Uranium mining activities have the potential to impact aquatic systems through mine drainage (runoff) and the release of treated effluent into nearby watersheds. Such anthropogenic exposure can lead to elevated concentrations of metals and major ions, which may impact aquatic biota. Previous studies have looked at the effects of water quality on aquatic biota within flooded pit lakes and natural lakes that have been exposed to various mechanisms of mining exposure. However, the literature often only examines the effects of a limited number of contaminants on a limited number of species. Researchers have rarely looked at the effects of multiple contaminants on species composition, biodiversity and ecosystem function in aquatic systems. This study uses a multivariate approach to look for relationships between water quality (24 variables), plankton species composition and abundance, biodiversity (richness and evenness) and ecosystem function among lakes exposed to mining activities (n = 18) and non-exposed reference lakes (n = 8). Lake water quality data was used to cluster lakes into groups. Lake groups were then overlain onto multivariate ordinations derived from species composition-abundance data to determine if species composition was related to water quality. Ecosystem function variables included planktonic phosphorus cycling and planktonic respiration. The classified lake groups clustered well on ordinations derived from species composition-abundance data suggesting that relationships exist between water quality and plankton species composition. However, ecosystem function was similar among the majority of lakes and flooded pits despite differences in species richness, species composition and species abundance. Only a small number of aquatic systems had ecosystem function properties that were different from the majority of lakes and pits. These systems had the greatest concentrations of contaminants and had very low biodiversity (richness and evenness) compared to the other systems. Despite having differences in plankton species composition and species richness, all lake groups were functionally similar. This suggests that functional redundancy in species composition may be present in the majority of lakes and pits in such a way that ecosystem function is maintained.

Periodic monitoring of contaminant levels in fish from the Yukon Territory indicated that organochlorine (OC) contaminants had rapidly declined since the early 1990s. This study examined OC concentrations, including chlordane (sigma-CHL), sigma-DDT, hexachlorocyclohexane (sigma-HCH), toxaphene (sigma-CHB), sigma-PCB and chlorinated benzenes (sigma-CBz) in sentinel fish (species of consistent annual observation and collection) from two Yukon lakes (Kusawa, Quiet), and from the aquatic food web of a focus lake (Lake Laberge) across several temporal points between 1993 and 2003. OC analysis and phytoplankton counts from dated sediment cores as well as climate data were also collected. Population, morphological (length, weight, age), biochemical (lipid content, delta-13C, delta-15N) and OC contaminant data for fish and invertebrates (zooplankton, snails, clams) were reviewed to elucidate the primary causes for these OC declines. Although some spatial differences in contaminant levels exist between the Yukon lakes, OC concentrations were declining for lake trout in all three lakes, with declines also noted for burbot from Lake Laberge. Several other fish species as well as zooplankton from Lake Laberge exhibited decreases in contaminant levels except northern pike, which registered consistently higher levels from 1993 to 2001. There was no evidence to support the hypotheses of changes in fish trophic levels or food sources with the exception of burbot, which marginally decreased, and northern pike, which climbed a half trophic level. Through OC flux analysis in dated sediments, the hypothesis that declines in abiotic deposition affected the contaminant levels in the food web was also negated. The closure of the Lake Laberge commercial fishery resulted in faster fish growth and larger fish populations, which are contributing to biomass dilution of OC concentrations, higher OC biomagnification factors for some species and likely changes in predator-prey interactions as resource competition increases. The large ratio of OC decreases in the lower vs. higher trophic levels of Lake Laberge have increased food web magnification factors (FWMF) for all six OC groups. It is also suspected that above-average temperatures and below-average precipitation in the lower Yukon region over the 1990s may have contributed towards an increase in lake primary production resulting in biomass dilution of contaminants in zooplankton for all three study lakes. Concurrently, shifts in the Lake Laberge zooplankton community, from climate fluctuations or increased fish predation, have gone from an abundance of Cyclops scutifer in 1993 to dominance by Diaptomus pribilofensis in 2001, although sample sites were limited. Characteristics specific to each species (e.g. body size, composition and metabolism) likely play a role in the significant OC declines measured in zooplankton. Fluctuations in population dynamics, species characteristics and OC contaminant concentrations in the Lake Laberge ecosystem may continue for several years to come. Sentinel species such as lake trout, burbot, whitefish, cisco and plankton should continue to be monitored in all three Yukon lakes for future temporal correlations with contaminants or climate change. / May 2006

