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Identifying the processes and mechanisms that govern communities of organisms is the main goal of community ecology. Locally operating mechanisms such as environmental filtering, in which the environment determines what species are found in a given location, as well as regional processes such as dispersal have all been identified as potential drivers of community processes. However, the relative importance of these drivers may vary temporally and spatially. In dendritic stream networks, headwater streams are isolated when compared to more centrally located mainstem stream sections. I investigated the potential for stream networks to influence the relative influence of local and regional processes via a survey and field experiment based approaches. I found that headwater streams can influence mainstem stream communities, potentially as a result of the dispersal of organisms or abiotic materials. Additionally, I demonstrated that macroinvertebrate communities in headwater streams respond more strongly to manipulations of local environment than do mainstem streams, both in terms of community composition as determined taxonomically and as functional traits. These results indicate that headwater streams may be affected differently than mainstem streams by anthropogenic activity and as such, management strategies and restorations may need to be specifically tailored to address the relative influences of local and regional processes at varying points within a stream network. / Ph. D.

Black Creek is a small watershed located in Wise County, Virginia, west of the town of Norton. At the time of this survey, the watershed encompassed approximately 929 hectares of mine and forest lands with a small recreational area. Black Creek proper is a third-order stream approximately 6.7 km in length from its headwaters to its confluence with the Powell River in Kent Junction. Black Creek and several of the tributaries within the watershed were previously identified as areas impacted by acid mine drainage. The watershed was used in a study to identify sources of acid mine drainage and the best methods for its evaluation. The acid mine drainage sources were first identified using visual inspection and field chemistry. Additional stream segments were then included in the assessment process using metal (aluminum, copper, iron, magnesium, manganese, and zinc) analyses of both overlying water column and sediments. Using an upstream reach of Black Creek as a reference, short-term toxicity testing was employed, as well as a long-term purge study. The pH at sampling locations ranged from 2.75 to 7.87 SU, and conductivity ranged from 196 μmhos/cm to 2040 μmhos/cm. All metals were elevated when compared to the reference. Water column samples collected from locations with low pH were acutely toxic to Daphnia magna and Pimephales promelas. Mortality was high in the elutriant test at locations where pH was low, conductivity was elevated, metals were high, or a combination of these. In the initial sediment tests, all sampling locations were significantly different than the reference for survival of Chironomus tentans and reproduction of D. magna. One location was significantly different than the reference for survival of D. magna. In the sediment tests completed after two months, survival of C. tentans was only different from the control in three locations but was significantly different for growth at all locations. Reproduction by D. magna was again significantly less than the reference at all locations. At eight months, only two locations were significant for survival of C. tentans and after 15 months, no significant differences occurred between any stations. The study indicates that stream segments that are severely impaired by acid mine drainage are easy to identify using visual inspection and field water chemistry. Those that are moderately impaired require more investigation and may not be responsive to short-term toxicity tests. Benthic macroinvertebrates, leaf packs, and periphyton were evaluated in the field. Benthic macroinvertebrate communities and leaf-pack breakdown were evaluated at nine locations, while periphyton was evaluated at the mouth of Black Creek, as well as five sites in the Powell River receiving system. While leaf-pack information and benthic macroinvertebrate samples yielded similar information, benthic sampling was much simpler and less time consuming. Additionally, benthic macroinvertebrate sampling, particularly over several sampling events, was more sensitive at the most severely impacted AMD stations. The stations were broken down into five different categories in order to better determine which evaluation techniques were most sensitive and cost-effective. The five categories were Non-Impaired, Slightly Impaired, Moderately Impaired, Severely Impaired, and Severely pH impaired. Once the locations were categorized, each method used to evaluate toxicity was examined to determine which methods best identified acid mine drainage impairment in the Black Creek watershed. The methods utilized include the following: basic water chemistry; metals analysis of sediments and water column; acute toxicity testing using both D. magna and P. promelas; short-term elutriant and sediment tests; chronic sediment test using C. tentans and D. magna; a purge study; benthic macroinvertebrate sampling; leaf-pack and algal-tile studies. After evaluating these methods, it was determined that using basic water chemistry and benthic macroinvertebrate sampling were the best methods for evaluating acid mine drainage impairment in this watershed. The reference station was identified as Non-Impaired. Two stations located in the lower portions of Black Creek (L11 and L1) were also Non-Impaired or only Slightly Impaired with the benthic macroinvertebrate results indicating little impairment. Stations U2, U6, U7, and BBM were also found to be Slightly Impaired. The station on the margin of the wetland, U5, was Moderately Impaired. Two previously identified areas of impairment, U9 and U10, (Cherry et al. 1995) were identified as Severely pH Impaired and Severely Impaired, respectively. / Master of Science

