The effect of copper on kairomone-mediated responses by wild Daphnia pulicaria clones from along a copper gradient

Authors:	Inglis, Colleen
Files in This Item: File Description Size Format Inglis_Colleen_M_200912_MSc.pdf 1.44 MB Adobe PDF
Keywords:	Daphnia metal-tolerance kairomone antipredator defenses copper
Issue Date:	2009
Series/Report no.:	Canadian theses
Abstract:	Kairomones are infochemicals that benefit a heterospecific receiver. Chaoborus spp. release a kairomone from their gut when feeding on Daphnia spp. Daphnia respond to kairomone by shifting life history parameters or producing neonates with induced morphological defenses, increasing their chance of survival. When laboratory-cultured Daphnia are exposed to environmentally-relevant metal concentrations, a kairomone response is not induced, increasing predation vulnerability. Currently Daphnia live in metal-contaminated lakes in Sudbury, ON. It is possible the extant population is tolerant of relatively high copper (Cu) concentrations and can still induce a kairomone response. In comparison, it is hypothesized clones found in lakes isolated from anthropogenic sources of metal-contamination would be less tolerant as they have not been exposed to high Cu concentrations. The purpose of this study was to examine how multiple clones of D. pulicaria obtained from lakes along a Cu gradient respond to kairomone in the absence and presence of copper. Several different clones from Ontario lakes located in the Canadian Shield were exposed to environmentally-relevant Cu concentrations and Chaoborus kairomone. Neonates were collected and measured to assess predator-induced defenses. Results indicate that kairomone-mediated responses and Cu-tolerance vary among D. pulicaria clones. Clones from the Sudbury area were able to induce a response to kairomone when exposed to Cu, indicating a Cu-tolerance. However, this was not true for all Sudbury clones. In contrast, most clones from clean lakes did not respond to kairomone when exposed to Cu; while some clones exhibited a Cu-tolerance. Clones that were not tolerant of Cu were affected at concentrations much lower than those predicted by the Biotic Ligand Model (BLM) that induce acute toxicity. Predictions generated by the BLM can be conservative making them useful when creating water quality criteria; however, my results indicate these predictions can also be under-protective. Chemosensory cues mediate vital life processes that are essential for survival. Populations may be devastated if metals interfere with chemosensory cues. Overall, the results of my study suggest that genetic variation is important for population establishment and maintenance, specifically when exposed to multiple stressors, and that directional selection may result in stress tolerance.

DIATOM ASSEMBLAGES IN RELATION TO WATER-DEPTH GRADIENTS IN EIGHT BOREAL SHIELD LAKES FROM NORTHWESTERN ONTARIO, CANADA

Authors:	Kingsbury, Melanie V.
Files in This Item: File Description Size Format Kingsbury_Melanie_V_201007_MSc.pdf 3.26 MB Adobe PDF
Keywords:	paleolimnology diatoms ecology northwestern Ontario
Issue Date:	2010
Series/Report no.:	Canadian theses
Abstract:	The uncertainty surrounding the impact of future changes in climate and water resources has created renewed interest on how lakes have responded to drought in the past. There is a need to determine potential future available water by understanding past changes in water levels; the underlying ecological characteristics of using diatoms as a proxy for lake-level reconstructions is the basis of this thesis. By integrating knowledge from past water-level fluctuation studies and theories, along with developing a better understanding of diatom ecology in lake systems, more effective techniques are being developed to improve water-depth reconstructions. Diatom assemblages were examined from eight lakes in northwestern Ontario collected in surface sediments along a depth gradient at ~1-m water-depth intervals. Three major zones, based on the composition of diatom assemblages in each lake were consistently identified in all lakes: i) a near-shore assemblage of Achnanthes (sensu lato) species and other benthic taxa (Nitzschia, Cymbella); ii) a mid-depth small Fragilaria (sensu lato)/ small Aulacoseira zone with various Navicula taxa, and iii) a deep-water planktonic zone. The depths at which transitions between these zones are located varied among lakes, and the depth of the transition between the planktonic and benthic zones was consistent with water chemistry variables (e.g. DOC, TP) that are related to light attenuation. Deeper pelagic to benthic transitions occurred in lakes with the lowest DOC and TP (i.e. generally more light attenuation in lakes with higher concentrations of TP or DOC). Other findings included a decrease in species evenness and numbers with depth, along with an increase in scaled chrysophyte relative to diatoms.

Climate change and water availability over the last two millennia in Little Raleigh Lake, northwestern Ontario.

Authors:	Ma, Susan
Files in This Item: File Description Size Format Ma_Susan_201107_MSc.pdf 5.93 MB Adobe PDF
Keywords:	Paleolimnology Drought Depth Model Diatoms
Issue Date:	10-Aug-2011
Series/Report no.:	Canadian theses
Abstract:	The Winnipeg River Drainage Basin (WRDB), located in the boreal forest region of Canada, is a pivotal region of focus for the assessment of water availability to determine susceptibility to drought in the past. To date, there have been relatively few paleolimnological studies focusing on how lake levels have changed in the past and whether these changes have been synchronous in the WRDB. This study investigates temporal patterns in effective moisture from Little Raleigh Lake over the last two millennia. Analyses are based on diatoms from two near-shore sediment cores from different locations and water depth in Little Raleigh Lake. Changes in diatom assemblages are used to reconstruct quantitative estimates of effective moisture in the past through the calibration of a diatom-inferred depth model developed from diatom assemblages in surficial sediments along a depth transect in Little Raleigh Lake. Declines of ~1-3m occurred during the late Holocene, with prolonged periods of aridity consistent with the timing of the Medieval Climate Anamoly (~950-1250AD) and the Little Ice Age (~1650-1750AD). The nearshore core retrieved closer to the present-day ecotone between the benthic and planktonic diatom assemblages was more sensitive to tracking water level changes in the lake than the deeper core. Conditions during the last two millennia can be used for the assessment of water availability in the past, and may offer insight on future conditions under increasing temperatures.

