Factors that influence the distribution of the Arctic endemic kelp, Laminaria solidungula (J. Agardh 1868)

Foundation species, including kelps, have a disproportionate effect on ecosystems by exerting strong influence on food webs and community structure. Shifts in kelp species’ distributions are occurring worldwide, and are especially anticipated in the Arctic due to habitat modification by climate change. On Arctic inner shelves, the kelp Laminaria solidungula (J. Agardh 1868) can dominate nearshore rocky areas, and provide physical structure and subsidies of year-round primary production in a highly seasonal region. However, controls over the distribution of this Arctic endemic species are not well understood. A species’ interactions with the abiotic and biotic environment, its dispersal dynamics, and evolutionary history all control its ultimate range and spatial arrangement. This work describes how these factors impact L. solidungula distribution across multiple scales, with focus on the Stefansson Sound Boulder Patch, Beaufort Sea, Alaska. First, although the Stefansson Sound open-water season has lengthened by ~17 days since 1979, annual kelp growth shows no long-term trends because attenuation by suspended sediments causes pervasive low-light conditions during summer (mean light attenuation: 0.5-0.8 m⁻¹), negating any positive impacts of decreased ice-cover. Second, the abiotic environment of the Boulder Patch undergoes significant seasonal changes, mediated by physiography and bathymetry, which impact the spatial arrangement of L. solidungula and other epilithic species. A site within 4 km of river inputs experiences salinity drops of ~30 corresponding to the spring freshet. Crustose coralline algae (0-19% average cover) is completely absent at this site, but cover increases with distance from river inputs. Red algae (47-79%) and kelp (2-19%) cover shows no clear environmental correlations, and are likely regulated by multiple factors. Importantly, no L. solidungula recruited to settlement tiles after three years of deployment. Finally, population genetics suggest Beaufort Sea L. solidungula is one large interbreeding population (population differentiation as global F[subscript ST]: 0.01) assisted by the regional current regime, though smaller scale differentiation occurs within the Boulder Patch. Additionally, Beaufort Sea L. solidungula is genetically distinct from those in other areas of the Western Arctic Ocean Basin. This work represents an important baseline in ecological and genetic characteristics of L. solidungula in the rapidly changing Arctic OceanMarine Scienc

Salinity and pH variations in the nearshore Arctic Ocean : implications for benthic species physiology and biodiversity

Benthic communities are formed by species-specific tolerances to environmental factors and further shaped by biological interactions that inhibit or enhance post-settlement processes. Abiotic conditions affect species differently, and one example of this in the marine world is the influence of ocean water carbonate chemistry on calcifying organisms. Crustose coralline algae (CCA) are dominant space occupiers, ecosystem engineers that often shape community structure are early responders to water chemistry changes, and are prevalent benthic species in the Stefansson Sound Boulder Patch. The Boulder Patch is located off the north coast of Alaska and receives large pulses of freshwater each spring from the Sagavanirktok River, reducing salinities to less than five on the benthos in certain locations. Continuous pH, temperature and salinity data (including under-ice data) revealed seasonal variability and the influence of the Sagavanirktok River runoff, which caused short (3-5 week) pulses of highly buffered pH (>8), low A[subscript T] (<1900 μmEq L⁻¹) and low salinity (<5) waters into the Boulder Patch. Through manipulative laboratory experiments we noted that low salinity waters (10) negatively affected CCA physiology and likely drive their distributions within the Boulder Patch, which range from 77% cover to completely absent on rock substrata at nearshore sites where river runoff is prevalent during break-up in spring. Samples were collected and analyzed for algal and invertebrate species and biomass when CCA were present and absent, with a specific focus on the effects on population densities of the Arctic endemic kelp, Laminaria solidungula, an important foundation species. Areas with CCA had significantly higher densities of L. solidunugla adults (4.72 m⁻¹) than the site without CCA (0.36 m⁻¹). Experiments with early life history stages of L. solidungula raised in culture showed that low salinities (10) prevented recruitment. However, during winter, when early microscopic stages are present in the Boulder Patch, salinity levels are consistently high (32). These results point to other post-recruitment processes affecting the distribution of L. solidungula. In our system, CCA outcompeted turf and fleshy algal and other invertebrate species, creating more habitable space for kelp recruitment. This competitive interaction facilitates L. solidungula recruitment and survival and highlights the importance of abiotic factors in structuring benthic marine communities. The role of CCA in facilitating recruitment of a major foundation species and its susceptibility to low salinity events is critical to our understanding of this complex benthic ecosystemMarine Scienc

