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.

Past monitoring has noted benthic macroinvertebrate community impairment downstream of both the Key Lake and Rabbit Lake uranium operations in northern Saskatchewan, Canada. The objective of this research was to try to identify the cause(s) of these impacts using a weight-of-evidence approach. Given that sediments generally accumulate contaminants that are related to metal mining activities (such as metals and radionuclides), the initial hypothesis for this research was that contaminated sediments were the primary cause of benthic community impairment at both operations.<p>In 2003 and 2004 a Sediment Quality Triad (SQT) approach confirmed the presence of an effect on benthic community structure, in addition to significant differences in surface-water, pore-water and whole-sediment chemistry at the immediate down-stream exposure sites at both uranium operations. However, no significant adverse effects were noted in 10-d whole-sediment bioassays with <i>Hyalella azteca</i>, although this lack of response could be partially due to sediment pore-water dilution resulting from the automated clean overlying water renewal process employed. Potential causes of benthic community impairment identified through the 2003 and 2004 SQTs for Key Lake include physical sediment composition, surface water pH and total ammonia, in addition to pore-water total ammonia and arsenic. Potential stressors identified at Rabbit Lake included high surface water manganese and uranium concentrations, and increases in pore-water total ammonia, manganese, iron, arsenic, and uranium levels.<p>In the summer of 2004, 4-d in-situ bioassays using <i>H. azteca</i> were conducted along with the SQTs to investigate the role both contaminated surface water and sediment played in benthic community impairment in-situ. Results from the Key Lake in-situ bioassay demonstrated that surface-water was the primary cause of acute toxicity to <i>H. azteca</i>. Results from the Rabbit Lake in-situ study also demonstrated that surface water as the primary cause of acute toxicity to <i>H. azteca</i>, although the relationship was not as strong. The cause of in-situ toxicity at Key Lake could not be correlated with any of the variables measured within the in-situ study, including trace metals, total ammonia, and pH. Of the measured constituents at Rabbit Lake, only concentrations of uranium in both surface water and pore-water were suspected of causing the observed in-situ mortality. Two data sets from two methods of surface water and pore-water collection supported these conclusions.<p>Due to time constraints and stronger cause-effect relationships, efforts were focused on the in-situ toxicity observed at Key Lake. Surface water collected in 2004 at the time of the related in-situ study was also found to be acutely toxic to <i>H. azteca</i> in separate laboratory surface water bioassays, thus verifying that contaminated surface water, not sediment, was the primary cause of the observed in-situ <i>H. azteca</i> mortality. Further information revealed that organic mill-process chemicals, which have been previously linked with sporadic effluent toxicity, were released at the Key Lake operation during the time of the in-situ experiment and associated surface water collection. Additional surface water samples collected in June and August, 2005, were not acutely toxic to <i>H. azteca</i>. Furthermore, a second bioassay with archived surface waters from the initial 2004 collection demonstrated that the water was no longer acutely toxic (i.e., acute toxicity disappeared after one-year storage). Chemistry comparisons of the toxic and non-toxic surface water samples, verified that trace metals, ammonia, pH, and major ions, including sulphate, were not the cause of toxicity, leaving only organic mill-process chemicals as a possible cause. Subsequent 4-d laboratory toxicity tests demonstrated that these process chemicals (kerosene, amine, and isodecanol) are toxic to H. azteca at the levels released in 2004, and are therefore believed to be the cause of the <i>H. azteca</i> mortality seen in the earlier in-situ experiment.<p>In short, this weight-of-evidence research provided new information on the possible causes of benthic macroinvertebrate community impairment downstream of both the Key Lake and Rabbit Lake uranium operations.

