Ice-free Period Research Articles

Traditional Ecological Knowledge of Polar Bears in the Northern Eeyou Marine Region, Québec, Canada + Supplementary Appendix 1 (See Article Tools)

Polar bears are important socio-cultural symbols in the communities of the Eeyou Marine Region (EMR) in northwestern Québec, Canada. Members of the Cree communities in this region are generally not active polar bear hunters, but they encounter polar bears when fishing, trapping, or hunting during the ice-free season. A growing body of scientific evidence suggests that reduced annual sea ice cover in Hudson Bay has led to declines in body condition of polar bears in the local Southern Hudson Bay subpopulation and to a population decline in the neighboring Western Hudson Bay subpopulation. In June 2012, we conducted 15 semi-directed interviews on the subject of polar bear biology and climate change with local elders and hunters in three communities in the northern EMR: Wemindji, Chisasibi, and Whapmagoostui. The interviews held in Whapmagoostui included informants from Kuujjuarapik, the adjacent Inuit community. The interviews addressed knowledge gaps in the Recovery Strategy for Polar Bear in Ontario. Transcripts of the interviews were coded thematically and analyzed using both qualitative and quantitative methods. The interviews revealed important insights into polar bear distribution, terrestrial habitat use, denning, and foraging patterns. Participants were unanimous in their recognition of a warming climate and prolonged ice-free season in the area in recent years. However, communities differed in their observations on other issues, with latitudinal trends evident in observations of polar bear distribution, denning activity, and foraging habits. Communities also differed in their perception of the prevalence of problem polar bears and the conservation status of the species, with one-third of participants reporting that polar bears will be unaffected by, or even benefit from, longer ice-free periods. A majority of participants indicated that the local polar bear population was stable or increasing. Interviewees also identified future research priorities pertinent to the communities, and provided comments on the methods employed by polar bear biologists. Our results demonstrate that communities in the EMR have important knowledge about polar bear ecology and illustrate the unique opportunities and challenges of combining traditional ecological knowledge with wildlife science in the context of a rapidly changing subarctic environment.

Long-term patterns of benthic irradiance and kelp production in the central Beaufort sea reveal implications of warming for Arctic inner shelves

This study synthesizes a multidecadal dataset of annual growth of the Arctic endemic kelp Laminaria solidungula and corresponding measurements of in situ benthic irradiance from Stefansson Sound in the central Beaufort Sea. We incorporate long-term data on sea ice concentration (National Sea Ice Data Center) and wind (National Weather Service) to assess how ice extent and summer wind dynamics affect the benthic light environment and annual kelp production. We find evidence of significant changes in sea ice extent in Stefansson Sound, with an extension of the ice-free season by approximately 17 days since 1979. Although kelp elongation at 5–7 m depths varies significantly among sites and years (3.8–49.8 cm yr−1), there is no evidence for increased production with either earlier ice break-up or a longer summer ice-free period. This is explained by very low light transmittance to the benthos during the summer season (mean daily percent surface irradiance ± SD: 1.7 ± 3.6 to 4.5 ± 6.6, depending on depth, with light attenuation values ranging from 0.5 to 0.8 m−1), resulting in minimal potential for kelp production on most days. Additionally, on month-long timescales (35 days) in the ice-free summer, benthic light levels are negatively related to wind speed. The frequent, wind-driven resuspension of sediments following ice break-up significantly reduce light to the seabed, effectively nullifying the benefits of an increased ice-free season on annual kelp growth. Instead, benthic light and primary production may depend substantially on the 1–3 week period surrounding ice break-up when intermediate sea ice concentrations reduce wind-driven sediment resuspension. These results suggest that both benthic and water column primary production along the inner shelf of Arctic marginal seas may decrease, not increase, with reductions in sea ice extent.

