Arundo donax, or giant reed, is a large, bamboo-like plant native to Spain that has invaded several thousand acres of the Rio Grande riparian in Texas. The plant grows to 18-24 feet, consuming large quantities of water per acre per year. With concern of increased water demands in the Texas Lower Rio Grande Valley region, the United States Department of Agriculture-Agricultural Research Service (USDA)ARS) is investigating four herbivorous insects as potential biological control agents for Arundo donax to facilitate increased water supply. This study examines select economic implications for agricultural water users in the United States of applying these biological control agents along the Rio Grande. The research includes (a) estimating the value of the water saved due to the reduction of Arundo donax, (b) a benefit-cost analysis, (c) regional economic impact analysis, and (d) an estimate of the per-unit cost of water saved over a 50-year planning horizon (2009 through 2058). The model ArundoEcon is used to perform a deterministic analyses using low- and high-marginal-composite acre values. Regional results indicate present values of farmlevel benefits ranging from $97.80 to $159.87 million. Benefit-cost ratios are calculated with normalized prices and range from 4.38 to 8.81. Sensitivity analyses provide a robust set of results for Arundo water use, replacement species water use, Arundo expansion rate after control, value of water, and the cost of the program. The pre-production processes and farm-gate economic impact analysis is estimated using multipliers from the IMPLAN model. Regional results reveal a range of $8.90 to $17.94 million annually in economic output and 197 to 351 new jobs for the year 2025. Further results show the cost per acre-foot of water saved is $44.08. This amount is comparable to other projects designed to conserve water in the region. The USDA)ARS, Weslaco, Texas Arundo donax biological control project realizes positive results for the benefit-cost ratios, economic impact analyses, and competitive results for the per-unit cost of saving water. These positive results indicate this project will have positive economic implications for the U.S. and the Texas Lower Rio Grande Valley.

