Univ., Diss.--Toronto, 2002.

Note:

Freshwater ecological issues are increasingly being recognized within the context of multiple stressors, even though relatively little is known about the limnological and biological consequences of the interactions between various environmental impacts. Moreover, long-term monitoring data are often lacking. To help address these issues, the overall goal of this thesis was to use paleolimnological approaches to document how multiple environmental stressors have altered limnological communities in south-central Ontario lakes. During the last two centuries, Ontario lakes have been subjected to varying intensities of different environmental impacts, including increases in shoreline residential development, forest clearance and regrowth, the deposition of strong acids via the atmosphere, invasion by non-indigenous species, and climate change. I used multiple paleolimnological approaches to: 1) demonstrate how multiple natural and anthropogenic stressors have affected biological assemblages across lakes in the Muskoka-Haliburton region of south-central Ontario, and 2) reconstruct the limnological histories of four lakes from Algonquin Park that have recorded the near complete extirpation of native crayfish species. In the Muskoka-Haliburton lakes, I assessed the extent of limnological changes that have occurred during the past ~15 years by resampling lakes from an earlier survey, using identical paleolimnological methods. Limnological monitoring data document that, since 1992, the lakes have experienced declines in lakewater calcium and SO4 concentrations, while pH declined marginally; in contrast dissolved organic carbon, silica and Total Kjeldahl Nitrogen increased. Marked regional increases in planktonic diatom taxa, including Cyclotella stelligera, Asterionella formosa and Fragilaria crotonensis, occurred in many lake systems, while colonial scaled chrysophyte algae have undergone a widespread decline in favour of unicellular forms (i.e., Mallomonas spp.), driven by interactions between resource limitation and climate change. In the Algonquin Park study lakes, crustacean zooplankton remains revealed a marked decline in daphniid species with high Ca requirements, in favour of smaller Bosmina spp., while diatom and chrysophyte analysis suggest varying degrees of industrial acidification in the four study lakes. The paleolimnological data suggest that the crayfish decline may have began prior to the long-term monitoring record, likely as a result of declines in pH and lakewater Ca related to atmospheric acid deposition. / Thesis (Ph.D, Biology) -- Queen's University, 2012-09-27 12:53:20.518

Open and throughfall precipitation samples were collected at Haliburton Forest for a total of nine events from July – November of 2009. The following species were analyzed quantitatively: NO3-, SO42-, Cl-, HCOO-, C2O42-, NH4+, Na+, K+, Ca2+, and Mg2+. Wet deposition inputs to the system were quantified and the sources of wet-deposited species were probed. The throughfall method was employed to quantify inputs to the forest floor and probe canopy-precipitation interactions. Leaf wash samples at three heights aided in the interpretation of throughfall data and allowed for an examination of vertical profiles of dry deposition to the canopy. Results suggest possible nitrate foliar leaching during the growing season, although this appears to cease during senescence. This finding supports previous evidence that Haliburton Forest has shifted from nitrogen-limitation toward nitrogen-saturation and estimated total atmospheric N inputs to the system are close to the proposed critical load of 10 kg N ha-1 yr-1.

Open and throughfall precipitation samples were collected at Haliburton Forest for a total of nine events from July – November of 2009. The following species were analyzed quantitatively: NO3-, SO42-, Cl-, HCOO-, C2O42-, NH4+, Na+, K+, Ca2+, and Mg2+. Wet deposition inputs to the system were quantified and the sources of wet-deposited species were probed. The throughfall method was employed to quantify inputs to the forest floor and probe canopy-precipitation interactions. Leaf wash samples at three heights aided in the interpretation of throughfall data and allowed for an examination of vertical profiles of dry deposition to the canopy. Results suggest possible nitrate foliar leaching during the growing season, although this appears to cease during senescence. This finding supports previous evidence that Haliburton Forest has shifted from nitrogen-limitation toward nitrogen-saturation and estimated total atmospheric N inputs to the system are close to the proposed critical load of 10 kg N ha-1 yr-1.

A petrographic study has been made of the contact relations between metagabbro and nepheline gneiss underlain by marble, in Monmouth township, Haliburton County, Ontario. A bad of hornblende nepheline-garnet gneiss about 80 feetwide trending north-south is underlain at a shear contact by marble. Round inclusion up to 18 inches across of red pyroxene with some spinel and rimmed by olivine occur in the marble a few feet below the contact. For a few inches above the contact the nepheline gneiss sometimes is biotite-bearing. To the east the nepheline gneiss grades into a band of hybrid nepheline metagabbro (containing pink augite) about 50 feet wide. This in turn is followed by a zone of garnetiferous clinozoisite metagabbro about 220 feet wide. Clinozoisite persists in the metagabbro for 100 feet beyond this zone and is followed by hornblende-(pyroxene)-plagioclase metagabbro. Pyroxene-garnet-(nepheline) skarn is interlayered with nepheline gneiss at one outcrop ear the fault contact with marble. It appears that gabbroic magma has intruded limestone and developed a skarn at the contact. Assimilation of lime by the magma has developed pink augite (titanaugite ?) , clinozoisite and grossularite in the gabbro. Subsequent injection of a highly fluid nepheline magma, or of solutions containing soda, alumina and iron and not saturated with silica, formed nepheline-bearing rock between marble and gabbro. Soda metasomatism produced a hybrid nepheline gabbro adjacent to the nepheline-bearirg rock. Regional metamorphism later imparted a foliation to the marble and nepheline rock, and produced a metamorphic texture the gabbro. Faulting of a unknown age brought nepheline gneiss and marble into sharp contact and probably trapped the skarn as horses only one of which is now exposed. / Thesis / Doctor of Philosophy (PhD)