Seafloor and sediment characteristics of pulp mill waste discharges in the 20th century: Framework data for Boat Harbour, Nova Scotia, remediation projects and for baseline surveys of new pulp waste outfall installations in Northumberland Strait

During the 20th century, contamination of marine environments by Canadian pulp and paper mill effluent (PPE) resulted in the imposition of federal government regulations in 1971 that were revised and strengthened in 1992. This report reviews seafloor sediment features for three marine settings (intertidal, subtidal and prodelta) arising from 20th century PPE discharges from four pulp and paper mills, one located near New Richmond, Quebec, and three situated along the lower reaches of the Saguenay River, Quebec. The four mills began operations between 1965 and the early 1900’s. Observations of their proximal and distal sediment and Foraminifera characteristics in relation to PPE discharge outfalls offer guidance for the remediation of potentially toxic, multi-decadal waste accumulations in several lagoons of Boat Harbour, Nova Scotia. Seafloor environmental data discussed for a fifth mill’s subtidal outfall, located on the eastern shore of Canso Strait, may be particularly germane for selecting the site and baseline environmental survey criteria for a new PPE submarine outfall that has been proposed (presently rejected) by Northern Pulp Company for the Caribou Harbour area of the Northumberland Strait coast, in the event that the currently closed mill is permitted to be reactivated in the future. Keywords: effluent, environmental effects, organic matter, pulp mill waste, sediments

Sill Processes in the Saguenay Fjord

<p>The Saguenay Fjord is a 110 km long and 250 m deep (max depth) multi-silled glacial valley that connects the Saguenay River at its head with the St. Lawrence Estuary at its mouth. The bathymetry is characterized with 3 sills: a shallow 20-m deep sill at the mouth, an intermediate 60-m deep 20 km landward sill and a deep 120-m sill 35 km landward. These sills separate 3 basins, the outer, the intermediate and the inner basins. The circulation in the fjord is forced by the Saguenay River at its head that brings freshwater, large tides (up to 6 m range) at its mouth that brings salt water and by wind. The large-scale circulation has been characterized by three seasonally dependent regimes during which the deep, intermediate and subsurface waters of the inner basin are being renewed, respectively, during early winter, summer and late winter. There are indirect indications that those regimes are determined by turbulent processes occurring locally at each of these three sills. Here, we carried out a field experiment to more directly investigate the detailed dynamics of tidally-driven sill processes and water mass modifications occurring across these three sills. Our measurements provide to date the most accurate and complete description of the stratified tidal flow structures around these sills. We also found that an internal hydraulic jump seems to form every ebb tide on the seaward side of the intermediate sill but not during flood tide on the landward side. Research is ongoing to better understand this asymmetry but our hypothesis is that it is the presence of a salty pool landward of the sill that prevents the formation of a hydraulic jump, a process that may be similar to that documented in Knight Inlet (British Columbia, Canada).</p>

Photomineralization and photomethanification of dissolved organic matter in Saguenay River surface water

