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The disaggregated inorganic grain size (DIGS) of bottom sediment analyzed with a Coulter Counter (CC) has been used to show that the fraction of sediment deposited in flocs (floc fraction) increased in both the near and far field after the introduction of open cage salmon aquaculture, altering benthic habitat and species composition. As a result, DIGS was identified as a potential indicator of regional environmental changes due to aquaculture. Laser diffraction is an attractive alternative to the CC because of its greater efficiency and larger size range. To determine if a laser diffraction instrument, Beckman-Coulter LS 13 320 (LS), could replace the CC within a Canadian national aquaculture monitoring program, the DIGS of 581 samples from five different regions in eastern Canada were analyzed with an LS and a CC. Results show that the LS could not be used to calculate floc fraction. Instead, % sortable silt and the volume % of inorganic particles < 16 µm were evaluated as alternative proxies for fine sediment properties. LS and CC values for these parameters were correlated, but they were significantly different and the relationship between the instruments was dependent on the area sampled. The LS did not capture variations between areas seen in the CC DIGS data. Where the DIGS from the CC found no sorting in the finest size classes, all the LS samples had similar size distributions characterized by smooth modal peaks. The LS and CC both return values that can be used to monitor changes in the deposition of fine-grained sediment, but the LS cannot determine changes in floc deposition and caution is required if comparing different sedimentary environments. [ABSTRACT FROM AUTHOR]

Anthropogenic stressors such as agriculture and urbanization can increase river turbidity, which can negatively impact fish gill morphology and growth due to reduced oxygen in the benthic environment. We assessed the gill morphology, field metabolic rate (FMR), and two hypoxia tolerance metrics (oxygen partial pressure at loss of equilibrium, PO2 at LOE, and critical oxygen tension, Pcrit) of eastern sand darter (Ammocrypta pellucida), a small benthic fish listed as threatened under the Species at Risk Act in Canada, from rivers in southern Ontario. Field trials were conducted streamside in the Grand River (August 2019; mean NTU 8) and in the comparatively more turbid Thames River (August 2020; mean NTU 94) to test the effect of turbidity on each physiological endpoint. Gills were collected from incidental mortalities and museum specimens, and were assessed using hematoxylin and eosin and immunofluorescent staining. The between‐river comparison indicated that turbidity significantly increased interlamellar space and filament width but had no significant influence on other gill morphometrics or FMR. Turbidity significantly increased PO2 at LOE (i.e., fish had a lower hypoxia tolerance) but did not significantly impact Pcrit. Therefore, although turbidity influences hypoxia tolerance through LOE, turbidity levels were not sufficiently high in the study rivers to contribute to measurable changes in gill morphology or metabolism in the wild. Determining whether changes in gill morphology or metabolism occur under higherturbidity levels would help resolve the ecological importance of turbidity on species physiology in urban and agricultural ecosystems. [ABSTRACT FROM AUTHOR]

Abundance estimation of wildlife populations is frequently derived from systematic survey data. Accuracy and precision of estimates, however, depend on the number of replicate surveys, and on adjustments made for animals unavailable to (availability bias), or available but undetected (perception bias) by observers. This study offers a comprehensive analysis of the relative influence of methodological, environmental and behavioral factors on availability bias estimates from photographic and visual aerial surveys of a small cetacean with a highly clumped distribution, the beluga (Delphinapterus leucas). It also estimates the effect of the number of surveys on accuracy and precision of abundance estimates, using 28 replicate visual surveys flown within a 16--29 day window depending on survey year. Availability bias was estimated using detailed dive data from 27 beluga from the St. Lawrence Estuary, Canada, and applied to systematic visual and photographic aerial surveys of this population, flown using various survey platforms. Dive and surface interval durations varied among individuals, and averaged (weighted) 176.6 s (weighted s.e. = 12.6 s) and 51.6 s (weighted s.e. = 4.5 s), respectively. Dive time and instantaneous availability, but not surface time, were affected by local turbidity, seafloor depth, whale behavior (i.e., whether beluga were likely in transit or not), and latent processes that were habitat-specific. Overall, adjustments of availability for these effects remained minor compared to effects from survey design (photographic or visual) and type of platform, and observer search patterns. For instance, mean availability varied from 0.33--0.38 among photographic surveys depending on sightings distribution across the study area, but exceeded 0.40 for all visual surveys. Availability also varied considerably depending on whether observers searched within 0-90° (0.42--0.60) or 170° (0.70--0.80). Simulation-based power analysis indicates a large benefit associated with conducting more than 1 or 2 survey reps, but a declining benefit of conducting > 5--10 survey reps. An increase in sample size from 2, to 5, and 10 reps decreased the CV from 30, to 19 and 13%, respectively, and increased the probability of the abundance estimate being within 15% of true abundance from 0.42, to 0.59 and 0.69 in species like beluga. [ABSTRACT FROM AUTHOR]

