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Early life history traits of small pelagic fish are usually affected by environmental conditions. Patagonian sprat, Sprattus fuegensis, is a small pelagic fish that inhabits the continental shelf, fjords and channels of Patagonia. Their larvae are usually exposed to large variations in physical and biological conditions. We evaluated the effects of environmental conditions on early life history traits of this key species encompassing over 20 years of information. The characterization of oceanographic features, larval abundance and distribution was carried out in western Patagonia between 1996 and 2019, while the growth and mortality rates were estimated for the austral spring 2019 between 49°54′S and 53°55′S. Larval abundance decreased three to ten times from 1996 to 1997 to the rest of the study period (2008–2010 and 2014–2019), with larger abundances being found over the shelf. In spring 2019, the growth rate was 0.20 ± 0.05 mm d−1 for larvae between 9 and 19 days after hatching. The growth rate was similar in partially stratified (7–50 J m−3) and stratified waters (50–100 J m−3), but slower in mixed waters (< 7 J m−3). GAM modelling showed that the faster larval growth occurred in partially stratified waters with temperatures above 7.5°C. Natural mortality rates were higher in partially stratified waters (24% of daily loss), lower in stratified areas (14%) and the lowest in the mixed water column (12%). Accordingly, larvae living in channels had faster growth rates but higher daily mortality, while those that hatched or were advected to water parcels on the continental shelf had slower growth but lower daily mortality. Finally, these latter traits may be an example of an inverse growth‐selective survival strategy. [ABSTRACT FROM AUTHOR]

Metal contamination in the Arctic region has increased over the years despite its remote and isolated location. Thus, to evaluate the bioavailable fractions of various metals and their effects on sediment-associated biota, the surface sediments from the fjords were analyzed for bulk concentration of metals and their speciation in different fractions. Metals concentrations were higher in the inner fjord region and decreased towards the outer fjord, supported by the terrigenous influence (TI%) calculated. Cr and Pb showed higher excess values attributed to their additional source other than the catchment rocks. So, to assess the metal-related ecological risk, the bulk concentration of metals was compared with Arctic sediment quality guidelines (ASQGs). Cr, Cd, and Pb concentrations were high, indicating potential adverse biological effects in the study. To avoid the risk of overestimation, metal speciation was conducted, showing that overall metal concentrations were higher in the residual fraction; however, higher concentrations of Mn in labile phases pose a moderate risk to the sediment-associated biota. Additionally, the population density of foraminifera in the sediments was calculated to assess the influence of bioavailable metal on benthic foraminifera. It was found that the presence of metals in bioavailable fractions affected the abundance of the foraminifera. However, no morphological abnormalities were observed in the species. [ABSTRACT FROM AUTHOR]

Microbes residing in cryoconite holes (debris, water, and nutrient-rich ecosystems) on the glacier surface actively participate in carbon and nutrient cycling. Not much is known about how these communities and their functions change during the summer melt-season when intense ablation and runoff alter the influx and outflux of nutrients and microbes. Here, we use high-throughput-amplicon sequencing, predictive metabolic tools and Phenotype MicroArray techniques to track changes in bacterial communities and functions in cryoconite holes in a coastal Antarctic site and the surrounding fjord, during the summer season. The bacterial diversity in cryoconite hole meltwater was predominantly composed of heterotrophs (Proteobacteria) throughout the season. The associated functional potentials were related to heterotrophic-assimilatory and -dissimilatory pathways. Autotrophic Cyanobacterial lineages dominated the debris community at the beginning and end of summer, while heterotrophic Bacteroidota- and Proteobacteria-related phyla increased during the peak melt period. Predictive functional analyses based on taxonomy show a shift from predominantly phototrophy-related functions to heterotrophic assimilatory pathways as the melt-season progressed. This shift from autotrophic to heterotrophic communities within cryoconite holes can affect carbon drawdown and nutrient liberation from the glacier surface during the summer. In addition, the flushing out and export of cryoconite hole communities to the fjord could influence the biogeochemical dynamics of the fjord ecosystem. [ABSTRACT FROM AUTHOR]

Metal contamination in the Arctic region has increased over the years despite its remote and isolated location. Thus, to evaluate the bioavailable fractions of various metals and their effects on sediment-associated biota, the surface sediments from the fjords were analyzed for bulk concentration of metals and their speciation in different fractions. Metals concentrations were higher in the inner fjord region and decreased towards the outer fjord, supported by the terrigenous influence (TI%) calculated. Cr and Pb showed higher excess values attributed to their additional source other than the catchment rocks. So, to assess the metal-related ecological risk, the bulk concentration of metals was compared with Arctic sediment quality guidelines (ASQGs). Cr, Cd, and Pb concentrations were high, indicating potential adverse biological effects in the study. To avoid the risk of overestimation, metal speciation was conducted, showing that overall metal concentrations were higher in the residual fraction; however, higher concentrations of Mn in labile phases pose a moderate risk to the sediment-associated biota. Additionally, the population density of foraminifera in the sediments was calculated to assess the influence of bioavailable metal on benthic foraminifera. It was found that the presence of metals in bioavailable fractions affected the abundance of the foraminifera. However, no morphological abnormalities were observed in the species.

Blue mussels Mytilus have returned to the high Arctic region of Svalbard in the beginning of twenty-first century after being absent for almost a 1000 years. Not only M. edulis had arrived in Svalbard, but also a complex of sympatric species including M. edulis, M. galloprovincialis, M. trossulus, and some of their hybrids, which may have a wide range of origins from both sides of the North Atlantic. Mussels were first found in the sublittoral at the entrance to Isfjorden, west coast of Spitsbergen island, and are spreading in other areas, and recently were also found in the intertidal zone. Here, we report viable larvae that were recovered from within the mantle cavity of mussels from the lower intertidal shore collected in late July 2019 and 2021 in Trygghamna, Isfjorden. The identity of larval and adult mussels was confirmed by sequencing of barcode region. Larvae ranged in size from 178 to 376 µm, from mussels 21 to 57 mm in shell length, and estimated to range over 3 to 12 years. It remains unclear whether the larval retention within the mantle cavity results from an intake of near shore concentrations and whether this may lead to larviphagy. [ABSTRACT FROM AUTHOR]

Simple Summary: Information on epibionts and symbionts of the introduced Barents Sea red king crab during the winter period is currently lacking. To address this gap, we examined the species composition and infestation indices of epibionts on this host in the northern part of Kola Bay in November. Our findings indicate a higher infestation rate of barnacles and amphipods during the winter season compared to the summer. In contrast, infestation rates of other species remained low during winter, reflecting seasonal fluctuations in both the size distribution of red king crabs and prevailing temperature conditions. Our research provides novel data on the growth patterns of commonly associated organisms, which could prove invaluable in determining the age of red king crabs in the Barents Sea. The species composition of epibiotic communities on red king crab was investigated in Sayda Bay, Russia, during November of 2015 and 2016. The community consisted of 12 species in total. Among epibionts, the barnacle Balanus crenatus was most prevalent (67.0%), while the amphipod Ischyrocerus commensalis was the most frequent symbiont (77.3%). Infestation levels in May–June 2005 and September 2004 were higher, as a larger proportion of small crabs without fouling species were present during those seasons. The lower infestation intensities recorded for other common associated organisms during winter can be attributed to their increased mortality due to unfavorable temperature conditions. The localization of epibionts and symbionts were related to larval settlement patterns of attached species and feeding behavior of mobile species. Monthly growth increments for I. commensalis and B. crenatus were estimated at 2 mm in body length and 1.35 mm in basal diameter, respectively. Size-at-age data for epibionts can aid in the age determination of large male crabs that may skip an annual molt. [ABSTRACT FROM AUTHOR]

