Southeastern Hudson Bay Research Articles

In situ spectroradiometric estimation of microalgal biomass in first-year sea ice

First- and multi-year sea ice are colonized by microalgae, whose biomass modifies the spectral distribution of underice downwelling irradiance. It is proposed that an index of algal biomass in the first-year ice may be derived from the ratio of underice irradiance at a wavelength where absorption by chlorophyll a is high to a wavelength where absorption by the photosynthetic pigments is low and transmission through the ice is high. In southeastern Hudson Bay (Canadian Arctic), the irradiance ratio (671∶540 nm) accounts for 55% of the variance in chlorophyll a, indicating that the in situ biomass of algae in first-year ice can be estimated from spectral measurements of underice downwelling irradiance.

Coupling between ice microalgal productivity and the pelagic, metazoan food web in southeastern Hudson Bay: a synthesis of results

A multidisciplinary study of the ice algal production cycle in southeastern Hudson Bay in spring, 1986, provided an exceptional opportunity to observe trophic interaction between ice algae and metazoan zooplankton. During the ice algal bloom, females of the biomass-dominant copepod species, Calanus glacialis and Pseudocalanus spp. (predominantly P. minutus), grazed at night near the ice-waste interface. Feeding activity of these copepods significantly increased after the start of ice melt in mid-May when ice algae were released in large quantities into the water column. Copepod egg production was negligible during the ice algal bloom, then increased by approximately two orders of magnitude by mid-June. While changes in Calanus productivity can be attributed to increases in female-specific egg production rates alone, Pseudocalanus productivity was also substantially augmented by the appearance in late May of females of a second species, P. newmani. The data are consistent with the hypothesis that the major sources of nutrition for copepod production during this period are scdimenting ice algae (during and immediately after the bloom at the ice-water interface) and diatoms seeded from the interfacial layer and actively growing in the water column (in late May and Junnc). Larvae of Arctic cod and sand lance, the yolk-sac stages of which were found in samples immediately after the onset of ice melt, were in a good position to feed on the resulting high concentrations of copepod nauplii in mid-June. These results therefore suggest a strong coupling between the ice algal production cycle and production cycles in the pelagic food web in this region.

Production of fish larvae and their prey in subarctic southeastern Hudson Bay

In the ice-covered southeastern Hudson Bay (northern QuCbec, Canada), marine fish exhibited 2 distinct reproduction strategies. Sand lance Amrnodytes sp. and Arctic cod Boreogadus saida produced large numbers of small larvae that hatched before the ice break-up when the abundance of prey (copepod eggs and nauplii) was low. Feeding incidence was low and the larvae fed on relatively small prey. A morphometric index of condition suggested that the 2 species suffered from starvation at first feeding. This critical period was approximately synchronized with peak abundance of prey, possibly an adaptation to minimize starvation mortality. Shchaeidae and Cottidae produced small numbers of large larvae that fed efficiently on relatively large prey before yolk resorption. These larvae emerged after the ice break-up, when phytoplankton production was well under way and prey were abundant. Interannual variations in the timing between first feeding and the production of prey could influence recruitment in sand lance and Arctic cod but are unlikely to affect the early survival of Stichaeidae and Cottidae.

Dynamical evaluation of the surface circulation using remote sensing of drifting ice floes

An analysis of ice drift from consecutive Landsat multispectral scanner images of the same area taken at 24‐h interval allowed the calculation of the surface circulation using a dynamical approach. Comparison between calculated and measured values shows that this method leads to a good approximation of the surface circulation in a region where ice floes are free drifting. On the other hand, the sole use of the floe drift over time to evaluate the currents leads to results that are far from the measured values. Tests made using various air and ice drag coefficients, and wind speeds and directions for different drift distances show that the error associated with these parameters is small. Although the values obtained using the numerical data involved considerably more effort and expense, the results were not significantly better than those found using photographic products. A good approximation of the surface circulation can thus be made using a simple digitization of the floe positions on photographic products. Application of the methodology to a set of four image pairs led to the recognition of two modes of circulation in southeastern Hudson Bay in spring 1985. This method can thus become a useful tool for rapid evaluations of surface currents in ice‐covered areas that can hardly be sampled otherwise.