Rates and apparent quantum yields of photomineralization (AQYDOC) and photomethanification (AQYCH4) of chromophoric dissolved organic matter (CDOM) in Saguenay River surface water were determined at three widely differing dissolved oxygen concentrations ([O2]) (suboxic, air saturation, and oxygenated) using simulated-solar radiation. Photomineralization increased linearly with CDOM absorbance photobleaching for all three O2 treatments. Whereas the rate of photochemical dissolved organic carbon (DOC) loss increased with increasing [O2], the ratio of fractional DOC loss to fractional absorbance loss showed an inverse trend. CDOM photodegradation led to a higher degree of mineralization under suboxic conditions than under oxic conditions. AQYDOC determined under oxygenated, suboxic, and air-saturated conditions increased, decreased, and remained largely constant with photobleaching, respectively; AQYDOC obtained under air saturation with short-term irradiations could thus be applied to longer exposures. AQYDOC decreased successively from ultraviolet B (UVB) to ultraviolet A (UVA) to visible (VIS), which, alongside the solar irradiance spectrum, points to VIS and UVA being the primary drivers for photomineralization in the water column. The photomineralization rate in the Saguenay River was estimated to be 2.31 × 108 mol C yr−1, accounting for only 1 % of the annual DOC input into this system. Photoproduction of CH4 occurred under both suboxic and oxic conditions and increased with decreasing [O2], with the rate under suboxic conditions ~ 7–8 times that under oxic conditions. Photoproduction of CH4 under oxic conditions increased linearly with photomineralization and photobleaching. Under air saturation, 0.00057 % of the photochemical DOC loss was diverted to CH4, giving a photochemical CH4 production rate of 4.36 × 10−6 mol m−2 yr−1 in the Saguenay River and, by extrapolation, of (1.9–8.1) × 108 mol yr−1 in the global ocean. AQYCH4 changed little with photobleaching under air saturation but increased exponentially under suboxic conditions. Spectrally, AQYCH4 decreased sequentially from UVB to UVA to VIS, with UVB being more efficient under suboxic conditions than under oxic conditions. On a depth-integrated basis, VIS prevailed over UVB in controlling CH4 photoproduction under air saturation while the opposite held true under O2-deficiency. An addition of micromolar levels of dissolved dimethyl sulfide (DMS) substantially increased CH4 photoproduction, particularly under O2-deficiency; DMS at nanomolar ambient concentrations in surface oceans is, however, unlikely a significant CH4 precursor. Results from this study suggest that CDOM-based CH4 photoproduction only marginally contributes to the CH4 supersaturation in modern surface oceans and to both the modern and Archean atmospheric CH4 budgets, but that the photochemical term can be comparable to microbial CH4 oxidation in modern oxic oceans. Our results also suggest that anoxic microniches in particulate organic matter and phytoplankton cells containing elevated concentrations of precursors of the methyl radical such as DMS may provide potential hotspots for CH4 photoproduction.

Photomineralization and photomethanification of dissolved organic matter in Saguenay River surface water

Rates and apparent quantum yields of photomineralization (AQYDOC) and photomethanification (AQYCH4) of chromophoric dissolved organic matter (CDOM) in Saguenay River surface water were determined at three widely differing dissolved oxygen concentrations ([O2]) (suboxic, air-saturation, and oxygenated) using simulated-solar radiation. Photomineralization increased linearly with CDOM absorbance photobleaching for all three O2 treatments. Whereas the rate of photochemical dissolved organic carbon (DOC) loss increased with increasing [O2], the ratio of fractional DOC loss to fractional absorbance loss showed an inverse trend. CDOM photodegradation led to a nearly complete mineralization under suboxic conditions but to only a partial mineralization under oxic conditions. AQYDOC determined under oxygenated, suboxic, and air-saturated conditions increased, decreased, and remained largely constant with photobleaching, respectively; AQYDOC obtained under air-saturation with short-term irradiations could thus be applied to longer exposures. AQYDOC decreased successively from ultraviolet B (UVB) to ultraviolet A (UVA) to visible (VIS), which, alongside the solar irradiance spectrum, points to VIS and UVA being the primary drivers for photomineralization in the water column. The photomineralization rate in the Saguenay River was estimated to be 2.31 × 108 mol C yr−1, accounting for only 1 % of the annual DOC input into this system. Photoproduction of CH4 occurred under both suboxic and oxic conditions and increased with decreasing [O2], with the rate under suboxic conditions ~ 7–8 times that under oxic conditions. Photoproduction of CH4 under oxic conditions increased linearly with photomineralization and photobleaching. Under air-saturation, 0.00057 % of the photochemical DOC loss was diverted to CH4, giving a photochemical CH4 production rate of 4.36 × 10−6 mol m−2 yr−1 in the Saguenay River and, by extrapolation, of (1.9–8.1) × 108 mol yr−1 in the global ocean. AQYCH4 changed little with photobleaching under air-saturation but increased exponentially under suboxic conditions. Spectrally, AQYCH4 decreased sequentially from UVB to UVA to VIS, with UVB being more efficient under suboxic conditions than under oxic conditions. On a depth-integrated basis, VIS prevailed over UVB in controlling CH4 photoproduction under air-saturation while the opposite held true under O2-deficiency. An addition of micromolar levels of dissolved dimethyl sulfide (DMS) substantially increased CH4 photoproduction, particularly under O2-deficiency; DMS at nanomolar ambient concentrations in surface oceans is, however, unlikely a significant CH4 precursor. Results from this study suggest that CDOM-based CH4 photoproduction only marginally contributes to the CH4 supersaturation in modern surface oceans and to both the modern and Archean atmospheric CH4 budgets, but that the photochemical term can be comparable to microbial CH4 oxidation in modern oxic oceans. Our results also suggest that anoxic microniches in particulate organic matter and phytoplankton cells containing elevated concentrations of precursors of the methyl radical such as DMS may provide potential hotspots for CH4 photoproduction.

