Global climate change is threatening both our water quality and quantity. Specifically, the influence of climate change on freshwater lakes includes decreased water availability, increased evapotranspiration, changes in nutrient availability, and shifts in species composition. Understanding the changes that are occurring to our freshwater ecosystems is imperative to understanding the full impact of climate change on both the environment and society. This thesis examines a shift in sedimentary diatom assemblages towards increased relative abundances of Discostella species, a phenomenon that has been documented across the Northern Hemisphere. One of the central tenants of this work is that it has been done at the Experimental Lakes Area (ELA) in the boreal region of Canada, a study site that is uniquely devoid of large-scale anthropogenic disturbances. An analysis of the long-term monitoring records at the ELA show that Discostella species are primarily spring bloomers, and recent increases in their abundance is linked to changes in spring thermal conditions. To link the changes recorded in the sedimentary records of eight lakes to climate change, and assess whether Discostella species are in fact showing a response to climate change, a novel approach utilizing the theory of temporal synchrony was applied to eight paleo records. Discostella stelligera was found to be synchronous in all eight lakes studied, suggesting that a broad-scale forcing factor is influencing its abundance. Further, it was significantly correlated with annual and winter temperatures, supporting a link to changes in spring thermal conditions as a possible explanation. To assess the relative sensitivity of the study lakes, particularly in comparison to other boreal and temperate region lakes, an analysis was conducted of the timing of the first change in Discostella species. Several statistical techniques were employed and all approaches showed that the study lakes from ELA responded earlier in comparison to other lakes studied from other boreal and temperate regions (ca. 1900 vs ca. 1970), but later than Arctic and Sub-Arctic lakes. We suggest that this may be due to the lack of local disturbances at the ELA and/or the comparably small size of our study lakes. / Thesis (Ph.D, Biology) -- Queen's University, 2014-06-30 15:03:04.447

Anthropogenic disruptions in the form of hydrological alterations, such as dam construction and the associated water diversions are a cause of much upheaval to local and regional ecosystems. Lake 626 within the Experimental Lakes Area of north-west Ontario, along with its downstream wetlands, 626A and 626B are one such system. Construction of a dam at the L626 inflow has completely restricted water flow, reducing and reshaping the watershed, increasing water retention time, and decreasing outflow into the wetlands. This study investigates the state of each wetland through physical and geochemical characterization during the first year following the diversion. Previous studies have found that hydrological diversions in wetlands can lower water table levels, altering soil chemistry and producing a shift in floral and faunal communities. Ultimate consequences involve significant loss of wetland area through conversion to upland habitat. This provides a model for climatic warming scenarios, wherein sustained drought conditions can produce the same result. Boreal wetlands are surprising fragile ecosystems that store massive quantities of carbon and are at risk of releasing it in such situations. One study showed that an extended summer drought in an otherwise average year with above average precipitation produced losses of 90 g C/m2 over the course of the year. Maintenance of reduced-flow in wetlands 626A and 626B is expected to convert the system into a carbon source and reduce overall wetland area. Radiocarbon dating has revealed that following deglaciation, both 626A and 626B basins were open water wetlands, depositing limnic peat for about 3200 and 1300 years respectively. Each site then transitioned into open sedge dominated fen – 626B to the present and 626A until about 2.5 ka BP when Sphagnum began to develop. Wetland 626B is decidedly an open shrub/sedge fen, supporting Myrica gale, Chamaedaphne calyculata and Carex rostrata / lasiocarpa communities. Wetland 626A is a bog/fen complex, sharing similar communities in the fen areas, but housing a large, centrally located bog of shrub species overlying Sphagnum hummocks. Tritium values in 626A were similar to cosmic background levels, indicating that recharge of basal pore water has not occurred in at least 60 years. Tritium in 626B was much higher, suggesting a substantial difference in hydrology or peat hydraulic conductivity between the basins. Measurement of DOC profiles showed high concentrations in near-surface water, reaching over 80 mg/L, and dropping to about 20 mg/L at maximum depths. An opposite trend was seen for DIC and CH4 profiles which increased concentration with depth (25 – 70 mg/L DIC; 75 – 700 μmol/L CH4). Isotopically however, 13C signatures from basal DIC were more positive while signatures from CH4 were typically more negative (-6 ‰ to +4 ‰ DIC; -57 ‰ to -73 ‰ CH4). Breakdown of DOC by LC-OCD showed high concentrations of humic substances and low molecular weight neutrals. The origin of humic substances in surface water became more pedogenic with increasing distance from the L626 outflow, indicating the influence of decaying wetland vegetation on the DOC of adjacent water. A comparison between contemporary and future characterization of boreal peatlands under drought-like conditions will provide a better understanding of the impacts suffered by wetlands during hydrological alterations. The high sensitivity of wetlands to changing hydrology should also provide a measure for gauging the effects of long term climate warming. This will assist in the development of environmental policies to better govern both the establishment of water diversions and the multitude of other practices leading to climate change.