This study elaborates the preliminary information on the meiofaunal assemblage pattern in the Krossfjorden system of the Svalbard Archipelago based on the samples collected during the Summer Phase Indian Arctic Expeditions of 2017 and 2018. The results from the study divulged the meiofaunal assemblage pattern. It is diversified with the presence of ten meiofaunal groups represented by Foraminifera, Tintinnida, Nematoda, Polychaeta, Copepoda, Kinorhyncha, Tanaidacea, Ostracoda, Acarina and Priapulida larvae. Meiofaunal abundance was observed to be low during the year 2018 (5646 ± 874 ind./10 cm2) compared with previous reports from adjacent fjord systems and the samples collected during the 2017 study (8826 ± 1501 ind./10 cm2). The decrease in meiofaunal assemblage in the fjord is associated with changes in environmental constraints and organic matter availability. The diminishing sea ice habitats in the Arctic waters are expected to have pronounced impacts on meiofaunal communities and their appearances in the coming future. In this regard, data gathered during the present study will form a baseline information on meiofaunal communities in the Krossfjorden system for understanding future changes in the benthic habitat and have important implications on predicting the direction of change with regard to meiobenthic productivity. [ABSTRACT FROM AUTHOR]

The temporal dynamics of five copepod species common to coastal waters of the Pacific Northwest were examined in relation to variability in spring temperature and phytoplankton dynamics in 2008, 2009, and 2010 in Rivers Inlet, British Columbia, Canada. The five species were differentiated by life history strategies. Acartia longiremis, Metridia pacifica, and Paraeuchaeta elongata remained active over most of the year. By contrast, the reproductive effort of Eucalanus bungii and Calanus marshallae was concentrated over the spring period and they spent most of the year in diapause as C5 copepodites. A delay in the timing of the spring bloom was associated with a shift in the phenology of all species. However, following the delay in spring bloom timing, recruitment to the G1 cohort was reduced only for E. bungii and C. marshallae. Recruitment successes of E. bungii and C. marshallae was also drastically reduced in 2010, an El Niño year, when spring temperatures were highest. Reasons for the observed differential response to spring environmental forcing, and its effect on upper trophic levels, are discussed.

Arctic outflow winds bring cold air from the continent to the coastline through mountain passes. Using observational data and a 2‐D model, we show that a February 2019 outflow event caused the upper 100 m in Bute Inlet, British Columbia (within the traditional territory of the Homalco Nation) to cool up to 1.9°C and gain up to 4.1 mLL−1 of oxygen. The cold, oxygenated water persisted for almost 1 year within the 1,023–1,023.5 kgm−3 isopycnal range (∼50–150 m). Atmospheric (from 1929 to 2022) and oceanographic (from 1951 to 2022) data showed a statistically significant relationship between continental air temperature at Tatlayoko Lake and temperature and oxygen in Bute Inlet. This local mechanism that counters some effects of climate change could create a biological refugium as surrounding waters warm and lose oxygen at a faster rate. The number of outflow events decreased from 1951 to 2018, and increased since. Plain Language Summary: There are times during most winters that Arctic air masses settle over the British Columbia (BC) interior east of the coast mountain range. Some of this cold air is transported to the coast as an outflow wind via coast mountain valleys. Using observational air and ocean data and a model, we examine an outflow event in February 2019. During this event, we find that outflow winds can cause mixing of the upper 100 m in Bute Inlet and this mixing can cause the ocean to rapidly cool and gain oxygen. Historical air data from 1929 to 2022 and ocean data from 1951 to 2022 were examined and it was found that the number of outflow events have generally decreased from the 1950s to 2018s, and increased afterward. This work identifies an important mechanism that could protect parts of BC's coastal ocean from climate change induced warming and loss of oxygen. Key Points: In February 2019, Arctic outflow winds caused the upper 100 m in Bute Inlet to cool by up to 1.9°C and gain up to 4.1 mLL−1 of oxygenApril to October Bute Inlet intermediate water properties are significantly correlated continental air temperature from the previous winterArctic outflow events decreased since the 1950s, but disruption of the polar vortex may increase these events with climate change [ABSTRACT FROM AUTHOR]

Ecological carryover effects occur in any situation in which an individual's previous history and experience (e.g., pelagic larval stages) influence performance in a subsequent state (e.g., benthic or demersal juveniles). Using a combination of geometric morphometrics, otolith microstructure analysis, satellite data, and numerical modeling, we studied the potential carryover effect between environmental conditions, larval growth, and the morphology of rockfish Sebastes oculatus settlers in a fjord-type inlet in southern Chile. We detected two sympatric morphotypes of young-of-the-year rockfish, one with a robust head, taller preoperculum, larger mouth, and frontally inserted pectoral fins, and a second with a slender head, shorter preoperculum and mouth, and distally inserted pectoral fins. Body conditions, otolith size, and age were similar between morphs. When past growth was analyzed, however, different increment width trajectories were found, particularly between 40- and 60-days post-hatch. The combination of otolith growth trajectories from each morph with the spatial heterogeneity of satellite data (seawater temperatures between 9 and 15 °C, chlorophyll-a between 4 and 10 mg m−3), within the inner sea of northern Chilean Patagonia, along with particle tracking and back-tracking hydrodynamical models, suggests that the focal site (i.e., where YOY were collected) was supplied by discrete cohorts of larvae with different patterns of phenotypic variation, which may have traveled through distinct water masses. Therefore, these results suggest ecological carryover effects of the growth history of larval stages on the phenotype of rockfish settlers. The identification of carryover effects at different temporal scales of the life history of demersal fish may lead to a better understanding of the factors affecting variation in individual fitness. [ABSTRACT FROM AUTHOR]

Environmental changes for the past ca. 50 years were studied in a short sediment core from inner Krossfjorden, Svalbard, investigating benthic foraminifera and stable isotopes (δ18O, δ13C). A depth–age model based on anthropogenic 137Cs time markers indicates that record covers the period from 1955 to 2007 and has sediment accumulation rates of ca. 0.3 to 1 cm/year. The benthic foraminifera are arctic and/or common in glaciomarine environments. Six fauna assemblages were identified using stratigraphically constrained cluster analysis. Benthic foraminiferal fauna assemblages are mainly dominated by Cassidulina reniforme. Elphidium clavatum is dominant from 1973 to 1986 and 2002 to 2007, likely due to greater turbidity in the water column. We interpret the increased percentages of Spiroplectammina biformis over the same intervals to reflect a slightly lower salinity probably caused by meltwater. During a short time period, 1970 to 1973, Stainforthia concava dominates the benthic foraminiferal fauna interpreted to reflect increased productivity within a marginal ice zone. Other species as Islandiella norcrossi, Nonionellina labradorica, Islandiella helenae, and Melonis barleanus also indicate more nutrient-rich waters are present but not very abundant throughout the record probably due to the glacier proximal position of the study site. The stable isotope record (δ18O) shows lighter values from 2001 to 2007, which seem to correlate well with oceanographic monitoring data showing increasing core temperatures of West Spitsbergen Current.

Abstract Arctic outflow winds bring cold air from the continent to the coastline through mountain passes. Using observational data and a 2‐D model, we show that a February 2019 outflow event caused the upper 100 m in Bute Inlet, British Columbia (within the traditional territory of the Homalco Nation) to cool up to 1.9°C and gain up to 4.1 mLL−1 of oxygen. The cold, oxygenated water persisted for almost 1 year within the 1,023–1,023.5 kgm−3 isopycnal range (∼50–150 m). Atmospheric (from 1929 to 2022) and oceanographic (from 1951 to 2022) data showed a statistically significant relationship between continental air temperature at Tatlayoko Lake and temperature and oxygen in Bute Inlet. This local mechanism that counters some effects of climate change could create a biological refugium as surrounding waters warm and lose oxygen at a faster rate. The number of outflow events decreased from 1951 to 2018, and increased since.

