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We combine consistently dated benthic carbon isotopic records distributed over the entire Atlantic Ocean with numerical simulations performed by a glacial configuration of the Norwegian Earth System Model with active ocean biogeochemistry, in order to interpret the observed Cibicides δ13C changes at the stadial-interstadial transition corresponding to the end of Heinrich Stadial 4 (HS4) in terms of ocean circulation and remineralization changes. We show that the marked increase in Cibicides δ13C observed at the end of HS4 between ~2000 and 4200 m in the Atlantic can be explained by changes in nutrient concentrations as simulated by the model in response to the halting of freshwater input in the high latitude glacial North Atlantic. Our model results show that this Cibicides δ13C signal is associated with changes in the ratio of southern-sourced (SSW) versus northern-sourced (NSW) water masses at the core sites, whereby SSW is replaced by NSW as a consequence of the resumption of deep water formation in the northern North Atlantic and Nordic Seas after the freshwater input is halted. Our results further suggest that the contribution of ocean circulation changes to this signal increases from ~40 % at 2000 m to ~80 % at 4000 m. Below ~4200 m, the model shows little ocean circulation change but an increase in remineralization across the transition marking the end of HS4. The simulated lower remineralization during stadials than interstadials is particularly pronounced in deep subantarctic sites, in agreement with the decrease in the export production of carbon to the deep Southern Ocean during stadials found in previous studies.

Knowledge gaps pertaining to the remediation of freshwater lakes impacted by oil spills have persisted despite recent record highs for oil production and transportation across vulnerable regions in North America. The multiyear Freshwater Oil Spill Remediation Study (FOReSt), conducted at the IISD-Experimental Lakes Area in Canada, is focusing on the efficacy of minimally invasive methods for remediating oil spills in freshwater boreal lakes. In this thesis, the impacts and remediation of diluted bitumen (dilbit) and conventional heavy crude oil (CHV) spills were investigated (year 1), as were a variety of different remediation methods for spills of dilbit on different shoreline substrates (year 2). Two common small-bodied fish, fathead minnows (Promephales promelas) and finescale dace (Chrosomus neogaeus), were used to assess exposure to petrogenic polycyclic aromatic compounds (PACs) in model enclosed shoreline ecosystems impacted by spills and remediated using minimally invasive techniques. Short-term exposure to PACs, the most toxicologically relevant compounds in oil, was assessed in fish using biliary metabolite concentrations. In year one, finescale dace and fathead minnows residing in oil treated enclosures each had biliary pyrene metabolite concentrations that were positively correlated with pyrene concentrations in the water of the enclosures. Three months after the initial spills, fish in the enclosure receiving dilbit were significantly more exposed to PACs than fish in reference enclosures that did not receive oil. In year two, both finescale dace and fathead minnows residing in oil-treated exposures, regardless of shoreline substrate, showed increased exposure to PACs compared to fish in reference enclosures and the pristine lake environment two and a half months after the spills. No significant differences in exposure were observed among the remediation treatments. Biliary PAC metabolite concentrations were positively predicted by parent PAC concentrations in periphyton. PACs in periphyton two and a half months after oil introduction were positively correlated with PACs in the enclosures one week after spills, suggesting fish also had increased exposure to periphyton-bound alkyl-PACs. This thesis validates the use of small-bodied fish in assessing PAC exposure following freshwater oil spills and demonstrates the difficulties in estimating exposure using environmental concentrations in natural systems.

