Forests are an important component of the global carbon (C) cycle and contribute to climate change mitigation through atmospheric C uptake and storage in biomass and soils. However, the forest C sink is susceptible to disturbance, which modifies physical and biological structure and limits spatial extent of forests. Unlike severe, stand-replacing disturbances that reset forest successional trajectories and may simplify ecosystem structure, moderate severity disturbances may instead introduce complexity in ways that sustain net primary production (NPP), leading to the phenomenon of “NPP resilience.” In this study, we examined the linkage between disturbance severity and ecosystem biological and physical structural change, and implications for NPP within an experimentally disturbed forest in northern Michigan, USA. We computed spatially resolved and spatially agnostic metrics of forest biological and physical structure before and 10 years after disturbance across a continuum of severity. We found that while biological structure did not change in response to disturbance, three of four physical structural measures increased or were unimodally related to disturbance severity. Physical structural shifts mediated by disturbance were not found to directly influence processes coupled with NPP. However, decadal changes in the spatial aggregation index of Clark and Evans, though not a function of disturbance severity, were found to predict canopy light uptake, leaf physiological variability, and relative NPP within plots. We conclude that ecosystem structural shifts across disturbance severity continua are variable and differ in their relationship to NPP resilience.

The objective of this study was to characterize water quality and hydrologic properties of urban streams in the Richmond metropolitan area. Water quality data were analyzed for six urban sites and two non-urban sites. Geomorphological surveys and conservative tracer studies were performed at four urban sites and one non-urban site to describe intra- and inter- site variability in transient storage, channel geomorphology, and related hydrologic parameters. Urban sites showed elevated concentrations of nitrogen and more variable TSS concentrations relative to reference sites. Urban channels were deeply incised with unstable banks and low sinuosity. Little Westham Creek exhibited the greatest transient storage. This site was characterized by large, deep pools and therefore it is likely that transient storage was associated with surface water storage. Transient storage was low at all other sites, particularly for the study reach at Reedy Creek, which flowed through a concrete channel. Lowest transient storage was observed at this site in spring, though higher values were measured in summer corresponding to the presence of biofilms, A lower, more naturalized section of the concrete channel was found to have greater transient storage suggesting the possibility of passive restoration of concrete channels in urban environments. This study documents variability in the structure and function of urban streams. Restoration projects should work to improve impairments that are specific to each site at both the reach and watershed scale to maximize the efficacy of restoration.

To assess how urbanization impacts stream nutrient uptake, a series of instantaneous (i.e. slug) nutrient additions were conducted in 3 urban and 3 non-urban streams during open and closed canopy conditions. Single additions of N, P, and combined additions of N and P were performed at each site. These data were used to test the hypothesis that high N:P concentrations in urban streams would result in P-limited conditions, and to assess differences in nutrient uptake kinetics (i.e., the relationship between uptake and concentration) between urban and non-urban streams. The results show that there were no consistent differences in N vs. P limitation among urban and non-urban streams suggesting that ambient N:P ratios are not useful predictors of nutrient limitation at the ecosystem scale. Areal uptake rates of N in urban streams were greater than non-urban streams coinciding with elevated N concentrations. Conversely, areal uptake rates of P were similar between urban and non-urban streams because these systems have similar ambient concentrations of P. Urban and non-urban streams demonstrated similar uptake velocity and areal uptake rate responses to increasing nutrient concentrations. However, unique to this study, urban streams had greater uptake velocities at ambient nutrient concentrations. These findings suggest that urban streams could have a greater capacity for nutrient uptake over a broad range of nutrient concentrations, but prior work indicates that this capacity may be constrained by the duration of the nutrient addition.