Past monitoring has noted benthic macroinvertebrate community impairment downstream of both the Key Lake and Rabbit Lake uranium operations in northern Saskatchewan, Canada. The objective of this research was to try to identify the cause(s) of these impacts using a weight-of-evidence approach. Given that sediments generally accumulate contaminants that are related to metal mining activities (such as metals and radionuclides), the initial hypothesis for this research was that contaminated sediments were the primary cause of benthic community impairment at both operations.<p>In 2003 and 2004 a Sediment Quality Triad (SQT) approach confirmed the presence of an effect on benthic community structure, in addition to significant differences in surface-water, pore-water and whole-sediment chemistry at the immediate down-stream exposure sites at both uranium operations. However, no significant adverse effects were noted in 10-d whole-sediment bioassays with <i>Hyalella azteca</i>, although this lack of response could be partially due to sediment pore-water dilution resulting from the automated clean overlying water renewal process employed. Potential causes of benthic community impairment identified through the 2003 and 2004 SQTs for Key Lake include physical sediment composition, surface water pH and total ammonia, in addition to pore-water total ammonia and arsenic. Potential stressors identified at Rabbit Lake included high surface water manganese and uranium concentrations, and increases in pore-water total ammonia, manganese, iron, arsenic, and uranium levels.<p>In the summer of 2004, 4-d in-situ bioassays using <i>H. azteca</i> were conducted along with the SQTs to investigate the role both contaminated surface water and sediment played in benthic community impairment in-situ. Results from the Key Lake in-situ bioassay demonstrated that surface-water was the primary cause of acute toxicity to <i>H. azteca</i>. Results from the Rabbit Lake in-situ study also demonstrated that surface water as the primary cause of acute toxicity to <i>H. azteca</i>, although the relationship was not as strong. The cause of in-situ toxicity at Key Lake could not be correlated with any of the variables measured within the in-situ study, including trace metals, total ammonia, and pH. Of the measured constituents at Rabbit Lake, only concentrations of uranium in both surface water and pore-water were suspected of causing the observed in-situ mortality. Two data sets from two methods of surface water and pore-water collection supported these conclusions.<p>Due to time constraints and stronger cause-effect relationships, efforts were focused on the in-situ toxicity observed at Key Lake. Surface water collected in 2004 at the time of the related in-situ study was also found to be acutely toxic to <i>H. azteca</i> in separate laboratory surface water bioassays, thus verifying that contaminated surface water, not sediment, was the primary cause of the observed in-situ <i>H. azteca</i> mortality. Further information revealed that organic mill-process chemicals, which have been previously linked with sporadic effluent toxicity, were released at the Key Lake operation during the time of the in-situ experiment and associated surface water collection. Additional surface water samples collected in June and August, 2005, were not acutely toxic to <i>H. azteca</i>. Furthermore, a second bioassay with archived surface waters from the initial 2004 collection demonstrated that the water was no longer acutely toxic (i.e., acute toxicity disappeared after one-year storage). Chemistry comparisons of the toxic and non-toxic surface water samples, verified that trace metals, ammonia, pH, and major ions, including sulphate, were not the cause of toxicity, leaving only organic mill-process chemicals as a possible cause. Subsequent 4-d laboratory toxicity tests demonstrated that these process chemicals (kerosene, amine, and isodecanol) are toxic to H. azteca at the levels released in 2004, and are therefore believed to be the cause of the <i>H. azteca</i> mortality seen in the earlier in-situ experiment.<p>In short, this weight-of-evidence research provided new information on the possible causes of benthic macroinvertebrate community impairment downstream of both the Key Lake and Rabbit Lake uranium operations.

