Lethal biotic interactions strongly influence the potential for aquatic non-native species to establish and endure in habitats to which they are introduced. Predators in the recipient area, including native and previously established non-native predators, can prevent establishment, limit habitat use, and reduce abundance of non-native species. Management efforts by humans using methods designed to cause mass mortality (e.g., trapping, biocide applications) can reduce or eradicate non-native populations. However, the impacts of predator and human induced mortality may be mitigated by the behavior or population-level responses of a given non-native species. My dissertation examined the responses of non-native aquatic species to the risk of predation by novel (i.e., no previous exposure) predators in the recipient community and indicators of potential compensatory responses by non-native populations to increased mortality resulting from removal efforts. My dissertation addresses four primary questions. 1) Can first generation, naïve invaders recognize and defend against predators found within the region of invasion through the expression of inducible defenses? 2) Can the overcompensatory potential of a population be predicted through examinations of intraspecific interactions of individuals from the population? 3) What is the relationship between removal effort outcome (i.e., successful or unsuccessful reduction of the target population) and compensatory population responses? 4) Is there a relationship between characteristics of removal efforts that are typically available to managers (e.g., target area size, target area connectivity, removal methodology) and compensatory population responses that could indicate the relative likelihood of compensation resulting from removal efforts? An invading species should be more likely to establish if it can successfully identify and defend against predators in the recipient range, such as through the expression of inducible defenses. Inducible defenses are behavioral or physiological changes that reduce an organism's susceptibility to predation. Through a series of laboratory experiments, I tested whether inducible defenses, in the form of increased burrowing depth, may have benefited the early stage of invasion of Nuttallia obscurata (purple varnish clam), an established Northeast Pacific invader. Specimens of N. obscurata were collected from introduced populations in the Northeast Pacific and from a native population in Japan. The clams were exposed to chemical and physical cues from Northeast Pacific crab predators, including the native Metacarcinus magister (Dungeness crab), an abundant and frequent predator of N. obscurata. While introduced N. obscurata increased their burrowing depth in the physical presence of M. magister, clams collected from their native range showed no such response. This lack of increased burrowing depth by naïve clams in response to a predator native to the newly invaded range, but a significant increase in depth for clams from populations established in the range suggests that while inducible defenses likely did not contribute to the initial establishment of N. obscurata in the Northeast Pacific, they may contribute to their continued persistence and expansion in their introduced range. Some efforts to reduce invasive populations have paradoxically led to population increases. This phenomenon, referred to as overcompensation, occurs when strong negative density-dependent interactions are reduced through increased mortality within a population, resulting in an increase in the population's recruitment rate sufficient to increase the population's overall abundance. Increases in a population's recruitment rate can result from reduced cannibalism of juveniles resulting in lower mortality of new recruits, from increased adult reproductive output, which increases the number of potential recruits, or from reductions in size and/or age at maturity of the unharvested population, which increases the number of reproductive individuals. I predicted the overcompensatory potential of a population of Carcinus maenas (European green crab) in Bodega Harbor, California, using a series of laboratory and field experiments examining intraspecific pressures of adults on juveniles in the population. This measure of intraspecific pressure was used to predict the overcompensatory potential of the population in response to increased mortality from ongoing removal efforts. This prediction was then assessed using pre- and post-removal surveys of juvenile recruitment in Bodega Harbor compared to nearby populations, testing for evidence of overcompensation. While adult C. maenas in Bodega Harbor had limited negative impacts on juveniles, I concluded it was unlikely to result in overcompensation. Relative juvenile abundance did not statistically increase in removal compared to reference populations, consistent with my conclusion from the experiments. Increases in recruitment rates can occur as a result of efforts to remove non-native species. This increase in recruitment can result in overcompensation, but more commonly results in compensation, where recruitment rates increase relative to pre-removal