North temperate and boreal lakes are affected by a complex suite of anthropogenic stressors, yet little is known about how these ecosystems are faring across the most lake‐rich nation, Canada. The NSERC Canadian Lake Pulse Network is the first large‐scale national survey of its kind, with the aim of assessing the health of Canadian lakes, determined by the deviation of key variables from baseline pre‐industrial conditions (pre‐1880 CE).We examined midge remains (chironomids and Chaoborus) from modern and pre‐industrial sediment intervals in 67 lakes, spanning a range of sizes, ecozones, and degrees of catchment land‐use change. A marked northwest/southeast divide was evident in the modern chironomid assemblages, which was partially associated with water quality, physiographical and climatic variables, with a small portion of the variance explained by geography alone.Between the pre‐industrial and modern sediment intervals, taxa typically found in warmer waters increased across the country (p < 0.001); this pattern also was evident in the littoral assemblages (p = 0.01), providing additional support for the influence of warming.Turnover in chironomid assemblages varied across trophic classes. Mesotrophic lakes showed increases in macrophyte‐associated taxa, whereas eutrophic lakes showed declines in littoral taxa, perhaps reflecting increased turbidity, and the increase of low‐oxygen‐tolerant profundal taxa in eutrophic lakes with high human impacts.Overall, the distribution and dynamics of chironomid assemblages across Canadian lakes appear to be strongly linked to changes in climate and deep‐water oxygen conditions. [ABSTRACT FROM AUTHOR]

Climate‐driven changes including rising air temperatures, enhanced permafrost degradation, and altered precipitation patterns can have profound effects on contaminants, such as mercury (Hg), in High Arctic lakes. Two physically similar lakes, East Lake and West Lake at the Cape Bounty Arctic Watershed Observatory on Melville Island, Nunavut, Canada are being affected by climate change differently. Both lakes have experienced permafrost degradation in their catchments; however, West Lake has also undergone multiple underwater Mass Movement Events (MMEs; beginning in fall 2008), leading to a sustained 50‐fold increase in turbidity. This provided the unique opportunity to understand the potential impacts of permafrost degradation and other climate‐related effects on Hg concentrations and body condition of landlocked Arctic char (Salvelinus alpinus), an important sentinel species across the Circum‐Arctic. Our objectives were to assess temporal trends in char Hg concentrations and to determine potential mechanisms driving the trends. There was a significant decrease in Hg concentrations in East Lake char, averaging 6.5%/year and 3.8%/year for length‐adjusted and age‐adjusted means, respectively, from 2008 to 2019. Conversely, in West Lake there was a significant increase, averaging 7.9%/year and 8.0%/year for length‐adjusted and age‐adjusted mean Hg concentrations, respectively, for 2009 to 2017 (the last year with sufficient sample size). The best predictors of length‐adjusted Hg concentrations in West Lake were carbon and nitrogen stable isotope ratios, indicating a shift in diet including possible dietary starvation brought on by the profound increase in lake turbidity. Our study provides an example of how increasing lake turbidity, a likely consequence of climate warming in Arctic lakes, may influence fish condition and Hg concentrations. Environ Toxicol Chem 2023;42:2712–2725. © 2023 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada. [ABSTRACT FROM AUTHOR]

Rotationally‐modified gravity currents are known to occur on the ocean bottom in many locations around the world. Although their time scales are long enough that the Coriolis force is important in their dynamics, tidal forcing may also play a role in intermediate‐term variability by periodically enhancing or diminishing the flow and bottom friction, although the importance and implications of this variability has not previously been studied. Here we investigate hourly‐to‐tidal variations in the turbidity and density of intermittent gravity currents associated with deep‐water renewal events in the Strait of Georgia, Canada. We find that features such as the height and magnitude of the gravity current's nose, as well as bottom stress, undergo tidal variations, and that sediment resuspension largely occurs at the times of greatest stress at peak flood, with highest turbidities occurring in the hours following that peak. Larger particles soon settle again, but smaller ones can remain suspended. In addition, there is a significant tidally‐driven lateral advection of the gravity current, which results in density fluctuations in observations at a fixed location. Plain Language Summary: The ocean bottom is not flat, and in many cases heavy water moves from one ocean basin to another by flowing over sills and downhill into the next basin. These "gravity currents" are affected by both the earth's rotation, causing them to turn rightwards (in the northern hemisphere) into the slope, and by tidal currents in the ocean above. Here we find that tides speed up and slow down a gravity current in the Strait of Georgia, Canada, and that in turn means that the current can pick up particles off the bottom only at certain times in the tidal cycle when currents at the bottom are strongest. The tides also move the gravity current sideways, which makes it difficult to separate out the effects of tides within the current and their effect on the location of the current. Key Points: A rotationally‐modified gravity current in the Strait of Georgia, Canada, has strong tidal variations in its vertical structureSignificant sediment resuspension occurs at and just after the peak flood tides when tidal flow is added to the gravity currentThere is also a significant lateral advection of the current, associated with large‐scale tidal currents [ABSTRACT FROM AUTHOR]