Physical and Biological Drivers of Biogeochemical Tracers Within the Seasonal Sea Ice Zone of the Southern Ocean From Profiling Floats

AbstractHere we present initial findings from nine profiling floats equipped with pH, O2, , and other biogeochemical sensors that were deployed in the seasonal ice zone (SIZ) of the Southern Ocean in 2014 and 2015 through the Southern Ocean Carbon and Climate Observations and Modelling (SOCCOM) project. A large springtime phytoplankton bloom was observed that coincided with sea ice melt for all nine floats. We argue this bloom results from a shoaling of the mixed layer depth, increased vertical stability, and enhanced nutrient and light availability as the sea ice melts. This interpretation is supported by the absence of a springtime bloom when one of the floats left the SIZ in the second year of observations. During the sea ice covered period, net heterotrophic conditions were observed. The rate of uptake of O2 and release of dissolved inorganic carbon (derived from pH and estimated total alkalinity) and is reminiscent of biological respiration and is nearly Redfieldian for the nine floats. A simple model of mixed layer physics was developed to separate the physical and biological components of the signal in pH and O2 over one annual cycle for a float in the Ross Sea SIZ. The resulting annual net community production suggests that seasonal respiration during the ice covered period of the year nearly balances the production in the euphotic layer of up to 5 mol C m−2 during the ice free period leading to a net of near zero carbon exported to depth for this one float.

Heterogeneous changes in the surface area of lakes in the Kangerlussuaq area of southwestern Greenland between 1995 and 2017

ABSTRACT Global climate change has increased temperatures and precipitation in the Arctic throughout the past thirty years. Lakes across the Arctic have demonstrated spatially and temporally variable trends in size and number because of these climate changes. Modifications in the hydrological budget and surface hydrology of Arctic regions have important implications for aquatic ecosystems and biogeochemical cycles. Since 1960 the ice-free region of southwestern Greenland (between Sisimiut, Kangerlussuaq, and the ice margin) has experienced temperature increases, while precipitation has risen at the coast at Sisimiut and has fallen inland at Kangerlussuaq. However, it remains unknown whether the lakes in this region have responded to these temperature and precipitation changes. Therefore, the surface area of 186 lakes was calculated from Landsat imagery for 1995, 2002, 2015, 2016, and 2017 to establish whether lakes in this region have changed in size during a twenty-two-year period. Lake surface area decreased by 855,449 m2 between 1995 and 2017. The greatest lake surface area changes occurred between 2002 and 2015, with large variations also between 2015 and 2016. Lakes close to Kangerlussuaq (area 1) demonstrated the greatest loss in lake surface area (−1.40 km2). It is proposed that this trend reflects high evaporation totals as a result of increasing temperatures and longer ice-free periods in this area. Lakes close to Sisimiut at the coast (area 2) exhibit a net increase in lake surface area, which could reflect the increase in precipitation experienced in this area during the study period. However, not all lakes in the study areas responded in a uniform manner. These heterogeneous changes in lake surface area may reflect how changes in regional climate are interacting with catchment geomorphology, and highlight the importance of individual catchment and lake characteristics in determining lake response to climatic change in this region.

Water quality assessment of sacred glacial Lake Satopanth of Garhwal Himalaya, India

Satopanth Lake is a glacial lake, located at an altitude of 4600 m above sea level in Garhwal Himalaya of Uttarakhand state in India where an attempt was made to assess the water quality. A total of sixteen physico-chemical parameters including temperature, hardness, alkalinity, dissolved oxygen, conductivity, pH, calcium, magnesium, chlorides, nitrates, sulphates and phosphates were recorded during 2014 and 2015 between June and August in ice-free period. The mean values of pH ranged from 6.85 to 7.10; water temperature fluctuated from 0.1 to 0.3 °C; dissolved oxygen varied from 5.90 to 6.0 mg.L−1; free CO2 varied from 8.40 to 8.60 mg.L−1; total dissolved solids varied from 88.0 to 89.5 mg.L−1; calcium from 7.88 to 7.95 mg.L−1; magnesium from 0.53 to 0.66 mg.L−1. All the physico-chemical values were within the prescribed WHO/BIS limit for drinking water. Water Quality Index (WQI) calculated based on these parameters also revealed the excellent quality of lake water.