Invasive organisms are one of the major threats to the ecological integrity of aquatic systems in the 21st century. Among the most notorious and important aquatic invasive organisms are the dreissenid mussels, Dreissena polymorpha and D. rostriformis bugensis, which having originated in the Ponto-Caspian region are now common in many parts of Europe and North America. Dreissenids have large impacts on many aspects of lentic ecosystem functioning, the sum of which is thought to lead to the translocation of biological production from the pelagic to the littoral zones of lakes. In this thesis I explore the effects of dreissenids on the nearshore zones of large lakes, investigate the mechanisms by which dreissenids couple the pelagic and nearshore zones of lakes and attempt to elucidate the factors affecting the strength of the dreissenid-mediated connection between the pelagic and littoral zones. The effects of invasive organisms on an aquatic ecosystem will depend, in part, on the distribution and biomass of the invasive organisms in the system. In chapter 2 I present the results of a lake-wide survey of the distribution of invasive dreissenid mussels in Lake Simcoe, Ontario and discuss some of the factors that shape their distribution pattern in the lake. Dreissenid biomass averaged 27.2 (±24.3 SD) g shell-free dry mass (SFDM)/m2 in the main basin of Lake Simcoe and 12.4 (±16.9 SD) g SFDM/m2 in macrophyte-dominated Cook’s Bay. I argue that water movement is an important determinant of dreissenid distribution, both through catastrophic disturbance in shallow water and through non-catastrophic effects on substrate distribution and possibly food supply rates. In areas of dense macrophyte growth, mussel abundance was shown to be associated with that of preferred macrophyte taxa, in particular with that of Ceratophyllum demersum. I used the results of my survey and the relationships between environmental variables and dreissenid biomass to estimate the total biomass of dreissenids in Lake Simcoe: 12,000 tonnes SFDM. Most of the dreissenid biomass in Lake Simcoe was concentrated in the nearshore zone, where dreissenids would have maximal impacts on littoral biological production. One of the effects of the dreissenid invasion into the Laurentian Great Lakes appears to be a resurgence in the abundance of the nuisance alga Cladophora glomerata which experienced a marked decline following phosphorus abatement in the late 1970s and early 1980s. A subsidy of bioavailable phosphorus excreted by dreissenid mussels could be an important mechanism facilitating the growth of C. glomerata. In chapter 3, I describe a survey of dreissenid distribution and abundance followed by in situ experiments designed to measure dreissenid phosphorus excretion rates. Average dreissenid mussel abundance in our study area was 3674 (±2233 SD) individuals/m2, with an average biomass of 52.2 (±29.0 SD) g of shell free dry mass/m2. The mussels excreted bioavailable soluble reactive phosphorus (SRP) at an average rate of 7.0 μg SRP/g shell free dry mass/hour, contributing about 11 tonnes of SRP to the study area over the C. glomerata growing season. Dreissenids appear to be an important source of recycled bioavailable phosphorus to the littoral zone, potentially supplying more soluble reactive phosphorus to the study area than local watercourses and waste water treatment plants, and more phosphorus than is required to sustain local C. glomerata growth. Dreissenid establishment in many systems coincides with increases in the abundance and diversity of littoral benthic invertebrates and with changes to community composition of the benthos. Currently, there is a lack of long-term studies of the impact of dreissenid mussels on hard-substrate inhabiting littoral benthos. In chapter 4 I compare the littoral benthos of Lake Simcoe, Ontario just prior, and 14 years following the establishment of dreissenids in the lake. Densities of non-dreissenid invertebrates on hard substrata increased by nearly 50 times, from an average of 367.9 (±460.8 SD) individuals/m2 in 1993 to an average of 16,706.4 (±10,204.5 SD) individuals/m2 in 2008. The taxonomic diversity of the benthos increased significantly. The distribution of benthic organisms also changed; the numerical abundance of benthos has become more even across depths and sites, as has community composition. I suggest that in addition to increasing resource availability to benthic organisms dreissenids have also caused a homogenization of the littoral habitat by increasing the evenness of the distribution of food and habitat resources. The changes in the littoral benthic community in Lake Simcoe likely have wide-ranging implications to higher trophic levels and the cycling of energy in the lake. In addition to impacting nutrient cycling and the benthic invertebrate communities of littoral zones, dreissenid mussels can have large effects on food webs and energy cycling. In chapter 5 I used stable isotope analysis of pre- and post-dreissenid components of the nearshore food web of Lake Simcoe, Ontario to determine how dreissenids affected food sources and energy flow in the littoral zone of Lake Simcoe. Results suggest that the post-dreissenid food web relies about equally on two energy sources: dreissenid biodeposits (redirected pelagic primary production) and littoral benthic primary producers. Although the relative importance of pelagic and benthic primary production to benthic organisms has not changed much following dreissenid establishment, the absolute importance of both increased considerably in the post-dreissenid littoral zone: the large increase in invertebrate biomass that followed dreissenid establishment means that the amount of both pelagic and benthic primary production needed to sustain post-dreissenid organisms had to increase considerably. The results of this chapter suggest that dreissenids increase the availability to food to littoral organisms by redirecting pelagic primary production to the benthos and by stimulating littoral benthic primary production. The impacts of dreissenids on littoral benthic organisms probably have large effects on littoral and pelagic fish communities of lakes. Dreissenid mussels translocate biological production to the benthos by stimulating benthic primary production through nutrient excretion and increases in water clarity, by increasing habitat availability for benthic organisms and by biodepositing pelagic material that becomes available to benthic organisms and the fish that feed on them. I argue that hydrodynamic factors are important in controlling the strength of the dreissenid-mediated pelagic-littoral connection in lakes. Because hydrodynamics relate to lake size, a relationship between lake size and the ability of dreissenids to translocate production the littoral zone can be postulated, where dreissenid effects are maximal in intermediate-sized lakes.