The environment during early life history strongly impacts phenotypic development in all organisms, which further influences developmental trajectory and ecological fitness later in life. Depending on the developmental stage and magnitude of change in the environment, phenotypes may become irreversible and thus have a long-lasting effect later in life. This thesis was designed to better understand how changes in the environment may influence plasticity and variation of metabolic phenotypes of Lake Sturgeon (Acipenser fulvescens) within the first year of life. Broadly speaking, the thesis tested two hypotheses that 1) all measured phenotypes would be plastic; and 2) durations of environmental effects on phenotypic development would be correlated with distinct developmental windows. Studies were developed to examine 1) short-term effects of temperature or diet on metabolic phenotypes such as metabolic rate, energy density, fatty acid profiles, and growth (Chapters 2 and 3) and 2) longer-term effects of temperature or diet during early life on these metabolic phenotypes (Chapters 4, 5 and 6). The first experimental chapter (Chapter 2) examined ontogenetic development of metabolic rate and demonstrated that dietary shifts between Artemia to bloodworm resulted in cessation of growth with elevated routine metabolic rate. Chapter 3 examined how fatty acid profiles and plasma cortisol concentration were influenced by environmental temperature and showed that decreasing temperature led to increases in mono- and polyunsaturated fatty acids in both phospholipids and triglycerides, and food deprivation resulted in lack of difference between baseline and peak cortisol concentrations. Chapter 4 examined how temperature during early life influenced plasticity of growth and showed that temperature post-dietary transition resulted in a transient effect on growth and energy metabolism without long-term effects post-winter. Chapter 5 examined how temperature during early life could influence growth and fatty acid metabolism when fish were exposed to colder temperatures later in life and demonstrated that elevated temperatures resulted in a longer-term effect on growth but lack of transcriptional responses of desaturating fatty acids when exposed to a cold temperature (3.5°C) later in life. The final experimental chapter, Chapter 6 examined longer-term effects of diet at the onset of exogenous feeding on metabolism and growth and demonstrated that an enriched diet resulted in prolonged effects on growth, digestive enzyme activity and survival prior to a simulated overwintering. This doctoral thesis research revealed that all measured metabolic phenotypes were plastic, but subtle changes in temperature and diet during early life history resulted in transient or prolonged effects on growth and metabolism in age-0 lake sturgeon. Results will aid our understanding of cohort and population dynamics as well as contribute to the development of conservation strategies for lake sturgeon, a species at risk or endangered across its natural range.

The dataset compiles pigment content, absorptance data, photosynthetic parameters and primary production data as proxies for summertime photoacclimation of the temperate intertidal eelgrass Zostera marina after a 25-day exposure to a natural light intensity gradient (6, 36, 74, 133, 355, 503 and 860 µmol photons/m²/s) under laboratory conditions at the Pointe-au-Père research station, East Rimouski, Quebec, Canada. The data bundle contains: 1) photosynthetic and total absorptance data at the end of the experiment, which respectively represent the fraction of incident visible light absorbed by the photosynthetic tissues corrected and not corrected for non-photosynthetic absorption; 2) pigment content at the end of the experiment, which includes chlorophyll a and b and total carotenoids contents; 3) photosynthetic parameters obtained by Rapid Light Curves (RLC) on days 5 and 25, including photosynthetic apparatus efficiency (alpha), capacity (ETRmax) and saturation (Ek); 4) whole shoot primary production at the end of the experiment, which was calculated from oxygen fluxes under light and dark conditions, and normalized by leaf surface.

This data set contains temperature, salinity, oxygen, fluorescence, turbidity, currents, and lagrangian drift data collected in the bay of Sept-Îles, on the north shore of the Gulf of St. Lawrence, Canada. Five sampling campaigns were conducted from May to September of 2017, to assess seasonal variations in the oceanographic conditions. An additional campaign was conducted in May 2018, focusing on the measurement of currents. These surveys covered the inside of the bay and the nearby archipelago. The bay of Sept-Îles has recently been the subject of a multidisciplinary study by the Canadian Healthy Oceans Network (CHONe II) because it is a heavily industrialized and urban coastal area at Canadian midlatitudes. It is therefore a good site to study the impact of such human presence on adjacent marine ecosystems. The objective of this data set was to enable the development and calibration of hydrodynamic and biogeochemical models of the bay, which was hindered by scarce knowledge of the environmental conditions. Water properties were collected using a Seabird Electronics SBE19plus and a Sontek CastAway CTD probe. Currents were measured using a towed acoustic Doppler current profiler (ADCP) model Teledyne RDI Sentinel V, and passive surface drifters which used Spot GPS probes.