Polar Bear Foraging Behavior During the Ice-Free Period in Western Hudson Bay: Observations, Origins, and Potential Significance

During much of the year, polar bears in western Hudson Bay use energy-conserving hunting tactics, such as still-hunting and stalking, to capture seals from sea-ice platforms. Such hunting allows these bears to accumulate a majority of the annual fat reserves that sustain them on land through the ice-free season. As climate change has led to earlier spring sea-ice breakup in western Hudson Bay, polar bears have less time to hunt seals, especially seal pups in their spring birthing lairs. Concerns have been raised as to whether this will lead to a shortfall in the bears' annual energy budget. Research based on scat analyses indicates that over the past 40 years at least some of these polar bears eat a variety of food during the ice-free season and are opportunistically taking advantage of a changing and increasing terrestrial prey base. Whether this food will offset anticipated shortfalls and whether land-based foraging will spread throughout the population is not yet known, and full resolution of the issues requires detailed physiological and genetic research. For insight on these issues, we present detailed observations on polar bears hunting without an ice platform. We compare the hunting tactics to those of polar bears using an ice platform and to those of the closely related grizzly bear. We examine how the techniques are related and explore how they may have evolved. We also discuss how they may contribute to polar bear adaptability in the face of climate change projections.

Long term follow-up of pCO2, pCH4 and emissions from Eastmain 1 boreal reservoir, and the Rupert diversion bays, Canada

Eastmain 1 reservoir (James Bay area, Quebec, Canada) is a 600km2 boreal reservoir, created in November 2005 in the Eastmain River watershed. To increase the volume of water transiting in Eastmain 1 (EM 1), the Rupert River was diverted. Partial flooding of the Rupert diversion bays (RD) took place in 2009 and the flooding was completed in 2011. CO2 and CH4 partial pressures and emissions were monitored for 7 years on the reservoir and bays.According to field campaigns measurements at Eastmain-1 reservoir, average ice-free period pCO2 varied between 969μatm and 2230μatm, whereas the average pCO2 of the reference sampled lakes and Eastmain River stations was 592μatm (±101) before the impoundment. Contrary to pCO2, pCH4 partial pressures presented any pattern to outline after flooding of the Eastmain 1 reservoir and varied between 21 and 250μatm, with an overall average of 106μatm (SD±91). CO2 diffusive emissions at the air–water interface of the Eastmain-1 reservoir ranged between −113mg C-CO2m−2day−1 and 8237mg C-CO2m−2day−1. CH4 fluxes ranged from null to 102mg C-CH4m−2day−1. This article also shows that the impoundment of the Rupert River and the related transport of sediment and organic matter into Eastmain 1 Reservoir did not have a significant long term effect on pCO2.Remarkably, the different approaches/methods used to monitor these variables showed comparable results: a net decrease in CO2 emissions in the first three years followed by stabilization around seven years after the reservoir creation. Therefore, we advocate for long-term, around 10 years, GHG monitoring. The use of various methods, beforehand intercalibrated, offers a non-negligible flexibility, reducing the sampling costs, which should favor an increase in this kind of studies worldwide.

Delta progradation in Greenland driven by increasing glacial mass loss.

Climate changes are pronounced in Arctic regions and increase the vulnerability of the Arctic coastal zone. For example, increases in melting of the Greenland Ice Sheet and reductions in sea ice and permafrost distribution are likely to alter coastal morphodynamics. The deltas of Greenland are largely unaffected by human activity, but increased freshwater runoff and sediment fluxes may increase the size of the deltas, whereas increased wave activity in ice-free periods could reduce their size, with the net impact being unclear until now. Here we show that southwestern Greenland deltas were largely stable from the 1940s to 1980s, but prograded (that is, sediment deposition extended the delta into the sea) in a warming Arctic from the 1980s to 2010s. Our results are based on the areal changes of 121 deltas since the 1940s, assessed using newly discovered aerial photographs and remotely sensed imagery. We find that delta progradation was driven by high freshwater runoff from the Greenland Ice Sheet coinciding with periods of open water. Progradation was controlled by the local initial environmental conditions (that is, accumulated air temperatures above 0 °C per year, freshwater runoff and sea ice in the 1980s) rather than by local changes in these conditions from the 1980s to 2010s at each delta. This is in contrast to a dominantly eroding trend of Arctic sedimentary coasts along the coastal plains of Alaska, Siberia and western Canada, and to the spatially variable patterns of erosion and accretion along the large deltas of the main rivers in the Arctic. Our results improve the understanding of Arctic coastal evolution in a changing climate, and reveal the impacts on coastal areas of increasing ice mass loss and the associated freshwater runoff and lengthening of open-water periods.