Thermokarst lakes and ponds are a common landscape feature resulting from permafrost thaw, but their intense greenhouse gas emissions are still poorly constrained as a feedback mechanism for global warming because of their diversity, abundance, and remoteness. Thermokarst waterbodies may be small and optically diverse, posing specific challenges for optical remote sensing regarding detection, classification, and monitoring. This is especially relevant when accounting for external factors that affect water reflectance, such as scattering and vegetation shadow casts. In this study, we evaluated the effects of shadowing across optically diverse waterbodies located in the forest–tundra zone of northern Canada. We used ultra-high spatial resolution multispectral data and digital surface models obtained from unmanned aerial systems for modeling and analyzing shadow effects on water reflectance at Earth Observation satellite overpass time. Our results show that shadowing causes variations in reflectance, reducing the usable area of remotely sensed pixels for waterbody analysis in small lakes and ponds. The effects were greater on brighter and turbid inorganic thermokarst lakes embedded in post-glacial silt–clay marine deposits and littoral sands, where the mean reflectance decrease was from -51 to -70%, depending on the wavelength. These effects were also dependent on lake shape and vegetation height and were amplified in the cold season due to low solar elevations. Remote sensing will increasingly play a key role in assessing thermokarst lake responses and feedbacks to global change, and this study shows the magnitude and sources of optical variations caused by shading that need to be considered in future analyses. [ABSTRACT FROM AUTHOR]

In May 2000, the drinking water system in Walkerton, Canada, became contaminated with deadly bacteria. The losses were enormous, but the outbreak could have been minimized by common water treatment practices, including the use of chlorine residual and turbidity monitors. [ABSTRACT FROM AUTHOR]

Pugnose minnow (Opsopoeodus emiliae) is a small, reclusive species that is widespread in North America, but is one of the rarest fishes in Canada, found in less than 12 known localities in southwestern Ontario. In contrast to most pugnose minnow populations across the global range, Canadian populations are primarily found in turbid systems, potentially indicating persistence in suboptimal conditions. We used data from a multi‐gear species and habitat survey in the Canard River, Ontario, a system dominated by agricultural inputs and the best‐known capture site of the species in Canada, to parameterise multi‐gear occupancy models for understanding the relationship between pugnose minnow occupancy and microhabitat features, including the role of turbidity. Almost 300 pugnose minnow were captured, representing the largest single collection of the species in Canadian history. The best occupancy model indicated that the probability of pugnose minnow occupancy was highest in the deepest sites with the lowest water clarity (i.e. high turbidity); however, competing models suggested that occupancy was highest at sites with wild celery (Vallisneria americana) and higher water clarity, signifying that habitats with low turbidity may be utilised if sufficient physical cover exists. Together, our results suggest that Canadian pugnose minnow populations occupy and potentially favour turbid conditions, possibly to avoid visual predators in clearer habitats. It remains uncertain whether this abiotic association represents a long‐term, viable, local adaptation or whether persistence of pugnose minnow in the Canard River is at risk unless significant water quality improvements can be made. [ABSTRACT FROM AUTHOR]

We investigated temporal variations in turbidity in Base Mine Lake, an oil sands pit lake, located in northeast Alberta, Canada. The lake has a surface area of 7.8 km2, is 9 m deep, and exhibits seasonal thermal stratification similar to that of natural dimictic lakes. Water turbidity was measured continuously throughout the year with moored sensors, supplemented with turbidity profiles and bottle samples, from sites on the lake. During summer there was a gradual exponential (e-folding time of 25 days) decrease in epilimnetic turbidity due to relatively steady settling of solids from the epilimnion through the thermocline to the hypolimnion. Rapid oscillations (periods of approximately 1 day) in turbidity during summer were due to wind driven internal waves. Convective cooling and wind-shear driven stirring during fall storm events increased the turbidity to an annual high just before ice-on. During these storm events, similarity scaling indicated wind shear imparted greater energy than convective cooling to the turbulence at the base of the water column. Ice suppressed wind forcing and resulted in a rapid decrease in turbidity. The rate of decrease in turbidity following ice-on was initially greater than the rate of decrease in the epilimnion during summer, and then slowed until the under-ice turbidity was a relatively constant value which was sustained during the latter half of the ice-on period. The minimum turbidity during winter was greater than the minimum during summer. Following ice-melt in spring, wind driven stirring increased turbidity until summer stratification began. [ABSTRACT FROM AUTHOR]