We report a long-term (4.5 year) time-series with weekly resolution of iodide and iodate measurements made at 4 depths within the Bedford Basin: a 70 m deep, seasonally stratified, coastal fjord located near Halifax, Nova Scotia, Canada. The subsurface data (60 m) reveal strong inverse correlations of both iodide and total dissolved iodine (TDI) with dissolved oxygen and indicate that there is in-situ reduction of iodate in subsurface waters (in the presence of oxygen) as well as an additional external source of iodide from the remineralization of sinking organic matter, a flux from sediments, or both. Surface water (

The species composition of epibiotic communities on red king crab was investigated in Sayda Bay, Russia, during November of 2015 and 2016. The community consisted of 12 species in total. Among epibionts, the barnacle Balanus crenatus was most prevalent (67.0%), while the amphipod Ischyrocerus commensalis was the most frequent symbiont (77.3%). Infestation levels in May–June 2005 and September 2004 were higher, as a larger proportion of small crabs without fouling species were present during those seasons. The lower infestation intensities recorded for other common associated organisms during winter can be attributed to their increased mortality due to unfavorable temperature conditions. The localization of epibionts and symbionts were related to larval settlement patterns of attached species and feeding behavior of mobile species. Monthly growth increments for I. commensalis and B. crenatus were estimated at 2 mm in body length and 1.35 mm in basal diameter, respectively. Size-at-age data for epibionts can aid in the age determination of large male crabs that may skip an annual molt.

Deoxygenation of the ocean has been occurring over the last half century, particularly in poorly ventilated coastal waters. In coastal and estuarine environments, both the water column and sediments play key roles in controlling oxygen variability. In this study, we focus on controls of oxygen concentration in Bedford Basin (BB), a 70 m deep, seasonally hypoxic semi-enclosed fjord on the West Atlantic coast in Nova Scotia. The basin is connected to the Scotian Shelf via a narrow 20 m deep sill that restricts the resupply of bottom water. Hypoxia was recorded seasonally in 2018, 2019 and 2021 with minimum oxygen concentration of 5, 6.7 and 2.7 μM, respectively. Using a 1-D benthic-pelagic coupled model we investigate oxygen consumption and resupply processes during these years. The model was constrained with weekly water column measurements of temperature, salinity, chlorophyll-a fluorescence and dissolved oxygen from a monitoring station in the central basin together with seasonal measurements of benthic diffusive oxygen uptake. Our model suggested that 29-81%, and up to 36% of bottom water re-oxygenation occurred during the winter mixing period and through summer/fall intrusions of Scotian Shelf water, respectively. Occasional shelf water intrusions occurred rapidly, on a timescale of a few hours, and delivered equivalent amounts of oxygen as winter mixing and were sufficient to end bottom water hypoxia. Collectively, these mechanisms supplied the majority of the oxygen delivered to the bottom water. Oxygen supply to bottom waters during periods of water column stratification accounted for 19-36% of the annual flux. The mean benthic uptake was 12 ± 8 mmol m-2 d-1 and contributed ~20% of the total oxygen consumption below the sill depth. In 2021, sea surface temperature (SST) was unusually high and likely resulted in 50% less bottom water oxygenation compared to 2018 and 2019 due to increased stratification; SST in BB was found to be increasing at a rate of 0.11 ± 0.02 °C/year. Climate control on water column stratification are discussed and numerical experiments are used to compare the effects of different water column mixing scenarios on bottom water oxygenation.

Kola Bay is the most developed coastal area in the Russian part of the Barents Sea, but despite a long history of research, information about the local shallow-water benthic communities is lacking. For this reason, in this fjord area, we investigated the soft-bottom zoobenthos to determine its distribution and the factors influencing its abundance, biomass, and diversity. An analysis of 24 samples collected by divers at eight stations located at 7–8 and 10–15 m depths revealed 127 benthic taxa with an average abundance and biomass of 12,190 ± 4740 ind. m−2 and 30 ± 8 g m−2, respectively. The most severe abiotic conditions (high rates of sedimentation and eutrophication) were found at the head of the bay while the highest densities of predator red king crabs were registered in the middle part. The total benthic abundance and biomass, as well as the abundances of infauna, mobile taxa, subsurface deposit feeders, and surface deposit feeders, decreased towards the central part of the bay, reflecting gradients in the environmental conditions. In the inner part of the bay, we registered two communities: Cossura pygodactylata + Ciliatocardium ciliatum and Arctica islandica + Laonice cirrata, while the benthos of the middle part was less structured. Redundancy analysis indicated that the faunal abundances were influenced mainly by predator density (negative association) and the organic matter content (positive association). The total benthic biomass was negatively linked to water temperature due to the predominance of cold-water species in the area and a close positive association of this factor with crab abundance. In contrast, the highest diversity was registered at the warmer sites, which may have been a reflection of the borealization process in the Arctic. Our results contribute towards the proper management and conservation of the local benthic ecosystem and provide reference data for future monitoring programs and coastal management guidelines. [ABSTRACT FROM AUTHOR]

This study focuses on the distribution of some selected organochlorine pesticides and emerging contaminants within the surface sediments of an Arctic fjord, Kongsfjorden and nearby lakes. Organochlorine pesticides (OCPs) such as dicloran, p,p'-DDT, p,p'-DDE, p,p'-DDD were studied along with five emerging contaminants namely diuron, chlorpyrifos, dicofol, pendimethalin and bifenthrin. The highest values of OCPs recorded among the fjord and lake environments during the time of study was 0.3355 ng/g (dicloran), 0.0152 ng/g (p,p'-DDT), 0.0117 ng/g (p,p'-DDE), and 0.0137 ng/g (p,p'-DDD). Except dicofol, all other pesticides were found in both the years (2018 & 2019) with an elevated concentration during 2019. The presence of fresh as well as past input of contaminants was obtained from the values of DDTs ratio. The sediment quality guidelines of DDTs confirm that the fjord and lakes are clean to marginally polluted in which the adverse effects can rarely occur at this present juncture. • The study is on the distribution of organochlorine pesticides and emerging contaminants within the surface sediments of an Arctic fjord and lakes. • Organochlorine pesticides (OCPs) such as dicloran, p,p′-DDT, p,p′-DDE, p,p′-DDD and emerging contaminants namely diuron, chlorpyrifos, dicofol, pendimethalin and bifenthrin was studied. • The fjord and lakes are clean to marginally polluted in which the adverse effects can rarely occur. [ABSTRACT FROM AUTHOR]

We identified the nature and driving mechanisms of subinertial variability (variability at a time scale of several days) in four fjords in Southeast Greenland, in three high‐resolution numerical simulations. We find two dominant frequency ranges in along‐fjord velocity, volume transport of Atlantic Water, and along‐fjord heat transport: one around 2–4 days and one around 10 days. The higher frequency is most prominent in the two smaller fjords (Sermilik Fjord and Kangerdlugssuaq Fjord), while the lower frequency peak dominates in the larger fjords (Scoresby Sund and King Oscar Fjord). The cross‐fjord structure of variability patterns is determined by the fjord's dynamic width, while the vertical structure is determined by the stratification in the fjord. The dominant frequency range is a function of stratification and fjord length, through the travel time of resonant internal Kelvin waves. We find that the subinertial variability is the imprint of Coastal Trapped Waves, which manifest as Rossby‐type waves on the continental shelf and as internal Kelvin‐type waves inside the fjords. Between 50% and 80% of the variability in the fjord is directly forced by Coastal Trapped Waves propagating in from the shelf, with an additional role played by alongshore wind forcing on the shelf. Plain Language Summary: The Greenland Ice Sheet meets the Atlantic Ocean in Greenland's deep glacial fjords. The ocean currents in these fjords are highly variable, with most of the variability on timescales of several days. We determined which spatial structures are associated with this variability, and found that it is associated with a class of oceanic waves called Coastal Trapped Waves. Inside the fjord, the character of the variability is determined by the shape of the fjord and by the density stratification in the fjord, which in turn depends on the temperature and salinity structures found in the fjords. Most of the variability is forced by waves propagating in from the continental shelf, and by wind stress forcing the ocean near the fjord. Our new findings are helpful in determining to what extent findings based on a single fjord are more universally valid, as well as how we can better predict variability in the fjords. Key Points: Subinertial variability in Southeast Greenland fjords is manifested as Coastal Trapped WavesThe majority of this variability is forced by Coastal Trapped Waves on the continental shelf, with a lesser role played by wind forcingThe structure and dominant frequency ranges of subinertial variability in the fjords is determined by the fjord dimension and stratification [ABSTRACT FROM AUTHOR]

