 Perna Bed showed a high percentage of coverage during the summer sample (43.2%) and Dictyota Bed during the winter one (29.4%). In barnacles zone Chthamalus Bed was the dominant in all areas and seasons sampled. On areas 1 and 2 this settlement showed the highest values on as 1 during winter (87.9% and 64.6% respectively), while in Area 4 it happened during summer (80.7%). It is expected that Chapters 3 and 4 can subsidize communities monitoring, studies of other aspects of the Frances Island and also the work of environmental managers. The Chapter 5 aims to evaluate the relative precision of three variations (20, 50 and 100 points) of random points technique applied to analyze images for benthic marine communities. Statistical differences between the values of the percentage of coverage of the different techniques, were performed by correspondence analysis (CA), and the values obtained for the two major axes of variability were tested by ANOVA. Statistical tests did not present quantitative and qualitative differences comparing 50 and 100 random points to Manual Segmentation. It is possible to conclude here that the 50 or more points to analyze images of marine benthic communities supply precise qualitative and quantitative data in the case of the studied community. This work, beyond demonstrating the precision of the use of settlements, describes qualitatively and quantitatively the inter-tidal communities from Francês Island. The communities description presented here could constitute a guideline to monitoring possible alterations that can be caused by the economic development of the region. The map presented is an important tool for the Francês Islands management actions, as well as other researches concerning these communities. However, it is still fundamental a study about subtidal communities. The inclusion of these data will complement and could even modify the conclusions that we got here concerning the diversity and the dominant groups, allowing a global vision of the Francês Island benthic communities.

Understanding of the fundamental ecology of deep-sea ecosystems remains immature relative to more familiar shallow-water and terrestrial habitats, despite more than two hundred years of scientific investigation. This thesis aims to progress knowledge of deep-sea benthic ecology by the analysis of over three hundred box core samples collected from the Northwest Atlantic continental slope as part of the international NEREIDA programme. Aspects of the ecology of Peracarida (Crustacea) are studied, and this is facilitated by the coupling of a large faunal dataset with extensive environmental information. To further enhance the power of this dataset, phylogenetic and functional characteristics of assemblages are investigated. Using community phylogenetic methodology, it is demonstrated that the peracarid assemblages studied are structured more strongly by variation in environmental parameters than they are by competitive interactions. Analyses demonstrate that the intensity of bottom trawling, seafloor temperature, current speed, food availability, sediment characteristics and physical habitat heterogeneity all influence deep-sea peracarid assemblage biodiversity metrics. Further, the importance of high poriferan biomass for the promotion of peracarid assemblages of high density, biomass, richness and diversity is highlighted. Of relevance to the management of deep-sea ecosystems, the results of this thesis suggest that caution should be exercised when applying species distribution models to data-deficient environments, whilst the location of spatial closures in the NAFO Regulatory Area may not be fully optimal for the protection of all components of diverse benthic assemblages against the impacts of bottom trawling. The importance of deep-sea diversity is demonstrated by the finding of positive biodiversity – ecosystem functioning relationships. However, the form of these relationships is found to be dependent on the biodiversity and ecosystem functioning metrics employed, and a hypothesis for a generalised form of biodiversity – ecosystem functioning relationships is proposed. Finally, this thesis calls for more ambitious deep-sea ecological investigations, and it is hoped that its findings will encourage future research initiatives, helping to further illuminate this enigmatic and fascinating environment.

Com o intuito de conhecer o histórico da comunidade bentônica no reservatório do Guarapiranga para futuro estudo sobre a influência das diferentes formas de poluição na represa sobre o zoobentos, este trabalho foi desenvolvido a fim de coletar dados históricos da fauna de fundo e se houve variação na estrutura da comunidade ou não. Foram analisados quatro trabalhos realizados no período de inverno em quatro regiões médio-profundal do reservatório (Guarapiranga, Embu-Mirim, Embu-Guaçu e Parelheiros) ao longo dos anos, 1939, 1976, 1996 e 2010. A riqueza de dados presentada nos trabalhos refletiu a evolução do conhecimento em estudos limnológicos no Brasil e no mundo. A densidade de Oligochaeta apresentou aumento ao longo dos anos, assim como a de Chaoboridae. Por outro lado, Chironomidae que apresentava 30% em 1974 é pouco representativo em 2010. O ambiente mostrou forte e crescente enriquecimento orgânico em todos os pontos ao longo dos anos e isso colaborou para uma maior diversidade de grupos detritívoros (Tubificinae e Naidinae - Oligochaeta), por exemplo. Os níveis de oxigênio dissolvido no fundo diminuíram ao longo dos anos em todos as regiões. Chama-se a atenção para a necessidade de biomonitoramento nas 4 regiões da represa, utilizando inclusive os macroinvertebrados bentônicos e análises físicas e químicas do sedimento e a adoção de uma nova forma de gerenciamento deste manancial / With the purpose to know the history of the benthic community in Guarapiranga reservoir for future study about the influence of different sources of pollution in the reservoir over zoobenthos, this study was conducted to collect historical data of benthic fauna and variation in community structure. Four studies conducted during winter in four regions of the reservoir medium-profundal (Guarapiranga, Embu-Mirim, Embu-Guaçu and Parelheiros) over the years, 1939, 1976, 1996 and 2010 were analysed. The best richness of data presented in the works reflected the evolution of knowledge in limnological studies, in Brazil and worldwide. The density of Oligochaeta had an increase over the years as well as the Chaoboridae. On the other hand, Chironomidae presented 30% in the 70\' community and was not representative anymore in 2010. The environment showed strong organic enrichment for all regions along the years, and this has contributed to a greater diversity of detritivorous groups (Tubificinae and Naidinae - Oligochaeta), for example. The dissolved oxygen levels at the bottom declined over the years in all regions. Attention is called to the necessity of biomonitoring in 4 regions of the reservoir, using benthic macroinvertebrates and physical and chemical sediment analyses and the adoption of a new way of managing this system