recruitment but does not result in in the population's abundance exceeding pre-removal levels. However, a detailed and accurate prediction of the response of a population to harvest is time consuming and data intensive. This is not feasible for most efforts to eradicate non-native species, which have the greatest chance of success when enacted rapidly after detection. For my final chapter, I performed a literature review and accompanying statistical analysis to determine if typically available information related to the removal effort (site size, site connectivity, and removal technique) could be used to determine increased risk of compensation for a given effort to remove aquatic invasive species. Compensation was closely linked to unsuccessful removal efforts and was observed only among efforts utilizing physical removal methods. However, the frequency with which compensation occurred varied with the exact technique employed, occurring most frequently in removal utilizing electrofishing. Additionally, evidence of compensation was more frequent among larger removal areas with variable connectivity. While other predictors (temperature, effort, etc) might add to the predicative power, the findings of the review provide criteria for managers to determine the relative risk of compensation prior to the start of removal. Further understanding of how invasive species respond to lethal biotic interactions, including anthropogenically mediated control measures, can aid in assessing the risk of invasion for a given species and inform managers of the risk of complications resulting from removal efforts. While inducible defenses may contribute to the long-term success of an introduced species in their recipient range, my findings did not support the idea that inducible defenses triggered by predator cues contributed to their initial introduction in this case. However, research on other non-native species and offspring of previously naïve prey would allow for a clearer picture of the role of inducible defenses in the invasion process. Compensation resulting from removal efforts does not guarantee failure, and certain characteristics of removal efforts seem to indicate increased risk of compensation. Together these components help identify how biotic interactions surrounding mortality risk of an invading species help shape the trajectory of invasion.

Wastewater application to land can be a useful tool for mitigating impacts of nutrient enrichment on aquatic systems. A land application treatment system at VCU’s Rice Rivers Center in Charles City County, VA provided an opportunity to study the impact of wastewater addition on the biogeochemistry of forests representative of the Mid-Atlantic Coastal Plain. Nutrient concentrations in throughfall and leachate were measured at Treatment and Control sites to assess differences in nutrient deposition and retention. Wastewater amended plots from the Walter L. Rice education building received 20-fold (N) and 6-fold (P) higher inputs relative to Control plots and plots located at the Virginia Department of Game and Inland Fisheries building. Despite higher inputs, leaching losses of P from the Rice Treatment plots were comparable to Control plots, indicating that the land-based application system effectively mitigated wastewater loads. Leaching losses of nitrate were two-fold higher from Treatment plots relative to Controls, suggesting a potential N saturation effect and a reduction in N retention capacity of the treated forest. Nitrogen effects on vegetation were indicated by lower root biomass and greater root N content among Treatment plots relative to Control plots. Overall, these results suggest that wastewater–amended plots near the Rice education building receive appreciably higher nutrient inputs and could, therefore, serve as a model system for assessing effects on forest ecosystems.

Five captive Bornean orangutans (Pongo pygmaeus) were observed in order to better understand their spatial selection, behavior, and interaction with their environment and each other. A newly introduced adult male's interactions with a female group containing two adults, one adolescent, and one juvenile, was documented. Visual observations were performed to document individual behaviors, along with any interactions with silvery langur monkeys, public crowd levels, temperature, and enrichment props. Methods included 15 observation periods, 0.5-3 hours in length each, during which behaviors were verbally and visually confirmed using a HD video camera. Spatial locations of each individual were recorded every three minutes during each observation period. The orangutan enclosure was measured and mapped using terrestrial laser scanning (TLS), and observed behaviors and spatial locations were georeferenced to the resulting 3D model depicting the exhibit. Results were summarized as time-activity budgets and were geo-visualized using 3D plots and density maps. This research demonstrated how the application of spatiotemporal and behavioral analysis coupled with TLS and three-dimensional modelling can be used to better study captive primates. These types of studies are important as zoos increasingly become home to great ape species.