Uranium mining activities have the potential to impact aquatic systems through mine drainage (runoff) and the release of treated effluent into nearby watersheds. Such anthropogenic exposure can lead to elevated concentrations of metals and major ions, which may impact aquatic biota. Previous studies have looked at the effects of water quality on aquatic biota within flooded pit lakes and natural lakes that have been exposed to various mechanisms of mining exposure. However, the literature often only examines the effects of a limited number of contaminants on a limited number of species. Researchers have rarely looked at the effects of multiple contaminants on species composition, biodiversity and ecosystem function in aquatic systems. This study uses a multivariate approach to look for relationships between water quality (24 variables), plankton species composition and abundance, biodiversity (richness and evenness) and ecosystem function among lakes exposed to mining activities (n = 18) and non-exposed reference lakes (n = 8). Lake water quality data was used to cluster lakes into groups. Lake groups were then overlain onto multivariate ordinations derived from species composition-abundance data to determine if species composition was related to water quality. Ecosystem function variables included planktonic phosphorus cycling and planktonic respiration. The classified lake groups clustered well on ordinations derived from species composition-abundance data suggesting that relationships exist between water quality and plankton species composition. However, ecosystem function was similar among the majority of lakes and flooded pits despite differences in species richness, species composition and species abundance. Only a small number of aquatic systems had ecosystem function properties that were different from the majority of lakes and pits. These systems had the greatest concentrations of contaminants and had very low biodiversity (richness and evenness) compared to the other systems. Despite having differences in plankton species composition and species richness, all lake groups were functionally similar. This suggests that functional redundancy in species composition may be present in the majority of lakes and pits in such a way that ecosystem function is maintained.

Plankton communities are influenced, in part, by water exchange with adjacent estuarine and oceanic ecosystems. Reduced advective transport through tidal passes or with adjacent bay systems can affect chemical processes and biological interactions, such as nutrient cycling, phytoplankton abundance and productivity, community respiration, and zooplankton biovolume. The most threatened estuarine ecosystems are shallow, bar-built, microtidal estuaries with small water volumes and restricted connections through tidal passes and other water exchange points. This research explored spatio-temporal trends in plankton communities and the physicochemical environment in Mesquite Bay, Texas a microtidal, bar-built, subtropical estuary in the Gulf of Mexico. This research couples sampling at fixedstations for multiple physical and biological parameters with high-resolution spatial mapping of physicochemical parameters. Spatial trends were less in magnitude and affected fewer parameters in fixed station and spatial data. Two dimensional ordination plots indicated spatial heterogeneity with a more pronounced temporal trend affecting parameters including temperature, salinity as a function of inflow timing, and seasonal wind direction affecting primary production and zooplankton biovolume. Temperature was positively correlated with gross production and respiration rates during spring and late summer with sporadic positive and negative correlations with phytoplankton biomass. The timing and magnitude of freshwater inflow affected various physicochemical and biological parameters. Higher than 71-year inflow rates resulted in low salinity system wide, with spatial heterogeneity increasing over the course of the study, which was confirmed by spatial maps. Additionally, high inflow rates led to two periods of increased inorganic nutrients and dissolved organic matter. Low salinity periods coincided with persistence of higher turbidity, likely because of decreased sediment flocculation. Gross production was low at this time, and likely from light limitation. Additionally, wind magnitude and direction created spatial heterogeneity in turbidity levels and phytoplankton biomass. Zooplankton biovolume was highest during spring and late summer with high species diversity in total rotifers. Copepod biovolume and phytoplankton biomass were positively correlated. Other zooplankton taxonomic groups exhibited variable correlations with phytoplankton biomass and other taxonomic groups. Further long-term studies are needed to determine interactions of various components of trophic food-webs and account for interannual variability in all system parameters.

