Lady Bird Lake and Lake Austin are adjacent reservoirs in Austin, Texas, with the primary functions of electrical power generation, flood control, and recreation. In 1999, the invasive submerged aquatic macrophyte (SAV), Hydrilla verticillata, was observed in Lake Austin where it established over the span of the lake, though never establishing in Lady Bird Lake. Management strategies to eradicate hydrilla included the stocking of sterile Asian grass carp, Ctenopharyngodon idella. This practice nearly eliminated hydrilla and resulted in the decline of native aquatic vegetation and increased shoreline erosion. Conservation efforts to reestablish the vegetation are underway. SAV, in addition to facilitating nutrient uptake and retention, enhancing water clarity, stabilizing substrate, and attenuating wave energy, provides food and refugia for aquatic fauna. My research aims to understand the biological implications of the restoration of various SAV assemblages by analyzing the macroinvertebrate communities present within bare, mixed, and monocultured habitat regimes. The data suggests that mixed-cultured SAVs, site disturbance, substrate composition, and macroinvertebrate taxonomic resolution are the primary determinants of macroinvertebrate richness, abundance, and diversity.

Leaf litter is a major nutrient source for aquatic detrital food webs, fueling the microbes and macroinvertebrates that colonize it. Litter is especially important as a nutrient source for macroinvertebrates in headwater streams that tend to have lower primary production than higher-order stream systems. Understanding how litter decomposition and macroinvertebrates interact at large scales facilitates predictions about how stream ecosystems will change over space and time with regards to allochthonous nutrient inputs. We utilized a subset of the National Ecological Observatory Network's wadeable stream sites to deploy a litter pack study across the United States and Puerto Rico to determine the controlling factors for litter decomposition and associated macroinvertebrate assemblages, abundances, and species richness at a national scale. We found that litter species was the most important contributing factor to litter decomposition, and despite litter decomposition differences from stream to stream, the relative differences in decomposition rate between litter types was very similar. Stream identity, temperature, and flow also played roles in affecting decomposition patterns. In contrast to litter decomposition, litter species did not significantly contribute to variation in macroinvertebrate assemblages, abundance, or species richness, though environmental variables did impact abundance and species richness. These results suggest that there is functional redundancy in aquatic detritivore communities at large scales, and that the assemblages colonizing different species of leaf litter–despite being similar–might be functioning differently.

Master of Science / Department of Biology / Craig Paukert / The zebra mussel is an invasive bivalve that was first confirmed in Kansas in 2003, and has decreased zooplankton abundance and altered the aquatic community in other areas where it has invaded. However, little is known about its effects on the aquatic communities of warm-water Great Plains reservoirs. We analyzed zooplankton, benthic macroinvertebrate, and juvenile and small-bodied fish abundance in the littoral zone of an Eastern Kansas reservoir with an established zebra mussel population (El Dorado Reservoir) and a control reservoir without zebra mussels (Melvern Reservoir) for two years pre-zebra mussel invasion (2001-2002) and two years post-invasion (2008-2009). We found no difference in littoral zooplankton abundance between reservoirs across time, but abundance of some macroinvertebrate taxa increased, and abundance of juvenile Lepomis spp. and red shiners decreased in the littoral zone of El Dorado Reservoir in August of the post-zebra mussel invasion period in comparison to the control reservoir. We also analyzed abundance and condition of six adult reservoir fishes in El Dorado Reservoir and three control reservoirs in Eastern Kansas for ten years pre-zebra mussel invasion (1993-2002) and five years post-invasion (2004-2008). Adult white crappie abundance remained constant in El Dorado Reservoir but decreased in the control reservoirs during the post-zebra mussel invasion period, and condition of adult bluegill, white bass, and white crappie decreased in El Dorado Reservoir in the post-zebra mussel invasion period compared to the control reservoirs. Our findings suggest that zebra mussel invasion in El Dorado Reservoir may have affected some benthic macroinvertebrates, juvenile and small-bodied fishes, and adult fishes. We did not find evidence that zebra mussels have had substantial effects on the zooplankton community of El Dorado Reservoir. However, July-August zebra mussel veliger densities in El Dorado Reservoir averaged less than 12 veligers/L in four of the six post-zebra mussel invasion years. Additional research and long-term monitoring of zooplankton, macroinvertebrates, and fishes will be necessary to determine the full effects of zebra mussels on the aquatic communities of warm-water reservoirs throughout North America.