Thesis (M. Sc. (Zoology)) -- University of the North, 1994 / Refer to the document

Catchment geology is known to influence water chemistry, which can significantly affect both species composition and ecosystem processes in streams. However, current predictions of how stream water chemistry varies with geology are limited in both scope and precision, and we have not adequately tested the specific mechanisms by which water chemistry influences stream biota. My dissertation research goals were to (1) develop empirical models to predict natural base-flow water chemistry from catchment geology and other environmental factors, (2) extend these predictions to nutrients to establish more realistic criteria for evaluating water quality, and (3) test the hypothesis that catchment geology significantly influences the composition of stream invertebrate assemblages by restricting weak osmoregulators from streams with low total dissolved solids (TDS). To meet goal 1, I first mapped geologic chemical and physical influences by associating rock properties with geologic map units. I then used these maps and other environmental factors as predictors of electrical conductivity (EC, a measure of TDS), acid neutralization capacity, and calcium, magnesium, and sulfate concentrations. The models explained 58 – 92% of the variance in these five constituents. Rock chemistry was the best predictor of stream water chemistry, followed by temperature, precipitation and other factors. To meet goal 2, I developed empirical models predicting naturally occurring stream total nitrogen and total phosphorus concentrations. These models explained most of the spatial variation among sites in total nitrogen and phosphorus and produced better predictions than previous models. By determining upper prediction limits that incorporated model error, I demonstrated how predictions of nutrient concentrations could be used to set site-specific nutrient criteria and accounted for natural variation among sites better than regional criteria. To meet goal 3, I experimentally manipulated (high and low) EC in both stream-side and laboratory flowthrough microcosms and measured survival, growth, and emergence of 19 invertebrate taxa. Observed variation among taxa in survival between treatments predicted taxon EC optima estimated from field observations (r² = 0.60). Taxa with the greatest differences in survival between treatments also had the highest EC optima, indicating that the inability to persist in low EC likely restricts the distributions of some taxa.

Maintaining optimum levels of dissolved oxygen (DO) in natural water systems has become crucial for scientists and decision makers. In general, DO concentrations less than 5 mg/L stress many types of aquatic organisms including fishes. Uncontrolled growth of aquatic autotrophs (i.e., algae and macrophytes) may alter DO concentration if the growth exceeded the capacity of the aquatic food web structure. Primary production and respiration, the two main metabolic processes associated with aquatic autotrophs, were estimated, compared, and critiqued for three streams in Northern Utah, USA. These streams have been under consideration for many years due to their impaired water quality, as they supply water to Cutler Reservoir, the sink of all the transported sediment and nutrients. This study includes estimation of the metabolic rates, examination of the driving/limiting factors, examination of the consequences of the relevant rates on water quality, and a comparison of two methods of estimation of the metabolic rates. The outcome of this research will help scientists and decision makers build knowledgeable strategies to manage DO in the streams based on the given critiques on the cause and effect of the respective metabolic rates. It will also help reduce the cost and time associated with the frequent need to use physical field measurements to estimate metabolic rates in rivers and streams.

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.