Invasive plants are a significant threat to native ecosystems and to biodiversity. They are often strong competitors and have multiple techniques to outcompete native plants. Thus, controlling or removing invasive plants facilitates the restoration of native ecosystems. We used GPS technology coupled with field surveying techniques adapted from the U.S. Fish and Wildlife Service to locate and identify invasive plants present within VCU’s Rice Rivers Center. We digitally overlaid a 50-meter x 50-meter grid system over the property. In each grid cell we recorded visual estimations of invasive plant coverage sorted into modified Daubenmire cover classes and used ArcGIS for mapping and analysis. Altogether, we found 25 unique invasive plant species. 93% of the grid cells contained at least one invasive species, and one grid cell contained seven unique species. The influence of anthropogenic disturbance on invasive species distribution, analyzed by using a 50-meter wide buffer zone around each disturbance (e.g., roads, buildings, etc.), showed that the presence and coverage of invasive species was greater within disturbed areas compared to intact forest. Microstegium vimineum, Lonicera japonica, and Ligustrum sinense were most common and widely distributed within terrestrial habitats, while Murdannia keisak was most widely distributed in the restored wetland. Our results for M. vimineum were compared to a similar 2004 study: this species has since spread from 40% to 76% of the grid cells. The spatial maps we have created will be a foundation for an integrated invasive species management program at the Rice Rivers Center and will assist with management, control and restoration efforts within terrestrial and aquatic ecosystems.

Bull trout are a fish species listed as threatened under the Endangered Species Act.Historically, they ranged from Northern California at the southernmost extent, into Canada at the northern most extent, and east into Nevada and Montana. Bull trout are highly migratory and require large, unfragmented habitats to persist and are thus highly susceptible to human induced land-use practices. The goal of my thesis was to obtain a better understanding of bull trout movement patterns in the Walla Walla River, Washington using complimentary techniques; Passive Integrated Transponder (PIT)technology and otolith microchemistry. PIT tags can be injected into a fish body cavity, similar to how pets are “chipped”, and as the fish swim through antennas placed in the river, their location and movements are be documented.Otolith microchemistry is a technique that is similar to analysis of tree rings. The otolith, a hard bony structure of a fish’s ear, develops over a lifetime and as the rings of the otolith are created the chemical signature in the water in which they live is recorded and can be compared to chemical makeup of water samples collected through the river system. Using these two techniques, I found that the age or size of a fish and the season are important factors to explain both a fish’s movements and where in the river a fish might be located at a given time. Knowing at what size, age and season a fish is attempting to migrate allows managers to provide the best possible river conditions (e.g., temperatures, flow) to allow for unimpeded migrations to occur and to foster conservation and recovery of bull trout populations.

Brachylaima spp. (Digenea: Brachylaimidae) are terrestrial trematodes of mammals and birds and have land snails as their first and second intermediate hosts. This thesis describes a new species of Brachylaima and investigates infection in both snail intermediate hosts and definitive host animals. A laboratory life-cycle was established using brachylaimid eggs recovered from the faeces of an infected human. Five species of introduced European helicid and hygromiid snails, Theba pisana, Cernuella virgata, Cochlicella acuta, Cochlicella barbara and Microxeromagna armillata were susceptible first intermediate hosts. These same snails and introduced Helix aspersa as well as the native snails Succinea australis and Strangesta gawleri were suitable second intermediate hosts. Field and laboratory studies revealed that in addition to humans and mice, various species of birds and reptiles were also definitive hosts. On the basis of its unique morphological and lifecycle features, a new species, Brachylaima cribbi was described. The scanning electron microscopical appearances of the various life-cycle stages were detailed. Studies of Swiss albino outbred mice and 8 strains of inbred mice revealed that C57BL/6J mice were most susceptible to B. cribbi infection. The peak infection occurred 4 weeks after inoculation with metacercariae following which worms were expelled over the next few weeks. Exposure to a second infection in C57BL/6J mice did not result in accelerated expulsion of adult worms but did significantly inhibit their fecundity. In contrast, when immunodeficient NOD SCID mice were infected with B. cribbi metacercariae the adult worms persisted for the life span of the host mice. 6,432 land snails were collected over a distance of 3,000 km across southern Australia. Sporocyst-infected snails were found in all districts of South Australia and Victoria with the percentages of infected T. pisana, C. virgata, C. acuta and C. barbara ranging from 1.7 to 4.7%. These 4 species together with M. armillata, S. australis and S. gawleri were infected with metacercariae being found in 18-63% of snails and the mean number of metacercariae per infected snail ranged from 2.1 to 6.1. Laboratory studies revealed that eggs may remain viable for almost 12 months in mouse faeces. The prepatent period for a sporocyst infection is 7-10 weeks after egg ingestion. Metacercariae 7 weeks of age are capable of developing into adult worms. Detailed studies of seasonal variations in sporocyst and metacercarial infection rates were studied at 4 ecologically diverse sites on the Yorke Peninsula of South Australia. The clinical features and epidemiological circumstances of B. cribbi infections of 12 humans are detailed, as is their satisfactory response to treatment with praziquantel. / Thesis (Ph.D.)--School of Molecular and Biomedical Science, 2003.