Freshwater is a resource under threat due to anthropogenic actions. Stream restoration is a common method for mitigating disturbance. Inconsistent methodologies used for evaluating restorations have drawn criticism. Limited use of baseline data for guiding stream restoration activities is of particular concern. This study was developed to elucidate metrics that differentiate reference and disturbed sites in Upper Coastal Plain streams. This information could improve resource use and successes of restorations. Structural and functional variables were examined in 10 reference and 10 streams that meet the traditional definition of disturbance and would be restoration priorities. Disturbed streams were classified into two regimes, temporal, based on time since disturbance, and categorical, based on disturbance cause. Some metrics of geomorphology, water chemistry and macroinvertebrates differentiated reference from disturbed regimes and while other metrics separated streams within disturbance regimes. Surprisingly, leaf decay rate was not an effective metric for determining disturbance. However, macroinvertebrate leaf pack colonizers were found to be useful for differentiating reference sites and disturbance regimes. Of the 10 disturbed streams this study examined, my data suggests that only three are in immediate need of restoration. This study emphasizes the importance of baseline data and its potential benefits for guiding stream restoration.

With the formal adoption of the Water Framework Directive in 2000, into European legislation it committed all member states to ensure that all inland waterbodies should reach good ecological status by 2015. As a result examination of the influence of hydromorphology on the ecological health of riverine ecosystems has become an increasingly important priority for statutory monitoring agencies such as the Environment Agency of England and Wales and equivalents in other parts of the UK. It is anticipated that by increasing our understanding of the role that hydromorphological processes play in shaping river habitats and the ecosystems that they support, river management strategies can be developed that will help lead to waterbodies achieving good ecological status. In this thesis, the influence of river hydromorphology and instream channel management activities on instream macroinvertebrate communities is explored. A two-scale approach was used at a regional macro-scale and local / catchment micro-scale. The macro-scale study examines the ecological, hydrological and geomorphological data for 88 river reaches located within the Environment Agency , Anglian Central and Anglian Northern regions, over a twenty year period (1986-2005). At the micro-scale two sub-catchments were selected, the River Bain and River Lymn, both located in Lincolnshire, England for detailed investigation. The micro-scale study was undertaken using ecological, hydrological and geomorphological data collected over three successive seasons (Autumn 2008, Spring 2009 and Summer 2009) enabling the seasonal variations and the influence of both stream size and habitat biotope on macroinvertebrate community composition and structure to be explored. The hydromorphological characteristics and condition of the rivers were quantified using ecologically relevant hydrological indices, calculated from flow discharge paired with geomorphological indices from River Habitat Survey data. The response of the instream macroinvertebrate communities was examined using a range of ecological indices including the Lotic-invertebrate Index for Flow Evaluation (LIFE). The results of the macro-scale investigation demonstrate that the macroinvertebrate community is directly influenced by instream hydromorphology and the level of anthropogenic modification. The micro-scale study highlights important differences in macroinvertebrate communities associated with instream habitat / biotope composition. The quantification of river hydromorphology, with the use of ecologically relevant hydrological indices and geomorphological indices, derived from River Habitat Survey data, is discussed with regards its ability to help explain the structure and composition of macroinvertebrate communities within highly managed /regulated riverine ecosystems. The implications of this research for river managers and for implementing river restoration and rehabilitation schemes are explored.