DIATOM-INFERRED CHANGES IN EFFECTIVE MOISTURE FROM GALL LAKE, NORTHWESTERN, ONTARIO, OVER THE PAST TWO MILLENNIA

Authors:	HAIG, HEATHER A
Files in This Item: File Description Size Format Haig_Heather_A_201105_ MSc.pdf 18.3 MB Adobe PDF
Keywords:	Drought paleolimnology Diatom
Issue Date:	2011
Series/Report no.:	Canadian theses
Abstract:	The boreal forest of Canada extends across 58% of Canada’s land area providing a large range of ecosystem services including flood control, water filtration, and carbon storage. Despite conservation efforts to protect this ecosystem, the boreal region is still under stress from global stressors including climate change. Anthropogenic climate-change is expected to raise temperatures and decrease precipitation over much of the boreal region increasing the duration and magnitude of droughts. This potential change to a more arid climate could have drastic affects on water levels and stream flows across much of the boreal region. Changes in hydrology, as a consequence of anthropogenic climate change, may result in large changes to aquatic ecosystems. To assess the susceptibility of lakes to climate in northwestern Ontario over the past two millennia, sediment cores from a headwater lake were obtained from near-shore cores to reconstruct changes in drought. The cores were located at a depth where changes in pelagic and benthic diatom assemblages (P: B boundary) were apparent in modern-day sediments because the location has been shown to be susceptible to change. The lake chosen for reconstruction was Gall Lake, a small (surface area = 19 ha, max depth = 18 m, mean depth = 8.5 m), mesotrophic lake (total phosphorus (TP) level of 12.3 μg/L, July 2008), with a gentlysloping eastern basin. This headwater lake in the Winnipeg River Drainage Basin (WRDB) is part of a hydrologically-rich region that is expected to experience increased aridity. Multivariate analysis of diatom assemblages over the past two millennia suggested that the instrumental record does not encompassed the natural variability of this system. The largest decreases in diatom-inferred (DI) depth were synonymous with iii the Medieval Climate Anomaly (MCA), a phenomenon not yet observed this far northeast in North America. The MCA has been proposed as a surrogate for climate change over the next century, therefore the prolonged aridity observed in Gall Lake could aid in the calibration of general circulation models currently used to forecast changes in climate, as well as a scenario that can be used to develop adaptation strategies to future environmental change.

Assesing biological recovery from acidification and metal contamination in urban lakes from Sudbury, Canada : a paleolimological approach

Authors:	Tropea, Amy Elizabeth
Files in This Item: File Description Size Format Tropea_Amy_E_200807_MSc.pdf 15.25 MB Adobe PDF
Keywords:	Paleolimnology Diatoms Scaled chrysophytes Sudbury Metal contamination Acidification Cultural eutrophication
Issue Date:	2008
Series/Report no.:	Canadian theses
Abstract:	The acidification and metal contamination of freshwater resources are major environmental concerns in many areas, with Sudbury (Ontario, Canada) having been amongst the most severely impacted. Many scientific investigations have examined the effects of these environmental stressors on aquatic systems, but relatively little is known about the biological recovery process following smelter emission reductions. Therefore, paleolimnological techniques were utilized to determine if diatom and scaled chrysophyte assemblages have recovered toward their pre-disturbance conditions as a result of reduced anthropogenic inputs. Pre-industrial algal assemblages were primarily dominated by circumneutral to alkaline and pH-indifferent taxa. However, there was a shift toward acid-tolerant species in all study lakes with the onset of open pit roasting and smelting operations. Coinciding with emission reductions, scaled chrysophyte assemblages in two of the three study sites have shown evidence of biological recovery. Given the population growth of the city of Sudbury over the last century, and the lack of scientific information regarding cultural eutrophication trends in the region, paleolimnological techniques were also used to track long-term biological changes within diatom assemblages related to cultural disturbances. Historically, oligotrophic diatom taxa primarily dominated the algal assemblages in each of the four study lakes. With the onset of urban environmental stressors there was a shift toward taxa which thrive in more productive systems. In addition, diatom assemblages appear to track increased lakewater pH through time. Finally, geochemical analysis tracked the increase in copper and nickel concentrations in lake sediment with the onset of open pit roasting and smelting activities and the subsequent decline in concentration with emission controls. Metal concentrations in recently deposited lake sediments remain elevated compared to pre-industrial concentrations. Paleolimnological studies comparing pre- and post-disturbance algal assemblages are of interest to lake managers as these data will aid in setting realistic mitigation targets for freshwater systems impacted by acidification, cultural eutrophication, and metal contamination, and will help gauge biological recovery mechanisms. Furthermore, this study provides insight in to the role other environmental stressors (e.g., climate change) may play in the biological recovery process.