Rick Nordin

Water Level Drawdown Affects Physical and Biogeochemical Properties of Littoral Sediments of a Reservoir and a Natural Lake

ABSTRACT To determine the influence of water level drawdown on littoral areas, we compared the temporal and spatial changes in the water column and sediment in the littoral region of a drinking water reservoir and a natural lake. The reservoir (Sooke) experiences more than six meters of seasonal drawdown compared to a nearby, morphometrically and trophically similar lake (Shawnigan) that experiences less than one meter of drawdown. A greater drawdown in Sooke increased the littoral area and resulted in more littoral water column mixing, more solar warming, and higher PAR at a greater range of littoral depths than in Shawnigan. Based on sediment physical and chemical characteristics, sites farthest from shore were most similar, whereas sites in the drawdown exposure zone of Sooke and the upper littoral area of Shawnigan showed the largest differences. Low macrophyte abundance and loss of fine sediments, nutrients, and organic matter from the drawdown exposure zone in Sooke compared to the equivalent littoral area in Shawnigan suggest that drawdown enhances sediment erosion and focusing. Element and stable isotope ratios of sediment carbon and nitrogen suggest organic matter in the drawdown zone in Sooke is more allochthonous in origin and is coupled more strongly with deeper sites than in Shawnigan. Organic matter source and distribution also suggests that the littoral area extends out farther in Sooke than Shawnigan. This study demonstrates that drawdown has the potential to fundamentally change reservoir littoral sediment and biogeochemical characteristics. Understanding how littoral zones in reservoirs respond to drawdown compared to natural lakes may help water managers make more ecologically informed decisions regarding drawdown impacts on the ecology of littoral zones and water quality.

Effects of Water Level Fluctuation and Short-Term Climate Variation on Thermal and Stratification Regimes of a British Columbia Reservoir and Lake

ABSTRACT Stratification and thermal regimes of a reservoir with fluctuating water levels were compared to a natural lake of similar morphometry and trophic status over a two-year period (2000–2001) in coastal British Columbia, Canada. We compared the timing and duration of stratification, summer heat budgets and heat fluxes in two morphometrically contrasting basins of Sooke Lake Reservoir and Shawnigan Lake (one shallow and one deep basin per water body). In the second year of the study, a 100-year drought allowed us to compare responses of a reservoir and a lake to contrasting years of climatic conditions. Loss of volume from the reservoir during summer and fall caused stratification and thermal regimes to differ from Shawnigan Lake, but the magnitude of these differences was mediated by basin morphometry. Duration of summer stratification, timing of heat content, and the relative importance of seasonal heat fluxes in the shallow basin of Sooke Lake Reservoir were most different from Shawnigan Lake. While there were no major differences between years for Shawnigan Lake, contrasting years in precipitation and hydrology caused Sooke Lake Reservoir stratification and thermal regimes to differ between years. The magnitude of differences between years was mediated by basin size, with the shallower reservoir basin having greater differences between years. Our results indicate that reservoir physical processes are sensitive to short-term changes in hydrology, and that the combined impacts of short-term climate variation and anthropogenic manipulation of hydrology may be greater in shallow reservoir ecosystems.

Survival of Escherichia coli in Beef Cattle Fecal Pats Under Different Levels of Solar Exposure