Most studies of wetlands tend to focus on the biotic and abiotic interactions within the aquatic habitat. Though wetlands and associated biota may appear to be somewhat isolated from the influence of the wider landscape, wetland habitats are critically linked with adjacent terrestrial habitats and other wetlands through the two-way flows of energy and nutrients and provision of structure. While an understanding of these inter-habitat linkages is breaking down the perceived boundaries between &quotaquatic" and &quotterrestrial" ecosystems, there is more limited knowledge on the ecology of wetland animals that must meet critical needs in both aquatic and terrestrial habitats at some time during their life or seasonal cycles. Here, I examine the terrestrial ecology of a freshwater turtle, the eastern long-necked turtle (Chelodina longicollis) in the temporally dynamic and heterogeneous landscape of Booderee national park in south-east Australia by 1) providing a description of terrestrial behaviours, 2) identifying the factors driving terrestrial behaviour and its functional significance, 3) examining factors that may limit or constrain terrestrial behaviour and 4) demonstrating how various terrestrial behaviours can factor prominently in the overall biology of a nominally aquatic animal. Chelodina longicollis used terrestrial habitats for reasons other than nesting, including aestivation and movements between wetlands. Radio-telemetry of 60 turtles revealed that nearly 25 % of all locations were in terrestrial habitats up to 505 m from the wetland, where turtles remained for extended periods (up to 480 consecutive days) buried under sand and leaf litter in the forest. Individuals also maintained an association with a permanent lake and at least one temporary wetland within 1470 m, though some inter-wetland dispersal movements were much longer (5248 m). As a result of their associations with several wetlands and terrestrial aestivation sites, C. longicollis traversed large areas and long distances (13.8 +/- 2.8 ha home range, 2608 +/- 305 m moved), indicating that this species is highly vagile. In fact, a three-year capture-mark-recapture study conducted in 25 wetlands revealed that 33% of the population moved overland between wetlands. After scaling this rate to the number of generations elapsed during the study, C. longicollis moved between discrete water bodies at a rate of 88-132% per generation. This rate is not only high for freshwater turtles, but is among the highest rates of inter-patch movement for any vertebrate or invertebrate. Chelodina longicollis demonstrated an impressive capacity for individual variation in nearly every aspect of its behaviour examined. Most of the variation in space use, movements, terrestrial aestivation and activity could be attributed to extrinsic local and landscape factors, seasonal influences and rainfall, whereas intrinsic attributes of the individual such as sex, body size, body condition and maturity status were less important. Turtles increased movement distance and home range size in regions where inter-wetland distances were farther and with increasing wetland size. Individuals spent more time in terrestrial habitats with decreasing wetland hydroperiod and increasing distance to the nearest permanent lake. Overland movements between wetlands were correlated with rainfall, but the directionality of these movements and the frequency with which they occurred varied according to the prevalent rainfall patterns; movements were to permanent lakes during drought, but turtles returned to temporary wetlands en masse upon the return of heavy rainfall. However, deteriorating conditions in drying wetlands forced turtles to move even in the absence of rainfall. Captures at a terrestrial drift fence revealed that immature turtles as small as 72.3 mm plastron length may move overland between wetlands with similar frequency as larger adults. Taken together, these results suggest that C. longicollis behaviour is in part conditional or state-dependent (i.e., plastic) and shaped by the spatiotemporal variation and heterogeneity of the landscape. Perhaps the most surprising aspect of individual variation was the alternate responses to wetland drying. Turtles either aestivated in terrestrial habitats (for variable lengths of time), or moved to other wetlands. Movement to other wetlands was the near universal strategy when only a short distance from permanent lakes, but the proportion of individuals that aestivated terrestrially increased with distance to the nearest permanent lake. When long distances must be travelled, both behaviours were employed by turtles in the same wetland, suggesting that individuals differentially weigh the costs and benefits of residing terrestrially versus those of long-distance movement. I propose that diversity in response to wetland drying in the population is maintained by stochastic fluctuations in resource quality. The quality of temporary wetlands relative to permanent wetlands at our study site varies considerably and unpredictably with annual rainfall and with it the cost-benefit ratio of each strategy or tactic. Residency in or near temporary wetlands is more successful during wet periods due to production benefits (high growth, reproduction and increased body condition), but movement to permanent wetlands is more successful, or least costly, during dry periods due to