Aquatic ecosystems are especially vulnerable to human impacts associated with agricultural land-use, which provide multiple stressors altering community composition, important ecosystem functions and human valued properties of freshwaters. However, the increased occurrence of excessive levels of nitrate-nitrogen has raised major concerns about toxicity and stress on aquatic life, especially in regions such as the Canterbury Plains, New Zealand. The aims of this thesis were to identify nitrate-nitrogen effects on stream communities, and additionally provide field data to inform proposed national bottom lines for nutrients in New Zealand streams. A field survey was conducted on 41 small streams on the Canterbury Plains spanning a nitrate-nitrogen gradient (mean 0.4 – 11.3 mg/L). Spot nitrate-nitrogen was collected during and after the field survey to measure temporal variation in stream nitrate-nitrogen concentration for six months. This showed nitrate-nitrogen concentration varied between season and sub-region, where concentrations increased in winter and Ashburton had higher nitrate-nitrogen than Rangiora and Lincoln, respectively. These regimes of nitrate-nitrogen showed similar patterns in mean, median and maximum concentrations. To be confident my spot nitrate-nitrogen provided a true representation of long-term water chemistry, I compared Environment Canterbury 12 monthly data with my six monthly data in a sub-set of 15 sites. This comparison showed similar nitrate-nitrogen patterns and range of values between the two datasets. I then compared 12 common benthic invertebrate biotic metrics with my nitrate-nitrogen data and found none were correlated with this contaminant. For example, the Macroinvertebrate Community Index and quantitative variant (QMCI) derived to measure the response to organic pollution provided inconsistent results when applied to my streams. Nevertheless, gut content stoichiometry of the common mayfly grazer Deleatidium spp. indicated improvement in food quality (lower C:N ratio) with higher nitrate-nitrogen concentrations. These results indicated either nitrate-nitrogen does not alter invertebrate structural metrics across this nitrate-nitrogen gradient, or that these biotic metrics measure community structure aspects not affected by nitrate-nitrogen. I then investigated possible community composition patterns across the nitrate-nitrogen gradient. Unconstrained ordination (on presence/absence data) showed invertebrate communities at my sites were influenced primarily by discharge and shade, with the next most important driver being nitrate-nitrogen. A constrained ordination (on the same data) testing the singular effect of nitrate-nitrogen showed a marginally non-significant change in composition, with higher variability in community composition at higher nitrate-nitrogen concentrations. A further aim of my study was to test the draft nitrate-nitrogen bands proposed by Hickey (2013). These nitrate-nitrogen bands may advise guidelines to protect aquatic organisms as required by the National Policy Statement on Freshwater. Analysis of my invertebrate communities showed differences in composition, particularly at < 1 and > 6.9 mg/L bands. Several predatory caddisfly taxa: Triplectides, Neurochorema and Oeconesus were identified as potential indicator species of communities associated with low nitrate-nitrogen. These findings show that nitrate-nitrogen effects are difficult to detect, and that it is not the main driver of community composition in Canterbury streams. However, nitrate-nitrogen may be an important stressor for sensitive benthic invertebrate communities, as effects were observed on pollution tolerant organisms in this study. Therefore, this research has implications for freshwater ecologists and environmental managers striving to improve the health of streams on the Canterbury Plains.

Excess fine sediment from human activity is a major pollutant to streams across the U.S.; however, distinguishing human-induced sedimentation from natural fine sediment is complex. The U.S. Environmental Protection Agency recently implemented a protocol for the quantitative field assessment of human-induced sedimentation using measurements of stream geomorphology. Macroinvertebrate community composition, streambed sediment stability, and sediment composition were studied at 49 sites in the James River watershed in central Virginia. Sediment composition was found to be a stronger driver of community composition than sediment stability. Although I was not able to show that macroinvertebrate metrics were related to sediment stability independently of actual fine sediment composition, some metrics, including percent Ephemeridae, a family of burrowing mayflies (order = Ephemeroptera) show promise as valuable tools for regional biologists and resource managers to discriminate among streams considered impaired for sediment pollution.

Benthic macroinvertebrate diversity influences stream food web dynamics, nutrient cycling and material exchange between the benthos and the water column. Stream bioassessment has moved to the forefront of water quality monitoring in terms of benthic macroinvertebrate diversity in the recent past. The objectives of this study were to determine optimum subsample size and level of taxonomic resolution necessary to accurately and precisely describe macroinvertebrate diversity in streams flowing in the Piedmont province of the James River watershed in Virginia. Forty-nine sampling sites were selected from streams within the Piedmont Physiographic Province of the James River watershed. Ten sites were randomly selected to have all macroinvertebrates in the sample identified to the genus level whenever possible. Optimum subsampling intensities and Virginia Stream Condition Index (VSCI) metrics and scores were determined. For samples with the total number of individuals at less than 500, the genus level of taxonomy provided lower overall optimum subsampling intensities. However, for samples with total individuals over 1000, optimum subsampling intensities at the genus level of taxonomy were higher than the family level for more than 50% of the metrics. For both family and genus levels of taxonomy, the majority of optimum subsampling intensities were well over 50% of the total individuals in the sample, with some as high as 100% of the individuals. While optimum subsampling intensities were valuable in comparing family and genus level taxonomy, they are not reasonable for stream bioassessment protocols; the cost:benefit ratio would be highly unbalanced. A minimum subsample size of 200 individuals is optimum for determining VSCI scores, while optimum taxonomic resolution is dependent on several factors. Thus, the level of taxonomic resolution for a particular study should be determined by the study objectives, level of site impairment and sample size.