At tidewater glacier termini, ocean‐glacier interactions hinge on two sources of freshwater—submarine melt and subglacial discharge—yet these freshwater fluxes are often unconstrained in their magnitude, seasonality, and relationship. With measurements of ocean velocity, temperature and salinity, fjord budgets can be evaluated to partition the freshwater flux into submarine melt and subglacial discharge. We apply these methods to calculate the freshwater fluxes at LeConte Glacier, Alaska, across a wide range of oceanic and atmospheric conditions during six surveys in 2016–2018. We compare these ocean‐derived fluxes with an estimate of subglacial discharge from a surface mass balance model and with estimates of submarine melt from multibeam sonar and autonomous kayaks, finding relatively good agreement between these independent estimates. Across spring, summer, and fall, the relationship between subglacial discharge and submarine melt follows a scaling law predicted by standard theory (melt ∼ discharge1/3), although the total magnitude of melt is an order of magnitude larger than theoretical estimates. Subglacial discharge is the dominant driver of variability in melt, while the dependence of melt on fjord properties is not discernible. A comparison of oceanic budgets with glacier records indicates that submarine melt removes 33%–49% of the ice flux into the terminus across spring, summer, and fall periods. Thus, melt is a significant component of the glacier's mass balance, and we find that melt correlates with seasonal retreat; however, melt does not appear to directly amplify calving. Plain Language Summary: Two main sources of freshwater enter the ocean at the fronts of tidewater glaciers: submarine melt and subglacial discharge. Submarine melt is thought to play a role in triggering ice loss at glaciers around the globe. Submarine melt, in turn, is modulated by subglacial discharge and fjord conditions. However, we have few direct measurements of submarine melt and subglacial discharge at tidewater glaciers. Instead, many studies rely on theory to predict melt rates as a function of modeled subglacial discharge and fjord conditions. In this study, we use measurements of ocean velocity and water properties to estimate the fluxes of submarine melt and subglacial discharge from LeConte Glacier, Alaska. We find that melt varies as a function of discharge in the manner predicted by theory, but the overall magnitude of melt is substantially higher than theory. The impact of fjord temperature and stratification on melt is secondary and does not form a clear signal in the data. Overall, submarine melt removes approximately half of the ice flux into the terminus and is correlated with terminus retreat in summer. However, there is no clear relationship between melt and calving, suggesting that submarine melt does not directly amplify calving on seasonal timescales. Key Points: Submarine melt and subglacial discharge follow theoretical scaling (melt ∼ discharge⅓), but the magnitude of melt is much larger than theorySubglacial discharge has a stronger influence on submarine melt than fjord conditions, because discharge varies by 2+ orders of magnitudeSubmarine melt removes up to ∼50% of the ice flux into the terminus and is correlated with terminus retreat in summer [ABSTRACT FROM AUTHOR]

While fjords often have low oxygen concentrations in their deep waters, this research identified seasonal, near-surface hypoxia (≤ 2 mL L-1 or 2.9 mg L-1) through a year-long monthly time series in Clayoquot Sound, British Columbia. Temperature, salinity, and oxygen data were collected monthly in the upper 50 m at three stations in Herbert Inlet from June 2020 to July 2021, marking the first time series of its kind in a Clayoquot Sound fjord. Hypoxic conditions were shallowest (minimum depth of 12 m) and most intensified in summer; near-surface hypoxia was recorded at one or more stations in all months except in winter. Considering that many local marine species, including wild Pacific salmon, experience adverse effects at oxygen concentrations much higher than the hypoxic threshold, we note that 50 to 100% of the upper 50 m of Herbert Inlet consistently presented low oxygen concentrations (defined here as a guideline as ≤ 4.9 mL L-1 or 6.9 mg L-1) during the 14-month study period. Previous observations collected sporadically since May 1959 confirmed the presence of hypoxic conditions in the past. These findings suggest that long-term, multidisciplinary studies are needed to understand and predict the impact of hypoxia and deoxygenation on wild salmon stocks as climate changes.

The polar night has recently received increased attention as a surprisingly active biological season. Yet, polar night microbial ecology is a vastly understudied field. To identify the physical and biogeochemical parameters driving microbial activity over the dark season, we studied a sub-Arctic fjord system in northern Norway from autumn to early spring with detailed monthly sampling. We focused on the impact of mixing, terrestrial organic matter input and light on microbial ecosystem dynamics. Our study highlights strong differences in the key drivers between spring, autumn, and winter. The spring bloom started in March in a fully mixed water column, opposing the traditional critical depth hypothesis. Incident solar radiation was the key driver maximum Chlorophyll was reached in April. The onset of the autumn phytoplankton bloom was controlled by vertical mixing, causing nutrient upwelling and dilution of zooplankton grazers, which had their highest biomass during this time. According to the dilution-recoupling hypothesis grazer dilution reduced grazing stress and allowed the fall bloom formation. Mixing at that time was initiated by strong winds and reduced stratification as a consequence of freezing temperatures and lower freshwater runoff. During the light-limited polar night, the primary production was extremely low but bacteria continued growing on decaying algae, their exudates and also allochthonous organic matter. A melting event in January could have increased input of organic matter from land, supporting a mid-winter bacterial bloom. In conclusion, polar night biogeochemistry and microbial ecology was not only driven by light availability, but strongly affected by variability in reshwater discharge and allochthonous carbon input. With climate change freshwater discharge will increase in the Arctic, which will likely increase importance of the dynamics described in this study.

Glacier-fed hydrological systems in high latitude regions experience high seasonal variation in meltwater runoff. The peak in runoff usually coincides with the highest air temperatures which drive meltwater production. This process is often accompanied by the release of sediments from within the glacier system that are transported and suspended in high concentrations as they reach the proglacial realm. Sediment-laden meltwater is later transported to the marine environment and is expressed on the surface of fjords and coastal waters as sediment plumes. Direct monitoring of these processes requires complex and time-intensive fieldwork, meaning studies of these processes are rare. This paper demonstrates the seasonal dynamics of the Trebrevatnet lake complex and evolution of suspended sediment in the lake and sediment plumes in the adjacent Ekmanfjorden. We use the Normalized Difference Suspended Sediment Index (NDSSI) derived from multi-temporal Sentinel-2 images for the period between 2016–2021. We propose a new SSL index combining the areal extent of the sediment plume with the NDSSI for quantification of the sediment influx to the marine environment. The largest observed sediment plume was recorded on 30 July 2018 and extended to more than 40 km2 and a SSL index of 10.4. We identified the greatest sediment concentrations in the lake in the beginning of August, whereas the highest activity of the sediment plumes is concentrated at the end of July. The temporal pattern of these processes stays relatively stable throughout all ablation seasons studied. Sediment plumes observed with the use of optical satellite remote sensing data may be used as a proxy for meltwater runoff from the glacier-fed Trebrevatnet system. We have shown that remote-sensing-derived suspended sediment indexes can (after proper in situ calibration) serve for large scale quantification of sediment flux to fjord and coastal environments. [ABSTRACT FROM AUTHOR]