The mechanisms that allow invasive species to flourish in novel habitats are poorly understood. A. petiolata (Alliaria petiolata) is an invader of North American forest edge and understory communities. A. petiolata’s success may result from high competitive ability due to its suppression of mycorrhizal fungi used by other species. In a greenhouse experiment, I grew 27 target species in the presence and absence of A.petiolata in soil with and without a history of A. petiolata. I found that soil with a history of A. petiolata had depleted plant available nitrogen and reduced mycorrhizal fungal colonization of target species. A. petiolata competition suppressed the growth of target species less in soils with than without A. petiolata history. Furthermore, I found that tall plants with finer roots more effectively suppressed the growth of A. petiolata. My results suggest that soil feedback effects do not improve A. petiolata’s competitive ability and are unlikely to contribute to A. petiolata invasion.

Invasive species are a known stressor on aquatic ecosystems, particularly in the waters of the Great Lakes basin. A recent invader, Hemimysis anomala, has had significant impacts on the food webs of Europe, where it invaded previous to its spread to North America. However, despite the fact that Hemimysis is now widespread in the Great Lakes basin, no analysis has been done on the trophic position of Hemimysis in North America invaded sites. This thesis used carbon (??13C) and nitrogen (??15N) stable isotopes to examine spatial and temporal patterns in Hemimysis trophic niche use in invaded North American sites in an attempt to broaden the knowledge base on this invader and to examine potential impacts this invader may have on the food webs of the Great Lakes. A spatial comparison of trophic niche use by Hemimysis among 13 sites in Lake Erie, Lake Ontario, and the St. Lawrence River was conducted between late July and mid-September of 2011. Main sources of carbon (benthic versus pelagic production) and trophic offset, or trophic distance from basal food web items, of Hemimysis were quantified using Hemimysis ??13C and ??15N values. Results indicated that: 1) Hemimysis relied predominantly on pelagic carbon sources at the majority of sites, and isotopic differences between life-stages existed at two of the 13 sites examined, 2) the trophic offset and reliance on pelagic food sources did not differ significantly between lotic and lentic sites, and 3) the isotopic niche width of Hemimysis was spatially heterogeneous, varying by an order of magnitude among sites, but was unrelated to the degree of isotopic variation in the basal food web at each site. Observed ranges in trophic offset and the pelagic fraction of dietary carbon indicate that Hemimysis derives carbon from both benthic and water column sources, as well as at multiple trophic levels. Results support the notion that Hemimysis is an opportunistic omnivore that displays significant dietary flexibility. To test the relative importance of key biotic and abiotic factors, taken from the literature, in driving Hemimysis isotopic variation, a temporal analysis was conducted at two North American sites, one in Lake Ontario and one in the St. Lawrence River, which were repeatedly sampled for Hemimysis and related food web items between September 2008 and January 2012. Seasonal patterns of winter enrichment ??? summer depletion were found in Hemimysis ??15N in Lake Ontario, but a similar pattern was not seen in the St. Lawrence River. Multiple regression models were used to determine the importance of water temperature, Hemimysis C:N ratios, Hemimysis length, and the isotopic values of basal food web components in explaining observed variation in Hemimysis ??13C and ??15N values. Significant relationships were found between Hemimysis isotopic values and water temperature, but relationships with the isotopic signatures of the pelagic basal food web were weak or nonexistent. Hemimysis ??13C values were significantly correlated with C:N ratios. Strong evidence of an ontogenetic dietary shift was found in Lake Ontario, with length showing a significant positive correlation with Hemimysis ??15N. All together the factors included in the models explained little of the observed variation in Hemimysis isotopic values, with approximately 20 % of the observed variation in Hemimysis ??13C, and just under half of Hemimysis ??15N variation, being explained by the included factors. As such, Hemimysis isotopic variation must be explained by factors not included in this study and may include factors such as species composition of the invaded site and availability of prey. Overall, the results of this thesis highlight the opportunistic and flexible nature of Hemimysis diet, and demonstrate the need for future work to determine the main drivers of isotopic variability and trophic niche selection of Hemimysis. The degree of trophic flexibility seen in Hemimysis implies that potential food web impacts will be site specific and heavily reliant on food web dynamics and environmental characteristics of the invaded site.