Submitted by Mendes Eduardo (dasilva@ufba.br) on 2013-07-17T23:43:33Z No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Approved for entry into archive by Vilma Conceição(vilmagc@ufba.br) on 2013-07-19T18:58:18Z (GMT) No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Made available in DSpace on 2013-07-19T18:58:19Z (GMT). No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Capes, Fapesb / A relação entre diversidade, complexidade e estabilidade com função do ecossistema tem sido uma importante questão na história da ecologia (Bengtsson, 1998). Tilman (1999) destaca que inicialmente o interesse desta relação residia nos efeitos da diversidade e complexidade trófica sobre a estabilidade dos ecossistemas e comunidades, contudo, este interesse enfraqueceu-se e apenas no início da década de 1990 começou a reaparecer, com interesses principalmente na relação da biodiversidade com os processos e serviços ecossistêmicos. Desde então, nesses últimos vinte anos, este programa de pesquisa tem crescido e recebendo destaque na literatura de ecologia (ver revisões de Giller et al., 2004; Reiss et al., 2009; Sandini e Solomini, 2009). Em uma abordagem de ciênciometria realizada por Caliman et al. (2010), os autores verificaram que os artigos publicados sobre o tema foi a uma baixa freqüência em relação a literatura ecológica no início da década de 90, aumentando bastante a partir de 1997, e conquistando uma significante freqüência ao longo dos quatro últimos anos analisados, de 2003 a 2007. Alguns estudos analisando esta questão têm utilizado a decomposição foliar como processo funcional de estudo (Briones e Ineson, 1996; Salamanca et al., 1998), principalmente na última década (Lecerf et al., 2007; ; Ball et al., 2008; Chapman e Newman, 2010; Barantal et al., 2011). Porém em menor quantidade nos ecossistemas aquáticos (Swan e Palmer, 2004; Kominoski et al., 2007; Moretti et al., 2007a; Abelho, 2009; Kominoski et al., 2009; Hoorens et al., 2010). Em ecossistemas lóticos, a vegetação circundante (ripária) constitui uma zona de transição entre o rio e os terrenos adjacentes mais acima (Mishall e Rugensk 2006). Esta vegetação ripária está intimamente relacionada à cadeia alimentar do rio, através do fornecimento de detritos foliares originária do folhiço como principal suprimento de energia (Benfield, 2006; Abelho, 2009). Os estudos iniciais de decomposição foliar se focavam em folhas de espécies individuais e a comparação entre elas, visando estabelecer os fatores principais que influenciam neste processo (Webster e Benfield, 1986; Abelho, 2001; Gartner e Cardon, 2004). A composição química do detrito foliar em decomposição é um importante fator para determinar a taxa de decomposição em muitos sistemas 2 (Hoorens et al., 2010; Bonanomi et al., 2010). E, juntamente com os fatores físicos e químicos, podem interferir nos mecanismos da biota que atua na decomposição (Webster e Benfield, 1986; Suberkropp e Chauvet, 1995; Jonsson e Wardle, 2008). Posteriormente, dado a existência de grande quantidade de espécies nas formações vegetais, e ao fato de o processo de decomposição de seus detritos ocorrerem em conjunto, misturadas uns com os outros, a indagação passou a ser se elas podem se influenciar, (Gartner e Cardon, 2004; Abelho, 2009). Nesta perspectiva, muitos estudos verificaram o efeito da riqueza de espécies em uma mistura na decomposição da mistura como um todo (Swan e Palmer, 2004; Sanpera-Calbet et al., 2009; Bonanomi et al., 2010), e outros verificaram a partir da comparação da decomposição observada da mistura, e o esperado em relação á decomposição individual de cada componente da mistura (Gartner e Cardon, 2004; Ball et al., 2008; Abelho, 2009). Nestes, é verificado ausência de efeito quando o esperado e o observado da variável de resposta não diferem significativamente, e um efeito quando diferem, significando que ocorreu algum tipo de interferência de um ou mais componentes da mistura sobre outros (Lecerf et al., 2007). Contudo, os resultados com experimentos de misturas têm sido diversos, mostrando efeitos positivos (aumento da decomposição), negativos (redução da decomposição) ou sem efeitos (Swan e Palmer, 2004; Moretti et al., 2007a; Abelho, 2009; Hoorens et al., 2010). Também são diversos quanto ao efeito da mistura na comunidade colonizadora e vice-versa, podendo ocorrer estimulo da colonização ou ausência de efeito (Leroy e Marks, 2006; Kominoski et al., 2007; Kominoski et al., 2009; Chapman e Newman, 2010). Além disso, poucos estudos têm verificado os mecanismos pelos quais os efeitos ocorrem, ou seja, quais componentes foliares da mistura estão sofrendo o efeito (Salamanca et al. 1998; Moretti et al. 2007a, Sanpera-Calbet et al., 2009; Hoorens et al., 2010). Portanto, os mecanismos pelo quais como a composição de espécies de uma mistura afeta as taxas de decomposição em misturas ainda é uma questão em aberto, (Hoorens et al., 2010) e necessitando de esforços e estudos para uma melhor compreensão do processo. / Salvador

