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. / Thesis (Master, Biology) -- Queen's University, 2008-07-10 12:04:59.828

In response to sulphur dioxide emission reductions in North America and Europe, there has been a recent shift in research focus towards understanding ecosystem recovery. Evidence for reversibility in the effects of acidification on lake ecosystems within North America has been, for the most part, constrained to a single locality (Sudbury, Ontario). Lakes in a fume-kill area near Wawa, Ontario, present a new and rare opportunity for studying potentially rapid chemical and biological recovery patterns from extreme acidification. Several lakes acidified (pH ~3) during a period of local iron sintering from 1939 to 1998, and although minimal historical data are available, striking biological recovery has recently been observed. This study used paleolimnological techniques to track diatom (class Bacillariophyceae) responses to historical water quality changes in five fume-kill lakes near Wawa. Prior to the onset of iron sintering, the sediment-recorded diatom assemblages were dominated by species that are typically found in circumneutral or slightly alkaline lakes. Following the known occurrence of lake acidification, there was a striking shift in the sediment record towards dominance by acid- and metal-tolerant species. Water quality of the fume-kill lakes has since improved (i.e. pH has increased from ~3 to ~7 and metal concentrations have decreased). In four of the five lake cores, this was reflected by a decrease in the relative abundance of acid-tolerant species. Surprisingly, diatom communities were not progressing towards pre-disturbance species assemblages. Factors impeding the return of native species might include metal enrichment in surface sediment and potentially altered lake thermal regimes. Documenting and understanding recovery trajectories is necessary to help lake managers evaluate policy decisions regarding the efficacy of emission reduction programs and mitigation measures. This thesis provides evidence from one location in addition to Sudbury that the ecological effects of severe lake acidification can be reversed if SO2 emissions are sufficiently reduced. It also further demonstrates the complexity of recovery patterns in acidified and metal-contaminated lakes. / Thesis (Master, Biology) -- Queen's University, 2009-04-26 18:38:20.58

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

Lakes in the Adirondack Park (NY, USA) are undergoing chemical recovery from acidification. There is now a pressing research need to define recovery targets for acid-impacted sites. Researchers attempting to designate such targets are hampered by two issues: 1) a lack of long-term monitoring data, and 2) the influence of multiple stressors on recovering lakes. This thesis addresses both difficulties by applying paleolimnological techniques within a regional reference lake framework. Using a set of stringent selection criteria, 31 lakes protected from acidification, eutrophication, road salt seepage, and piscivore introductions were identified from 1,469 Adirondack lakes. Ordination techniques showed that the lakes are representative of 24-36% of the chemical/morphological variation of Adirondack lakes. Qualitative and quantitative historic analyses found that many of the lakes experienced early watershed and/or fisheries disturbance, highlighting the danger of assuming that a lake’s condition remains static over time. A top-bottom paleolimnological study revealed that the reference lakes have undergone a ‘shifting baseline’ in species assemblages, with increases in colonial and/or warm-water chrysophyte taxa from pre-1900 to present, changes most likely due to regional warming and/or oligotrophication. A subset of three reference lakes were then paired with two Adirondack lakes that acidified and are undergoing chemical recovery from acidification. The acidified lakes underwent a significant shift in species composition since the 1995 implementation of the US Acid Rain Program, indicating biological recovery from acidification. However, both reference and acidified lakes showed increases in colonial chrysophytes since ca. 1970-1980, a trend correlated with mean annual air temperature and ice-cover measures in the two reference lakes. Long-term species changes in acidified/reference lakes suggest that the recovering lakes will not return to their pre-disturbance state but will instead move to a state characterized by an increased abundance of colonial taxa/warm-water species. Overall, this thesis demonstrates the utility of pairing paleolimnological techniques with a regional reference site dataset for tracking shifting baselines and defining recovery targets, a method that could be applied to examine other stressors in other regions, thereby addressing a critical management need. / Thesis (Ph.D, Biology) -- Queen's University, 2014-05-03 13:17:09.613