The herbivory experienced by non-native invasive plants may depend on their local environments, such as herbivore abundance. In this study, I performed a common garden experiment with plants sampled from 11 populations of Arctium minus, from southern Ontario to near its northern range limit. I also compared performance and herbivory of burdock in open and understory habitats. Finally, I conducted freezing tolerance experiments with the lepidopteran seed predator Metzneria lapella, and palatability tests with plants from different populations. Results suggested that the previously described latitudinal trends in herbivore damage among populations are due to environmental differences rather than genotypic differences among populations. At a local scale, plants of open habitat were less damaged and had better performance than understory plants. Burdock has not escaped damage by herbivores in its invaded range; instead variation among sites in herbivore populations and impacts may significantly affect the invasiveness of this species.

The herbivory experienced by non-native invasive plants may depend on their local environments, such as herbivore abundance. In this study, I performed a common garden experiment with plants sampled from 11 populations of Arctium minus, from southern Ontario to near its northern range limit. I also compared performance and herbivory of burdock in open and understory habitats. Finally, I conducted freezing tolerance experiments with the lepidopteran seed predator Metzneria lapella, and palatability tests with plants from different populations. Results suggested that the previously described latitudinal trends in herbivore damage among populations are due to environmental differences rather than genotypic differences among populations. At a local scale, plants of open habitat were less damaged and had better performance than understory plants. Burdock has not escaped damage by herbivores in its invaded range; instead variation among sites in herbivore populations and impacts may significantly affect the invasiveness of this species.

An average of three to five billion tons of ballast water (BW) is transported globally per year; 79 million tons of which is released into U. S. waters. Ballast water is necessary for large ships to maintain balance and stability while loading and unloading cargo as well as during transit. As a ship unloads it’s cargo at a port, it takes on ballast water and then when it loads cargo at the next port, it discharges the ballast water, thus transferring water from port to port. Aquatic organisms are transported around the globe via ballast water. These organisms can potentially cause serious environmental and human health impacts. Historically, transfer of macro-organisms such as fish, snails, and vascular plants via ballast water have been the focus of ballast water research. More recently, microorganisms such as toxin producing dinoflagellates and diatoms i.e. ‘harmful algal blooms’ and pathogenic bacteria (e.g. Vibrio cholerae), have been found to survive in ballast tanks for several weeks. These organisms have moved to the forefront of ballast water management (BWM) trepidations because they compose serious threats to human health as well as Marine Protected Area (MPA) ecosystems such as coral reefs. Ballasting activities of ships calling at the Port of Houston were used as a model for other major ports in U.S. Gulf States. Ballast water management reports, submitted to the U.S. Coast Guard by all overseas vessels calling at the Port of Houston in 2010 were examined for the ballast management strategies utilized prior to docking. Currently, all “coastwise” ships are not required to conduct ballast water exchanges (BWE) if they do not transit beyond the 200nm EEZ. Close inspection of BW management report forms for “overseas” ships determined that the degree of completeness was variable. By comparing the frequency of vessels entering the Port of Houston, ballast water capacities, the management types utilized, and the locations of ballast water exchanges and discharges, it can be concluded that larger vessels present the highest risk of bacterial transfer to coral reefs. Five coral diseases were discovered to be prevalent throughout the ballast management areas their presence has significantly increased in these areas over the past thirty years. The combination of this disease growth along with an increase in shipping and ballast exchanges suggests that the vector at which pathogens are being displaced must lie within the shipping lanes.