To understand the effects of the glacial meltwater supply on carbonate chemistry and the air–sea CO2 flux within the fjord, water samples were collected in Bowdoin Fjord in northwestern Greenland for dissolved inorganic carbon (DIC) concentration, total alkalinity (TA), oxygen isotopic ratio (δ18O), and chlorophyll a concentration analyses in the summers of 2016 and 2017. The partial pressure of CO2 (pCO2) in surface water, calculated from DIC and TA, was less than 200 µatm, and was significantly lower than that in the atmosphere (399 ± 3 µatm). Therefore, surface water of the fjord acts as sink for CO2 in the atmosphere (–4.9 ± 0.7 mmol m–2 d–1). To evaluate the effects of freshwater and land-derived substances by glacial meltwater on pCO2 in the fjord, we calculated the changes of pCO2 in salinity and carbonate chemistry that would result from the inflow of glacial meltwater into the fjord. The calculated pCO2 was high near the calving front, where the contribution of glacier meltwater was significant. Examination of the relationship between salinity-normalized DIC and TA, which was considered DIC and TA input from the land, suggested that the land-derived high pCO2 freshwater affected mainly by the remineralization of the organic matter by bacterial activity was supplied to the Bowdoin Fjord.

Iron plays a pivotal role in marine primary production and the carbon cycle. Glaciers have been recognized as a regional iron source to the ocean. Understanding both the endmember values and the transport processes of glacial iron passing through coastal waters to the ocean is essential to comprehend the fate and flux of iron derived from glaciers to the ocean. Fjords are typical coastal pathways in polar marine environments, connecting glacial meltwater to the open ocean. To better estimate iron transport from glacial meltwater to the ocean, we examined dissolved iron (dFe), dissolved aluminum (dAl), iron stable isotopes (δ56Fe), and other biochemical parameters, including dissolved organic carbon, total suspended matter, and chlorophyll a in an Arctic fjord system, Kongsfjorden, Svalbard. In surface Kongsfjorden, low dFe levels averaging 5.23 ± 0.43 nM were detected in the inflow along the southern bank of the outer fjord, while elevated dFe concentrations were observed in both the inner and middle fjord regions (10.74 ± 5.22 nM), as well as in the outflow along the northern bank of the outer fjord (9.37 ± 2.85 nM). The association of dFe distribution with circulation patterns, in addition to the correlation between dFe and salinity, emphasizes that both glacial input and circulation regulate dFe distribution in Kongsfjorden. dFe and dAl endmember values from glacial meltwater were estimated as 82 ± 21 nM and 1089 ± 200.7 nM, respectively. The summer flux of glacier-derived dissolved iron and aluminum in Kongsfjorden were calculated to be 4.6–19 Mg/summer and 29 ± 5.4 Mg/summer, respectively. A short residence time for dFe in the Surface Water of Kongsfjorden was estimated at approximately a few days to a week, while dAl exhibited nearly conservative behavior, suggesting a possible application as a tracer for glacier input. The average δ56Fe value in Kongsfjorden surface water was 0.08 ± 0.19‰, and our extrapolated glacial δ56Fe input fingerprint ranged from 0.1‰ to 0.3‰ as iron traveled from the glacier towards the ocean. Our results emphasize the transport pattern of glacier-derived iron towards the ocean through Arctic fjord systems. • Both glacial input and circulation dominate dFe distribution in Kongsfjorden. • dFe versus salinity suggests glacial iron endmember of 82 ± 21 nM. • The average δ56Fe value measured at 0.08 ± 0.19‰ in Surface Water. [ABSTRACT FROM AUTHOR]

Grain-size end-member (EM) modelling is a robust statistical approach for identifying and quantifying dominant grain-size distributions. This approach provides a novel perspective for understanding the impact of interactions between depositional processes in complex sedimentary environments. This study examines grain-size distributions of six glacimarine sediment cores collected along an N S transect from the continental shelf to the Wijdefjorden system in northern Svalbard. In addition, we integrate grain-size EMs with lithologic and acoustic facies, allowing us to identify three distinct groups of EMs (EM1–3), each closely associated with specific depositional processes: turbid meltwater discharge (EM1), sediment winnowing by bottom currents (EM2), and the deposition of ice-rafted debris in glacimarine conditions and subglacial till (EM3). An analysis of the three EM groups reveals that the glacial retreat during the last deglaciation and the Atlantic Water inflow significantly impacted depositional changes within the Wijdefjorden system. In contrast, a decrease in the Atlantic Water inflow during the late Holocene corresponds to glacial re-advance, resulting in shifts in the depositional environment. This study demonstrates the utility of EM modelling in deciphering complex grain-size distributions and reconstructing different climate-driven depositional processes in glacimarine sediments in Svalbard fjords. This integrated approach enhances our understanding of the intricate interplay among climate change, glacier dynamics, and oceanic forcing in polar fjord environments. • Grain-size EM modelling provides a better understanding of the fjord environment. • Each EM reflects specific processes related to glacier dynamics. • Glacier dynamics strongly affected by AW inflow. • EM variations are useful for reconstructing the fjord depositional environment. [ABSTRACT FROM AUTHOR]

Greenland's glacial fjords are a key bottleneck in the earth system, regulating exchange of heat, freshwater and nutrients between the ice sheet and ocean and hosting societally important fisheries. We combine recent bathymetric, atmospheric, and oceanographic data with a buoyant plume model to show that summer subglacial discharge from 136 tidewater glaciers, amounting to 0.02 Sv of freshwater, drives 0.6–1.6 Sv of upwelling. Bathymetric analysis suggests that this is sufficient to renew most major fjords within a single summer, and that these fjords provide a path to the continental shelf that is deeper than 200 m for two‐thirds of the glaciers. Our study provides a first pan‐Greenland inventory of tidewater glacier fjords and quantifies regional and ice sheet‐wide upwelling fluxes. This analysis provides important context for site‐specific studies and is a step toward implementing fjord‐scale heat, freshwater and nutrient fluxes in large‐scale ice sheet and climate models. Plain Language Summary: The interaction between the Greenland Ice Sheet and the surrounding ocean is one of the key links in the regional climate system. Ocean heat melts the edges of the ice sheet, causing glacier speed‐up, retreat and sea level contribution. Meltwater from the ice sheet enters the ocean where it alters ocean properties and potentially ocean currents. This meltwater also drives upwelling of nutrients that can impact local ecosystems. All of these processes occur in long, deep and narrow fjords that connect the ice sheet and ocean. In this study, we present a first continent‐wide overview of the geometry and dynamics of Greenland's fjords. We combine recent bathymetric, atmospheric, and oceanographic datasets with a simple model to show that many fjords are well connected to the ocean in both bathymetry and circulation, suggesting that changes in the ocean on the continental shelf will be quickly transmitted to the ice sheet margin. We also suggest that meltwater from the ice sheet is rapidly mixed within fjords and will enter the wider ocean as a dilute subsurface mixture. This study is a step toward implementing fjord heat, freshwater and nutrient fluxes into large‐scale models that cannot resolve fjords. Key Points: We present a first ice sheet‐wide inventory of subglacial discharge‐driven upwelling plumes around the margin of the Greenland Ice SheetJust 0.02 Sv of subglacial discharge drives 0.6–1.6 Sv of upwelling that settles at 0–260 m depth and can renew most fjords within a summerFjords provide a path to the ocean deeper than 200 m for 82 out of 136 glaciers considered, suggesting warm waters reach most major glaciers [ABSTRACT FROM AUTHOR]

