Katharine E. Duff

Limnological characteristics of lakes located across arctic treeline in northern Russia

Limnological data (e.g., water chemistry, lakewater temperature, vegetation zone and degree of human impact) were collected from lakes spanning the Russian arctic treeline in three regions: on the Taimyr Peninsula and near the mouth of the Lena River, both in central arctic Siberia, and near the mouth of the Pechora River, western arctic Russia. Pearson correlation and canonical variates analyses revealed similar environmental gradients in all three regions. Variables expressing ionic composition of the water (i.e., cations, anions, dissolved inorganic carbon and conductivity) were highly intercorrelated, as were nutrients, chlorophyll a, particulate organic matter and metal (i.e., Fe and Mn) concentrations. Lakewater transparency was related to water colour (i.e., Fe, Mn and dissolved organic carbon) and productivity. Regional differences among the lakes were strong and appeared to reflect differences in geology, hydrology and human impact. For example, Na and Cl concentrations were related to proximity to the ocean in the Lena and Pechora River regions but not in the more inland Taimyr region. Extensive mining and smelting at Norilsk, on the Taimyr Peninsula, has apparently resulted in elevated major ion and metal concentrations in lakes closer to the city. Surface water temperatures, nutrients, and related variables were particularly useful for distinguishing lakes in different vegetation biomes. Forest lakes were typically warmer, with slightly elevated concentrations of dissolved organic carbon (DOC). Lakes in the forest–tundra zone often had higher concentrations of particulate organic matter, Fe and Mn. Tundra lakes were characterized by low nutrient and DOC concentrations. These data will facilitate the development of models that predict the outcome of future climatic change on arctic and subarctic aquatic ecosystems, as well as provide baseline data for future limnological studies in these remote regions.

Morphological descriptions and stratigraphic distributions of the chrysophycean stomatocysts from a recently acidified lake (Adirondack Park, N.Y.)

The chrysophycean stomatocyst flora from the sediments of Upper Wallface Pond, a recently acidified Adirondack lake, was described according to the guidelines of the International Statospore Working Group. Sixty-six morphotypes were distinguished, using scanning electron microscopy. Twenty-eight of these cysts were distinguishable using the light microscope (LM), whereas 30 required grouping into 11 collective categories from LM identification, and 7 could not be identified using LM. None of our morphotypes could be linked definitively to the living chrysophyte species that produced them. Stratigraphic analysis showed that a marked change in the cyst assemblage occurred in the 1930s. Previous paleoecological studies inferred a pronouced pH decline at this time. Redundancy analysis of our data showed that diatom-inferred pH explained a significant amount of variation (Monte Carlo permutation test; p=0.01). This suggests that pH influences chrysophyte populations, and that stomatocysts could eventually be used to reconstruct pH and other variables.

Regional Contamination in Lakes from the Noril'sk Region in Siberia, Russia

Sediment and water chemistry data were collected from ten lakes within a 110 km radius of Norilsk in Siberia, the largest smelting complex in the world. Metals showing the most pronounced increase in enrichment near the smelters were Cu, Ni, Co, Ba and Zn. Cu and Ni appear to be as or more enriched in lake sediments around Norilsk compared with levels previously reported for other locations. Although SO4 concentrations were highly elevated in the areas closest to the smelting complex, lake water pH remained elevated due to high concentrations of base cations in the waters. Sediment mercury enrichment was high in sediments near the smelting complex, but not more so than in other parts of the Arctic, suggesting that Hg either is not a major smelting product at Norilsk, or that Hg is transported greater distances than other metals due to its longer atmospheric residence time.

Chrysophycean cysts in Sierra Nevada (California) lake sediments: paleoecological potential

Thirty-three lakes in the Sierra Nevada range of California were investigated as part of a paleoecological study of the potential effects of acid deposition on sensitive lake/watershed ecosystems. Chrysophyte cysts from surface sediment samples were analyzed and compared with data on pH and alkalinity. This paper identifies the twenty-five dominant chrysophyte cyst taxa and provides information on their morphology, abundance, distribution and ecology.Chrysophycean cysts were generally abundant and well-preserved in lake sediments of our study sites. Twelve taxa occurred in more than twenty of the thirty-three lakes; these taxa were often quite abundant. In contrast, only nine taxa occurred in ten or fewer lakes. Abundance Weighted Mean (AWM) pH varied from 6.45 to 8.34 and AWM alkalinity varied from 46 to 588 μeq/L. We delineated pH preference categories, based on AWM pH values and frequency diagrams of cyst abundance vs. lake-water pH. We classified five taxa as acidophilous, nine as circumneutrals, six as alkaliphilous and five as indifferent. Given that the cyst types differ greatly in their abundance relative to pH and alkalinity, it is clear that they have potential for paleolimnological studies of Sierra lakes biogeochemistry.

Recent Eutrophication Histories in Lac Ste. Anne and Lake Isle, Alberta, Canada, Inferred Using Paleolimnological Methods

ABSTRACT A paleolimnological analysis of Lac Ste. Anne and Lake Isle, two eutrophic lakes in central Alberta, Canada, confirmed that they were naturally eutrophic, but have become increasingly eutrophic after the 1960s as 27% and 24% of their watersheds, respectively, were developed for urban and agricultural purposes. This was shown by a predominance of Chironomidae head capsules indicating periodic anoxia in bottom waters, high abundances of eutrophic diatoms (e.g., Aulacoseira granulata, Fragilaria crotonensis, Stephanodiscus niagarae and S. parvus), and, in Lac Ste. Anne, an enrichment of pigments from filamentous cyanobacteria (e.g., myxoxanthophyll) in post-1960 sediments. Evidence of periodic anoxia in the profundal zone was also provided by a scarcity of reducible phosphorus in the sediments. Lac Ste. Anne showed the largest changes during the 1960s and 1970s, when increases were observed in the abundance of hyper-eutrophic diatoms (e.g., S. parvus) as well as sedimentary phosphorus fractions and algal pigments. The changes in Lake Isle were similar, but more subtle. Results indicate that reduced anthropogenic activities would still result in eutrophic systems, but some improvements in water quality would be achieved, particularly in Lac Ste. Anne.