Macroalgae distribution among varying glacial fjords as an indicator of light and nutrient availability

Arctic macroalgae (kelp) are critical primary producers, contributing significantly to a wide variety of ecosystem services. Kelp extent has been predicted to increase due to decreasing sea ice cover that increases light reaching the coastal ocean. However, climate change-induced factors, such as increasing coastal turbidity and glacier melt, could also impact kelp growth in the Arctic. This thesis examines the role that light and nutrient availability play in understanding kelp cover and depth extent. This study used GoPro videos to determine kelp cover and depth extent as well as macroalgae samples to determine the nutritive state of kelp within two Greenlandic fjords. Results reveal significant turbidity and nutrient gradients throughout the fjords. Where light was limited due to glacial discharge and resuspension of sediments, kelp growth at depth was limited; and where there was increased light availability, kelp cover was greater. Additionally, kelp located nearest the marine-terminating glacier had greater nitrogen concentration than kelp located further from the marine-terminating glacier or the land-terminating glacier, revealing the influence of estuarine circulation on nutrient availability. Where light and nutrients were abundant, kelp biomass and subsequent production was greatest. Additionally, we concluded that sea urchin grazing provided an additional influence with light on kelp depth extent and distribution in both shallow and deep waters. These results are necessary and important to consider when assessing kelp distribution and change, both now and into the future.May 202

Drivers of trophic ecology and food web structure of epibenthic communities exposed to different sea-ice concentrations across the Canadian Arctic Ocean