The activity of marine microorganisms depends on community composition, yet, in some oceans, less is known about the environmental and ecological processes that structure their distribution. The objective of this study was to test the effect of geographical distance and environmental parameters on prokaryotic community structure in the Southern Ocean (SO). We described the total (16S rRNA gene) and the active fraction (16S rRNA-based) of surface microbial communities over a ~6,500 km longitudinal transect in the SO. We found that the community composition of the total fraction was different from the active fraction across the zones investigated. In addition, higher α-diversity and stronger species turnover were displayed in the active community compared to the total community. Oceanospirillales, Alteromonadales, Rhodobacterales , and Flavobacteriales dominated the composition of the bacterioplankton communities; however, there were marked differences at the order level. Temperature, salinity, silicic acid, particulate organic nitrogen, and particulate organic carbon correlated with the composition of bacterioplankton communities. A strong distance–decay pattern between closer and distant communities was observed. We hypothesize that it was related to the different oceanic fronts present in the Antarctic Circumpolar Current. Our findings contribute to a better understanding of the complex arrangement that shapes the structure of bacterioplankton communities in the SO. [ABSTRACT FROM AUTHOR]

In this study, we reconstructed for the first time the recent 1000-yr-long history of Goluboi tidewater glacier at the eastern side of the Novaya Zemlya, Kara Sea, based on accelerator mass spectrometry 14C dating with higher-resolution age control on the basis of 210Pb and 137Cs radionuclides for the time period after AD 1885, using multiproxy analyses (lithology, mineralogy, and geochemistry) of proximal glaciomarine sediments from the Oga Fjord. Against the background of the active glacial dynamics and the intense meltwater runoff until the end of the sixteenth century, there was a sudden cooling at the beginning of the seventeenth century, which manifested itself in a significant decrease in the sedimentation rates. In time, this event coincides with the strongest volcanic eruption, AD 1600, in South America (in Peru) in the history of human settlement of the continent, which may have plunged the globe into cold climate chaos (Witze, 2008), and caused the Great Famine, AD 1601 to AD 1603, in Russia. The synchronicity of the described events may be an additional fact confirming the global impact of the eruption on the climate of our planet. [ABSTRACT FROM AUTHOR]

A subsurface oxygen minimum layer (OML) in intermediate water is identified and characterized in Rivers Inlet, a fjord on British Columbia's central coast, using data from 1998 to 2018. The OML was observed in most years from May to September and was most persistent at the middle and head of the fjord. The Rivers Inlet OML develops in three stages: (i) in early spring, the cessation of winter storms from downwelling-favourable winds stops the ventilation of the water column; (ii) throughout spring and summer, the remineralization of organic matter, likely primarily phytoplankton, consumes oxygen in the intermediate waters; (iii) in late spring, deep-water renewal by oxygenated offshore water forms the base of the OML inside the inlet. The strength and persistence of the OML vary interannually, mainly due to variability in hemispheric-scale winds and primary production. In some years, the OML was hypoxic, which could influence the local marine ecosystem. Changes to downwelling, upwelling, or primary production in Rivers Inlet could affect the OML in the future. [ABSTRACT FROM AUTHOR]

The activity of marine microorganisms depends on community composition, yet, in some oceans, less is known about the environmental and ecological processes that structure their distribution. The objective of this study was to test the effect of geographical distance and environmental parameters on prokaryotic community structure in the Southern Ocean (SO). We described the total (16S rRNA gene) and the active fraction (16S rRNA-based) of surface microbial communities over a ~6,500 km longitudinal transect in the SO. We found that the community composition of the total fraction was different from the active fraction across the zones investigated. In addition, higher α-diversity and stronger species turnover were displayed in the active community compared to the total community. Oceanospirillales, Alteromonadales, Rhodobacterales, and Flavobacteriales dominated the composition of the bacterioplankton communities; however, there were marked differences at the order level. Temperature, salinity, silicic acid, particulate organic nitrogen, and particulate organic carbon correlated with the composition of bacterioplankton communities. A strong distance–decay pattern between closer and distant communities was observed. We hypothesize that it was related to the different oceanic fronts present in the Antarctic Circumpolar Current. Our findings contribute to a better understanding of the complex arrangement that shapes the structure of bacterioplankton communities in the SO.

In a period of high rates of glacier retreat, increasing meltwater discharge from tidewater glaciers can influence marine fjord ecosystems due to increase sediment delivery and accumulation rates in the proglacial environment. Glacier variations and associated changes in glacimarine processes are recorded in the sedimentary record and submarine geomorphology of fjords. In October-November 2017, CIMAR23 Cruise surveyed several fjords adjacent to the Southern Patagonian Icefield (SPI). In this study, we show detailed results of the multibeam bathymetry, backscatter and sub-bottom seismic profiles, and sediment core samples from Europa Fjord, located west of the central SPI area, to improve the analysis of the fjord glacial and sedimentary evolution and to connect its behavior with the other fjords in the region. For the cores 210Pb chronology, magnetic susceptibility, organic carbon, total nitrogen, and stable isotopes (δ13Corg, δ15N) were performed. The seafloor geomorphology showed that the most prominent submarine landforms are transverse morainal ridges, which indicate past stillstand glacier positions; these features formed during the deglaciation of the fjord (latest Pleistocene), and some, perhaps more recently during short episodic advance/retreat events. In the central and mouth fjord areas, erosional features such as lineations are found on the rocky bottom and interpreted as formed by past grounded glaciers. Several submarine moraines are generally well preserved, but some parts are crumbled by slope failures and erosion. Most of the seismic sections are interpreted as the expected subglacial-ice proximal-ice distal succession of facies, characteristic of single retreat environments. The sedimentary record includes bioturbed muds with muddy laminations and variable amounts of coarse sediments interpreted as ice rafted debris, suggesting a proglacial environment, punctuated by calving. From the beginning of the twentieth century there is a tendency to an increase in the terrigenous organic material content, including an abrupt increase during the 80–90s, and a decline in the last decade. This behavior is indicating possibly a general increase of surface terrestrial runoff and, for the last decade, an increase of glacial meltwater input which would be caused by an accelerated deglaciation.

Submarine mass wasting events have damaged underwater structures and propagated waves that have inundated towns and affected human populations in nearby coastal areas. Susceptibility to submarine landslides can be pronounced in degrading cryospheric environments, where existing glaciers can provide high volumes of sediment, while cycles of glaciation and ice-loss can damage and destabilize slopes. Despite their contribution to potential tsunami hazard, submarine landslides can be difficult to study because of limited access and data collection in underwater environments. Here we present a method to quantify and map the submarine landslide susceptibility of sediment-covered slopes in Glacier Bay, Glacier Bay National Park and Preserve, Alaska, using multibeam-sonar bathymetric digital elevation models (DEMs) and historical maps of glacial extents over the last ∼250 years. After mapping an inventory of >7,000 landslide scarps in submarine sediments, we filtered the inventory by size to account for limitations in DEM resolution and spatial scales relevant to tsunami hazards. We then assessed landslide concentration, accounting for the age of the initial exposure of submarine slopes by deglaciation. We found a positive correlation between landslide concentration and deglaciation age, which we interpreted as a mean landslide accumulation rate over the period of record. Local deviations from this rate indicated differences in susceptibility. Additionally, we accounted for some of the effect of material and morphometric properties by estimating the submarine bedrock-sediment distribution using a morphometric model and assessing the relationship between slope angle and landslide incidence. Finally, we supplemented our susceptibility assessment with a geomorphic component based on the propensity of active submarine fans and deltas to produce landslides. Thus, our map of submarine landslide susceptibility incorporates three components: age-adjusted landslide concentration, slope angle, and geomorphology. We find that areas of mapped high susceptibility correlate broadly with areas of high sediment input and availability, locations of fans and deltas, and steep sediment-covered glacially carved fjords and troughs. Areas of high submarine landslide susceptibility in Glacier Bay moderately correspond with locations of known high-hazard subaerial slopes, but more research on submarine and subaerial landslides in degrading cryospheric environments would be beneficial to better understand landslide and tsunami hazards.