Effect of roughness lengths on surface energy and the planetary boundary layer height over high-altitude Ngoring Lake

The special climate environment creates a distinctive air-lake interaction characteristic in the Tibetan Plateau (TP) lakes, where the variations of surface roughness lengths also differ somewhat from those of other regions. However, how different categories of roughness lengths affect the lake surface energy exchange and the planetary boundary layer height (PBLH) remains unclear in the TP lakes. In this study, we used a tuned Weather Research and Forecasting (WRF) model version 3.6.1 to investigate the responses of the freeze-up date, turbulent fluxes, meteorological variables, and PBLH to surface roughness length variations in Ngoring Lake. Of all meteorological variables, the lake surface temperature responded to roughness length variations most sensitively; increasing roughness lengths can put the lake freeze-up date forward. The effect of momentum roughness length on wind speed was significantly affected by the fetch length. The increase in the roughness length for heat can induce the increment of the nightly PBLH in most months, especially for the central lake area in autumn. The primary factors that contribute to sensible heat flux (H) and latent heat flux (LE) were the roughness lengths for heat and momentum during the ice-free period, respectively. Increasing roughness length for heat can increase the nightly PBLH, and decreasing roughness length for moisture can also promote growth of the PBLH, but there was no obvious correlation between the momentum roughness length and the PBLH.

Assessing landscape and contaminant point-sources as spatial determinants of water quality in the Vermilion River System, Ontario, Canada.

The Vermilion River and major tributaries (VRMT) are located in the Vermilion watershed (4272km2) in north-central Ontario, Canada. This watershed not only is dominated by natural land-cover but also has a legacy of mining and other development activities. The VRMT receive various point (e.g., sewage effluent) and non-point (e.g., mining activity runoff) inputs, in addition to flow regulation features. Further development in the Vermilion watershed has been proposed, raising concerns about cumulative impacts to ecosystem health in the VRMT. Due to the lack of historical assessments on riverine-health in the VRMT, a comprehensive suite of water quality parameters was collected monthly at 28 sites during the ice-free period of 2013 and 2014. Canadian water quality guidelines and objectives were not met by an assortment of water quality parameters, including nutrients and metals. This demonstrates that the VRMT is an impacted system with several pollution hotspots, particularly downstream of wastewater treatment facilities. Water quality throughout the river system appeared to be influenced by three distinct land-cover categories: forest, barren, and agriculture. Three spatial pathway models (geographical, topographical, and river network) were employed to assess the complex interactions between spatial pathways, stressors, and water quality condition. Topographical landscape analyses were performed at five different scales, where the strongest relationships between water quality and land-use occurred at the catchment scale. Sites on the main stem of Junction Creek, a tributary impacted by industrial and urban development, had above average concentrations for the majority of water quality parameters measured, including metals and nitrogen. The river network pathway (i.e., asymmetric eigenvector map (AEM)) and topographical feature (i.e., catchment land-use) models explained most of the variation in water quality (62.2%), indicating that they may be useful tools in assessing the spatial determinants of water quality decline.

Environmental feedbacks in temperate aquatic ecosystems under global change: why do we need to consider chemical stressors?

Globally increasing temperature and modifications in precipitation patterns induce major environmental alterations in aquatic ecosystems. Particularly profound changes are predicted for arctic to temperate shallow lakes where modifications in temperature affect the distribution of ice and ice-free periods, thereby altering the timing of peak productivity, while changes in precipitation strongly alter water table depth with concomitant modifications in light distribution, temperature, and water chemistry, collectively altering the balance between primary production, organic matter consumption, and decomposition. Due to direct effects of temperature on primary productivity and microbial decomposition, raising temperatures alter the capacity of aquatic ecosystems for carbon sequestration and greenhouse gas release, and this affects atmospheric greenhouse gas concentrations and temperature, implying a feedback loop between environmental effects on ecosystems and climate change. Moreover, elevated temperature can modify the bioavailability of pollutants deposited in the past, and increase the probability for their uptake by aquatic organisms. The latter processes in turn reduce primary productivity and alter microbial decomposition, creating thus another key feedback loop between productivity, climate change, and environmental pollutants. However, warming can also enhance eutrophication and deposition of pollutants in organic sediments, further speeding up productivity and eutrophication, with the overall net effects depending on the quantitative significance of different processes. Therefore, the feedbacks arising from pollution stress must be incorporated in models intending to predict the carbon balance of aquatic ecosystems under globally changing environmental conditions. Further work on carbon balance and greenhouse gas release of aquatic ecosystems should focus on quantitative characterization of the feedback loops operative, and on how global change affects these feedback loops.