Submitted by Mendes Eduardo (dasilva@ufba.br) on 2013-08-02T20:12:44Z No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Approved for entry into archive by Vilma Conceição (vilmagc@ufba.br) on 2014-02-06T13:34:10Z (GMT) No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Made available in DSpace on 2014-02-06T13:34:11Z (GMT). No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Capes, Fapesb / A relação entre diversidade, complexidade e estabilidade com função do ecossistema tem sido uma importante questão na história da ecologia (Bengtsson, 1998). Tilman (1999) destaca que inicialmente o interesse desta relação residia nos efeitos da diversidade e complexidade trófica sobre a estabilidade dos ecossistemas e comunidades, contudo, este interesse enfraqueceu-se e apenas no início da década de 1990 começou a reaparecer, com interesses principalmente na relação da biodiversidade com os processos e serviços ecossistêmicos. Desde então, nesses últimos vinte anos, este programa de pesquisa tem crescido e recebendo destaque na literatura de ecologia (ver revisões de Giller et al., 2004; Reiss et al., 2009; Sandini e Solomini, 2009). Em uma abordagem de ciênciometria realizada por Caliman et al. (2010), os autores verificaram que os artigos publicados sobre o tema foi a uma baixa freqüência em relação a literatura ecológica no início da década de 90, aumentando bastante a partir de 1997, e conquistando uma significante freqüência ao longo dos quatro últimos anos analisados, de 2003 a 2007. Alguns estudos analisando esta questão têm utilizado a decomposição foliar como processo funcional de estudo (Briones e Ineson, 1996; Salamanca et al., 1998), principalmente na última década (Lecerf et al., 2007; ; Ball et al., 2008; Chapman e Newman, 2010; Barantal et al., 2011). Porém em menor quantidade nos ecossistemas aquáticos (Swan e Palmer, 2004; Kominoski et al., 2007; Moretti et al., 2007a; Abelho, 2009; Kominoski et al., 2009; Hoorens et al., 2010). Em ecossistemas lóticos, a vegetação circundante (ripária) constitui uma zona de transição entre o rio e os terrenos adjacentes mais acima (Mishall e Rugensk 2006). Esta vegetação ripária está intimamente relacionada à cadeia alimentar do rio, através do fornecimento de detritos foliares originária do folhiço como principal suprimento de energia (Benfield, 2006; Abelho, 2009). Os estudos iniciais de decomposição foliar se focavam em folhas de espécies individuais e a comparação entre elas, visando estabelecer os fatores principais que influenciam neste processo (Webster e Benfield, 1986; Abelho, 2001; Gartner e Cardon, 2004). A composição química do detrito foliar em decomposição é um importante fator para determinar a taxa de decomposição em muitos sistemas(Hoorens et al., 2010; Bonanomi et al., 2010). E, juntamente com os fatores físicos e químicos, podem interferir nos mecanismos da biota que atua na decomposição (Webster e Benfield, 1986; Suberkropp e Chauvet, 1995; Jonsson e Wardle, 2008). Posteriormente, dado a existência de grande quantidade de espécies nas formações vegetais, e ao fato de o processo de decomposição de seus detritos ocorrerem em conjunto, misturadas uns com os outros, a indagação passou a ser se elas podem se influenciar, (Gartner e Cardon, 2004; Abelho, 2009). Nesta perspectiva, muitos estudos verificaram o efeito da riqueza de espécies em uma mistura na decomposição da mistura como um todo (Swan e Palmer, 2004; Sanpera-Calbet et al., 2009; Bonanomi et al., 2010), e outros verificaram a partir da comparação da decomposição observada da mistura, e o esperado em relação á decomposição individual de cada componente da mistura (Gartner e Cardon, 2004; Ball et al., 2008; Abelho, 2009). Nestes, é verificado ausência de efeito quando o esperado e o observado da variável de resposta não diferem significativamente, e um efeito quando diferem, significando que ocorreu algum tipo de interferência de um