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Water hyacinth (Eichhornia crassipes) is a floating non-native plant that has been reoccurring in Lake Chapala, Jalisco, Mexico for more than 100 years. In this research, I explore the effects of water hyacinth on freshwater ecosystems worldwide and specifically on Lake Chapala. In chapter 1, I reviewed studies conducted on water hyacinth worldwide and found that the effects of water hyacinth on water quality are similar but the magnitude of effects is dependent on the percent cover and potentially the spatial configuration of water hyacinth mats. Water hyacinth's effect on aquatic invertebrates, fish, and waterbirds is less predictable and dependent on conditions prior to invasion. In chapter 2, I tested for relationships between percent water hyacinth cover and waterbird abundance, species diversity, community composition, and habitat use. In general, I found a weak positive relationship or no relationship between these variables. In Chapter 3, I monitored habitat use by American Coots (Fulica americana) in a variety of habitats around Lake Chapala. I found that the time spent in water hyacinth positively corresponded to the percent water hyacinth cover and that the time foraging in water hyacinth was positively related to the time spent in water hyacinth. In Chapter 4, I compared invertebrate assemblages in open water to those within and at the edge of water hyacinth mats, emergent vegetation, and submerged trees. I also examined invertebrate assemblages within the roots of water hyacinth plants and compared assemblages between patch and shoreline water hyacinth plants. I found that density and taxonomic richness of water column invertebrates were generally higher in association with water hyacinth, but that mean percent cover of water hyacinth affected the magnitude of differences among habitats and vegetation types. I did not find significant differences in root invertebrate density and taxonomic richness between patch and shoreline water hyacinth plants. In chapter 5, I discuss how water hyacinth affected dissolved oxygen and water transparency on a small, localized scale, but was not the driving factor for seasonal differences. The overall results suggest that water hyacinth had a minimal ecological effect on Lake Chapala during this study. / Ph. D.

The trophic level impact of structural changes in Aufwuchs communities resulting from low levels of stress can be assessed through analyses of the nutritive value of the microfloral community in conjunction with measurements of grazer consumption rates and assimilation efficiencies. Artificial streams dosed with either intermittent chlorination (20 minute doses 3 times per day) or continuous treatments of copper (0.05 ppm) or dextrose (1 or 2 ppm) were used to obtain Aufwuchs communities from stressed environments. Aufwuchs communities were also sampled from the New River within and around a chlorinated-thermal, power plant discharge. Food quality analyses included quantification of organic carbon, protein, carbohydrate, and caloric content through gravimetric, Coomassie blue staining, anthrone staining, and wet chemical oxidation procedures, respectively. Snail (Pleuroceridae:Anculosa) utilization of Aufwuchs from the variously perturbed environments was assessed through laboratory feeding studies employing radiolabeled (sulfur-35) Aufwuchs to determine snail feeding rates and assimilation efficiencies. The heterotrophically dominated Aufwuchs communities developing under the dextrose enrichment contained more protein, carbohydrate, and calories compared to reference communities. These increases were attributed to the copious extracellular mucilage associated with the bacteria. There was no significant change in snail consumption of Aufwuchs from the dextrose enriched streams, although this community was consistently assimilated with greater efficiency relative to reference communities. When Aufwuchs developing under the chlorine or copper treatments became dominated by blue-green algae, the protein content of these communities increased as a result of the algal proteinatious sheath. Carbohydrate content was generally less than reference values for Aufwuchs developing under chlorine or copper stress. Aufwuchs from these treated streams were consumed to a less extent than reference communities and assimilated with 2 to 12% less efficiency. These results agree with literature reports that blue-green algae are a less preferred food for aquatic grazers and are assimilated with less efficiency. Aufwuchs sampled from habitats influenced by the power plant discharge were of less nutritive value compared to samples from uninfluenced stations. Snails consumed more of the reference communities and assimilated them with greater efficiency compared to Aufwuchs influenced by the power plant discharge. Both the autotrophic and heterotrophic components of the Aufwuchs community were labeled with sulfur-35, allowing sensitive measurements of the feeding parameters. Snail feeding studies demonstrated that low levels of stress may not alter grazer consumption of Aufwuchs until substantial changes in algal composition occur. Snail assimilation efficiency was generally a sensitive parameter in assessing trophic level effects of changes in Aufwuchs communities resulting from pollutant impacts. Food quality analyses provided useful information regarding changes in Aufwuchs community structure. A lack of correlation among Aufwuchs food quality parameters and snail utilization measurements reflected the opportunistic feeding strategy of the grazer. / Ph. D.