In this study, we built a two-dimensional sediment transport model of Lake Diefenbaker, Saskatchewan, Canada. It was calibrated by using measured turbidity data from stations along the reservoir and satellite images based on a flood event in 2013. In June 2013, there was heavy rainfall for two consecutive days on the frozen and snow-covered ground in the higher elevations of western Alberta, Canada. The runoff from the rainfall and the melted snow caused one of the largest recorded inflows to the headwaters of the South Saskatchewan River and Lake Diefenbaker downstream. An estimated discharge peak of over 5200 m/s arrived at the reservoir inlet with a thick sediment front within a few days. The sediment plume moved quickly through the entire reservoir and remained visible from satellite images for over 2 weeks along most of the reservoir, leading to concerns regarding water quality. The aims of this study are to compare, quantitatively and qualitatively, the efficacy of using turbidity data and satellite images for sediment transport model calibration and to determine how accurately a sediment transport model can simulate sediment transport based on each of them. Both turbidity data and satellite images were very useful for calibrating the sediment transport model quantitatively and qualitatively. Model predictions and turbidity measurements show that the flood water and suspended sediments entered upstream fairly well mixed and moved downstream as overflow with a sharp gradient at the plume front. The model results suggest that the settling and resuspension rates of sediment are directly proportional to flow characteristics and that the use of constant coefficients leads to model underestimation or overestimation unless more data on sediment formation become available. Hence, this study reiterates the significance of the availability of data on sediment distribution and characteristics for building a robust and reliable sediment transport model. [ABSTRACT FROM AUTHOR]

Glaciers are major agents of erosion that increase sediment load to the downstream fluvial system. The Castle Creek Glacier, British Columbia, Canada, has retreated ~1.0 km in the past 70 years. Suspended sediment concentration (SSC) and streamflow ( Q) were monitored independently at five sites within its pro-glacial zone over a 60 day period from July to September 2011, representing part of the ablation season. Meteorological data were collected from two automatic weather stations proximal to the glacier. The time-series were divided into hydrologic days and the shape and magnitude of the SSC response to hydro-meteorological conditions ('cold and wet', 'hot and dry', 'warm and damp', and 'storm') were categorized using principal component analysis (PCA) and cluster analysis (CA). Suspended sediment load (SSL) was computed and summarized for the categories. The distribution of monitoring sites and results of the multivariate statistical analyses describe the temporal and spatial variability of suspended sediment flux and the relative importance of glacial and para-glacial sediment sources in the pro-glacial zone. During the 2011 study period, ~ 60% of the total SSL was derived from the glacial stream and sediment deposits proximal to the terminus of the glacier; during 'storm' events, that contribution dropped to ~40% as the contribution from diffuse and point sources of sediment throughout the pro-glacial zone and within the meltwater channels increased. While 'storm' events accounted for just 3% of the study period, SSL was ~600% higher than the average over the monitoring period, and ~20% of the total SSL was generated in that time. Determining how hydro-meteorological conditions and sediment sources control sediment fluxes will assist attempts to predict how pro-glacial zones respond to future climate changes. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Canadian Prairies are subject to cold winter dynamics, spring snowmelt runoff, and summer storms; a process variability that makes it difficult to identify an adequate sampling strategy for capturing representative water quality data. Hence, our research objective was to compare multiple water quality sampling strategies for Prairie watersheds and rank them based on operational and statistical criteria. The focus was on the Catfish Creek Watershed (Manitoba, Canada), which drains into the hypereutrophic Lake Winnipeg. Water samples were collected every 7 h during the 2013 open-water season and notably analyzed for nitrate and orthophosphate. The original high-frequency dataset (7 h) was then deconstructed into lower-frequency datasets to mimic strategies involving sample collection on a daily, weekly, bi-weekly, monthly, and seasonal basis. A comparison and decision matrix was also built to assess the ability of the lower-frequency datasets to retain the statistical properties of the original (7 h) dataset. Results indicate that nutrient concentrations vary significantly over short timescales and are affected by both sampling time (day versus night) and water level fluctuations. The decision matrix revealed that seasonal sampling is sufficient when the goal is only to capture mean water quality conditions; however, sub-daily to daily sampling is required for accurate process signal representation. While we acknowledge that sampling programs designed by researchers and public agencies are often driven by different goals, we found daily sampling to be the most parsimonious strategy for the study watershed and suggest that it would help to better quantify nutrient loads to Lake Winnipeg. [ABSTRACT FROM AUTHOR]

A 14 month pilot-scale coagulation optimization study was conducted at the Peterborough Water Treatment Plant (Ontario, Canada) to compare treatment performance resulting from the application of aluminum sulfate vs. polyaluminum chloride (PACl). This paper describes results obtained from applying a statistical analysis approach to evaluate impacts on pH, turbidity, total organic carbon (TOC), ultraviolet absorbance (UVA), particle counts, chlorine residuals, filter head loss, flow rate, trihalomethanes (THMs), and nine haloacetic acids (HAA9). To allow a direct comparison, parallel pilot trains were operated such that they achieved equal settled water TOC by adjusting PACl dose, (52-74% of the alum dose by weight). Settled water turbidity was significantly higher (on average 0.23 NTU) in the alum treated water when compared to PACl. For equivalent filter run-times, head loss was greater by 0.002-0.011 m hr1 when applying alum. An increase in pH by approximately 0.7 units when using PACl was observed to cause a significant increase in THM formation (10-30%). [ABSTRACT FROM AUTHOR]