Environmental changes for the past ca. 50 years were studied in a short sediment core from inner Krossfjorden, Svalbard, investigating benthic foraminifera and stable isotopes ƹ18O, ƹ13C). A depth-age model based on anthropogenic 137Cs time markers indicates that record covers the period from 1955 to 2007 and has sediment accumulation rates of ca. 0.3 to 1 cm/year. The benthic foraminifera are arctic and/or common in glaciomarine environments. Six fauna assemblages were identified using stratigraphically constrained cluster analysis. Benthic foraminiferal fauna assemblages are mainly dominated by Cassidulina reniforme. Elphidium clavatum is dominant from 1973 to 1986 and 2002 to 2007, likely due to greater turbidity in the water column. We interpret the increased percentages of Spiroplectammina biformis over the same intervals to reflect a slightly lower salinity probably caused by meltwater. During a short time period, 1970 to 1973, Stainforthia concava dominates the benthic foraminiferal fauna interpreted to reflect increased productivity within a marginal ice zone. Other species as Islandiella norcrossi, Nonionellina labradorica, Islandiella helenae, and Melonis barleanus also indicate more nutrient-rich waters are present but not very abundant throughout the record probably due to the glacier proximal position of the study site. The stable isotope record (ƹ18O) shows lighter values from 2001 to 2007, which seem to correlate well with oceanographic monitoring data showing increasing core temperatures of West Spitsbergen Current. [ABSTRACT FROM AUTHOR]

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Stable isotope measurements of seawater from fjords in the Southern Patagonian Icefields area are presented for the first time. Stable water isotope variability was associated with physiographic and oceanographic factors. Isotope depletion and lower salinity were observed at lower depths, which is consistent with shallow estuarine waters. At greater depths, the characteristics of the modified Subantarctic water mass are inferred, and the glacier proximity and temperature do not show a clear relationship with the isotopic contents. These results could be a robust basis for a possible new proxy associated with changes in water masses, freshwater mixing, and paleoclimatic studies. [ABSTRACT FROM AUTHOR]

Greenland's coastal zone encompasses a large number of fjords, many of which are impacted by glacial meltwater runoff from land‐terminating glaciers. This type of fjord has received limited research attention, yet may represent the future of other fjords currently impacted by marine‐terminating glaciers that are retreating. In this study we describe the seasonal hydrography of Ameralik, a fjord on the southwest coast of Greenland impacted by a land‐terminating glacier. To complement this analysis we compare our results with observations from the neighbouring Godthåbsfjord, which receives meltwater from both land‐ and marine‐terminating glaciers. We find that the absence of subglacial discharge and glacial ice in Ameralik has a strong impact on the inner fjord density profiles and on circulation. The mean temperature of the upper 50 m layer was lower in Ameralik than Godthåbsfjord in May, but by September was 2°C higher in Ameralik. Dense coastal inflows occur in the late winter months in Ameralik, flushing the fjord and contributing to the return to a weakly stratified state. During the runoff period the surface waters are subject to estuarine circulation and wind forcing, while at intermediate depths a density gradient between the inner and outer fjord regions produces an intermediate baroclinic circulation, resulting in the exchange of water in this layer and the deepening of isopycnals. During summer a large fraction of the meltwater runoff is retained within the fjord rather than being exported. A substantial export of this summer accumulated freshwater occurs in connection with coastal inflows during winter. Plain Language Summary: Marine‐terminating glaciers around Greenland are retreating, impacting the adjacent fjords with potential changes in the pathways taken by glacial meltwater. Few studies focus on fjords that receive meltwater only from land‐terminating glaciers, although knowledge of these systems can help us better understand how water from melting glaciers eventually ends up in the ocean in a future warmer climate. Here we present a full year of temperature and salinity observations from one such fjord on the southwest coast of Greenland and use these measurements to describe seasonal changes in water properties and circulation patterns. We compare the results with observations from a neighbouring fjord which receives meltwater from both land‐ and marine‐terminating glaciers. This comparison allows us to link differences observed between the fjords with the water movements associated with the type of glacier. While physical properties of the fjords, such as sill depth, play an important role in the circulation, the meltwater pathway also influences fjord hydrography, most prominently in the surface layers. This study will help us to understand the potential future state for many Greenland fjords with glaciers that are presently marine‐terminating. Key Points: We present seasonal hydrography from a fjord system (Ameralik) in southwest Greenland impacted by a land‐terminating glacierWe compare our observations with the neighbouring Godthåbsfjord, which receives meltwater from both land‐ and marine‐terminating glaciersA large fraction of the seasonal freshwater input is retained in the fjord in summer and autumn, and is exported primarily in winter [ABSTRACT FROM AUTHOR]

Kola Bay is the most developed coastal area in the Russian part of the Barents Sea, but despite a long history of research, information about the local shallow-water benthic communities is lacking. For this reason, in this fjord area, we investigated the soft-bottom zoobenthos to determine its distribution and the factors influencing its abundance, biomass, and diversity. An analysis of 24 samples collected by divers at eight stations located at 7–8 and 10–15 m depths revealed 127 benthic taxa with an average abundance and biomass of 12,190 ± 4740 ind. m−2 and 30 ± 8 g m−2, respectively. The most severe abiotic conditions (high rates of sedimentation and eutrophication) were found at the head of the bay while the highest densities of predator red king crabs were registered in the middle part. The total benthic abundance and biomass, as well as the abundances of infauna, mobile taxa, subsurface deposit feeders, and surface deposit feeders, decreased towards the central part of the bay, reflecting gradients in the environmental conditions. In the inner part of the bay, we registered two communities: Cossura pygodactylata + Ciliatocardium ciliatum and Arctica islandica + Laonice cirrata, while the benthos of the middle part was less structured. Redundancy analysis indicated that the faunal abundances were influenced mainly by predator density (negative association) and the organic matter content (positive association). The total benthic biomass was negatively linked to water temperature due to the predominance of cold-water species in the area and a close positive association of this factor with crab abundance. In contrast, the highest diversity was registered at the warmer sites, which may have been a reflection of the borealization process in the Arctic. Our results contribute towards the proper management and conservation of the local benthic ecosystem and provide reference data for future monitoring programs and coastal management guidelines.

Labrador Inuit have expressed concern about the impacts of climate change on their health and well-being and their future access to marine resources, including fisheries. This study filled important knowledge gaps identified by the Nunatsiavut Government and Inuit communities regarding benthic biodiversity and habitat structure within major geomorphology features. Marine benthic surveys were conducted in three areas of ecological, cultural, and historical significance: Hebron Fjord, Okak Fjard, and the Nain archipelago, inclusive of a polynya, using a camera sled and a baited remote underwater video system. We documented the spatial extent of megabenthic diversity components and the high densities of dominant taxa, notably tube-dwelling anemones (cerianthids), brittle stars (ophiuroids), soft corals ( Gersemia sp.), and bristle worms (polychaetes). Species accumulation curves indicated that new species records are likely to be discovered. Vulnerable marine ecosystem (VME) indicator species and other key taxa provide seafloor structure for mobile species and important ecosystem functions, such as energy cycling, especially in the deeper areas of the fjord and fjard that are dominated by soft sediment. The sites with the highest benthic diversity, including the greatest densities of scallops and fish fauna, were in the archipelago and polynya, areas frequently used by Inuit for traditional harvesting. These findings were suggestive of a more direct linkage between these areas and trophic levels of greatest importance to Labrador Inuit. Understanding these patterns from the combined perspectives of Inuit and Western science in Nunatsiavut marine waters will guide resource management and protected area decisions, including those in the Nunatsiavut Government’s Imappivut Marine Planning Initiative.