Agriculture, urbanization, and human activities, if not managed carefully, can expose a water body to environmental degradation, decreased water quality, and ultimately impaired benthic macroinvertebrate assemblage conditions. In streams where the benthic macroinvertebrates are impaired, the stream itself will not be meeting the water quality standards set forth in the Clean Water Act. As a result, the goal of this study was to establish relationships between benthic macroinvertebrates and their stressors so that stressor levels that would not adversely impact the benthic macroinvertebrates could be determined. Stressors such as sediment, habitat, water quality, landuse, watershed characteristics, and livestock numbers impact the benthic macroinvertebrate assemblage conditions. Since sediment is recognized as the Nation's leading pollutant and since the benthic macroinvertebrates live in the sediment on a stream bottom, this study placed emphasis upon the investigation of sediment as a primary stressor to the benthic macroinvertebrates. The specific objectives of this study were to develop relationships between the benthic macroinvertebrates and sediment and other stressors for Virginia streams, to evaluate the accuracy of the stressor/benthos relationships, and to discuss the implications of the study results for development of benthic TMDLs. A procedure to determine the relationships between stressors and benthic macroinvertebrate assemblage conditions was developed. Existing data on sediment, habitat, water quality, landuse, watershed characteristics, livestock numbers, and benthic macroinvertebrate assemblage conditions were compiled for 34 stations with 105 samples collected from the fall of 1996 to the fall of 1998. The 34 stations were located within 13 counties in Virginia (Rockbridge, Rockingham, Augusta, Frederick, Shenandoah, Page, Loudoun, Fairfax, Prince William, Fauquier, Culpeper, Rappahannock, and Madison) and in watersheds dominated by agricultural, urban, and forested landuses. Virginia currently uses the Rapid Bioassessment Protocol (RBP) method in its Biological Assessment Program. The RBP compares habitat and biological measures of the benthic macroinvertebrates to reference conditions using individual metrics. VADEQ's Biomonitoring Database, together with Ambient Water Quality Monitoring reports, GIS data layers, and VADCR's Hydrologic Unit Animal Census Database provided all of the necessary information for the stressor variables and benthic macroinvertebrate conditions. Accordingly, the stressor/benthos relationships were evaluated using statistical analyses procedures such as forward, backward, and stepwise multiple regression techniques; correlation analysis; principal component analysis; and r-square analysis. The statistical results indicated that sediment alone cannot be used to assess the benthic macroinvertebrate assemblage conditions. Other stressors such as dissolved oxygen, flow, % urban land, total suspended solids, temperature, stream velocity, substrate, hardness and alkalinity greatly impact the benthic macroinvertebrate assemblage conditions. The study results also indicate that the individual metrics within the RBP procedure are just as critical as the final RBP values in describing the benthic macroinvertebrate assemblage conditions. Upon completing the steps needed to develop stressor/benthos relationships, the validity of the relationships were verified for their application to other streams in Virginia. Validation was completed using 10 stations with 29 samples from the fall of 1996 to the fall of 1998. The 10 stations were located within 8 counties in Virginia (Bedford, Montgomery, Pulaski, Giles, Botetourt, Albemarle, Orange, and Culpeper) and in watersheds dominated by agricultural, urban, and forested landuses to correspond with the stations used to develop the stressor/benthos relationships. The implications of the relationships with regard to TMDLs were also studied using total suspended solids (TSS) loadings, turbidity levels, and embeddedness levels as the stressors of concern. The results for all benthic stations within Virginia showed that moderately impaired streams generally need to reduce the amount of embeddedness by 11, reduce turbidity levels by 5 FTU (57%), and reduce TSS values by 7 mg/L (68%) to meet a threshold value that would no longer adversely impact the benthic macroinvertebrates. Similarly, for the severely impaired stations throughout Virginia to meet threshold values, embeddedness amounts need to be reduced by 22, turbidity reduced by 57 FTU (93%), and TSS reduced by 74 mg/L (96%). This study was important since the proposed stressor/benthos relationships can provide policymakers with a useful tool to determine stressor thresholds that will not adversely impact the benthic macroinvertebrate assemblage conditions for use in developing benthic TMDLs in Virginia. The stressor/benthos relationships could also be used to determine the impact of certain activities or stressors on the benthic macroinvertebrates assemblage conditions in a given stream. / Master of Science

The term hydropeaking refers to anthropogenically induced, short-duration, high-magnitude discharge pulses that are generated in lotic systems for electricity production. The practice of hydropeaking produces the largest source of renewable energy worldwide, and its use is projected to increase through the year 2040. The primary objective of this work was to evaluate the effects of hydropeaking on benthic macroinvertebrate assemblages, which are important components of lotic ecosystems. Results of this work show that, across a wide range of impacted systems worldwide, the consistently observed patterns of elevated benthic macroinvertebrate drift in response to hydropeaking pulses are primarily related to the rate at which discharge is increased (i.e., ramping rate) and secondarily to the time between pulses. In addition, it was shown that taxa inhabiting depositional habitat patches (i.e. fine substrates and slow water velocities) were most susceptible to peaking-induced drift, and that these taxa were also those most prevalent in hydropeaking-impacted systems. Collectively, these results suggest that increased pulse ramping rate and the resulting elevated macroinvertebrate drift may be positive selective forces, which benefit populations adapted for life in hydropeaking-impacted lotic ecosystems. These results provide a greater understanding of the factors that are most important for governing the effects of hydropeaking on benthic assemblages.