the fitness benefits of increased survival and body condition. I used the doubly-labelled water (DLW) method to provide the first estimates of water and energy costs of aestivation and overland movement for any freshwater turtle behaving naturally in the field. Chelodina longicollis remained hydrated while terrestrial with water flux rates (14.3-19.3 ml kg-1 d-1) on par with those of strictly terrestrial turtles, but field metabolic rate during aestivation (20.0-24.6 kJ kg-1 d-1) did not indicate substantial physiological specializations in metabolism during aestivation. Energy reserves, but not water, are predicted to limit survival in aestivation to an estimated 49-261 days, which is in close agreement with the durations of natural aestivation. The energy costs of overland movement were 46-99 kJ (kg d)-1, or 1.6-1.7 times more expensive than aestivation. When a wetland dries, a turtle that foregoes movement to other wetlands can free sufficient energy to fuel up to 134 days in aestivation. The increasing value of this energy &quottrade-off" with travel distance fits our behavioural observations of variance in response to wetland drying. Taken together, this evidence indicates that terrestrial habitats provide more than just organic and structural inputs and filtering services and that nearby wetlands are important for reasons other than potential sources of occasional colonists to a population. Terrestrial habitats are used for aestivation in response to wetland drying and different wetlands are diverse in their functions of meeting the annual or life-cycle requirements of C. longicollis in temporally dynamic wetland systems. As overland movements between these various habitat types are in response to spatiotemporal variation in habitat quality and associated shifts in the fitness gradient between them, I suggest that terrestrial and different aquatic habitats in Booderee offer complementary resources contributing to regional carrying capacity and population persistence of the turtle population. Thus, important ecological processes regulating C. longicollis in a focal wetland should not be viewed as operating independently of other nearby wetlands and their adjacent terrestrial habitats. Collectively, these findings highlight the complex and dynamic associations between a population of freshwater turtles and the wider terrestrial and aquatic landscape, demonstrating that turtle populations and the factors that impact them can extend well beyond the boundaries of a focal wetland.

<p>Meiofauna, and especially marine nematodes are common in sediments around the world. Despite very wide ranging distributions in many nematode species, little is presently known about their dispersal mechanisms shaping these patterns. Rafting, and perhaps ballast water transport has been suggested as viable means for nematode long-range transport. On a much smaller scale other processes have been suggested for their dispersal. They generally include some form of passive suspension into the water column and later on a passive, haphazard settling back towards the bottom.</p><p>Small-scale phenomena in nematode dispersal were studied by conducting a series of studies at Askö field station, Trosa Archipelago, Baltic proper. Studied aspects were one case of macrofaunal influence on nematode dispersal rate, using an amphipod, <i>Monoporeia affinis</i> as disturbing agent, and three different studies on mechanisms related to settling. The experiments were conducted both in laboratory and field settings.</p><p>The amphipod <i>Monoporeia affinis</i> did not exert any influence on the dispersal rate in the nematodes. The nematode dispersal was only an effect of time, in the aspect that the more time that past, the more nematodes dispersed from their place of origin. The settling experiments revealed that nematodes do have an active component in their settling behaviour, as they were able to exert influence on the spot where they were to settle. They were able to choose settling spot in response to the food quality of the sediment. It also became evident that contrary to common belief, nematodes are able to extend their presence in the water column far beyond the times that would be predicted considering settling velocities and hydrodynamic conditions alone.</p>

<p>The work in this thesis deals with effects of changed species richness on process rates among stream-living macroinvertebrates. Global biodiversity is decreasing rapidly and it is poorly known what the consequences of this loss may be for ecosystems and the services they provide. Hence, it is important to investigate the potential effects of losing species. In streams, deforestation, introduction of non-native species, pollution and channelization are examples of events that may affect species richness negatively. In this thesis emphasis is on changes in species richness within functional feeding groups (FFGs) of stream-living macroinvertebrates. The FFGs used were shredding detritivores, grazers, filter feeders and predators - all of which uphold important ecological processes in streams. Along with an observational field study, species richness was manipulated in laboratory and field experiments to investigate the effects of changed species richness on process rates and thus ecosystem functioning.