Gametogenesis of an intertidal population of Mytilus trossulus in NW Greenland: not a limitation for potential Arctic range expansion

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 574:65-74 (2017) - DOI: https://doi.org/10.3354/meps12179 Gametogenesis of an intertidal population of Mytilus trossulus in NW Greenland: not a limitation for potential Arctic range expansion Jakob Thyrring1,2,*, K. Thomas Jensen3, Mikael K. Sejr1 1Arctic Research Centre, Department of Bioscience, Aarhus University, Ny Munkegade 114, Building 1540, 8000 Aarhus C, Denmark 2Marine Ecology, Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark 3Aquatic Biology, Department of Bioscience, Aarhus University, Ole Worms Allé 1, Building 1134, 8000 Aarhus C, Denmark *Corresponding author: thyrring@bios.au.dk ABSTRACT: The drivers determining species’ northern distribution limits remain elusive and, combined with inadequate knowledge of past and current distribution ranges, this prevents accurate determination of potential changes in the Arctic. The northernmost population of the bivalve Mytilus trossulus is found in north Greenland, an area characterized by low temperature, prolonged winters and a short productive period. This population, therefore, provides a unique opportunity to study whether a temperate bivalve species can sustain a population near its pole-ward distribution limit through reproduction. We assessed gametogenesis and biochemical composition in intertidal M. trossulus specimens during the ice-free period (July-September). Results showed that the qualitative traits of gametogenesis and oocyte production in this population were comparable to M. trossulus found in temperate regions. In addition, we found that M. trossulus larvae settle annually in the lowest intertidal zone, indicating successful fertilization of eggs and larval survival. Our combined results suggest that gonadal development or larval survival do not limit the northern distribution of this species, even in a region characterized by limited food supply and sub-zero water temperatures for 9 mo of the year. Instead, for this marine invertebrate with a larval life-stage, oceanographic conditions and dispersal barriers, rather than physiological constraints, could be more important in determining the northern range limit. KEY WORDS: Arctic benthos · Biochemical composition · Blue mussels · Glycogen · Gametogenesis · Spawning · Temperature · Oogenesis Full text in pdf format PreviousNextCite this article as: Thyrring J, Jensen KT, Sejr MK (2017) Gametogenesis of an intertidal population of Mytilus trossulus in NW Greenland: not a limitation for potential Arctic range expansion. Mar Ecol Prog Ser 574:65-74. https://doi.org/10.3354/meps12179 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 574. Online publication date: July 04, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Phytoplankton ecology of a culturally eutrophic embayment: Hamilton Harbour, Lake Ontario

Hamilton Harbour is a chronically eutrophic embayment located at the western end of Lake Ontario that has experienced many decades of agricultural, industrial, and urban contamination. It has been identified as an Area of Concern under the terms of the Great Lakes Water Quality Agreement between Canada and the United States. This study examines the ecology of the phytoplankton communities at one centrally located station during the ice-free period (May–October) of three non-consecutive years: 2002, 2004 and 2006. This was the first comprehensive study to be conducted since the 1970s. It was found that the phytoplankton communities are diverse and fluctuate throughout the year, along with changing nutrient, physical and environmental conditions. No consistent patterns of seasonal succession were observed throughout the study. Phytoflagellates including Cryptophyceae and Dinophyceae had a tendency to outnumber and out-compete other phytoplankton since they are mobile and able to seek out optimal habitats within the water column. For a highly eutrophic water body, algal biomass (annual mean ≈ 2.0 g m−3) was lower than expected and more consistent with mesotrophic conditions–an observation first made by researchers in the 1970s and attributed to the highly variable physical environment. While our study supports these earlier results, we also conclude that zooplankton grazing likely has a significant role in limiting the size of the algal standing crop. Several algal bloom events were captured during our study. In addition to the somewhat predictable blooms of Diatomeae in the spring and Cyanophyta in the summer, we also observed blooms of Cryptophyceae and Dinophyceae. In one case we observed a bloom with no dominant taxon–it contained a diverse mixture of Cryptophyceae, Euglenophyta and Dinophyceae–challenging the commonly held notion that algal blooms are essentially monocultures. Our results show that such a variable and stressed ecosystem requires frequent sampling to capture the rapid changes that occur.