As atividades agrícolas, principalmente as monoculturas, exigem grande utilização de insumos. A aplicação constante de defensivos agrícolas, como herbicidas, pesticidas e fungicidas, tem promovido crescentes impactos sobre os recursos hídricos e biota neles presentes, principalmente em organismos não alvo dessas substâncias. O presente estudo teve como principal objetivo avaliar os efeitos do fungicida Pyrimethanil na comunidade de macroinvertebrados bentônicos, por meio do monitoramento ambiental em unidades experimentais de campo (mesocosmos) e ensaios ecotoxicológicos laboratoriais com indivíduos da espécie Chironomus sancticaroli. Os mesocosmos foram construídos utilizando-se seis caixas de água com volume equivalente a 1500 litros. A contaminação dos mesocosmos com Pyrimethanil foi realizada por meio de pulverização direta na superfície da água aplicando-se uma concentração equivalente a 0,1 mg/L de Pyrimethanil nos mesocosmos contaminados. Dessa maneira, os mesocosmos foram divididos em três réplicas contaminadas e três réplicas controles. O monitoramento e coleta de amostras de água e macroinvertebrados bentônicos foram realizados com frequência mensal, durante o período de um ano. O fungicida Pyrimethanil não ocasionou alterações significativas nas variáveis monitoradas. Da mesma forma, a estrutura comunitária de macroinvertebrados bentônicos apresentou características semelhantes entre os mesocosmos contaminados e controles. Entretanto, durante o monitoramento, os mesocosmos controles apresentaram valores significativamente mais elevados na abundância de indivíduos e quantidade total de táxons quando comparados aos valores observados nos mesocosmos contaminados com Pyrimethanil. / Agricultural activities, mainly monocultures, require large use of inputs. The constant application of agrochemicals, as herbicides, pesticides and fungicides, has promoted impacts on water resources and biota at the center, especially on non-target organisms such substances. This study aimed to evaluate the effects of fungicide Pyrimethanil in benthic macroinvertebrate community through environmental monitoring experimental units of field (mesocosms) and laboratory ecotoxicological tests with individuals of Chironomus sancticaroli. The mesocosms were made using six tanks with maximum volume equivalent to 1500 liters. The contamination of the tanks with Pyrimethanil was performed by spraying of water on the surface by applying a fungicide concentration equivalent to 0,1 mg/L. Thus, the mesocosms were divided into three contaminated replicas and three controls replicas. The monitoring and sampling of water and benthic macroinvertebrates were performed on a monthly basis during the period of one year. The fungicide Pyrimethanil does not cause significant changes in monitored variables. Similarly, the community structure of benthic macroinvertebrates were similar characteristics between the contaminated and control mesocosms. However, during the monitoring, the mesocosms controls had significantly higher values in the abundance of individuals and total number of taxa compared to the values observed in the mesocosms contaminated with Pyrimethanil.