</p><p>The results show that effects of changed species richness on process rates may be dramatic. Among the shredding detritivores there were negative effects on leaf mass loss, regardless whether fixed, random or predicted sequences of species loss was investigated. These effects could be attributed to either species richness per se or species composition. However, among the other FFGs the relationship between species richness and process rates was less consistent. In filter feeders, there was no or a negative effect of decreasing species richness while both grazers and predators showed positive effects of species loss.</p><p>The results also show that the most important interactions between species in an experiment, thus potentially in a natural community, are likely to determine what the effect of species loss on process rates will be. Facilitation and niche differentiation lead to reduced process rates if species are lost, while mechanisms, such as interspecific resource or interference competition, produce the opposite effect. Furthermore, in systems with a diminishing resource, the first two mechanisms may become more important over time enhancing the effect of species loss in the long term.</p><p>In conclusion, effects of species loss may be dramatically negative or positive even if lost species are classified as redundant. The effect in the short term most likely depends on which species are lost, on the original species composition and on the underlying mechanisms. Questions remaining to be answered are how important the observed effects are in more complex systems and if they are persistent over time? Future studies will tell. </p>

<p>This thesis deals with the dynamics of tundra living voles with emphasis on the most common one, the grey-sided vole (Clethrionomys rufocanus). The tundra area chosen for the study was Finnmarksvidda, a vast flatland in northernmost Norway. All small mammal herbivores in the area showed dramatic fluctuations, and field experiment were conducted in order to elucidate these density fluctuations. The specific subjects addressed included: 1/ Temporal and spatial appearance of density fluctuations of voles and lemmings in the area, 2/ The generality of the density patterns observed, 3/ The impact of predation by vole predators during summertime, 4/ The impact of grey-sided vole grazing on food plants of different preference in a predator free environment, in the presence and absence of extra food, and 5/ The impact of food availability on density and demography of grey-sided voles in a predator free environment.</p><p>The results achieved showed that voles in the slope and lowland had cyclic density fluctuations with 5 years duration. The cycles consisted of four phases: an increase phase, a peak phase, a decline phase and a crash phase. In the unproductive lowland and on the moderately productive slope, small pockets of productive habitats seemed to work as “triggers” for the cycles. The lemming fluctuations in the upper plateau (separated from the slope by a steep zone of boulders) differed markedly from the vole patterns in the lowland.</p><p>Only two lemming peaks were recorded in twenty years. Both peaks had very short increase phases, a knife-sharppeak phase and no decline phase before the crash. A comparison between our results and lemming and vole populations from two other areas in Fennoscandia revealed the same difference in fluctuation pattern between lemmings and voles as seen in our area. This results suggests that lemmings in barren tundra highlands and voles in slightly more productive tundra lowlands are regulated by different mechanisms.</p><p>The exclusion of vole predators from vole populations during summertime led to increase in overall vole density. Densities of the clumsy field vole (Microtus agrestis) and juveniles of all species showed the strongest positive effects of the exclusion.</p><p>An experiment analysing the effects of food availability was conducted in islands in a large lake where grey-sided voles were introduced to predator free islands . Supplemental food was given to the voles in two unproductive, and two productive islands. Two unproductive and two productive islands were used as reference islands. The density of voles and the vole weight were higher in both the islands with supplemental food and those with high natural productivity. Increased vole density did not significantly increase grazing damage to plants. The cyclic density pattern of the voles in the nearby mainland (that harboured resident vole specialist predators as stoat and weasel) showed little resemblance to the seasonal fluctuations found in the islands (devoid of resident vole specialist predators). This result suggested that predation by stoat and weasel on grey-sided vole populations may cause the cyclic vole fluctuations seen in the area.</p>