Predicting microalgae growth and phosphorus removal in cold region waste stabilization ponds using a stochastic modelling approach.

A stochastic ecological model with an integrated equilibrium temperature model was developed to predict microalgae growth and phosphorus removal in cold region waste stabilization ponds (WSPs). The model utilized a Monte Carlo simulation to account for parameter uncertainty. The equilibrium temperature model was parameterized using field data collected from two WSPs in Nunavut, Canada, from 2012 to 2014. The equilibrium temperature model provided good agreement with field data on a daily time step. The full model was run using historic (1956-2005) temperature and solar radiation data from five communities (Baker Lake, Cambridge Bay, Coral Harbour, Hall Beach, Resolute) in Nunavut, Canada. The communities represented a range of geographical locations and environmental conditions. Logistic regression on pooled model outputs showed that mean July temperature and mean treatment season temperature (June 1-September 15, ice-free period) provided the best predictors for microalgae growth. They had a predictive success rate of 93 and 88%, respectively. The modelled threshold (50% probability from the Monte Carlo simulation) for microalgae growth was 8.7 and 5.6°C for the July temperature and mean treatment season temperature, respectively. The logistic regression was applied to each community (except Sanikiluaq) in Nunavut using historic climate data and a probability of microalgae growth was calculated. Based on the model results, soluble phosphorus concentrations consistent with secondary treatment could be achieved if WSP depth is less than 2m. The model demonstrated a robust method to predict whether a microalgae bloom will occur under a range of model parameters.

Anthropogenic climate change has altered primary productivity in Lake Superior

Anthropogenic climate change has the potential to alter many facets of Earth’s freshwater resources, especially lacustrine ecosystems. The effects of anthropogenic changes in Lake Superior, which is Earth’s largest freshwater lake by area, are not well documented (spatially or temporally) and predicted future states in response to climate change vary. Here we show that Lake Superior experienced a slow, steady increase in production throughout the Holocene using (paleo)productivity proxies in lacustrine sediments to reconstruct past changes in primary production. Furthermore, data from the last century indicate a rapid increase in primary production, which we attribute to increasing surface water temperatures and longer seasonal stratification related to longer ice-free periods in Lake Superior due to anthropogenic climate warming. These observations demonstrate that anthropogenic effects have become a prominent influence on one of Earth’s largest, most pristine lacustrine ecosystems.

Carbon Bioavailability in a High Arctic Fjord Influenced by Glacial Meltwater, NE Greenland

The land-to-ocean flux of organic carbon is increasing in glacierized regions in response to increasing temperatures in the Arctic (Hood et al., 2015). In order to understand the response in ecosystem metabolism to the organic carbon input it is essential to determine the bioavailability of the different carbon sources in the system. We quantified the bacterial turnover of organic carbon in a high Arctic fjord system (Young Sound, NE Greenland) during the ice-free period (July-October 2014) and assessed the quality and quantity of the 3 major organic carbon sources; 1) local phytoplankton production 2) runoff from land-terminating glaciers and a lowland river and 3) inflow from the ocean shelf. We found that despite relatively low concentrations of DOC in the rivers, the bioavailability of the river–DOC was significantly higher than in the fjord, and characterized by high cell-specific bacterial production and low C:N ratios. In contrast, the allochthonous DOC source entering via inflow of coastal shelf waters had elevated DOC concentrations with low bioavailability, high C:N and low specific bacterial production. The phytoplankton production in the fjord could not sustain the bacterial carbon demand, but was still the major source of organic carbon for bacterial growth. We assessed the bacterial community composition and found that communities were specific for the different water types i.e. the bacterial community of the coastal coastal inflow water could be traced mainly in the subsurface water, while the glacial river community strongly dominated the surface water in the fjord.