La diminution de la couverture de glace de mer due au réchauffement de l'Arctique pourrait entraîner des changements complexes et indéterminés dans l'apport en nourriture qui pourraient altérer le fonctionnement des écosystèmes marins de l'Arctique. Les organismes benthiques sont des membres essentiels du réseau trophique de l'Arctique et constituent une source de nourriture importante pour les consommateurs des niveaux trophiques supérieurs. Dans l'océan Arctique, les consommateurs benthiques dépendent en grande partie des pulsations saisonnières de l'approvisionnement en nourriture provenant du phytoplancton (c.-à-d. la communauté pélagique) et des algues de glace de mer (c.-à-d. la communauté sympagique), mais nous ignorons encore comment les changements de la productivité primaire pourraient influer sur la dynamique trophique benthique. Afin de prévoir les tendances futures de la dynamique et du fonctionnement des écosystèmes, il est de plus en plus important de comprendre les facteurs environnementaux et biologiques qui influencent les interactions trophiques, les régimes alimentaires des consommateurs benthiques, et la cooccurrence des espèces dans les régions sujettes à des changements environnementaux rapides. En utilisant de multiples marqueurs trophiques, trois études connexes ont été réalisées et présentées dans cette thèse dans le but de (i) déterminer les facteurs qui influencent l'écologie trophique et la structure du réseau trophique benthique; (ii) quantifier la contribution relative du carbone sympagique dans le régime alimentaire des consommateurs benthiques et établir le rôle de la concentration de glace de mer dans le régime alimentaire des consommateurs benthiques et la structure du réseau trophique; et (iii) déterminer le rôle des individus dans les interactions trophiques et la structure du réseau trophique benthique. Dans le chapitre 1, nous avons étudié la structure du réseau trophique de la communauté macrobenthique à l'échelle de l'Arctique pancanadien afin de déterminer les facteurs influençant la dynamique des niches écologiques. Nous avons trouvé que la niche écologique fluctuait entre les régions présentant des concentrations différentes de glace de mer (SIC) sous l'effet d'une série de facteurs, notamment les conditions environnementales, les ressources disponibles et les pressions biotiques comme la prédation et la compétition. Les résultats ont mis en évidence une réduction de la richesse isotopique (c.-à-d. longueurs et largeurs de chaînes trophiques plus courtes) associée aux zones ayant des concentrations de glace de mer faibles et élevées, ce qui suggère une homogénéité et une faible variabilité des ressources consommées par les organismes. En revanche, nous avons observé une augmentation de la richesse isotopique (c.-à-d. une niche plus étendue) dans les zones de glace avec une concentration de glace de mer modérée, ce qui correspond à une plus grande hétérogénéité dans les sources de nourriture basale et des consommateurs utilisant des niches trophiques individuelles. Nos résultats appuient l'idée que la glace de mer est un facteur déterminant important de la dynamique et de la structure du réseau trophique benthique dans l'océan Arctique canadien. Dans le chapitre 2, les régimes alimentaires de la macrofaune benthique des grands fonds marins et la structure de son réseau alimentaire ont été étudiés dans la région de la baie de Baffin. Nous sommes les premiers à combiner des biomarqueurs lipidiques de type isoprénoïdes hautement ramifiés (HBI) avec des rapports d'isotopes stables (δ¹³C, δ¹⁵N) pour mieux comprendre la relation entre la disponibilité des sources de carbone dans les sédiments et l'assimilation et le transfert du carbone sympagique dans le réseau alimentaire benthique. Les HBI ont révélé une corrélation entre la consommation par les organismes benthiques de carbone organique particulaire dérivé de la glace de mer et les concentrations de glace de mer. D'après nos résultats, les diminutions de la quantité de carbone sympagique atteignant les fonds marins pourraient entraîner des changements temporels dans la composition des régimes alimentaires des consommateurs benthiques, les affectant de différentes manières selon leur guilde alimentaire et leur degré de plasticité alimentaire, ce qui pourrait alors affecter la dynamique du transfert de carbone. Dans le chapitre 3, les isotopes stables (δ¹³C, δ¹⁵N) ont été utilisés en conjonction avec l'approche des ellipses bayésiennes pour explorer les tendances spatiales des niches isotopiques quant à leur chevauchement et à leur largeur pour trois ophiures cooccurrentes: Ophiacantha bidentata, Ophiocten sericeum et Ophiopleura borealis, dans des régions arctiques spécifiques de la baie de Baffin (BB), de l'archipel arctique canadien (CAA), et de la polynie des eaux du Nord (NOW). Les différences de disponibilité et de diversité des aliments à l'échelle locale ont entraîné la variabilité de l'utilisation des ressources entre les stations au niveau individuel, ce qui a affecté les interactions trophiques, les chevauchements de niche et les structures de niche isotopique des ophiures. Nous avons observé un plus grand chevauchement de niches dans la région hautement productive de NOW, où les consommateurs présentaient une sélectivité alimentaire similaire, tandis que les régions présentant une plus grande concentration de glace de mer présentaient une augmentation de la ségrégation des niches. Enfin, les résultats ont mis en évidence que les ophiures pourraient être des espèces écologiques critiques gouvernant la dynamique, le fonctionnement et la stabilité des réseaux alimentaires benthiques dans l'océan Arctique.Declines in sea-ice cover due to the Arctic warming could lead to complex and undetermined changes in food supply that could alter negatively the functioning of Arctic marine ecosystems. Benthic organisms are essential members of the Arctic food web, constituting an important food source for higher-trophic level consumers. In the Arctic Ocean, benthic consumers depend mainly on seasonal pulses of food supply from phytoplankton (i.e., pelagic) and sea ice-associated algae (i.e., sympagic community), yet it is still unknown how changes in primary productivity might affect benthic trophic dynamics. In order to predict future trends in ecosystem dynamics and functioning, it is becoming increasingly important to understand the environmental and biological drivers influencing trophic interactions, benthic consumer diets, and species co-occurrence in regions subject to rapid environmental changes. Using multiple trophic markers approaches, three inter-related studies were performed here with the ultimate purpose of (i) determine the drivers of trophic ecology and benthic food web structure; (ii) quantify the relative contribution of sympagic carbon in benthic consumers' diets and establish the role of sea-ice concentration (SIC) in benthic consumers' diets and food web structure; and (iii) determine the role of individuals in trophic interactions and benthic food web structure. In Chapter 1, the food web structure of the macrobenthic community was studied at a Pan-Canadian Arctic scale to identify drivers of ecological niche dynamics. The ecological niche fluctuated between areas with different SIC by a series of drivers including environmental conditions, resource supply, and biotic pressures such as predation and competition. Results highlighted a reduction in the isotopic richness (i.e., shorter chain length and width) linked to ice areas with low and high SIC, suggesting homogeneity and low variability of resources consumed by organisms. In contrast, an increase in isotopic richness (i.e., broad niche) was observed in ice areas with moderate SIC, implying higher heterogeneity in basal food sources and consumers using individual trophic niches. Our results support the idea that sea ice is an important driver of benthic food web dynamics and structure across the Canadian Arctic Ocean. In Chapter 2, deep-sea benthic macrofauna diets and food web structure were studied in the Baffin Bay region. We were the first at combining highly branched isoprenoid (HBI) lipid biomarkers and stable isotope ratios (δ¹³C, δ¹⁵N) to better understand the relationship between the availability of carbon sources in sediments and the assimilation and transfer of sea-ice algae carbon through the benthic food web. Highly branched isoprenoid (HBI) biomarkers revealed a correlation between sea ice-derived particulate organic carbon (Sympagic carbon or SC) consumption in benthic organisms and sea-ice concentrations. Based on our results, decreases in the quantity of SC reaching the seabed could lead to temporal changes in the composition of benthic consumer diets, affecting them in different ways according to their feeding guilds and degree of dietary plasticity that could, in turn, affect carbon transfer dynamics. In Chapter 3, stable isotopes (δ¹³C, δ¹⁵N) in conjunction with the Bayesian ellipses approach were used to explore spatial trends in population isotopic niche width and overlap of three coexisting ophiuroids: Ophiacantha bidentata, Ophiocten sericeum, and Ophiopleura borealis, in specific Arctic regions of Baffin Bay (BB), Canadian Arctic Archipelago (CAA), and North Water Polynya (NOW). Differences in the availability and the diversity of local food items drove variability of resource utilization across stations at the individual-level, which in turn affected trophic interactions, niche overlaps, and isotopic niche structures of ophiuroids. A greater niche overlap was associated with the highly productive region of NOW, where consumers exhibited similar food selectivity, whereas regions with more sea-ice concentration (SIC) showed an increase in niche segregation. Finally, results highlighted that brittle stars could be critical ecological species driving dynamics, functioning and stability of benthic food webs in the Arctic Ocean