<p>The oak district of Östergötland is one of the largest oak forests left in Europe and it harbours many threatened species dependent on old hollow trees. In this study, the saproxylic beetle <em>Osmoderma eremita</em> living in hollow oaks was used as a model species and parameterised for a metapopulation model (the incidence function model) at the level of individual trees. The aim was to set up a number of conservation management scenarios, where new oaks were added to increase the quality of the matrix and then simulate the resulting metapopulation occupancy, using three levels of dispersal. A real data set of hollow oaks was used as the base for modeling. Oaks were added to cells in a lattice covering the study landscape, where cell size, cell position and numbers of oaks per hectare were varied. The results show that a larger area of added oaks and a greater number of oaks per hectare will give a higher increase in total occupancy, no matter the dispersal, but the second smallest cell size used (3.4 km2 ) will give the highest response per effort for medium and high dispersal abilities, and smaller cells with greater number of oaks per area can be more effective. The spatial position of the increase in occupancy differs depending on dispersal ability of the focal species and should be considered in conservation management work. For unoccupied cells, the effort required to get the cell occupied will be smaller for cells having a greater number of oaks.</p>

<p>Most urban areas of developing countries were hitherto experiencing unprecedented growth in their population, the phenomenon commonly referred to as urbanization, which in this study can be said to be the proportion of urban population relative to the total population of a region. </p><p>This phenomenon has opportunities vis-à-vis challenges, whose impact on natural resources in general and water resources in particular, cannot be over- emphasized. It is within the context of these urban challenges that this study attempts to look into and possibly assess the situation in the urban and peri- urban areas of Kumasi Metropolitan Area (KMA) in Ghana, whose urbanization processes is prejudiced by this study to be increasing rapidly. </p><p>The study specifically attempted to assess thechanges in the urbanization patterns and the possible future urbanization trend of the area within a specific time frame. The study also attempts to look at the causes of this urbanization, and its impact on water resources in the Area, both qualitatively and quantitatively, envisaged to be the results of socio-economic activities taking place in the Area. Finally, the study attempts to look into the measures put in place to curb these challenges. </p><p>Amid paucity of data, however, the study reveals that the most single contributor of urbanization processes in the area has been migration from the countryside, and in particular from the northern part of the country. The study also reveals the fact that even though the general quality standard of some water resources is better, the largely uncontrolled socio-economic activities, coupled with the deplorable sanitary conditions in the KMA, has potential to degrade the water resources in the KMA. In addition, the study reveals that little attention is given, in terms of policy formulation to curb this urbanization processes and to protect water resources in the area.</p>

<p>An understanding of the impacts on freshwater systems from water management and development practices and the recognition that freshwater ecosystems are dependent on various aspects of the natural hydrological variability has given rise to a relatively new field of science commonly referred to as environmental flows. The assessment and application of environmental flows has advanced considerably in the last ten years. To coincide with the emergence and expansion of the environmental flows concept around the world, this survey study was undertaken aiming to identify people’s perceptions and interpretations of the environmental flows concept and its role in water management. It also aims to add to existing knowledge of the extent to which the concept is being applied, how it is being translated into policy and practice and the major challenges and opportunities that exist for continued understanding and implementation. The survey was distributed to a range of people representing different water-related sectors and regions around the world. A total of 272 responses representing 64 countries in the six major regions of the world was received. The responses were compiled and analysis of aspects of the respondents backgrounds as well as the questions were conducted using the computer statistical program SPSS. Representation of specific groups, particularly water user groups, and specific regions in the survey however was low, demonstrating possible limitations of the survey distribution method as well as the lack of concept awareness and application in many parts of the world. The ways in which people define and interpret the concept varied widely. The degree to which the concept was applied shows the growing recognition around the world of the need to consider the environmental water requirements when making decisions on water allocations. Despite the growing recognition many areas do not yet apply the concept. The survey allowed the opportunity for respondents to highlight what they perceived asthe major obstacles and difficulties for the concept within their respective areas. Lack of understanding among stakeholders of the socio-economic costs and benefits associated with concept implementation and a lack of political will were the two most common obstacles for the continued adoption and application of environmental flows around the world. Overall, the survey delivered promising signs for the continued evolution of environmental flows within water management. There was widespread opinion that the concept of environmental flows was an essential element in the efforts to achieve sustainable management of water resources.</p>