This research considers human impacts on three components of biodiversity (composition, spatial structure and function). Given the relict character and unusual biogeochemical balance of tropical montane cloud forests in Mexico, logging poses a pressing threat to their survival. Specifically, this thesis explores the effect of selective logging and above-ground secondary succession on the biogeochemical cycling and soil macroinvertebrate community in a cloud forest in Oaxaca, Mexico. The research investigates: (1) whether the above-ground chain of successional changes in tree dominance, litterfall, litter diversity and soil microenvironmental conditions are coupled with a below-ground succession of soil nutrient availability and macroinvertebrate communities, (2) the role of spatial structuring of environmental conditions and litter resources as determinates of the nutrient availability and macroinvertebrate taxa abundance, (3) the implications of successional changes for decomposition and (4) whether the local influence of single trees explains the spatial structure of macroinvertebrate communities in late successional forests. The work was carried out in three chronosequences (c.15, 45, 75 and 100 year-old stages) of high altitude (1500-2000m) tropical montane cloud forest, two recently logged sites and two pristine sites. the macroinvertebrates in the litter and mineral soil were hand sorted from monoliths. Parametric statistics and canonical correspondance analysis were used to determine mean successional trends, and Spatial Analysis by Distance Indices and geostatistical methods were used in combination to determine spatial patterns. Two decompositional experiments were performed to explore the relationship between decompositional rate, litter quality and macroinvertebrate community higher taxa composition in different successional stages and under the canopy of different tree species. The research showed that: 1. The macroinvertebrate community composition in both recently logged sites and pristine forests were distinct compared to secondary successional stages. A decrease in soil temperature and nutrient availablity but increase in litter diversity and soil organic matter recorded through succession were accompanied by an increase in the number of macroinvertebrate taxa in the soil. For exampl, Collembola were most abundant in recently logged sites and earthworms (Megascolecidae) were almost excluvely found in pristine forests. 2. The oldest secondary forest (100 year-old) showed the highest frequency of aggregation in the abundance of individual macroinvertebrate taxa, and the highest and most uniform value of Shannon's diversity. This suggests that high levels of diversity in litter resources and soil chemistry in late succession are associated with complex spatial structuring of highly diverse macroinvertebrate communities. 3. The leaves of a late successional species (Persea americana)decomposed at a slightly slower rate than an early successional species (Pinus chiapensis) in all successional stages, yet the number and Shannon's diversity of macroinvertebrate taxa that invaded decomposing P.Americana leaves was consistently higher. The preference of macroinvertebrate taxa for the late-successional leaves was ultimately explained by differences in leaf quality during decomposition. P.americana leaves had higher concentrations of cations throughout decomposition and their concentration of lignin and nitrogen became higher. 4. In the 100-year-old forest, the effect of seasonal variation on soil microenvironmental conditions and litter availability was different under the canopy of different tree species. Furthermore, the chemical evolution of the same leaf type (e.g. Oreopanax xalapensis) was differentwhen decomposing under different canopies. The highly diverse and spatially complex macroinvertebrate community found in late succession (and experimental litter) was largely explained by the interactive effects of seasonal variation, tree species, litter quality and availability of the decomposing leaf type. The results provide the first analysis of the relationship between soil biodiversity and the tight biogeochemical cycling in this relict ecosystem type. Overall the results indicate that mature cloud forests sustain a diverse and spatially heterogenous macroinvertebrate community. The compositional and spatial components of soil biodiversity are compromised by logging and full recovery may take mopre than 100 years.

Physical factors, such as hydrologic variability, are major structuring forces of prairie stream communities. Macroinvertebrate and algae densities can both decrease sharply in response to floods and drying. Less is known about the influences of biological factors, such as fishes. The influence of fishes on macroinvertebrate communities varies with environmental factors and other biologic interactions, ranging from neutral to strong negative effects on some populations, and the strength of these interactions sometimes appear linked to hydrology. Drying intermittent streams leave permanent water refugia that may be hotspots for interactions between fishes and invertebrates. Effects of fishes on macroinvertebrate communities may vary with invertebrate life cycle stages (e.g., larvae, emerging adults, colonizing adults). I examined macroinvertebrate communities (benthic and emerging) and algal biomass across a range of permanent stream pool sites at Konza Prairie Biological Station with naturally varying densities of fishes. I also manipulated fish densities in a mesocosm experiment to address how fishes may also be effecting colonization during recovery from hydrologic disturbance. Fish biomass had a negative impact on invertebrate abundance, but not biomass or taxa richness, in natural pools. Total fish biomass was not correlated with total insect emergence in natural pools, but orangethroat darter (Etheostoma spectabile) biomass was inversely correlated with emerging Chironomidae biomass (r2 = 0.43, p = 0.047) and individual midge body size (r2 = 0.61, p = 0.014). Predatory fish biomass and a date interaction appeared in top linear models, indicating fish may also delay insect emergence from natural pools. Fish presence reduced abundance of colonizing insects (p < 0.001) and total invertebrate biomass (p = 0.001) in mesocosms. Mesocosm insect communities in pools without fishes were characterized by more Chironomidae, Culicidae, and Corduliidae (p < 0.001 for all). Chlorophyll-a increased between sampling dates in mesocosms, but did not differ between treatments. Not all life stages showed the same response to fishes, illustrating the need for understanding life histories in order to interpret the influence of fishes. Understanding how fishes in prairie streams affect ecosystem structure and function is critical for conservation and management of remaining grassland streams. Results suggest fishes can influence colonization and community structure in prairie stream pools, which serve as important refugia during hydrologic disturbance and source areas for colonists during recovery.