Palynological and sedimentological analyses were performed on the sediment core HH16-1205-GC retrieved from the central Isfjorden, West Spitsbergen in order to retrace the climate of the last 7000 years. The record revealed an overall cooling trend with an important climate shift between 4.4 and 3.8 cal. ka BP, and millennial-scale oscillations. Over the last 7000 years, sea-surface reconstruction from dinocyst assemblages indicates a decrease in summer sea-surface temperature, from 2.5 to 1.5 °C, and primary productivity, from 750 to 650 gC m-² a-1. Predominant sediment supply from the inner part of the fjord, ice rafting, dense sea-ice cover, strongly stratified water masses, and high primary productivity is observed in the sedimentological and palynological data between 6.8 and 5.8 cal. ka BP. The interval from 4.4 to 3.8 cal. ka BP is marked by a layer of coarser material followed by a significant decrease in the grain size mode, as well as changes in geochemical properties. large-amplitude fluctuations is observed in our geochemical data after 2.0 cal. ka BP, while an increase of the dinocysts Impagidinium pallidum and Spiniferites elongatus from 2.0 to 1.2 cal. ka BP suggests enhanced Atlantic Water inflow. The sea surface conditions reconstructions and XRF ratios also reveal large-amplitude millennial fluctuations. Wavelet analysis and cross-wavelet analysis performed on multiple variables confirm a strong cyclic signal with a periodicity of 1200 to 1500 years.

Palaeo-environmental and -climatic data from core CEN-17.4 from the central Congo peatlands, Likouala Department (1°11'0.49"N, 17°38'23.7"E) and data from supporting cores. Bulk organic (TOC, TN, C/N) data and Rock Eval data to assess peat occurrence and degradation status for the central core CEN-17.4 and supporting cores. Radiocarbon dates on fine fractions for all cores. Plant-wax derived n-alkane stable carbon (δ^13^C) and stable hydrogen (δD) isotope data to assess vegetation changes and rainfall changes for the central core CEN-17.4. Selected pollen data for the central core CEN-17.4 to assess palaeo-ecological changes.

Despite the importance of surface energy budgets (SEBs) for land-climate interactions in the Arctic, uncertainties in their prediction persist. In-situ observational data of SEB components - useful for research and model validation - are collected at relatively few sites across the terrestrial Arctic, and not all available datasets are readily interoperable. Furthermore, the terrestrial Arctic consists of a diversity of vegetation types, which are generally not well represented in land surface schemes of current Earth system models. Therefore, we here provide four datasets comprising: 1. Harmonized, standardized and aggregated in situ observations of SEB components at 64 vegetated and glaciated sites north of 60° latitude, in the time period 1994-2021 2. A description of all study sites and associated environmental conditions, including the vegetation types, which correspond to the classification of the Circumpolar Arctic Vegetation Map (CAVM, Raynolds et al. 2019). 3. Data generated in a literature synthesis from 358 study sites on vegetation or glacier (>=60°N latitude) covered by 148 publications. 4. Metadata, including data contributor information and measurement heights of variables associated with Oehri et al. 2022.

The data sets are composed of analyses derived from punctual water samples. Samples were collected in peat porewater and at the surface of pools of a boreal ombrotrophic peatland. The main objective of the project is to characterize the source and composition of dissolved organic matter between peat porewater and pools and understanding which processes might drives its composition between both environments. Samplings were performed during 5 campaigns in 2018 and 4 campaigns in 2019, covering the ice-free season at the study site (from June to October). The study site in a boreal ombrotrophic peatland located in Romain river watershed in the Quebec province of northeastern Canada (50°31'N, 63°12'W). The peatland covers an area of 1.5 km2 at an average altitude of 108 m above sea level. Peat porewater were collected into six PVC wells inserted in peat, resulting in the collection of the first 60 cm of the water table. Water was collected at the surface of six pools in 2018 and 5 pools were added in 2019 for a total of nine pools. In June, August and September 2019, additional data were collected in a hollow and a lawn adjacent to a pool (M11) three different depths (-0.3m, -0.7m and -1m) using pomp connected to a tube of 3 mm diameter inserted directly in the peat with a metal rod guides. Water table depth variation and water table temperature were recorded during the ice-free season of 2018 and 2019 as well as water level and water temperature of a pool (M11) and air temperature.

The melting of marine terminating glaciers in Northeast Greenland is a visible sign that our climate is changing. This melt has been partly attributed to changes in oceanic heat fluxes, particularly warming of Atlantic Water (AW). Yet our understanding of the interaction between glaciers and the ocean is limited by the length of instrumental records. The multi-proxy dataset presented in this study is derived from Gravity Core DA17-NG-ST08-092G collected in September 2017 on-board the research vessel DANA as part of the NorthGreen2017 expedition. The 585 cm long core was collected at 583 m water depth on the NEG continental shelf. The new high resolution data presented here (benthic foraminifera, grain size, XRF, stable isotopes) provide an overview of ocean circulation patterns, as well as glacial extent on the Northeast Greenland continental shelf during the Holocene.