The taxonomic concept of the algal genus Mallomonas (Synurales, Synurophyceae) was based on an extraordinary morphological diversity of their siliceous scales. The main aims of this study were elucidation of phylogenetic relationships among its representatives and reconstruction of shape evolution of particular siliceous structures of their scales. Molecular data for six species were acquired for the first time, enabling a successful assessment of their phylogenetic relationships with the other representatives of the genus. On the basis of molecular data, the genus Mallomonas can be divided in two evolutionary lineages and this division is also reflected morphologically (with only a few exceptions) through presence or absence of a V-rib structure. Fine ornamentation of siliceous scales is species-specific and interestingly, the overall differences in morphology of siliceous scales are mostly reflecting phylogenetic relationships among representatives of the genus. In this context, morphological species concept of Mallomonas seems to be justified. Morphologically-based sections of the genus are often paraphyletic, because small sections (frequently containing only single species) tend to be nested within particular larger sections. The main reason for this discrepancy is accelerated morphological...

A Holocene lake sediment record spanning 7300 years from Wishart Lake, in the Turkey Lakes Watershed central Ontario, was produced to determine the main drivers of long-term change in the lake ecosystem. The mid-Holocene sediments are dominated by benthic diatoms, around 4000 yrs BP, diatoms in the genera Cyclotella and Tabellaria increase. Comparisons with nearby pollen records show that changes in local vegetation and diatom assemblages occurred synchronously, suggesting a response to nutrient changes caused by vegetation succession. The most recent sediments, dated using activity of 210Pb and the Ambrosia pollen rise, show increases in planktonic Cyclotella spp., particularly around the Ambrosia rise (1880 AD). Thus, the diatom changes in the recent sediments suggest a response to multiple stressors. However, due to some buffering capacity in watershed soil, recent acidification of the lake has not taken place despite nearby industrial air pollution, tracked since 1980 by an on-site monitoring program.

A Holocene lake sediment record spanning 7300 years from Wishart Lake, in the Turkey Lakes Watershed central Ontario, was produced to determine the main drivers of long-term change in the lake ecosystem. The mid-Holocene sediments are dominated by benthic diatoms, around 4000 yrs BP, diatoms in the genera Cyclotella and Tabellaria increase. Comparisons with nearby pollen records show that changes in local vegetation and diatom assemblages occurred synchronously, suggesting a response to nutrient changes caused by vegetation succession. The most recent sediments, dated using activity of 210Pb and the Ambrosia pollen rise, show increases in planktonic Cyclotella spp., particularly around the Ambrosia rise (1880 AD). Thus, the diatom changes in the recent sediments suggest a response to multiple stressors. However, due to some buffering capacity in watershed soil, recent acidification of the lake has not taken place despite nearby industrial air pollution, tracked since 1980 by an on-site monitoring program.

In protists a biodiversity hotspot could be defined as region with exceptionally high ratio of local to global species diversity. In 2012 Aquitaine (France) was revealed to represent a hotspot of Synurales (lineage within silica-scaled chrysophytes). To investigate how the diversity is distributed and where the species are hidden, samples from 42 lakes were collected during spring peak of Chrysophyte occurrence (from March 27th to March 31st ). Samples were taken in two microbiotopes - phytoplankton and metaphyton. Metaphyton was represented by different substrates (aquatic plants). I identified seventy-six species from genera Mallomonas and Synura, which confirmed Aquitaine to be a hotspot. In this thesis, I investigated ecological drivers of chrysophytes diversity and community structure. The chrysophyte diversity was driven mostly by mutual impact of pH and conductivity, north-south gradient of lakes location and sampled microbiotopes. Number of identified species increased with increasing pH and conductivity, with increasing size of waterbody and with location of the lake more towards the South. More taxa were revealed from metaphyton (77) than from plankton (61), substrates played an important role. Lakes in Aquitaine are rich in different species of aquatic plant, which immersed create...