Headwaters may be small relative to other aquatic ecosystems, but they are neither simple nor static environments. Heterogeneous stream corridors constitute the majority of river network length and regulate cycling of carbon and oxygen as they expand and contract their connections across the landscape. Though headwater streams integrate many biogeochemical signals from the watersheds they drain and provide important ecosystem services, their diverse habitats and dynamic changes in wet length have been under- examined compared to dendritic, perennial streams. This oversight complicates efforts to identify biogeochemical patterns at larger scales. This dissertation sets out to expand our knowledge of stream biogeochemical responses to variable connections both within the channel and the wider stream corridor. First, I investigated how the presence and arrangement of different habitat patches in the stream corridor affected overall emissions of carbon dioxide (CO2) and methane (CH4) from sub-watersheds of a forested mountain stream network. To do this I measured concentration and flux of both gasses along and around 4 streams, including dry reaches and adjacent vernal pools as well as flowing water. I found that emissions were highly variable over space and time; in particular, the presence of a vernal pool enhanced total carbon emissions from the stream corridor. Next, to quantify carbon cycling and export from a non-perennial headwater stream, I monitored concentrations of CO2 and dissolved organic carbon (DOC) at the stream outlet. I found that CO2 concentration had a negative relationship with stream discharge, and that exports of both CO2 and DOC were driven by storms reconnecting isolated surface water reaches. I also found that carbon biogeochemistry of intermediate flow states were unique from driest and highest-flow conditions. Finally, to explore how isolated pools in the stream channel respond to flow decrease and cessation, I measured dissolved oxygen (DO) as well as CO2 and CH4 from persistent pools of two non- perennial streams throughout an unusually dry summer and fall. I found that hypoxia was common in all isolated pools, but swings in DO were not consistent between pools even of the same stream. In using diel changes in DO to estimate metabolism, I also found that ecosystem respiration varied by stream, but gross primary production was more driven by stream surface water connectivity. Climate change is inducing many new patterns in stream hydrology with critical implications for biogeochemical activity, from reducing durations of connectivity to causing stronger storms. Improving our understanding of how surface water and landscape connectivity both influence the movement of carbon within and through streams is essential to resolving questions about the contributions of freshwaters to the global carbon cycle. / Doctor of Philosophy / Headwater streams may seem inconsequential to larger ecosystem processes due to their small size. However, the majority of a river's network length, or the total length of all the streams and rivers from spring to ocean, is made up of headwater streams. The widespread presence of headwater streams over all types of land, along with the unique layout of different aquatic habitats near streams and the fact that small streams often grow and shrink in length, mean that studying headwaters can tell us many things about how energy moves through ecosystems. This dissertation explores how we can use changing headwater connectivity to understand how carbon moves through ecosystems. Connectivity in aquatic science refers to how water can move through space in ways that rocks and trees and even many animals cannot. This idea is useful because water carries things around as it moves, and its presence or absence enables reactions that are essential for the cycling of energy and nutrients. For instance, when water moves from high ground to low ground, it navigates through soil and holes in the ground; it may get slowed down at flat spots where little pools form. I measured emissions of carbon dioxide and methane from streams as well as soils, holes, and pools near mountain streams to try to understand how the path water takes influences how much carbon dioxide and methane escapes into the air. My measurements were surprisingly different depending on where and when I took them. I found that if a seasonal pond is connected to a stream channel, the stream will emit more greenhouse gasses than if the pond goes dry. Connectivity can also describe if water moves continuously along a stream, or if the stream goes dry in places and is then disconnected from different parts of itself. I asked how a stream becoming disconnected affected carbon dioxide emissions as well as the movement of dissolved organic carbon, a food source for microorganisms. I found that the less water moving through the stream channel, the higher carbon dioxide concentrations were. I also found that storms move both carbon dioxide and dissolved organic carbon out of streams quickly, even if the stream had been disconnected. Finally, I investigated the water that is left when streams disconnect. I measured dissolved oxygen, carbon dioxide, and methane in isolated pools of two disconnected streams. By tracking how microbes and algae consume and produce oxygen when a stream is not flowing, I can understand how these lifeforms adapt. I found that isolated pools frequently have very low levels of dissolved oxygen. This means that microorganisms in the pools have to use special ways of getting energy, which in turn affects how different forms of carbon move through the stream ecosystems. Headwater stream ecosystems are very sensitive to small changes in flow and precipitation; however, climate change means that streams are going dry more often than they used to. My findings contribute to our understanding of how changes in stream connectivity have many biological effects that are important for water quality and ecosystem health.