LIGHT AND NUTRIENT LIMITATION OF SEA‐ICE MICROALGAE (HUDSON BAY, CANADIAN ARCTIC)1

ABSTRACTChanges in the biochemical composition of sea‐ice microalgae (southeastern Hudson Bay, Canadian Arctic) were used to assess the light and nutrient status of cells growing at the ire‐water interface. These changes allowed us to test the hypothesis that ire algae are limited by light at the beginning of their growth season and become periodically limited by nutrients as the season progresses. During the vernal growth season, three patterns of variation in cellular components were found in response to changes in environmental conditions. 1) Chlorophyllsaandc,ATP, carbohydrate, and carbon followed the seasonal increase in under‐ice irradiance, which was mainly mused by melting of the snow cover. 2) Dissolved and biogenic silicon underwent periodic variations, which were coupled to the fortnightly neap‐spring cycle of tidal mixing. 3) Cellular contents of free amino acids, protein, and total nitrogen remained relatively constant during the season. An early decrease in intracellular chlorophyllsaandcsuggests that ire algae did respond to small changes in solar irradiance by changing the pigment composition of their photosynthetic units. Seasonal increases in ATP, carbohydrate, and total carbon indicate light limitation in April, followed in May by a period of excess irradiance and/or nutrients in short supply. The seasonal increase in ATP and the high values of the ratio free amino acids: protein show that neither phosphorus nor nitrogen limited algal growth at the ire‐water interface. In May, higher values of carbohydrate: protein, carbon: nitrogen, carbon: chlorophylla,and also carbon: silicon and ATP: silicon indicate that the ice algae became silicon‐deficient in their natural environment. Following a period of light limitation, at the beginning of the season, ice‐algal growth became silicon‐limited, when in situ irradiance and the accumulated algal biomass were high and the tidally‐driven nutrient supply was not strong enough to satisfy algal nutrient requirements.

210Pb and 137Cs chronology of sediments from small, shallow Arctic lakes

Arctic environmental conditions present special difficulties with the use of nuclides 210Pb and 137Cs for measuring lake sediment chronology. Fluxes of these nuclides are lower in the Arctic than in mid-latitudes, shortening the history that can be resolved. Ice prevents atmospheric input of nuclides to sediment during much of the year and can cause redistribution of sediment in shallow lakes. Results from analyses of seven sediment cores from two lakes on the Belcher Islands in southeastern Hudson Bay show that sediment redistribution by ice is a major process in one of the lakes. In order to measure an undisturbed sedimentation rate, it is necessary that a total input or flux of 137Cs and 210Pb be measured or estimated. Total unsupported 210Pb in the area, 14.8 dpm/cm 2, is the average of measurements in three cores from two lakes that have consistent total 137Cs inventories closest to the estimated 137Cs flux. Cores from undisturbed sites have slower sedimentation rates, and 137Cs appears in layers dated before the early 1950s when it would have first appeared in sediment. 137Cs cannot be used for chronological evaluation of these cores. Mixing of surface sediment layers and lower dating resolution than in other cores are responsible for the apparent downward movement of this nuclide. 210Pb measurements of undisturbed sedimentation rates in the lakes range from 0.0044 to 0.0180 g/cm 2/a. The sedimentation rate in a lake used for raw sewage oxidation doubled after the beginning of sewage input. Rates at sites where sediment is redistributed range from 0.0259 to 0.0309 g/cm 2/a with similarly higher total 137Cs and unsupported 210Pb values. Dates of sediment layers measured using the constant rate of supply model are verified by 210Pb profile discontinuities corresponding to major storms in 1958 and in 1940.

Winter Offshore/Onshore Wind Differences in Southeastern Hudson Bay, Canada

Acquisition of two 38-day wind data sets collected over a fast-ice shelf and at a nearby coastal weather station (Kuujjuarapik) in Hudson Bay allowed the calculation for the first time of an offshore/onshore wind speed ratio for an ice-covered environment. Mean wind over the ice was 29% higher than at the coast, compared to values of 65% for open ocean locations. This reflects the effect of the higher drag coefficient of the sea ice that more strongly attenuates the wind than does the sea surface. The data set also allowed the evaluation of the change in the wind field by local topography. Thus, a strong orographic effect was found in the SW quadrant, as winds of less than 5 m/s were deflected toward the SE and NW.

Nitrogenous nutrition of sea-ice microalgae

There are indications that the final biomass attained by sea-ice microalgae in southeastern Hudson Bay is nitrogen limited. The present study investigates the possibility that the rate at which the final yield is approached is also nitrogen limited. Nutrient data suggest that nitrogen was actively taken up by the microalgae, and periodically replenished by mixing processes related to fortnightly tides. High molar C:N ratios (>15), typical of nitrogen-deficient cells, have been observed at times of low dissolved inorganic nitrogen. Absolute transport rates of nitrogen were estimated from natural changes in dissolved inorganic and particulate organic nitrogen. Cell losses and nitrogen uptake rates were highest during periods of maximum current speed, suggesting that the rate of biological production at the ice-water interface could be limited by the accumulated biomass. These results suggest (1) that the sea-ice microalgae in southeastern Hudson Bay are nitrogen limited in their natural environment, and (2) that nutrient replenishment and perhaps losses of biomass governed by fortnightly tidal mixing periodically enhance the growth of microalgae at the ice-water interface.