<p>Heterotrophic microorganisms are important for the flow of carbon and nutrients in the sea. Bacteria, nanoflagellates and ciliates are relevant components of the pelagic food web. In order to be able to predict the outcome of e.g. eutrophication or climate change we need to know how the different components of the pelagic food web are regulated. With the focus on the northern Baltic Sea food web, this thesis deals with limitation and control of heterotrophic protists, the effect of resource heterogeneity on food web efficiency and diversity of nanoflagellates.</p><p>In-situ microcosm experiments showed that the net growth of heterotrophic flagellates were resource limited throughout the year. Field data confirmed that the abundance of flagellates was bottom-up controlled. Furthermore, field data also showed that the annual average biomass of protists, flagellates and ciliates increased with primary productivity. On a smaller seasonal scale temperature and bacterial biomass were able to explain most of the variation in flagellate biovolume. The temporal variation in ciliate biovolume could not be explained by any bottom-up factors like bacterial biomass, flagellate biomass or chlorophyll a. This and an in-situ microcosm experiment implied that the seasonal dynamics of ciliates were more regulated by predators like mesozooplankton.</p><p>The food web efficiency i.e. how much of production at the resource level is converted to production at the top trophic level, may be affected by specific size or type of resource. Indoor mesocosms revealed that the food web efficiency was 11 times lower when heterotrophic bacteria dominated basal production instead of nano- and micro-sized phytoplankton. This was due to a lengthening of the food web when pico-sized bacteria constituted the main resource.</p><p>The PCR-DGGE molecular biological method was used to study the diversity of heterotrophic or mixotrophic chrysomonads. The focus was set on chrysomonads due to their relatively large contribution to the nanoflagellate community. Group-specific PCR primers were optimized for the target group. A field survey in the northern Baltic Sea showed that a handful of chrysomonad sequences were present throughout the year. Significantly more chrysomonads were recorded in the basin with higher primary productive and salinity. In total 15-16 different chrysomonad sequences were recorded. Most of them matched uncultured chrysomonad clones.</p>

Heterotrophic microorganisms are important for the flow of carbon and nutrients in the sea. Bacteria, nanoflagellates and ciliates are relevant components of the pelagic food web. In order to be able to predict the outcome of e.g. eutrophication or climate change we need to know how the different components of the pelagic food web are regulated. With the focus on the northern Baltic Sea food web, this thesis deals with limitation and control of heterotrophic protists, the effect of resource heterogeneity on food web efficiency and diversity of nanoflagellates. In-situ microcosm experiments showed that the net growth of heterotrophic flagellates were resource limited throughout the year. Field data confirmed that the abundance of flagellates was bottom-up controlled. Furthermore, field data also showed that the annual average biomass of protists, flagellates and ciliates increased with primary productivity. On a smaller seasonal scale temperature and bacterial biomass were able to explain most of the variation in flagellate biovolume. The temporal variation in ciliate biovolume could not be explained by any bottom-up factors like bacterial biomass, flagellate biomass or chlorophyll a. This and an in-situ microcosm experiment implied that the seasonal dynamics of ciliates were more regulated by predators like mesozooplankton. The food web efficiency i.e. how much of production at the resource level is converted to production at the top trophic level, may be affected by specific size or type of resource. Indoor mesocosms revealed that the food web efficiency was 11 times lower when heterotrophic bacteria dominated basal production instead of nano- and micro-sized phytoplankton. This was due to a lengthening of the food web when pico-sized bacteria constituted the main resource. The PCR-DGGE molecular biological method was used to study the diversity of heterotrophic or mixotrophic chrysomonads. The focus was set on chrysomonads due to their relatively large contribution to the nanoflagellate community. Group-specific PCR primers were optimized for the target group. A field survey in the northern Baltic Sea showed that a handful of chrysomonad sequences were present throughout the year. Significantly more chrysomonads were recorded in the basin with higher primary productive and salinity. In total 15-16 different chrysomonad sequences were recorded. Most of them matched uncultured chrysomonad clones.