Seafloor channel systems are well developed in several British Columbia (Canada) fjords, including Knight, Bute and Toba inlets. The channels are active conduits for turbidity currents during episodic failures of delta fronts at the fjord heads. Recently acquired swath multibeam bathymetric data enabled a complete and detailed assessment of the form of these channel systems. Repeated multibeam surveys in Bute and Toba inlets (Mar. 2008 and Nov. 2010) indicate that the deeply incised channels may undergo accretion or erosion over a period as short as 2.5 years. Locally significant (>15 m) bathymetric changes were documented in the channel systems, with bathymetric differences exceeding 5 m occurring along approx. 20-25% of the resurveyed channel lengths. Slope failure involving the upper delta front observed in Toba Inlet is a mechanism for the rapid initiation of new channel segments. Sediment accretion on the inner side of some channel bends indicates that point bars may form as lateral channel migration proceeds. Channel sidewall slumps are found at some outer channel bends and mounded deposits may occur at these sites. Lateral migration is accompanied by outer bend erosion, overall deepening of the channel and the development of terraces. [ABSTRACT FROM AUTHOR]

The aim of this work is to evaluate and discuss river water quality trends over the last decade in ten watersheds where diffuse pollution represents more than half of the annual load of phosphorus (P) and nitrogen (N). Trend analyses taking into account flow data indicate a significant reduction of total P in eight rivers, of ammonia N in five rivers, of nitrate + nitrite in four rivers, of total filtered N in three rivers and of suspended solids in two rivers. An increase of turbidity was observed in four rivers and, for fecal coliforms, no trends. P decrease can be explained by reduced mineral P inputs on cropped lands related to means such as agro-environmental fertilization plans and addition of phytase in pig and poultry feed. However, for seven of them, median P concentrations remain at least two times greater than the Québec water quality guideline for protection of rivers against eutrophication. Concentrations of other parameters remain problematic in some rivers too. These results indicate the need to continue the efforts for further diffuse pollution reduction. Future work should better quantify actions taken at the watershed scale to reduce diffuse pollution. [ABSTRACT FROM AUTHOR]

Abstract: Neoichnological (i.e., burrows, tracks and trails made by extant organisms) distributions are mapped across the active lower delta plain of the Fraser River Delta, British Columbia, Canada. The neoichnological character of the lower delta plain is best described as a moderate diversity trace assemblage mainly comprising simple, vertical burrows of filter-feeding animals and fewer dwellings of surface deposit feeders. Neoichnological trends generally parallel the coast, and bivalve-generated structures dominate in both muddy and sandy sediments. Given that all of the bivalves in sand-dominated sediments of the lower delta plain tidal flats are filter-feeding animals, the occurrence of large numbers of bivalve-generated structures in deltaic tidal flats may be indicative of at least moderate turbidity and possibly hypopycnal flow. These observations are not applicable to muddy substrates, however, as bivalve-generated structures in mud are made by both filter-feeding and deposit-feeding animals. Neoichnological trends on the active lower delta plain are compared to the neoichnological character of the effectively abandoned part of the lower delta plain at Boundary Bay (considered to be a fully marine equivalent of the lower delta plain). In comparison to Boundary Bay, there is a significant decrease in the diversity of infauna from Boundary Bay to the tidal flats on the active lower delta plain. Bivalves thrive in the more turbid waters of the active lower delta plain, whereas many large polychaetes cannot survive the low salinity conditions of this subenvironment. The Fraser delta is a tidally asymmetric delta with a net northward transport of sediment. However, at shallow depths (less than 10m water depth relative to low low tide), the delta exhibits a reversed asymmetry in its ichnological character. Waves exert a greater control on sediment and animal distributions in shallow water, such that the updrift tidal flats (those that are south of the main distributary channel) experience higher sedimentation, salinity, and turbidity stresses than the downdrift tidal flats. This is manifested by a reduced diversity of traces and intensity of burrowing on the tidal flats updrift of the main Fraser distributary. In addition, there is a higher proportion of filter-feeding animal burrows on the downdrift side of the main distributary. [Copyright &y& Elsevier]