Abstract Understanding the survival and transport of Escherichia coli in feces on land and in water is important when trying to assess contamination of water by grazing animals. A fecal-pat experiment was conducted in July and August of 2003 to investigate the survival of E. coli under 4 levels of solar exposure controlled by using shade cloth. Fresh beef cattle manure was uniformly blended to produce 2.5- and 1.6-kg fecal pats, which were placed in plastic trays or in contact with the soil and covered with 0%, 40%, 80%, or 100% shade cloth treatments and replicated 5 times. Samples from each fecal pat were collected at Time 0 to establish E. coli levels; sampling was repeated at Day 1, Day 3, and approximately weekly thereafter for 45 days to determine die-off. E. coli concentration and percent moisture were measured for each fecal sample. At the end of the experiment, fecal pats under the 0% shade cloth had the lowest E. coli concentrations, followed by the 40%, 80%, and 100% treatments, with 0.018, 0.040, 0.11, and 0.44 × 106 colony-forming units (CFU) · g−1, respectively. Fecal-pat size was significant only on Day 17, when large fecal pats had higher concentrations of E. coli (P < .0001). There was no significant difference (P = 0.43) in E. coli concentration between the fecal pats in contact with the soil vs. those in plastic trays. Percent moisture of fecal pats was not a good covariate. Age of fecal pats, as well as exposure to solar radiation negatively influences the survival of E. coli. From a management perspective, E. coli in fecal pats under forested situations would survive longer than in open grasslands due to shading, and any possible contamination by E. coli would be greatest within 7 days of removing cattle from a riparian area or pasture.

Evaluation of Repetitive Extragenic Palindromic-PCR for Discrimination of Fecal Escherichia coli from Humans, and Different Domestic- and Wild-Animals

The objective of this study was to investigate the potential of repetitive extragenic palindromic anchored polymerase chain reaction (rep‐PCR) in differentiating fecal Escherichia coli isolates of human, domestic‐ and wild‐animal origin that might be used as a molecular tool to identify the possible source(s) of fecal pollution of source water. A total of 625 fecal E. coli isolates of human, 3 domestic‐ (cow, dog and horse) and 7 wild‐animal (black bear, coyote, elk, marmot, mule deer, raccoon and wolf) species were characterized by rep‐PCR DNA fingerprinting technique coupled with BOX A1R primer and discriminant analysis. Discriminant analysis of rep‐PCR DNA fingerprints of fecal E. coli isolates from 11 host sources revealed an average rate of correct classification of 79.89%, and 84.6%, 83.8%, 83.3%, 82.5%, 81.6%, 80.8%, 79.8%, 79.3%, 77.4%, 73.2% and 63.6% of elk, human, marmot, mule deer, cow, coyote, raccoon, horse, dog, wolf and black bear fecal E. coli isolates were assigned to the correct host source. These results suggest that rep‐PCR DNA fingerprinting procedures can be used as a source tracking tool for detection of human‐ as well as animal‐derived fecal contamination of water.

Relationship between phytoplankton paleoproduction and diversity in contrasting trophic states

With the increasing rate of species extinctions following anthropogenic perturbation, there is a growing interest in biodiversity research. Although productivity and species richness relationships have been tested and applied in contemporary aquatic ecological studies, none have been applied to paleoecology with contrasting trophic states. The present study explores the applicability of a contemporary production and species richness relationship in high-resolution paleoecological records with low, intermediate and mid to high productive aquatic systems. Results from our study reveal that diatom species richness was positively correlated in low to intermediate productive lakes. In contrast, the relationship was hump shaped (unimodal) in a mid to high productive system concurrent with the species diversity analyses. Contrasting relationships between diatom species richness and stable isotope records (δ 13 C and δ 15 N) suggested that the nutrient biogeochemical cycle might play an important role in controlling species richness. From fossil pigment records we show that the variations in algal functional group signatures were highest in intermediate state. Collectively, these results suggest that the hump shaped (unimodal) relationship between diatom species richness and production might be limited to high productive systems with maximum richness and diversity in intermediate states, which is also supported in contemporary studies. Moreover, fossil pigment records as proxies for algal functional groups reveal that in a mid to high productive system with intense watershed scale disturbances, community composition of algal functional groups declined favoring certain diatoms. Our results demonstrate the applicability of production and diversity relationship theory in paleo-perspective and that recent watershed scale land use changes might affect the species diversity in aquatic systems.

Aminopeptidase activity in lake sediments

N), and carbon to nitrogen (C:N) elemental ratio. Protease enzymes are impor-tant breakdown of proteins, one of the major components of organic matter. Among the protease enzymes, L-Leucine-4-methylcoumarinyl-7-amide, which we considered in our study, is 3 times higher than other aminopeptidases and therefore considered to be model proteolytic enzyme.