Assessing terrestrial lichen biomass using ecoforest maps: a suitable approach to plan conservation areas for forest-dwelling caribou

Terrestrial lichens are an important part of the winter diet of forest-dwelling caribou ( Rangifer tarandus caribou (Gmelin, 1788)), and developing forest management guidelines to support high lichen biomass could enhance both individual- and population-level health of this threatened species. Our objective was to develop an index to assess terrestrial lichen biomass available to caribou at the landscape scale using ecoforest maps based on forest characteristics (age, density, and height) and geographical variables (slope, altitude, and latitude). We sampled 439 sites within 8340 km2 of the spruce–moss domain located >100 km north of the Saguenay River (Quebec, Canada). Since they are known to support terrestrial lichen, we sampled only spruce-dominated stands older than 50 years, representing 41.8% of the study area. Using a two-step approach, we first modeled lichen occurrence and thereafter lichen biomass in sites where lichens were found. Lichen occurrence was positively correlated with latitude but negatively with stand age, height, and density. Lichen biomass was primarily a function of altitude and tree density. Using this index could prioritize conservation of areas that are most likely to contain high lichen biomass, thus favoring caribou population maintenance in logged landscapes.

Marine feeding patterns of anadromous brook trout (Salvelinus fontinalis) inhabiting an estuarine river fjord

This study describes the ontogenetic and seasonal feeding patterns of anadromous brook trout (Salvelinus fontinalis, also known as sea trout) inhabiting the estuarine Saguenay River (Quebec, Canada) using both stomach content and stable isotope analyses. Sea trout of the Ste. Marguerite River (Quebec, Canada) entered the saline waters of the Ste. Marguerite Bay in early May before venturing into the Saguenay River fjord for the remainder of the summer period. Upon their arrival, first-year migrants stayed relatively close to river mouths and initially fed on freshwater aquatic invertebrates. However, they quickly shifted their diet to marine prey items such as amphipods and mysids for the rest of their first summer at sea. These prey items were generally larger than freshwater prey; the prey spectrum at sea was both larger and wider than that found in freshwater and, as such, likely contributed to the trout's rapid growth rates at sea. The diet of migrants in subsequent years at sea (second-year migrants) consisted primarily of marine crustaceans and fish, the latter being most important when feeding in the upper Saguenay River. Trout shifted to piscivory at all marine sites at a size of 25 cm, regardless of time spent at sea, although the importance of piscivory varied with season and site.

Novel Surface Feeding Tactics of Minke Whales, Balaenoptera acutorostrata, in the Saguenay-St. Lawrence National Marine Park

Surface feeding behaviours of Minke Whales (Balaenoptera acutorostrata) in the mouth and fjord of the Saguenay River, Québec, were documented between June and October 2003. Several novel behaviours associated with gathering prey into dense, nearsurface aggregations prior to a feeding strike were observed. To our knowledge, these behaviours have not been described in detail and may be exclusive to this area or to these individuals. A small number of known Minke Whales show strong site fidelity to the Saguenay region, providing an ideal opportunity for the study of foraging behaviour at the individual level.