O presente estudo propôs uma nova leitura dos dados do monitoramento hidrológico de sete microbacias experimentais, considerando que as variáveis que caracterizam os sistemas aquáticos destas microbacias constituem indicadores da qualidade do manejo florestal. Os objetivos do estudo foram: a) selecionar, entre as variáveis já monitoradas, os potenciais indicadores para o monitoramento hidrológico de florestas plantadas; b) testar a viabilidade da utilização da comunidade de macroinvertebrados bentônicos como indicador biológico. O estudo foi desenvolvido nas seguintes microbacias: na região do Município de Guaíba, RS, uma com floresta plantada e uma com pastagem; em Itatinga, SP, uma com floresta plantada; em Alagoinhas, BA, uma com floresta plantada e três em Imperatriz, MA, uma com floresta nativa, uma com floresta plantada de eucalipto e uma com pastagem. O estudo consistiu na análise de dados da medição contínua da vazão, da precipitação e de variáveis físicas e químicas da água dos córregos das microbacias durante diferentes períodos e também no estudo da comunidade de macroinvertebrados bentônicos por um período de um ano. Como resultado, foram selecionadas, para o início de um programa de monitoramento de florestas plantadas na escala da microbacia hidrográfica, 12 indicadores que atendem a três critérios. São eles: 1 - manutenção dos processos hidrológicos da microbacia e da qualidade das operações florestais com os indicadores balanço hídrico, picos de vazão, sólidos em suspensão, turbidez, condutividade elétrica, fósforo, oxigênio dissolvido, potássio, temperatura da água e macroinvertebrados bentônicos; 2 - manutenção do potencial produtivo do solo com os indicadores fósforo, nitrogênio, cálcio, potássio, magnésio, e sólidos em suspensão, e 3 - manutenção do equilíbrio dinâmico do ecossistema aquático, com os indicadores oxigênio dissolvido, fósforo, nitrogênio, temperatura da água, sólidos em suspensão, pH e macroinvertebrados bentônicos / This study proposes a new analysis of data from hydrological monitoring of seven experimental catchments considering that the monitored hydrological variables can be used as indicators for forest management quality. The objectives of the study were: a) select, among the monitored variables potential indicators for the hydrological monitoring of planted forests; b) investigate weather macroinvertebrate community can be used as biological variable. The study was carried out in catchments covered by Eucalyptus forests located in the Municipalities of Guaíba, State of Rio Grande do Sul, Itatinga, State of São Paulo, Alagoinhas, State of Bahia and Imperatriz, State of Maranhão; catchment covered by native forests in the Municipality of Imperatriz State of Maranhão and catchments used as pastureland in the Municipalities of Guaíba, State of Rio Grande do Sul and Imperatriz, State of Maranhão. The study involved data analysis of precipitation, streamflow and water quality variables measured during different periods and the study of the macroinvertebrate community during one-year period. As a result, 12 variables according to 3 criteria of forest sustainable management were selected. The criteria and indicators are the following: 1 - maintenance of catchment hydrologycal processes and forest management quality, for which the indicators are water balance, peak flow, suspended solids, turbidity, conductivity, phosphorus, dissolved oxygen, potassium, water temperature and benthic macroinvertebrate community; 2 – maintenance of soil productivity, with the indicators phosphorus, nitrogen, calcium, potassium, magnesium, and suspended solids, and the third criteria, maintenance of the dynamic equilibrium of aquatic ecosystem, with the indicators dissolved oxygen, phosphorus, nitrogen, water temperature, suspended solids, pH, and benthic macroinvertebrate community

A study of macroinvertebrate colonization and assemblages, including secondary productivity of the familiar bluet damselfly or Enallagma civile Hagen (Odonata: Coenagrionidae), associated with the aquatic macrophytes Heteranthera dubia (Jacq.) MacMill. (water stargrass) and Potamogeton nodosus Poir. (American pondweed) was conducted at the Dallas Floodway Extension Trinity River Project (DFE) Lower Chain of Wetlands (LCOW), Dallas, TX, from September 2010 through November 2011. Macroinvertebrate abundance, taxa richness, Simpson's index of diversity, and Simpson's evenness from the two macrophytes and from three different wetland cells of varying construction completion dates, water sources, and native aquatic vegetation establishment were analyzed along with basic water quality metrics (temperature °C, pH, dissolved oxygen mg/L, and conductivity µs/cm). E. civile nymphs were separated into five developmental classes for secondary productivity estimations between macrophytes and wetland cell types. Mean annual secondary productivity in the DFE LCOW among two macrophytes of E. civile was 1392.90 ash-free dry weight mg/m²/yr, standing stock biomass was 136.77 AFDW mg/m2/yr, cohort production / biomass (P/B) ratio was calculated to be 4.30 / yr and the annual production / biomass (P/B) ratio was 10.18 /yr.