As atividades agrícolas, principalmente as monoculturas, exigem grande utilização de insumos. A aplicação constante de defensivos agrícolas, como herbicidas, pesticidas e fungicidas, tem promovido crescentes impactos sobre os recursos hídricos e biota neles presentes, principalmente em organismos não alvo dessas substâncias. O presente estudo teve como principal objetivo avaliar os efeitos do fungicida Pyrimethanil na comunidade de macroinvertebrados bentônicos, por meio do monitoramento ambiental em unidades experimentais de campo (mesocosmos) e ensaios ecotoxicológicos laboratoriais com indivíduos da espécie Chironomus sancticaroli. Os mesocosmos foram construídos utilizando-se seis caixas de água com volume equivalente a 1500 litros. A contaminação dos mesocosmos com Pyrimethanil foi realizada por meio de pulverização direta na superfície da água aplicando-se uma concentração equivalente a 0,1 mg/L de Pyrimethanil nos mesocosmos contaminados. Dessa maneira, os mesocosmos foram divididos em três réplicas contaminadas e três réplicas controles. O monitoramento e coleta de amostras de água e macroinvertebrados bentônicos foram realizados com frequência mensal, durante o período de um ano. O fungicida Pyrimethanil não ocasionou alterações significativas nas variáveis monitoradas. Da mesma forma, a estrutura comunitária de macroinvertebrados bentônicos apresentou características semelhantes entre os mesocosmos contaminados e controles. Entretanto, durante o monitoramento, os mesocosmos controles apresentaram valores significativamente mais elevados na abundância de indivíduos e quantidade total de táxons quando comparados aos valores observados nos mesocosmos contaminados com Pyrimethanil. / Agricultural activities, mainly monocultures, require large use of inputs. The constant application of agrochemicals, as herbicides, pesticides and fungicides, has promoted impacts on water resources and biota at the center, especially on non-target organisms such substances. This study aimed to evaluate the effects of fungicide Pyrimethanil in benthic macroinvertebrate community through environmental monitoring experimental units of field (mesocosms) and laboratory ecotoxicological tests with individuals of Chironomus sancticaroli. The mesocosms were made using six tanks with maximum volume equivalent to 1500 liters. The contamination of the tanks with Pyrimethanil was performed by spraying of water on the surface by applying a fungicide concentration equivalent to 0,1 mg/L. Thus, the mesocosms were divided into three contaminated replicas and three controls replicas. The monitoring and sampling of water and benthic macroinvertebrates were performed on a monthly basis during the period of one year. The fungicide Pyrimethanil does not cause significant changes in monitored variables. Similarly, the community structure of benthic macroinvertebrates were similar characteristics between the contaminated and control mesocosms. However, during the monitoring, the mesocosms controls had significantly higher values in the abundance of individuals and total number of taxa compared to the values observed in the mesocosms contaminated with Pyrimethanil.

This Master thesis was focused on seasonal development of macrozoobenthos for season 2009-2010, its long-term changes and effects of extreme events on acidified brooks in headwater catchments of the Litavka river in the Brdy Mountains (the Czech Republic). The extreme events are considered: drought, floods and deforestation. Changes in composition of macrozoobenthos were compared with the previous research, which was provided there for season 1999-2000. Headwater catchment of the Litavka river consist of two streams: strongly acidified Litavka-krmelec (LK) and slightly acidified Litavka-hlavní (LH), which is taken as a reference stream. Measured pH levels of LK were in range of 4,00-4,22 (with median 4,10) and concentration of reactive aluminium (R-Al) were in range of 1381-2187 µg.L-1 (with median 1692 µg.L-1 ). Measured pH levels of LH were in range of 4,74-6,22 (with median 5,62) and concentration of reactive aluminium (R-Al) were in range of 8-400 µg.L-1 (with median 33 µg.L-1 ). Concentrations of R-Al are observed due to toxic forms of Al3+ ions on aquatic organisms. The significant differences in composition of macrozoobenthos were also observed. On strongly acidified study site LK were not present acidosensitive groups, such as mayflies, molluscs and some species of caddisflies. All of these...