Factors affecting fast‐ice consolidation in Southeastern Hudson Bay, Canada

Abstract Analysis of satellite images of southeastern Hudson Bay taken over aperiod of 13 years led to the classification of ice distribution into three categories. The first category is for complete fast‐ice cover of the area, the second for fast ice covering only half the area and the third for the absence of fast ice extending away from the coast. Of the three factors considered‐ wind, water circulation and air temperature—the occurrence of strong southwesterly winds during the freezing period is probably the main factor regulating the extent of the fast‐ice cover for the first two categories. Through melting action, above‐freezing air temperatures appear to prevent the consolidation of ice into a solid cover giving rise to the rare third category of ice distribution.

Grazing and sedimentation of ice algae during and immediately after a bloom at the ice-water interface

Sinking of pigmented particulate matter during and immediately after an ice algal bloom was studied in southeastern Hudson Bay at a 45 m deep station, using consecutive short-term deployments of sediment traps 30 m below the undersurface of the ice. Cell sinking and grazing by herbivores were assessed by measuring the vertical fluxes of chlorophyll a and phaeopigments. There were 2 peaks of cell sedimentation, a minor one during the first half of the bloom (mid-April) and a major one at the end of the bloom (mid-May); both were related to atmospheric warming events. The fluxes of both phaeopigments and fecal pellets (mainly from large herbivores) increased at the end of the bloom as ice algae were released from the ice environment. The total export of ice algae to the benthos (sinking cells + fecal pellets) was estimated to be ca 20 % of the ice algal production during the measurement period. A large proportion of ice algal production (ca 30 %) was still suspended in the upper water column at the end of the sampling season. The fate of the remaining 50 '10 is not known, but it is hypothesized that a significant fraction was retained in the pelagic environment.

The influence of a river plume on the sea-ice meiofauna in south-eastern Hudson Bay

Outflow from the Great Whale River produces a substantial freshwater layer (plume) beneath the winter ice cover and above water of higher salinity in south-eastern Hudson Bay. In 1983, samples of the lower-ice fauna and of zooplankton beneath the ice, were taken within, below and beyond the offshore reach of the plume. Nematodes accounted for the highest numbers (mean of 1956 1 1in the lower 3 cm of ice), and copepods, mainly Harpacticus and Halectinosoma with fewer Tisbe and Oithona, for the greatest biomass. All ice-inhabiting taxa were also found in the water below the ice, but many zooplankters occurring immediately beneath the ice did not form part of the ice fauna. No major qualitative differences were evident between the ice communities existing above the plume and offshore from it, but quantitative distinctions were readily apparent. Animals were consistently more concentrated (by 2–3 orders of magnitude) in the lower 3 cm of the ice than in the water immediately below, both over the plume and outside it. Except for the dominant rotifers in the plume, the concentration of zooplankton there was only 10% of that found in the surface water outside the plume. The river plume exerts a strong influence over the quantity of the fauna in the sea ice immediately above it. Changes in location and extent of the plume therefore may have an important effect on the food chain based in the sea ice.

Late winter – early spring sedimentation off the Great Whale River, southeastern Hudson Bay

Sediment traps were used to measure particle-settling fluxes in serial moorings offshore of Great Whale River (Hudson Bay), both under the late winter sea-ice cover and during and after breakup. Before breakup, the settling fluxes ranged between 0.25 and 2 g cm−2 100 a−1, increasing from April to May in response to the progressively larger under-ice algal biomass. Fluxes also increased with depth. During and after breakup, including the early summer period of peak runoff, sedimentation rates increased to values of up to 33 g cm−2100 a−1. These fluxes agree with the mean sedimentation rate determined from 210Pb activities in the underlying sediments.

Underice grazing by planktonic, calanoid copepods in relation to a bloom of ice microalgae in southeastern Hudson Bay

A spring bloom of ice microalgae was observed at a station on southeastern Hudson Bay. Levels of pheopigments in guts of females of Calanus glacialis and Pseudocalanus spp., the dominant calanoid copepods in this region, increased by an order of magnitude after onset of the bloom. Feeding had a diel cycle and was associated with a nighttime migration of females to the ice‐water interface. Fragments of pennate, ice diatoms were observed microscopically in most guts of Calanus and Metridia, but only rarely in Pseudocalanus, which may have been feeding on flagellates associated with the ice‐water interface. The results suggest that ice microalgae in Hudson Bay are a regular and significant source of nutrition for planktonic copepods before the phytoplankton bloom. The structure of the layer at the ice‐water interface may influence feeding behavior on ice microalgae by arctic copepods.