Monitoring and mitigation of the sound effects of hydrocarbon exploration activities on marine mammal populations

Offshore Exploration and Production (E&P) activities, such as seismic surveys and drilling, generate sound that can affect marine mammals in different ways. These effects range from permanent or temporary auditory impacts to disturbance or behavioral changes, and communication masking. Depending on the intensity and duration of these effects, and without implementation of appropriate mitigation measures, this can result in population-level consequences. The overarching objective of this study was to advance the protection of marine mammals during the implementation of E&P activities through the following themes: (1) enhancement of the state of knowledge of risk management, (2) efficacy of mitigation, (3) advanced monitoring technology, (4) implementation of advanced industry monitoring and mitigation measures and (5) measurement of heretofore unassessed E&P activities. In this study several marine mammal monitoring and mitigation programs associated with E&P projects are presented to further advance these themes. Topics being addressed include the use of autonomous camera systems for aerial monitoring of a narwhal population, long-term photo-identification studies of western gray whales to better understand site fidelity to their summer feeding grounds, mitigation of gray whales’ behavioral responses to a seismic survey near these feeding grounds and use of Passive Acoustic Monitoring to characterize seismic pulses and drilling activity as well as marine mammal presence in remote arctic areas. A synthesis of the main findings is provided that includes identification of future research needs. Conclusions and specific recommendations are made that will contribute to our ability to assess and mitigate risks of E&P sound to marine mammals