ou mais componentes da mistura sobre outros (Lecerf et al., 2007). Contudo, os resultados com experimentos de misturas têm sido diversos, mostrando efeitos positivos (aumento da decomposição), negativos (redução da decomposição) ou sem efeitos (Swan e Palmer, 2004; Moretti et al., 2007a; Abelho, 2009; Hoorens et al., 2010). Também são diversos quanto ao efeito da mistura na comunidade colonizadora e vice-versa, podendo ocorrer estimulo da colonização ou ausência de efeito (Leroy e Marks, 2006; Kominoski et al., 2007; Kominoski et al., 2009; Chapman e Newman, 2010). Além disso, poucos estudos têm verificado os mecanismos pelos quais os efeitos ocorrem, ou seja, quais componentes foliares da mistura estão sofrendo o efeito (Salamanca et al. 1998; Moretti et al. 2007a, Sanpera-Calbet et al., 2009; Hoorens et al., 2010). Portanto, os mecanismos pelo quais como a composição de espécies de uma mistura afeta as taxas de decomposição em misturas ainda é uma questão em aberto, (Hoorens et al., 2010) e necessitando de esforços e estudos para uma melhor compreensão do processo. / Salvador, Bahia

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.

Investigations were made examining the relationships between gastropod species richness and abundance across 20 phosphate and 20 natural lakes in Central Florida. In additional to lake category, age of phosphate lakes was used to determine if phosphate lakes ever approximate natural lakes. Additional physical, chemical, and biological parameters, including chlorophyll a, Ca, secchi, phosphorous, conductance, fish predation, and recreational lake use were investigated in order to determine if they affected gastropods with lake age. Comparisons were also made between gastropod species richness and average abundance and two groups of dominant vegetation categories: Panicum, a structurally complex macrophyte, and Typha, a less structurally complex macrophyte. After phosphate mining operations are completed, Florida state regulations require the establishment of ecologically viable habitat (created lakes) which reflects the properties of regional natural lakes including vegetation structure, littoral zone, bank slope, and lake depth. The littoral zone is part of the mandated structure of the lake, and is of considerable importance to the uptake, storage, transformation and release of nutrients. Within the littoral zone, gastropods are a critical link in the food web with implications for the long term structure and function of a lake. They are known for their close associations with macrophytes and are common environmental indicators since they have limited mobility, high diversity, are well studied, are representative of their habitat type and have a widespread geographic range. They are also an important food sources for many predators in aquatic environments, include migratory waterfowl and game fish. Gastropod species richness and abundance data were collected via standard net sweep methodology. Abundance was presented in catch per unit effort, therefore all abundance data were averages. Initial comparisons between gastropod species richness and average abundance yielded no significant differences between natural and phosphate lakes. However, when age was applied as a covariate, there was a significant difference between lake age as a continuous variable in species richness comparisons. Additionally, categorical comparisons between lakes older or younger than 30 years indicated significantly higher species richness and average abundance of gastropods in lakes phosphate lakes older than 30 years. Physical and chemical properties of the lakes did not appear to influence gastropod populations between lakes of different ages. Fish predation interactions did not indicate any significant influence either. However, the presence of boat ramps did indicate a positive relationship between average gastropod abundance and species richness and recreational lake use. Littoral zone macrophyte comparisons between dominant vegetation Typha and Panicum indicated a significantly positive relationship between gastropod species richness and average abundance in older phosphate lakes dominated by the more structurally complex Panicum macrophytes. Confidence in the Typha and Panicum results was confounded by lack of access to younger, Typha dominated, phosphate lakes. An increase in sample size for younger Typha lakes, with additional site access, may further support these findings.