Sedimentary environments in the Arctic are known to harbor diverse microbial communities playing a crucial role in the remineralization of organic matter and associated biogeochemical cycles. In this study, we used a combination of culture-dependent and culture-independent approaches to understanding the bacterial community composition associated with the sediments of a terrestrial versus fjord system in the Svalbard Arctic. Community-level metabolic profiling and growth response of retrieved bacterial isolates towards different carbon substrates at varying temperatures were also studied to assess the metabolic response of communities and isolates in the system. Bacterial species belonging to Cryobacterium and Psychrobacter dominated the terrestrial and fjord sediment retrievable fraction. Amplicon sequencing analysis revealed higher bacterial diversity in the terrestrial sediments (Shannon index; 8.135 and 7.935) as compared to the fjord sediments (4.5–5.37). Phylum Proteobacteria and Bacteroidetes dominated both terrestrial and fjord sediments. Phylum Verrucomicrobia and Cyanobacteria were abundant in terrestrial sediments while Epsilonbacteraeota and Fusobacteriia dominated the fjord sediments. Significant differences were observed in the carbon substrate utilization profiles between the terrestrial and fjord sediments at both 4 °C and 20 °C incubations (p < 0.005). Utilization of N-acetyl-D-glucosamine, D-mannitol and Tween-80 by the sediment communities and bacterial isolates from both systems, irrespective of their temperature incubations implies the affinity of bacteria for such substrates as energy sources and for their survival in cold environments. Our results suggest the ability of sediment bacterial communities to adjust their substrate utilization profiles according to condition changes in the ecosystems and are found to be less influenced by their phylogenetic relatedness. [ABSTRACT FROM AUTHOR]

Recent research has illuminated biological processes taking place during the polar night in the high Arctic, while simultaneously, the polar regions are undergoing rapid climate-driven change. There is a pressing need for research to establish baseline conditions and understand the influence of oceanographic factors on polar communities. We collected plankton samples in Kongsfjorden (Svalbard, Arctic) in January 2020, in order to study the early life-history stages of benthic invertebrates during the polar night. Specimens were identified using morphology and DNA barcoding. During our field campaign, a strong wind event occurred, which caused upwelling of Arctic water in the fjord. Therefore, we also investigated the influence of oceanographic factors on benthic invertebrate larvae, including temperature, salinity, and depth. Our samples included 19 different species or morphotypes belonging to ten invertebrate phyla, including three embryo morphotypes. The collection of embryos indicates that at least some taxa are reproducing in the polar night. Larval community structure at shallow stations was significantly different before and after the upwelling event. Our samples also reflected patchiness in the larval community and a significant influence of depth. The most common nutrition mode among the larval taxa we collected was lecithotrophy (energy derived from maternal yolk), but we also collected a few taxa that may be planktotrophic (feeding). Development via lecithotrophy could increase larval survival and settlement success in the low-food environment of the Arctic winter. This study provides essential data on the early life-history stages of benthic invertebrates in an understudied season. [ABSTRACT FROM AUTHOR]

The temporal dynamics of five copepod species common to coastal waters of the Pacific Northwest were examined in relation to variability in spring temperature and phytoplankton dynamics in 2008, 2009, and 2010 in Rivers Inlet, British Columbia, Canada. The five species were differentiated by life history strategies. Acartia longiremis, Metridia pacifica, and Paraeuchaeta elongata remained active over most of the year. By contrast, the reproductive effort of Eucalanus bungii and Calanus marshallae was concentrated over the spring period and they spent most of the year in diapause as C5 copepodites. A delay in the timing of the spring bloom was associated with a shift in the phenology of all species. However, following the delay in spring bloom timing, recruitment to the G1 cohort was reduced only for E. bungii and C. marshallae. Recruitment successes of E. bungii and C. marshallae was also drastically reduced in 2010, an El Niño year, when spring temperatures were highest. Reasons for the observed differential response to spring environmental forcing, and its effect on upper trophic levels, are discussed.

Around the Greenlandic and Antarctic coastlines, sediment plumes associated with glaciers are significant sources of lithogenic material to the ocean. These plumes contain elevated concentrations of a range of trace metals, especially in particle bound phases, but it is not clear how these particles affect dissolved (

Microorganisms play a crucial role in biogeochemical processes affecting the primary production and biogeochemical cycles of the ocean. In subpolar areas, the increment of the water temperature induced by climate change could lead to changes in the structure and activity of planktonic microbial communities. To understand how the structure of the microbial community in Chilean Patagonian fjords could be affected by climate change, we analyzed the composition of the prokaryotic community (bacteria-archaea) in two fjords (Pia and Yendegaia) with contrasting morphological and hydrological features. We targeted both the standing stock (16S rRNA genes) and the active fraction (16S rRNA transcripts) of the microbial communities during two consecutive austral winters. Our results showed that in both fjords, the active community had higher diversity and stronger biogeographic patterns when compared to the standing stock. Members of the Alpha-, Gamma-, and Deltaproteobacteria followed by archaea from the Marine Group I (Thaumarchaeota) dominated the active communities in both fjords. However, in Pia fjord, which has a marine-terminating glacier, the composition of the microbial community was directly influenced by the freshwater discharges from the adjacent glacier, and indirectly by a possible upwelling phenomenon that could bring deep sea bacteria such as SAR202 to the surface layer. In turn, in the Yendegaia, which has a land-terminating glacier, microbial communities were more similar to the ones described in oceanic waters. Furthermore, in Yendegaia fjord, inter-annual differences in the taxonomic composition and diversity of the microbial community were observed. In conclusion, Yendegaia fjord, without glacier calving, represents a fjord type that will likely be more common under future climate scenarios. Our results showing distinct Yendegaia communities, with for example more potential nitrogen-fixing microorganisms (Planctomycetes), indicate that as a result of climate change, changing planktonic communities could potentially impact biogeochemical processes and nutrient sources in subantarctic fjords.

Causes and consequences of jellyfish bloom formation are subject to controversial discussions worldwide. While medusae have been studied to a broader extent, the knowledge on polyp stages of scyphozoans is limited thus hampering reliable prediction of jellyfish bloom formation. This study describes the occurrence, abundance, habitat characteristics and interactions of scyphozoan Aurelia sp. polyp colonies with other fouling organisms in intertidal and subtidal sectors of Trondheimsfjorden (Norway). In total, 982 polyps were found on 70 substrata of varying material types during a field survey in spring-summer 2018 along a longitudinal gradient within and outside Trondheimsfjorden. The polyps were identified as Aurelia sp. based on molecular species identification. Most polyps were found in bays with macroalgae canopy on the down facing side of artificial and natural substrata (rocks, concrete, iron) and inside rock cracks. Polyp microhabitats included the surface of Ascidia mentula (solitary ascidian), increments of Pomatoceros triqueter (polychete) tubes and dead Balanus balanoides (barnacle) shells. Based on the deployment of settling plates, abundance of Aurelia sp. polyps ranged from 1.2 (± 0.7) to 0.12 (± 0.07) polyps cm–2. Settlement occurred either directly on the PVC settling plates or as epibionts on the ascidian Ascidia mentula and on barnacle shells of Balanus balanoides. This study provides insights into the potential of local Aurelia sp. polyps contributing to the seasonal occurrence and abundance of Aurelia sp. in fjord systems, where intensive blooms occur annually.