The largemouth bass (Micropterus salmoides) fishery was at an all time low on Lake Okeechobee when experimental supplemental stockings were done to try and enhance local bass populations. Largemouth bass had never been stocked on a large lake like Lake Okeechobee. The objectives were to develop a methodology, study dispersal, and compare stocked versus wild bass habitat choices. The methodology underwent considerable changes between studies. Bass dispersed to the edges by the second sampling period, so a larger sampling area may be needed. Water depth and pH were found to be significantly different between wild and stocked bass. Hatchery bass are naèive about predators, which may have resulted in stocked bass not moving to shallower areas like wild bass. The pH was weakly correlated with depth, so differences may be partially due to the fact that as depth increases, pH may also increase. / by Alyssa Jordan. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

M.Sc. / Please refer to full text to view abstract

M.Sc. (Zoology) / Please refer to full text to view abstract

This master thesis deals with conceptual knowledge of pupils of the primary school about the ecology of the freshwater ecosystem. Pupils get familiar mainly with typical representatives of organisms which are representing the ecosystem, however, understanding the ecology of the ecosystem demands having a deeper insight into many functions and relations characteristic for the specific ecosystem. The author emphasises the importance of the lessons being carried out through educational programmes in nature. A specific educational programme was designed and realised. Then, the knowledge of pupils of the 1st and 2nd grade was tested and compared on the basis who took part in the programme and who did not. In some tasks, a positive impact of the educational programme was achieved. In other tasks, the same or slightly better results were shown by pupils, who did not participate in this specific programme. In the thesis there are discussed factors, which influence the success rate of the educational programme and pupils' understanding of ecologic relations.