Benthic invertebrates inhabiting boreal rivers are exposed to very large seasonal variations in their physical environment. The extremes are in winter when the littoral area freezes solid and in spring when water flow increases rapidly. In the North Swedish river Vindelälven, the invertebrates fell into three main categories according to their seasonal lateral distribution. One category of animals was stationary in the littoral zone and let itselt freeze into the ice, adopting a "take it" alternative. The category consisted of many species belonging to several higher taxa. By overwintering in ice, the animals avoided predation for nearly half the year and they were in the productive littoral at the same time as they thawed out from the ice in spring. On the other hand the animals had to withstand sub-zero temperatures. A typical representative for this category of animals was the semivoltine snail Gyraulus acronicus. It is a less mobile species connected to dense stands of macrophytes, which are found only in the littoral zone of the river. Nearly the whole population was found overwintering successfully enclosed in ice. Its shell and epiphragm could serve as mechanical protection when frozen into the ice. G. acronicus was cold-hardy only during late autumn and early winter, but it could stand prolonged sub-zero exposure during the proper time. A second category of animlas avoided being frozen by performing lateral movements to deeper parts of the river, adopting the Vleave it" alternative. No species tested in this category were found cold-hardy. It consisted of mobile species known to utilize sedimentated detritus which was only found in greater amounts in the littoral zone of the river. In springtime, prior to spring flood peak, these species colonized promptly the former frozen zone. This behaviour was most pronounced in several lentie mayfly species. An extreme case of migratory behaviour was found in the mayfly Pararneletus chelifer which not only moved towards the river bank but continued up into small tributaries. The shoreward movements of mayflies both allowed the nymphs to avoid the high current velocities in the central part of the river during spring flood time and to utilize the food resources in the flooded areas. A third category of animals avoided the ice by living stationary in the sublittoral zone, adopting the "never face it" alternative. This category was dominated by filter feeders. / <p>Diss. (sammanfattning) Umeå : Umeå university, 1982, härtill 5 uppsatser</p> / digitalisering@umu

The potential relationship between riparian arachnids and aquatic insect productivity was assessed in forest streams throughout the central South Island of New Zealand. Initially, a survey was conducted of thirty seven, first-third order forest streams. Streams were selected to represent a range of benthic invertebrate standing crops (as a surrogate measure of "productivity") from Banks Peninsula streams with relatively high benthic invertebrate densities to acid mine drainage streams near Reefton that were almost devoid of aquatic life. At each site benthic invertebrate densities and biomass were measured in riffle habitats and adjacent gravel bars were sampled for terrestrial invertebrates. At a sub-set of 16 sites, a 20 metre longitudinal web-building spider survey was conducted along each bank of the stream. As an additional component, a 20 metre transect starting at the stream margin and running perpendicularly into the forest was used to survey the density of web-building spiders with increasing distance from the stream. Results from the survey of in-situ stream insect biomass and gravel bar invertebrates showed a strong relationship between aquatic insect biomass and the biomass of riparian arachnids (R2 = 0.42, P < 0.001) having accounted for potentially confounding factors such as stream size, elevation, substrate and disturbance. The 20 metre longitudinal survey showed that streams with the highest in-situ insect biomass had significantly higher densities of web-building spiders along their banks (R2 = 0.28, P < 0.05), having accounted for potential confounding variables of elevation, habitat architecture and stream and channel width. The stream to forest survey showed a strong exponential decay in web-building spider densities with increasing distance from the stream (R2 = 0.96, P < 0.0001). Regardless of stream productivity web-building spiders were most abundant at the stream margins and rapidly declined to very low densities 20 metres from the stream. In order to further test the relationship between riparian web-building spider densities and stream insect productivity, a stream fertilization experiment was conducted on six first-second order streams in the Maimai experimental catchment, Reefton. Three streams were enriched by the addition