A two-part paleolimnological study was conducted to: i) understand the important factors that are related to the present-day distribution of scaled-chrysophytes; ii) investigate changes in the scaled-chrysophyte assemblages in the Experimental Lakes Area northwestern Ontario, in response to recent climate warming. Scaled-chrysophyte assemblages were analyzed in the modern sediments of 40 ELA lakes to determine their relationship to measured environmental variables. The sediment record from 210Pb dated cores from six ELA lakes were analyzed at a sub-decadal resolution to evaluate if chrysophytes were changing in a consistent fashion and if these changes could be accounted for by measured climatic factors. Ordination analysis of the modern chrysophyte flora was significantly related to pH, lake depth, and the degree of thermal stratification, as well as water temperature. Mallomonas punctifera ‘small’ and Mallomonas acaroides were indicators of warm surface-waters. High-resolution analysis of six ELA lakes revealed pronounced shifts in the chrysophyte assemblages over the last ca. 150 years. The most notable shift in the chrysophyte assemblage was characterized by an overall shift towards higher relative abundances of colonial taxa. In several lakes increases in unicellular warm-water taxa were also observed. Breakpoint Analysis identified significant changes in the chrysophyte assemblages beginning in the late-1800s to mid-1900s in most lakes. An interclass correlation coefficient (ri) was used to assess the temporal coherency of the chrysophyte assemblages over the past ca. 100 years. All lakes displayed a similar directional change which was significantly coherent (p<0.05). A Brien’s Test identified sub-sets of lakes that were temporally coherent and homogenous. The high coherency of two groups, (Group A, grand mean=0.89, p-value=5.3x10-15; Group B, grand mean=0.38, p-value=0.038), suggests the dominance in extrinsic factors in governing the lake responses. The average PCA axis-1 scores of Group A (r-value=0.62, p=0.03) and Group B (r-value=0.60, p=0.038) were significantly correlated to regional mean annual temperature. Collectively, the results of this study suggest that changes observed in the scaled-chrysophyte assemblages in the ELA region are consistent with recent climate warming. / Thesis (Master, Biology) -- Queen's University, 2011-09-29 16:42:06.753

Anthropogenic disruptions in the form of hydrological alterations, such as dam construction and the associated water diversions are a cause of much upheaval to local and regional ecosystems. Lake 626 within the Experimental Lakes Area of north-west Ontario, along with its downstream wetlands, 626A and 626B are one such system. Construction of a dam at the L626 inflow has completely restricted water flow, reducing and reshaping the watershed, increasing water retention time, and decreasing outflow into the wetlands. This study investigates the state of each wetland through physical and geochemical characterization during the first year following the diversion. Previous studies have found that hydrological diversions in wetlands can lower water table levels, altering soil chemistry and producing a shift in floral and faunal communities. Ultimate consequences involve significant loss of wetland area through conversion to upland habitat. This provides a model for climatic warming scenarios, wherein sustained drought conditions can produce the same result. Boreal wetlands are surprising fragile ecosystems that store massive quantities of carbon and are at risk of releasing it in such situations. One study showed that an extended summer drought in an otherwise average year with above average precipitation produced losses of 90 g C/m2 over the course of the year. Maintenance of reduced-flow in wetlands 626A and 626B is expected to convert the system into a carbon source and reduce overall wetland area. Radiocarbon dating has revealed that following deglaciation, both 626A and 626B basins were open water wetlands, depositing limnic peat for about 3200 and 1300 years respectively. Each site then transitioned into open sedge dominated fen – 626B to the present and 626A until about 2.5 ka BP when Sphagnum began to develop. Wetland 626B is decidedly an open shrub/sedge fen, supporting Myrica gale, Chamaedaphne calyculata and Carex rostrata / lasiocarpa communities. Wetland 626A is a bog/fen complex, sharing similar communities in the fen areas, but housing a large, centrally located bog of shrub species overlying Sphagnum hummocks. Tritium values in 626A were similar to cosmic background levels, indicating that recharge of basal pore water has not occurred in at least 60 years. Tritium in 626B was much higher, suggesting a substantial difference in hydrology or peat hydraulic conductivity between the basins. Measurement of DOC profiles showed high concentrations in near-surface water, reaching over 80 mg/L, and dropping to about 20 mg/L at maximum depths. An opposite trend was seen for DIC and CH4 profiles which increased concentration with depth (25 – 70 mg/L DIC; 75 – 700 μmol/L CH4). Isotopically however, 13C signatures from basal DIC were more positive while signatures from CH4 were typically more negative (-6 ‰ to +4 ‰ DIC; -57 ‰ to -73 ‰ CH4). Breakdown of DOC by LC-OCD showed high concentrations of humic substances and low molecular weight neutrals. The origin of humic substances in surface water became more pedogenic with increasing distance from the L626 outflow, indicating the influence of decaying wetland vegetation on the DOC of adjacent water. A comparison between contemporary and future characterization of boreal peatlands under drought-like conditions will provide a better understanding of the impacts suffered by wetlands during hydrological alterations. The high sensitivity of wetlands to changing hydrology should also provide a measure for gauging the effects of long term climate warming. This will assist in the development of environmental policies to better govern both the establishment of water diversions and the multitude of other practices leading to climate change.