Subsidized harvest of invasive silver carp Hypopthalmichthys molitrix and bighead carp H. nobilis (collectively referred to as Asian carp) from the Illinois River have been initiated in an effort to control their populations. However, market-driven control strategies have been suggested in an effort to reduce or eliminate the need for subsidies. Given that Asian carp are not a favored food fish in the U.S. and exporting to Asian markets is currently not economically feasible, industrial applications such as fish meal production have been explored. Fish meal production to support aquafeed manufacturing is potentially a high-value, high-volume market which is essential to a market-driven approach. However, the nutrient composition of Asian carp as a raw material from the Illinois River needs to be evaluated as well as the nutrient digestibility and production performance of a rendered Asian carp fish meal product to fully assess its suitability for use in aquafeeds. To determine the suitability of Asian carp to support aquafeed manufacturing, we evaluated seasonal and geographical differences in Asian carp harvested from the Illinois River, performed standard digestibility trials with hybrid striped bass and rainbow trout, and assessed production performance through standard feeding trials with hybrid striped bass, rainbow trout, and cobia. Results indicate slight geographical and seasonal variation in body composition, though both species represent protein-dense raw materials suitable for fish meal production. Additionally, Asian carp fish meal is a highly digestible feedstuff that closely resembles the nutrient content of traditional menhaden fish meal sources, although it is slightly less digestible. Production performance of fish fed practical Asian carp fish meal based diets was similar to those that used menhaden fish meal. Overall, Asian carp fish meal appears to be a highly-digestible, nutrient-dense ingredient suitable for inclusion in aquafeeds. Therefore, rendering Asian carp into fish meal appears to be a viable market-driven approach to help control Asian carp populations.

Invasive plant species have widespread effects on the ecosystems they inhabit. Extensive research has been done on the economic and ecological impact of invasive species in relation to native plant species, but little is known about the effect of these species on native fauna. My study examined the impact of an invasive plant species Elaeagnus umbellata (autumn olive) on small mammals populations in southern Illinois. Elaeagnus umbellata is a native shrub of southeast Asia and was introduced to the United States in the 1830s. It is now the fifth most abundant invasive plant species in the state of Illinois. To determine the impact of this invasive shrub on small mammal populations, Sherman traps were set up in six separate trapping webs, three in upland forests with heavy E. umbellata cover and three in upland forests with little to no E. umbellata cover (control). Trapping spanned three seasons from March-August 2013. Through the use of capture and release methods, individuals were measured, weighed, and marked for possible recapture. Beginning in season 3, Cuterebra fontinella (bot fly) abundance in small mammals was also assessed. Differences in relative abundance of small mammal populations were determined using a repeated measures ANOVA with a Tukey test. T-tests were used to determine any significant difference among small mammals between forest types. Very little difference was found among the measured variables between the invaded and control forest sites. Prevalance of C. fontinella was also similar, but the resulting percentage of infection was much higher when compared to other studies in the literature. These results indicate there is little effect of E. umbellata on small mammal populations, although the long-term impacts of this invasive species may need further research.

An effective incentivized hunting program was initiated in the United States in 2002 to reduce the population of nutria (Myocastor coypus), an invasive species of rodent contributing to wetland erosion. In this thesis, I analyze the ethics of intervening through the nutria hunting program by applying four different non-anthropocentric theories of animal and environmental ethics to the case: Peter Singer’s utilitarianism, Tom Regan’s animal rights, Paul Taylor’s respect for nature, and Aldo Leopold’s land ethic. I explain why the theories of Singer and Leopold would support intervention, while Regan’s and Taylor’s would not. Additionally, due to its unique features, the situation with the nutria is a perfect test case for evaluating the merits of these four competing theories. After taking issue with Singer’s, Regan’s, and Taylor’s theories as they pertain to the nutria case, I conclude that Leopold’s land ethic is best able to account for our considered moral belief that killing the invasive nutria in order to protect the wetlands is morally appropriate. Because Leopold’s land ethic is holistic and inegalitarian, it can explain both why the nutria are a problem and why they are less morally valuable than the native wetland species they are destroying. Of the four theories, only Leopold’s includes the entire biotic community in the sphere of moral consideration, and in so doing, recognizes that what is at stake in this case is the wetland itself, and that we have a duty to preserve its integrity, even at the cost of nutria life.