Locomotion is a key characteristic of almost all forms of life and is often accomplished, whether on land, in water, or in the air, by reciprocal motion of two or more appendages. Among the zooplankton, many species propel themselves by rhythmically beating multiple pairs of closely spaced leg-like appendages in a back-to-front (metachronal) pattern. The focus of this study is to understand the mechanical design, kinematic operation, and hydrodynamic result of metachrony in the zooplankton. In the first part of this study, Antarctic krill (Euphausia superba) are investigated as an ecologically important model species that metachronally beats its swimming legs (pleopods) to perform drag-based propulsion. Based on high speed videos of freely swimming Antarctic krill, hovering, fast forward swimming, and upside down swimming are identified as three distinct swimming modes with significantly different stroke amplitudes and beat frequencies. When transitioning between hovering and fast forward swimming, Antarctic krill first increase beat amplitude and secondarily increase beat frequency. In considering the design components that contribute to metachrony being a successful swimming technique, a comparison among many different species shows that the ratio between the appendage separation distance and appendage length is limited to a narrow range of values (i.e. 0.2 - 0.65). In the second part of this study, metachrony is examined at smaller length and time scales by examining the impulsive escape jump of a calanoid copepod (Calanus finmarchicus). The wake generated by the copepod's metachronally beating swimming legs is experimentally measured using a novel (and newly developed) tomographic particle image velocimetry (PIV) system capable of making volumetric 3D velocity measurements with high temporal and spatial resolution using IR illumination. The flow generated by the escaping copepod consisted of a stronger posterior vortex ring generated by the metachronally stroking swimming legs and a weaker one generated anteriorly around the body by the impulsive start of the escape, both of which decayed over time. The experiments also revealed azimuthal asymmetry in the vortices caused by body yawing and the action of the swimming legs, flow features not considered in previous axisymmetric computational and theoretical models of copepod jumps. While not accounting for this asymmetry, an impulsive stresslet is nonetheless useful in modeling the flow created by the escaping copepod and represents the flow more accurately than an impulsive Stokeslet. In the final part of this study, the flow associated with metachronal hovering in Antarctic krill is experimentally and theoretically investigated in regards to the energy requirements of the pelagic lifestyle. Volumetric flow measurements of a hovering Antarctic krill show that each stroking pleopod drags flow behind it such that a downward stream develops medially. The lateral exopodites induce tip vortices which add to the lift force on each appendage. Furthermore, the flow beneath the hovering krill develops into a pulsed jet with a Strouhal number in the 'high-efficiency zone' of 0.2 < St < 0.4. Actuator disk theory is used to make theoretical estimates of the induced power necessary to hover, the results of which match induced power values calculated from measured flow gradients contributing to viscous energy dissipation.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 201-227).

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Life history theory assumes that correlations among fitness-related life history traits should be negative among individuals, reflecting resource allocation constraints among traits such as growth and reproduction. These traits trade off because they cannot be simultaneously maximized in individuals facing finite resource acquisition. Positive correlations among traits that are expected to be negative (e.g. between energetically costly traits) have been regularly observed, however, and have usually been ascribed to genetic or resource acquisition differences. In the freshwater zooplankton Cladoceran Daphnia, positive correlations have been particularly well documented even when genetic and environmental variation have been controlled. The sign of these correlations represent a problem for life history theory, which is underpinned by the notion of universal and unavoidable costs associated with investing in a given trait. It has been suggested, however, that costs vary with environment and thus can change the sign of a correlation. A change in correlation sign over an environmental gradient may indicate that the assumed universality of costs and constraints are not as universal as expected by life history theory. Few life history experiments have examined traits in multiple environments, and fewer have done so while controlling resource acquisition and genetic variation. Here I ask whether the positive genetic correlations among somatic growth rate, egg production rate, and longevity are present in the face of equal ingestion, clonal individuals, and a finely resolved gradient of food quality, an environmental factor that frequently affects Daphnia. I partition trait covariation into genetic and residual, or environmental, sources. All resulting genetic correlations were non-significant. Residual correlations trended from significantly positive to negative between longevity and growth rate and remained near zero between longevity and egg rate. The residual correlation between growth and reproduction, two expensive traits, displayed significantly positive residual correlations across the food quality gradient remained significantly positive. Given the experimental controls in place, I suggest that differences in individual ontogeny may give rise to differential resource utilization or assimilation efficiency. This may be a mechanism for differential resource acquisition in the absence of ingestion variation. Additionally, the different ways genetic and residual correlations change over an environmental gradient may provide insight on one manner by which genotypes might coexist and provide a candidate explanation for the second paradox of the plankton. / Thesis (Master, Biology) -- Queen's University, 2014-03-31 07:01:21.774