Environmental change in the Kitikmeot Region of western Nunavut and Ulukhaktok region of eastern Northwest Territories. Polar Knowledge: Aqhaliat Report - Volume 4

There are many impacts observed across the Canadian North because of changing environmental conditions. Increasing heat in the atmosphere caused by human pollution is causing the Arctic to warm up faster then anywhere else on Earth, and more frequent and intense weather has been occurring across the North. More unpredictable weather, tundra fires, forceful winds and storminess is expected to occur, with important impacts on northern communities. Air temperature controls all aspects of Arctic life, including which animals and plants can survive, when rivers and oceans freeze and break up, and the thickness of sea ice and permafrost. Canadian Arctic communities are warming the most in winter. Rainfall changes affect caribou and muskoxen, as they must break ice to get to their food. The snow season is shorter. Permafrost is warming and thawing. Arctic plants are changing in complex ways, in some areas climate change is causing them to grow more, shrubs becoming denser, and more grasses are present. Eventually, the tree line will move Northward. Ocean water is changing with increasing freshwater and sediments from melt, and this affects ocean life from microscopic species to fish and marine mammals. Global sea level rise will be less significant in the Canadian Arctic compered to low-laying islands elsewhere in the world. Arctic Sea Ice is melting, and this affects the safety of ice travel

YOUMARES 8 – Oceans Across Boundaries: Learning from each other : Proceedings of the 2017 conference for YOUng MARine RESearchers in Kiel, Germany

This open access book presents the proceedings volume of the YOUMARES 8 conference, which took place in Kiel, Germany, in September 2017, supported by the German Association for Marine Sciences (DGM). The YOUMARES conference series is entirely bottom-up organized by and for YOUng MARine RESearchers. Qualified early career scientists moderated the scientific sessions during the conference and provided literature reviews on aspects of their research field. These reviews and the presenters’ conference abstracts are compiled here. Thus, this book discusses highly topical fields of marine research and aims to act as a source of knowledge and inspiration for further reading and research

YOUMARES 8 – Oceans Across Boundaries: Learning from each other

This open access book presents the proceedings volume of the YOUMARES 8 conference, which took place in Kiel, Germany, in September 2017, supported by the German Association for Marine Sciences (DGM). The YOUMARES conference series is entirely bottom-up organized by and for YOUng MARine RESearchers. Qualified early career scientists moderated the scientific sessions during the conference and provided literature reviews on aspects of their research field. These reviews and the presenters’ conference abstracts are compiled here. Thus, this book discusses highly topical fields of marine research and aims to act as a source of knowledge and inspiration for further reading and research

Marine Nitrogen Fixation and Phytoplankton Ecology

Many oceans are currently undergoing rapid changes in environmental conditions such as warming temperature, acidic water condition, coastal hypoxia, etc. These changes could lead to dramatic changes in the biology and ecology of phytoplankton and consequently impact the entire marine ecosystems and global biogeochemical cycles. Marine phytoplankton can be an important indicator for the changes in marine environments and ecosystems since they are major primary producers that consolidate solar energy into various organic matter transferred to marine ecosystems throughout the food-webs. Similarly, the N2 fixers (diazotrophs) are also vulnerable to changing environmental conditions. It has been found that the polar regions can be introduced to diazotrophic activity under warming conditions and the increased N availability can lead to elevated primary productivity. Considering the fundamental roles of phytoplankton in marine ecosystems and global biogeochemical cycles, it is important to understand phytoplankton ecology and N2 fixation as a potential N source in various oceans. This Special Issue provides ecological and biogeochemical baselines in a wide range of geographic study regions for the changes in marine environments and ecosystems driven by global climate changes