<p>Industrial and domestic sewage effluents have been found to cause reproductive disorders in wild fish, often as a result of the interference of compounds in the effluents with the endocrine system. This thesis describes laboratory-based exposure experiments and a field survey that were conducted with juveniles of the three-spined stickleback, <i>Gasterosteus aculeatus</i>. This small teleost is a common fish in Swedish coastal waters and was chosen as an alternative to non-native test species commonly used in endocrine disruption studies, which allows the comparison of field data with results from laboratory experiments.</p><p>The aim of this thesis was to elucidate 1) if genetic sex determination and differentiation can be disturbed by natural and synthetic steroid hormones and 2) whether this provides an endpoint for the detection of endocrine disruption, 3) to evaluate the applicability of specific estrogen- and androgen-inducible marker proteins in juvenile three-spined sticklebacks, 4) to investigate whether estrogenic and/or androgenic endocrine disrupting activity can be detected in effluents from Swedish pulp mills and domestic sewage treatment plants and 5) whether such activity can be detected in coastal waters receiving these effluents.</p><p>Laboratory exposure experiments found juvenile three-spined sticklebacks to be sensitive to water-borne estrogenic and androgenic steroid substances. Intersex – the co-occurrence of ovarian and testicular tissue in gonads – was induced by 17β-estradiol (E2), 17α-ethinylestradiol (EE2), 17α-methyltestosterone (MT) and 5α-dihydrotestosterone (DHT). The first two weeks after hatching was the phase of highest sensitivity. MT was ambivalent by simultaneously eliciting masculinizing and feminizing effects. When applying a DNA-based method for genetic sex identification, it was found that application of MT only during the first two weeks after hatching caused total and apparently irreversible development of testis in genetic females. E2 caused gonad type reversal from male to female. E2 and EE2 induced vitellogenin - the estrogen-responsive yolk precursor protein, while DHT and MT induced spiggin – the androgen-responsive glue protein of the stickleback.</p><p>None of the effluents from two pulp mills and two domestic sewage treatment plants had any estrogenic or androgenic activity. Juvenile three-spined sticklebacks were collected during four subsequent summers at the Swedish Baltic Sea coast in recipients of effluents from pulp mills and a domestic sewage treatment plant as well as remote reference sites. No sings of endocrine disruption were observed at any site, when studying gonad development or marker proteins, except for a deviation of sex ratios at a reference site.</p><p>The three-spined stickleback – with focus on the juvenile stage – was found to be a sensitive species suitable for the study of estrogenic and androgenic endocrine disruption.</p>