Marine ecosystem-based management requires end to end models, which are models capable of representing the entire ecosystem including physical, chemical and biological processes, anthropogenic activities, and multiple species with different sizes, life histories and from different trophic levels. To adequately represent ecosystem dynamics in shallow coastal regions, end-to-end models may need to include macrobiota species (wild and aquacultured) and may have to allow feedbacks (i.e. two-way coupling) between macrobiota and planktonic ecosystem dynamics. This is because the biomass of macrobiota can locally exceed the biomass of plankton, thus influencing the distribution of planktonic ecosystem tracers and altering the overall food web structure. Here, I describe a hybrid (Eulerian/Individual-Based) ecosystem framework, implemented in the Regional Ocean Modeling System (ROMS), a state-of-the-art 3-D ocean circulation model. The framework was applied to a model of a synthetic embayment containing seagrass, rockweed and kelp beds, a wild oyster reef, a mussel ranch and a fish farm. I found that two-way coupling is essential to reproduce expected spatial patterns of all variables and to conserve mass in the system. I also developed a shellfish ecophysiology model (SHELL E) and compared its results against water samples collected over 5 years in Ship Harbour, a fjord with mussel aquaculture in Nova Scotia, Eastern Canada. Also, from a high-resolution bio-optical survey of the fjord, I found that mussels decrease phytoplankton biomass inside the farm, but also cause a bloom of phytoplankton outside the farm. Using ROMS/SHELL-E, I determined that the increase of phytoplankton around the farm is caused by the waste products of the farmed bivalves, which have a fertilization effect, enhancing phytoplankton production outside the farm during nutrient-limited and light-replete conditions (i.e. late spring to late fall in Ship Harbour). The main conclusion of this thesis is that—in shallow coastal regions—ecosystem models must represent bilateral interactions between macrobiota and physical-planktonic dynamics, in a spatially-explicit setting, to adequately represent mass flows and ecosystem dynamics. The hybrid end-to-end modelling system provides a computationally efficient framework for describing these interactions and, through careful comparisons against observations, can be a powerful tool to test hypotheses and generate insights into coastal ecosystems.

Periodic monitoring of contaminant levels in fish from the Yukon Territory indicated that organochlorine (OC) contaminants had rapidly declined since the early 1990s. This study examined OC concentrations, including chlordane (sigma-CHL), sigma-DDT, hexachlorocyclohexane (sigma-HCH), toxaphene (sigma-CHB), sigma-PCB and chlorinated benzenes (sigma-CBz) in sentinel fish (species of consistent annual observation and collection) from two Yukon lakes (Kusawa, Quiet), and from the aquatic food web of a focus lake (Lake Laberge) across several temporal points between 1993 and 2003. OC analysis and phytoplankton counts from dated sediment cores as well as climate data were also collected. Population, morphological (length, weight, age), biochemical (lipid content, delta-13C, delta-15N) and OC contaminant data for fish and invertebrates (zooplankton, snails, clams) were reviewed to elucidate the primary causes for these OC declines. Although some spatial differences in contaminant levels exist between the Yukon lakes, OC concentrations were declining for lake trout in all three lakes, with declines also noted for burbot from Lake Laberge. Several other fish species as well as zooplankton from Lake Laberge exhibited decreases in contaminant levels except northern pike, which registered consistently higher levels from 1993 to 2001. There was no evidence to support the hypotheses of changes in fish trophic levels or food sources with the exception of burbot, which marginally decreased, and northern pike, which climbed a half trophic level. Through OC flux analysis in dated sediments, the hypothesis that declines in abiotic deposition affected the contaminant levels in the food web was also negated. The closure of the Lake Laberge commercial fishery resulted in faster fish growth and larger fish populations, which are contributing to biomass dilution of OC concentrations, higher OC biomagnification factors for some species and likely changes in predator-prey interactions as resource competition increases. The large ratio of OC decreases in the lower vs. higher trophic levels of Lake Laberge have increased food web magnification factors (FWMF) for all six OC groups. It is also suspected that above-average temperatures and below-average precipitation in the lower Yukon region over the 1990s may have contributed towards an increase in lake primary production resulting in biomass dilution of contaminants in zooplankton for all three study lakes. Concurrently, shifts in the Lake Laberge zooplankton community, from climate fluctuations or increased fish predation, have gone from an abundance of Cyclops scutifer in 1993 to dominance by Diaptomus pribilofensis in 2001, although sample sites were limited. Characteristics specific to each species (e.g. body size, composition and metabolism) likely play a role in the significant OC declines measured in zooplankton. Fluctuations in population dynamics, species characteristics and OC contaminant concentrations in the Lake Laberge ecosystem may continue for several years to come. Sentinel species such as lake trout, burbot, whitefish, cisco and plankton should continue to be monitored in all three Yukon lakes for future temporal correlations with contaminants or climate change.