This research investigates the potential impacts of climate change on stormwater quantity and quality generated by urban residential areas on an event basis in the rainy season. An urban residential stormwater drainage area in southeast Calgary, Alberta, Canada is the focus of future climate projections from general circulation models (GCMs). A regression-based statistical downscaling tool was employed to conduct spatial downscaling of daily precipitation and daily mean temperature using projection outputs from the coupled GCM. Projected changes in precipitation and temperature were applied to current climate scenarios to generate future climate scenarios. Artificial neural networks (ANNs) developed for modelling stormwater runoff quantity and quality used projected climate scenarios as network inputs. The hydrological response to climate change was investigated through stormwater runoff volume and peak flow, while the water quality responses were investigated through the event mean value (EMV) of five parameters: turbidity, conductivity, water temperature, dissolved oxygen (DO) and pH. First flush (FF) effects were also noted. Under future climate scenarios, the EMVs of turbidity increased in all storms except for three events of short duration. The EMVs of conductivity were found to decline in small and frequent storms (return period < 5 years); but conductivity EMVs were observed to increase in intensive events (return period ≥ 5 years). In general, an increasing EMV was observed for water temperature, whereas a decreasing trend was found for DO EMV. No clear trend was found in the EMV of pH. In addition, projected future climate scenarios do not produce a stronger FF effect on dissolved solids and suspended solids compared to that produced by the current climate scenario. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The following manuscript provides a technical review of slow sand filters (SSFs) as well as two case studies from the province of Saskatchewan, Canada in which an optimized technology has been successfully designed and implemented to produce high quality potable water for very small populations. Renewed interest in SSF systems for small communities has resulted in enhanced plant and filter design, improved operating procedures for increased efficiency and expanded range of acceptable raw water quality input and an overall low maintenance system design. Despite some limitations to the use of SSFs, recent design modifications and improvements for operation and maintenance of SSFs have expanded their application to a broader range of contaminants under highly variable environmental and operating conditions. The flexible and modular design options inherent to SSF systems, along with the modifications in expanded application, make SSFs highly attractive for potable water treatment in rural and remote regions. The SSFs designed and tested in Saskatchewan are modular polyethylene systems that include pre- and posttreatment processes such as ozone oxidation, roughing, and biological activated carbon (BAC) filters to provide significant reductions in turbidity, heavy metals, colour, and organics. [ABSTRACT FROM AUTHOR]

Freeze-thaw conditioning of RBC (Rotating Biological Contactor) sludge was tested using a pilot-scale freezing bed placed in a mobile freezer operated at -10°C. Sludge samples from a remote mining exploration facility were flown in every 2 weeks, and added to the freezing bed in 8 layers of 10 cm thick. Approximately 4 months after the first layer of sludge was added, the pilot unit was removed from the freezer and thawed at ambient temperatures. After one day of thawing, the solids concentration increased from 2.6% to 16.2%. The final cake solids concentration was 21%. Melt water had increasing turbidity, COD, TSS, VSS, nitrogen and phosphorus concentrations during the thawing period. Freeze-thaw conditioning also decreased the initial densities of fecal coliforms and Salmonella in sludge. The results of this study showed that freeze-thaw technology successfully dewatered RBC sludge without the need for mechanical equipment, and is a sustainable option for sludge dewatering in cold and remote regions. [ABSTRACT FROM AUTHOR]

We characterized the morphological variation and algal species associations of the filamentous green alga, Acrosiphonia arcta (distinguishing it from its closely related sister genus Spongomorpha), in two contrasting environments in Nova Scotia, Canada. The habitats differed in seawater salinity and temperature (and fluctuations thereof), substratum, vertical position on the shore, wave exposure, turbidity, and diversity of macroalgae and macrofauna. Acrosiphonia arcta thalli exhibited distinct morphologies in the different environments. Thalli from the open-ocean Whitehead site (Atlantic coast) exhibited the typical A. arcta morphology of profuse, short, curved branches and rhizoids binding the filaments together to form hemispherical to spherical tufts. Thalli from the sheltered Pomquet Harbour Estuary (Gulf of St. Lawrence coast) consisted of matted clumps with extensive rhizoidal growth at the base but little branching otherwise. Acrosiphonia arcta was primarily associated with thick leathery and crustose (coralline) algae at Whitehead. In the Pomquet Harbour Estuary, a less stable habitat than Whitehead, sheet and filamentous algae were in greater abundance with A. arcta than at Whitehead. Damaged apical cells from thalli of both Pomquet and Whitehead A. arcta were able to regenerate new filamentous tips or to give rise to rhizoids, phenomena not previously documented for Acrosiphonia in North America. Morphological variation of A. arcta in different habitats points to its ability to respond to and persist in a wide range of abiotic (and possibly biotic) conditions, and helps to explain its seasonal dominance on the east and west coasts of North America. [ABSTRACT FROM AUTHOR]

Biophysical and above-water reflectance measurements collected in 2006 were used to evaluate the OC3M, standard GSM01, and a modified version of the GSM01 algorithms for estimating chlorophyll-a (chl) concentrations in the Strait of Georgia, located off the southwest coast of Canada. The Strait was generally a case 2 water body, transitioning from chromophoric dissolved organic matter (CDOM) dominant in the central region to possibly particulate dominant in Fraser River plume regions. Results showed that the OC3M algorithm was somewhat effective (R 2 =0.550) outside the most turbid areas of the Fraser River plume. However, a systematic overestimation of lower chl concentrations was found, which may have been related to the higher CDOM absorption observed throughout the Strait. The standard GSM01 algorithm had moderately good agreement with measured CDOM absorption (R 2 =0.593) and total suspended solids (TSS) concentrations (R 2 =0.888), but was ineffective at estimating chl concentrations. Localized characterization of the CDOM absorption, through a hyperbolic CDOM model, improved the modified GSM01 results with slightly better agreement with measure CDOM absorption (R 2 =0.614) and TSS concentrations (R 2 =0.933). When the modified GSM01 algorithm was limited to regions with lower combined CDOM and non-algal particulate absorption (a dg (443)<0.7 m−1), it was more effective then the OC3M algorithm at estimating chl concentrations. This suggests that a threshold value on the a dg (443) or b bp (443) estimated by the GSM01 algorithm may be beneficial for limiting turbidity influence on the algorithm. The further reinterpretation of phytoplankton absorption from the modified GSM01 algorithm with a two-component phytoplankton model resulted in a chl relationship with an R 2 =0.677 and a linear slope closer to one. [Copyright &y& Elsevier]