Spreading of the Amur River plume in the Amur Liman, Sakhalin Gulf, and the Strait of Tartary

This work focuses on a study of the Amur plume spreading during ice-free periods in the Amur Liman and adjacent areas of Sakhalin Gulf and the Strait of Tartary. It was found from MERIS/EnviSat satellite imagery, MERRA wind reanalysis, and Amur discharge data in 2002–2011 that regular transport of Amur plume waters from the Amur Liman to Sakhalin Gulf occurs in June–October. This process is caused by flood discharge of the Amur River in the absence of strong northern winds or when southern winds are strong during periods of moderate discharge. Estimates for the frequency and duration of this process have shown that it occurs on average during half of the days in June–October and can continue up to 2.5 months. Spreading of the Amur plume to the Strait of Tartary is a significantly rarer event. This process takes place only during the Amur’s freshet periods and for strong western wind forcing, which induces southward Ekman transport. The average duration of this process during the ice-free season is estimated as 15 days; however, in individual years, it can be as short as several days.

Life history differences and latitudinal variation in recruitment in two species of arctic-boreal perciform fishes, the fish doctor Gymnelus viridis and the Arctic shanny Stichaeus punctatus

Growth and recruitment were examined in two arctic-boreal, shallow water marine perciform species: the fish doctor Gymnelus viridis (Zoarcidae) and the Arctic shanny Stichaeus punctatus (Stichaeidae). G. viridis ranges in the Canadian Arctic from northern Hudson Bay to northern Ellesmere Island, whereas S. punctatus has a more southerly range from Nova Scotia coastal waters to northern Hudson Bay. At Nuvuk Islands in northeastern Hudson Bay, where the two species are sympatric in shallow water, they had comparable juvenile growth rates but temporal variation in 0+ recruitment was substantially greater in S. punctatus. This difference may stem from their contrasting early life histories. S. punctatus spawns large numbers of small demersal eggs that hatch into pelagic larvae, whereas G. viridis spawns small numbers of large demersal eggs that hatch directly into demersal juveniles with no pelagic stage, suggesting that recruitment in G. viridis should be less sensitive to yearly variation in the onset of the ice-free period in Hudson Bay and the subsequent pulse of pelagic invertebrate production. Relative to Nuvuk, recruitment variation in G. viridis was found to be greater at Resolute, Cornwallis Island, close to its northern range limit, whereas recruitment variation in S. punctatus was not evident in Newfoundland, closer to its southern range limit.

Phytoplankton Seasonality along a Trophic Gradient of Temperate Lakes: Convergence in Taxonomic Compostion during Winter Ice-Cover

A gap in our understanding of phytoplankton seasonality in temperate lakes exists mainly due to the lack of information collected during the winter months. We summarized seasonal changes of phytoplankton biomass and taxonomic composition relative to water-column biogeochemical conditions in 6 lakes located on Beaver Island and 1 site in Lake Michigan in close geographic proximity to each other (<20 km apart). A number of physical—chemical parameters (e.g., temperature, DOC) were similar between lakes, but lakes towards the interior of the island had lower pH, alkalinity, and conductivity. Moreover, lakes at the interior of the island supported 2-fold greater phytoplankton-chlorophyll and carbon compared with perimeter lakes, and phytoplankton taxonomic composition differed considerably during the ice-free period (April–December). Interestingly, the winter phytoplankton assemblages were strikingly similar in all 7 lakes, when large populations of phyto-flagellates (Chrysophyceae and Cryptophyceae) occurred under the ice at low light and temperatures < 4 °C. Given the mixotrophic capabilities of these phytoflagellates, we suggest seasonal convergence reflects the community response to under-ice conditions, which promotes the occurrence of an important component of annual phytoplankton biomass.

REDUCING ROAD SALT APPLICATION BY CONSIDERING WINTER MAINTENANCE NEEDS IN PARKING LOT DESIGN

INTRODUCTION Winter snow and ice can have a significant impact on our mobility, whether on foot or by car. Alongside plowing, arguably the greatest tool in combating snow and ice is salt. The most commonly used salt for winter maintenance is Sodium Chloride (NaCl), the same salt used in food and water softeners, is applied to roads, sidewalks, and parking lots as it is an effective deicer when temperatures are between 0°C and −12°C. Studies have shown that deicing with salt reduces accidents by 88% and injuries by 85% (Salt Institute 2017). The effectiveness of road salt, as well as its relative affordability, means that as much as four million tonnes may be applied annually in Canada for deicing (Environment Canada 2012). However, while salt is relatively inexpensive to purchase, there are a number of external costs that are becoming increasingly apparent. These include corrosion of vehicles and infrastructure like concrete, bridges, and water mains; damage and staining to the interior and exterior of bu...