Glacial lakes, such as those in the Midwest region of the United States, are ecologically and economically important, and they provide a wide range of ecosystem services, such as habitat for wildlife and fishes, flood control and recreational boating. Glacial lakes often support locally important sport fisheries, such as largemouth bass <i>Micropterus salmoides</i> and bluegill <i>Lepomis macrochirus</i>,<i> </i>which are partially dependent on suitable habitat within lakes. Nearshore vegetation is often removed by lakeshore landowners for perceived aesthetics and boat access, or by area managers as a form of indirect fisheries management and invasive species control. The connection between nearshore vegetation and fish population health, though widely studied is somewhat unclear. In the two research chapters of this thesis we attempted to further understanding of the environmental factors that influence vegetation abundance and distribution, how vegetation abundance and distribution influences fish population abundance and size structure, and how young-of-year (YOY) largemouth bass utilize habitats within the nearshore environment. In the first research chapter, we used structural equation modeling (SEM) and data collected by the Indiana Department of Natural Resources to quantify the complexity of relationships among catchment characteristics (e.g., catchment size), lake morphology, water quality, vegetation abundance and distribution, and fish population abundance and size structure. Across multiple lakes, lake productivity was more influential in explaining cross-lake variation of largemouth bass and bluegill proportional stock density (PSD) and largemouth bass catch per unit effort (CPUE) than vegetation. This may be a result of the feedback between phytoplankton production and rooted vegetation production. The models we constructed provide insights into the complexity of environmental variables that influence nearshore vegetation and fish populations. In the second research chapter we used stable isotopes (δ¹³ Carbon, δ¹⁵ Nitrogen, δ¹⁸ Oxygen and δ² Hydrogen) to examine the consistency of habitat use and foraging of YOY largemouth bass within Indiana glacial lakes. We observed spatial variation in stable isotope ratios of YOY largemouth bass between habitat types and sites. Additionally, there were significant, positive relationships between δ¹³C of locally collected potential prey items and δ¹³C of YOY largemouth bass suggesting localized foraging patterns. Later in the summer, as young bass grew in size and likely switched to piscivory, we did not observe similar spatial variation in young bass stable isotopes or spatial relationships between prey and the young bass suggesting more homogeneous foraging patterns. Understanding the habitat use patterns of young bass may allow for more efficient and effective management of the nearshore environment. Overall, a greater consideration for the complexity of relationships between nearshore habitat and fish populations may facilitate more effective management.

A diurnal study of biological, chemical, and physical parameters was made on the middle course of the, Tualatin River, which drains a 1840 km2 (711 mi2) basin adjacent to metropolitan Portland, Oregon. This portion of the river lies along land in transition of use from rural agriculture to highly urbanized development. There is no nutrient loading of the river from farming practices because there was no return of water from summer, sprinkler irrigation of commercial crops. However, irrigation significantly reduces the volume of water in the river in the summers. Effluents from sewage treatment plants flowing into the tributaries that drain the highly urbanized eastern areas of the river basin are the main cause of degraded water quality and algal biomass in the lower reaches of the river. The Tualatin River above the mouth of Rock Creek is relatively unpolluted, but downstream from Rock Creek the river is highly eutrophic and during the periods of low flow in the summer serves as a sewage oxidation channel. In this same portion of the river there is also evidence that nitrification occurs. Winter floods leach nitrate-nitrogen from the basin, but in the summer the possibility exists. that nitrate-nitrogen may be a limiting nutrient for algal productivity in the river above Hillsboro. The principal source of poly-phosphates is from sewage treatment plant effluents, but concentrations of poly-phosphates in the middle reaches of the river indicate that there is a natural source of poly- and/or ortho-phosphates in the watershed. Removal of phosphorous compounds from the effluents probably would not affect the large algal blooms occurring in the river below Hillsboro. Trace metal analyses indicated that iron, potassium, nickel, zinc, lead, copper, cobalt, and chromium concentrations were higher during flooding. Turbidity readings suggest that these trace elements are deposited on the floodplain. Melted snow water, which caused one of the winter floods, contained concentrations of zinc, ·copper, and lead greater than those found in the river during the flood. Greater concentrations of arsenic and zinc came from farmland than from urban areas. Diversities of the net plankton as measured by the Shannon-Weaver Index did not change from season to season, nor with downstream flow. Species in the net plankton were benthic forms at the upper stations and planktonic forms downstream from Hillsboro, especially in the summer when the reduced flow caused the river to pond. The enriched effluents from Rock Creek did not affect the diversity of the organisms downstream, but supported a larger biomass. By rating the diversities with other studies it was found that the middle course of the Tualatin River is eutrophic but not heavily polluted. A diurnal study was especially valuable from April to September, inclusive, when insolation and temperatures favored biological activities such as photosynthesis and decomposition. From November to January little diurnal change in the water quality was found. Farming had its greatest impact in the quantity of water and municipalities had a more serious impact on the water quality in the middle course of the Tualatin River. Even with the reduced flow from agricultural irrigation, the river can maintain relatively good water quality, except when effluents from sewage plants caused highly eutrophic conditions.