The goal is to determine the extent to which heterogeneous inland wetland vegetation communities and their dominant species, as well as adjacent upland vegetation types, can be mapped using 4-m hyperspectral Compact Airborne Spectrographic Imager (CASI) data. Two classification algorithms, the maximum-likelihood classifier (MLC) and the spectral angle mapper (SAM), are applied to CASI data acquired over an inland wetland complex located in southern Ontario, Canada. Application of the MLC algorithm to all bands of the CASI data produced better classification results than use of the SAM. Using the MLC, 10 classes were identified with an overall accuracy of 92%. This approach permitted differentiation between areas of shrub-dominated vegetation communities, floating aquatic communities, emergent aquatics and shallow open water. In the SAM classification, 11 image-derived spectral endmembers were generated. Wetland classes identified were shrub-dominated wetlands, floating aquatic vegetation communities, shallow open water and moderately turbid shallow open water. Upland vegetation types were accurately mapped with both algorithms. Reasons why the SAM did not perform as well as the MLC in this complex environment are suggested. It is concluded that high-resolution hyperspectral data can provide information needed by wetland managers about inland wetland plant communities and their dominant species. [ABSTRACT FROM AUTHOR]

There is a critical need for spatially and temporally extensive information on the trophic status of lakes to assist in scientifically sound forest management decisions. To meet this need, this study examined the utility of Landsat TM imagery in deriving indicators of trophic status in remote and relatively undisturbed lakes on the Boreal Plain of northern Alberta. Based on data collected during a survey of lakes in 2001, normalized exoatmospheric reflectance values of the red band explained 68, 82, and 47% of the variance in chlorophyll a, turbidity, and Secchi disk depth, respectively. To understand the natural variation in trophic status in the lakes, we applied the linear regression equations to images collected during late summer (i.e., August) for 18 out of 20 years from 1984 to 2003 and performed a two-way analysis of variance to decompose the total variation into space, time, and space×time interaction factors. We found that temporal factors accounted for 10% and spatial factors accounted for 50% of the total variation in trophic status, with a minimum of 10 years and 20 lakes needed to reach stability in the contributions of these factors. This study suggests that regional factors that are external to the lake explained the majority (60%) of the variation in trophic status of the lakes. [Copyright &y& Elsevier]

Spatial variability of recent lacustrine sedimentary structures and sedimentation rates are examined for Green Lake, a morphologically complex lake basin of the southern Coast Mountains, British Columbia. A dense, 100 m grid sampling scheme was used for sediment coring within the 2 km² lake basin. Deltaic, massive, weakly laminated, and varved sediment sequences are identified within the sediment record. Spatial patterns among these sedimentary deposits are related to within-lake sediment transfer processes, morphometric controls, and the extent of post-depositional mixing by bioturbation. Unconformities, turbidites, and cohesive slump failure deposits, observed within the contemporary varve sequences, could all be correlated with major flooding events in the catchment area and direct anthropogenic disturbances along the shoreline. There is an overall, non-linear decrease in sedimentation rates with increasing distance from the lake inflows; however, this pattern is disrupted in deep water sites of intervening lake sub-basins where locally higher accumulation rates are observed. Spatial sedimentation patterns are quantitatively described by an empirically-derived model. Systematic variations in the model parameters are observed for different lake sub-regions and are associated with changing sediment transfer dynamics between proximal and distal sub-basin settings. [ABSTRACT FROM AUTHOR]

After the ozone system was implemented at the A. H. Weeks Water Treatment Plant in June 2001, the plant was monitored to evaluate the effects that ozone had on the plant operation and filtered water quality. Filter performance showed an improvement since ozone was applied. Longer filter run time and lower filtered water turbidity and particle count were achieved. Average treated water turbidity was 0.07 NTU for the year before ozone was applied and 0.05 NTU for the year after ozone was applied. An optimization process was conducted to improve the operation. The benefits of the ozone system optimization resulted in more consistency in meeting performance objectives. Ozone generator power requirement was decreased while ozone generator efficiency was increased. Overdosing of ozone quenching agent was less frequent. Reduction in total operational cost was also observed for the year ozone was applied. [ABSTRACT FROM AUTHOR]