<p>The focus of this thesis is the early detection of stress in the environment. It has been proposed that studies on the cellular level would detect stress reactions earlier in time compared to common physiological methods. In a series of experiments we investigated how different stress factors, both natural and introduced by man, affect levels of stress proteins. One- and two-dimensional gels were used to determine individual proteins and families of proteins. The two-dimensional gels were also used in a proteomic approach, were the presence and absence of proteins after treatment was observed, and the protein expression signatures (PES) were identified. </p><p>Baltic <i>Mytilus edulis</i> was used in all experiments and it is evident that earlier observed differences in physiological rates and pollution sensitivity, compared to marine mussels, is also manifested as lower concentrations of stress proteins after exposure to copper and cadmium. When the Baltic mussels were allowed to acclimate for one month the difference decreased, suggesting an environmentally induced difference (paper I). Pre-exposure to heat before exposure to either a second heat-shock or cadmium was found to enhance the levels of HSP70 and thus tolerance, significantly (paper II). Exposure to a mixture of stress factors (PCB, copper and lowered salinity) revealed synergistic, additive and antagonistic effects in induction of 6 different stress proteins. When analyzing a large number of proteins it was shown that it is possible to identify PES with this technique, and we hypothesize that it could be possible to separate responses to mixtures of stress factors (Papers III and IV). Different techniques were also applied to analyze the protein expression pattern when mussels were exposed to PAH- and PCB-fractions extracted from Baltic Sea sediments. In this experiment the protein assays were accompanied by physiological measurements. All methods indicated stressed conditions, but the variation between individual mussels within treatments was smaller in terms of protein response than for physiological parameters (paper V). It is concluded that measuring the induction of stress proteins is a reliable way to detect stressful conditions. Proteins visualized on a one dimensional gel give a “gross” picture of an organism’s condition. The major challenge is to identify the origin and severity of the elucidated stress response. Further mapping of two-dimensional gels suggested that protein patterns are specific to type and level of stress. </p><p>A most important future step is to establish links between sub-cellular protein response to well known physiological effects. This should include long term experiments where altered protein expression signatures are linked to life history characteristics like survival, growth and reproductive success.</p>

<p>In the green-veined white butterfly (<i>Pieris napi</i>), females obtain direct fitness benefits from mating multiply and studies have shown that fitness increases seemingly monotonically with number of matings. The reason is that at mating males transfer a large nutritious gift (a so called nuptial gift) to the females that the females use to increase both their fecundity and lifespan. In addition, if exposed to poor food conditions as larvae, females mature at a smaller size compared to males. Accordingly, it was suggested that smaller females could compensate for their size through nuptial feeding by, for instance, mating more frequently. We did not find any support for that hypothesis. On the contrary, larger females remated sooner and had a higher lifetime number of matings. Neither were smaller females able to compensate in any other way, because singly mated females and multiply mated females suffered to the same extent from their smaller size. This thesis also shows that despite the positive relationship between fitness and number of matings, there is a large variation in female mating frequency in wild populations and about every second female mates only once or twice. This variation is not dependent on how often females get courted by males, because female mating frequency was shown not to be affected by male courtship intensity. Hence, the reason for the low mating frequency could either be that males have evolved the ability to manipulate females to mate at a suboptimal rate as a measure of protection against sperm competition, or alternatively, that female mating rate is suppressed by some costs. Using two selection lines, artificially selected for either a high or a low mating rate, we showed that the variation in mating rate was mainly a female trait because which line the females were from affected their mating rate whereas which line the male was from did not. This implies that females mate at a low rate due to hidden costs or due to constraints. The same study also showed that females with a high "intrinsic" mating rate lived shorter, but only when denied remating. This led us to test the hypothesis that the cost females face is to have the ability to mate at a high rate but the cost is only paid when remating opportunities are scarce. However, we found no support for such an idea, because females with a high intrinsic mating rate held in a cold environment where the butterflies were prevented from flying and feeding did not live shorter. Neither was there an effect of a female’s mating rate on her ability to quickly break down and convert male nutrient gifts into egg material. Female mating rate did, on the other hand, affect dispersal tendency, with low mating rate females being more inclined to fly between different habitats. The underlying reason for this is still to be explored.</p>

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