of a fertiliser solution mainly consisting of sodium nitrate for seven months, and the other three streams were used as controls. Water chemistry, benthic invertebrate communities, emerging aquatic adults, and the densities of web-building spiders along the stream corridor and in the forest were monitored in three seasons (spring, summer and autumn) over the course of the nutrient-addition. By the end of the experiment, conductivity was significantly higher in nutrient-addition streams than in the control streams (F = 80.5, P < 0.001), but chlorophyll concentrations showed no significant differences between treatments. Both benthic mayfly densities (F = 6.15, P < 0.05) and the biomass of adult aquatic dipterans (Chironomidae, Simuliidae) (F = 9.25, P < 0.01) were significantly higher in nutrient-addition streams in the last sampling round. Spiders recorded from intercept traps indicated that by the end of the experiment spider activity was significantly higher within 2.5 metres of the nutrient-addition streams (F = 5.70, P < 0.01). However, seasonal densities of web-building spiders along the stream margin and in the forest decreased with no significant differences observed between nutrient-addition and control streams. The results from these studies indicate that adult insects emerging from streams represent an important source of prey that could influence the biomass and abundance of riparian arachnids. Additionally, the results imply that stream productivity and size could mediate the strength of the interaction between riparian and stream habitats. Moreover, feedback mechanisms present in both systems could have implications for such interactions. The elevated densities of web-building spiders observed at the stream margin led to the proposal of the "Highway Robber" hypothesis. This hypothesis suggests that such higher densities of spiders are the result of increased insect activity along the stream corridor: the emergence of adult aquatic insects was predicted to vary less over temporal and spatial scales than that of terrestrial insects due to the poorly synchronized life histories in many New Zealand stream insects. I conclude by suggesting that there are numerous anthropocentric perturbations such as loss of heterogeneity, introduced species, pollution and habitat degradation that could undermine and decouple the intimate linkages between aquatic and terrestrial ecosystems.

Stream temperature (ST) is a primary determinant of individual stream species distributions and community composition. Moreover, thermal modifications associated with urbanization, agriculture, reservoirs, and climate change can significantly alter stream ecosystem structure and function. Despite its importance, we lack ST measurements for the vast majority of USA streams. To effectively manage these important systems, we need to understand how STs vary geographically, what the natural (reference) thermal condition of altered streams was, and how STs will respond to climate change. Empirical ST models, if calibrated with physically meaningful predictors, could provide this information. My dissertation objectives were to: (1) develop empirical models that predict reference- and nonreference-condition STs for the conterminous USA, (2) assess how well modeled STs represent measured STs for predicting stream biotic communities, and (3) predict potential climate-related alterations to STs. For objective 1, I used random forest modeling with environmental data from several thousand US Geological Survey sites to model geographic variation in nonreference mean summer, mean winter, and mean annual STs. I used these models to identify thresholds of watershed alteration below which there were negligible effects on ST. With these reference-condition sites, I then built ST models to predict summer, winter, and annual STs that should occur in the absence of human-related alteration (r2 = 0.87, 0.89, 0.95, respectively). To meet objective 2, I compared how well modeled and measured ST predicted stream benthic invertebrate composition across 92 streams. I also compared predicted and measured STs for estimating taxon-specific thermal optima. Modeled and measured STs performed equally well in both predicting invertebrate composition and estimating taxon-specific thermal optima (r2 between observation and model-derived optima = 0.97). For objective 3, I first showed that predicted and measured ST responded similarly to historical variation in air temperatures. I then used downscaled climate projections to predict that summer, winter, and annual STs will warm by 1.6 °C - 1.7 °C on average by 2099. Finally, I used additional modeling to identify initial stream and watershed conditions (i.e., low heat loss rates and small base-flow index) most strongly associated with ST vulnerability to climate change.