The parautochthonous Cloridorme Formation is a syn-orogenic flysch succession that was deposited in an elongate foredeep basin as mainly lower middle-fan, outer-fan, and basin-floor deposits. The basin-floor deposits (about 1.5 km thick) and confined to members β1, β2, and γ;1, and are characterized by graded, thick (1-10 m) mud-rich calcareous greywacke beds previously interpreted as deposits of concentrated, muddy, unidirectional turbidity currents that locally generated backset (antidune) lamination in internally stratified flows. The dominant flow direction were from east to west, but west to est transport also occurred, as seen in the orientation of ripples, climbing ripples, flutes, consistently overturned flames, and grain imbrication. We believe that the flows the deposited these thick calcareous greywacke beds reversed by roughly 1800° One or more times during deposition of the lower sandy part of the beds. Flow reversals are consistent with the sharp grain-size breaks and mud partings within sandy divisions. Measurement of grain fabric relative to stratification in the most celebrated `antidune' bedforms indicates flow from west to east: thus, the bedforms were produced by west-to-east migration of megaripples, not by the upcurrent migration of antidunes. The thick muddy beds were deposited by large-volume, muddy flows that were deflected and reflected from the side slopes and internal topographic highs of a confined basin floor, much like the `Contessa' and similar beds of the Italian Apennines. Large quantities of suspended mud were ponded above the irregular basin floor and settled to produce the thick silty mudstone caps seen on each bed. Because of their mode of emplacement, we propose that these beds be called contained turbidites. [ABSTRACT FROM AUTHOR]

The deposition of suspended sediment is an important process that helps wetlands accrete surface material and maintain elevation in the face of sea level rise. Optical remote sensing is often employed to map total suspended solids (TSS), though algorithms typically have limited transferability in space and time due to variability in water constituent compositions, mixtures, and inherent optical properties. This study used in situ spectral reflectances and their first derivatives to compare empirical algorithms for estimating TSS using hyperspectral and multispectral data. These algorithms were applied to imagery collected by NASA's Airborne Visible/Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) over coastal Louisiana, USA, and validated with a multiyear in situ dataset. The best performing models were then applied to independent spectroscopic data collected in the Peace–Athabasca Delta, Canada, and the San Francisco Bay–Delta Estuary, USA, to assess their robustness and transferability. A derivative-based partial least squares regression (PLSR) model applied to simulated AVIRIS-NG data showed the most accurate TSS retrievals (R2 = 0.83) in these contrasting deltaic environments. These results highlight the potential for a more broadly applicable generalized algorithm employing imaging spectroscopy for estimating suspended solids. [ABSTRACT FROM AUTHOR]

Increased agricultural land use leads to accelerated erosion and deposition of fine sediment in surface water. Monitoring of suspended sediment yields has proven challenging due to the spatial and temporal variability of sediment loading. Reliable sediment yield calculations depend on accurate monitoring of these highly episodic sediment loading events. This study aims to quantify precipitation-induced loading of suspended sediments on Prince Edward Island, Canada. Turbidity is considered to be a reasonably accurate proxy for suspended sediment data. In this study, turbidity was used to monitor suspended sediment concentration (SSC) and was measured for 2 years (December 2012–2014) in three subwatersheds with varying degrees of agricultural land use ranging from 10 to 69 %. Comparison of three turbidity meter calibration methods, two using suspended streambed sediment and one using automated sampling during rainfall events, revealed that the use of SSC samples constructed from streambed sediment was not an accurate replacement for water column sampling during rainfall events for calibration. Different particle size distributions in the three rivers produced significant impacts on the calibration methods demonstrating the need for river-specific calibration. Rainfall-induced sediment loading was significantly greater in the most agriculturally impacted site only when the load per rainfall event was corrected for runoff volume (total flow minus baseflow), flow increase intensity (the slope between the start of a runoff event and the peak of the hydrograph), and season. Monitoring turbidity, in combination with sediment modeling, may offer the best option for management purposes. [ABSTRACT FROM AUTHOR]

Surface water quality is particularly sensitive to land use practices and climatic events that affect its catchment. The relative influence of a set of watershed characteristics (climate, land use, morphology and pedology) and climatic variables on two key water quality parameters (turbidity and fecal coliforms (FC)) was examined in 24 eastern Canadian catchments at various spatial scales (1 km, 5 km, 10 km and the entire catchment). A regression analysis revealed that the entire catchment was a better predictor of water quality. Based on this information, linear mixed effect models for predicting turbidity and FC levels were developed. A set of land use and climate scenarios was considered and applied within the water quality models. Four land use scenarios (no change, same rate of variation, optimistic and pessimistic) and three climate change scenarios (B1, A1B and A2) were tested and variations for the near future (2025) were assessed and compared to the reference period (2000). Climate change impacts on water quality remained low annually for this time horizon (turbidity: +1.5%, FC: +1.6%, A2 scenario). On the other hand, the influence of land use changes appeared to predominate. Significant benefits for both parameters could be expected following the optimistic scenario (turbidity: -16.4%, FC: -6.3%; p < 0.05). However, pessimistic land use scenario led to significant increases on an annual basis (turbidity: +11.6%, FC: +15.2%; p < 0.05). Additional simulations conducted for the late 21st century (2090) revealed that climate change impacts could become equivalent to those modeled for land use for this horizon., (Copyright © 2014 Elsevier B.V. All rights reserved.)