Marine ecosystems are increasingly being subject to human impact from diverse recreational and commercial activities, not necessarily restricted to those of a marine nature. This has significant implications for biodiversity. The large dog cockle, Tucetona laticostata, once occurred live in Rangitoto Channel, Hauraki Gulf, although this species no longer appears to occur there, most likely as a consequence of repeated dredging and channel excavation and continued siltation. Tucetona laticostata still occurs in a few isolated pockets of sea bed throughout Hauraki Gulf, particularly off Otata Island, part of the Noises complex of islands, where it resides partially buried in shell and rock gravels in shallow water (to 15 metres depth). The shells of T. laticostata collect in large post-mortem deposits in an area ramping from the sea bed off southwestern Otata Island. These mounds differ significantly in structural complexity from those of adjacent, extensively fragmented shell and rock gravels. Using the mounds of T. laticostata shell as a proxy for structural complexity, in order to appraise the effect of complexity on benthic-invertebrate diversity, the sea bed off southwestern Otata Island was sampled quarterly at two depths and in both T. laticostata shell mounds and adjacent extensively fragmented shell and rock gravels. These data were complemented with those from additional surveys around Otata Island, and off eastern Motutapu Island to determine the distribution and composition of benthic-invertebrate community assemblages throughout the region, and from concurrent surveys throughout the Waitemata Harbour and inner Hauraki Gulf to determine the current distribution of T. laticostata in this region. The number of benthic invertebrate species and individuals within T. laticostata habitat almost always was higher than that occurring within extensively fragmented shell- and rock gravel habitat, with densities to 142,385 individuals m-2 encountered. Temporal and spatial variations in benthic community structure also are reported for the two habitats, T. laticostata-based shells and extensively fragmented shell- and rock gravels. The numbers of species were higher amongst samples collected off the southwestern and eastern sides of Otata Island than elsewhere around this island, or of eastern Motutapu Island. Of the 351 species reported from all Otata and Motutapu Island samples combined, 73% of them occurred off southwestern Otata Island, 30% of which were found exclusively within T. laticostata shell habitat, and 10.5% within extensively fragmented shell and rock gravel habitat. The sea bed off southwestern Otata Island is regularly, seasonally dredged by recreational scallop fishers, in addition to being a popular small-vessel anchorage site. Both of these activities, dredging and anchorage, stand to reduce substratum complexity by fragmentation and dispersal of the valves of T. laticostata. Given the unique benthic invertebrates reported from T. laticostata shell deposits reported from southwestern Otata Island, any activity that damages the shells of this species, regardless of whether they are live or dead, is likely to result in loss of biodiversity. Admittedly, many of species identified as major contributors to differences in benthic invertebrate assemblages between T. laticostata shell-based habitats and those of extensively fragmented shell and rock gravels are not particularly charismatic or large, but each likely plays a role in local food webs and/or sediment and water column chemistry. It was not the intention of this research to determine the effects of anthropogenic disturbances like dredging or vessel anchorage on benthic-invertebrate communities off southwestern Otata Island. However, given the reported differences in species diversity within the structurally complex substratum provided by T. laticostata, conservation of biogenic reef-forming species like it might be a prudent, precautionary measure to take.

Thredbo Village is a year round alpine resort located in Kosciusko National Park, south eastern New South Wales. Treated sewage effluent from Thredbo Village is discharged to the upper Thredbo River. The river is a rocky bottomed, high mountain stream (> 1,200 m altitude in the study area) flowing predominantly through subalpine woodland, the only major impact on the river within the study area was that of the Thredbo Village alpine ski resort. Nutrient concentrations were measured in the upper Thredbo River monthly from January to September 1983 at 9 sites along the river, both upstream and downstream of the effluent discharge. In addition, invertebrates were collected at the same sites in January, April and July 1983. The near pristine section of the upper Thredbo River upstream of Thredbo Village was low in phosphorus and nitrogen (<20 mg m-3 and <100 mg m-3 respectively). The sewage effluent discharge was high in phosphorus and nitrogen (up to 5,000 mg m-3 and 28,000 mg m-3 respectively). Phosphorus generally returned to concentrations similar to those measured in the pristine sections by 3.5 kilometres downstream of the discharge. Nitrogen (mostly in the form of nitrate and nitrite) often remained elevated down to the most downstream site, 8 kilometres downstream of the effluent discharge. The elevated nutrient concentrations immediately downstream of the effluent discharge stimulated the growth of attached filamentous algae in January when conditions for growth were most favourable. It is concluded that this growth provided an additional food source for several invertebrate taxa, Cricolopus sp. 12E and 160E (Diptera, Chironomidae), Conoesucidae sp. TR6, Oxyethira columba (Trichoptera), Nais sp., Aeolosomatus niveum (Oligochaeta), and Austrocercella tillyardi (Plecoptera), which occurred in higher numbers downstream of the effluent discharge. Downstream of the effluent discharge the taxonomic composition of the invertebrate community was not altered substantially from that upstream, although there was a significant increase in the abundance of the taxa which could take advantage of the increased food resource. The changes in the invertebrate community were not evident 3.5 kilometres downstream of the effluent discharge, which corresponded to the return of phosphorus concentrations to background levels. There were increased abundances of several invertebrate taxa downstream of both Thredbo Village and the rubbish tip in January which were consistent with, but not as great as, those downstream of the sewage effluent discharge. This was likely to be a result of increased nutrient loads from urban runoff and tip leachate at these sites which possibly lead to increased algal productivity. However, nutrient concentrations at these sites were not notably higher than at the control site. The sewage effluent discharge resulted in only small changes to the invertebrate community in April or July 1983.