Proterozoic ministromatolites with radial‐fibrous fabric

ABSTRACTSmall digitate stromatolites with diameters in the range of 0·2–20 mm (ministromatolites) are common in Early and Middle Proterozoic carbonate sequences, and extend stratigraphically from the Archaean to the Holocene. An occurrence of columnar and stratiform types exhibiting a primary or early diagenetic radial‐fibrous fabric and microscopically crinkled (microcrenate) lamination is described from the ˜ 1·9 Gyr old Belcher Supergroup (McLeary Formation) in southeastern Hudson Bay, Canada. The structures, which can be considered to be a variety of tufa, are unusually well preserved because of early diagenetic silicification. Columnar types are referable to Pseudogymnosolen (Asperia), and are morphologically similar to other occurrences of these taxa in coeval dolostones in northwestern and eastern Canada, where the fabric is normally preserved by a secondary mosaic of dolomite. The textural evidence of angulate cross‐sections and rectilinear divergent patterns indicates that the radial‐fibrous fabric represents primary or very early diagenetic precipitation, and that pseudogymnosolenids with mosaic dolomite originally also had radial‐fibrous structure. The precipitation may have been within, or on, microbial mats.

Photosynthetic and pigment responses of sea-ice microalgae to changes in light intensity and quality

Responses of sea-ice microalgae to changes in light intensity and quality were studied from March to May 1983 on the first-year ice of southeastern Hudson Bay (Canadian Arctic). Photosynthetic parameters P B max , α B and β B of the ice algae progressively increased throughout the sampling season. This increase paralleled the under-ice irradiance; it also paralleled the progressive increase of the diatom Nitzschia frigida in the population, from ≈45% of the cells at the end of March to almost 100% in May. The photosynthetic efficiency ( α B ) and several other photosynthetic parameters doubled when the algae were incubated under blue light, as compared with white light. This result stresses the importance of considering the photosynthetically usable radiant energy (PUR) rather than the photosynthetically available radiation (PAR), when measuring photosynthetic responses to light colour. Ice algae generally had high concentrations of chlorophyll c, which could be an adaptive response to their blue-green light environment. When incubated under white illumination, which corresponded to widening the light spectrum, the algae responded by increasing their proportions of carotenoids and chlorophyll c. These changes were in agreement with the theory of complementary chromatic adaptation. The bottom ice environment of Hudson Bay being limited by light intensity and nutrient resources, the ability to chromatically adapt may become a critical factor in species competition.

Nutrient limitation of the bottom‐ice microalgal biomass (southeastern Hudson Bay, Canadian Arctic)1

In April 1983, differential‐enrichment bioassays were conducted on natural sea‐ice microalgae from Hudson Bay, Canadian Arctic. Incubations were done both in the laboratory (at about 4°– 5°C), and in situ at the ice‐water interface (−1.5°C). Actual growth of the cultures was nutrient limited. On the basis of our observations and using recalculated data from the literature, we tentatively set the mean generation time of Arctic‐ice microalgae between 8 and 17 days. Nitrogen was demonstrated to govern the algal yield when illumination and grazing allowed the algae to grow. The low (NO3− + NO2− + NH4+):PO43− mean ratio (5.9) in the water at the ice interface leads to the same conclusion. In situ dissolved inorganic nitrogen and phosphorus progressively decreased during the course of sampling, but were never exhausted. We hypothesize that the Ks of epontic as well as of other benthic microalgae is higher than that of phytoplankton, so that they cannot deplete the natural nutrient reservoir. We conclude that the bottom‐ice dynamics is controlled not only from above, by the seasonal (climatic) changes in light intensity as generally assumed, but also from below, by the shorter term (hydrodynamic) events of vertical mixing that replenish the ice‐water interface with nutrients.

Physical control of the horizontal patchiness of sea-ice microalgae

Factors controlling the horizontal distribution of sea-ice microalgae were studied in Southeastern Hudson Bay and adjacent Manitounuk Sound (Canadian Arctic). Both large (-30 km) and small (0.3 to 500m) scales of variability were investigated. Results showed that salinity was the most important factor controlling large scale distribution of the ice-microalgal biomass, through its effect on the structure of the ice (surface available for colonization). Variation in the thickness of the snow-ice cover, which determines irradiance at the bottom of the ice, was the factor controlling distribution of the algal biomass at smaller scale (diameter of patches of microalgal biomass ranging between 20 and 90 m). The relation between ice-algal abundance and snow-ice thickness changed however over the season. At the beginning of the growing season (in April when the bottom-ice irradiance was higher than a minimum critical irradiance), maximum algal biomass was observed under areas covered by the smallest snow depths. Towards the end of the season, when light transmitted through the snow-lce cover increased, maximum algal biomass was observed under areas covered by the deepest snow. This suggests that ice algae have both minimum and maximum critical light levels. The minimum level is the irradiance below which there is no photosynthetic activity (Imi, 7.6 CL Einst m-2 S-') and the maximum level corresponds to the inhibiting light intensity, which may vary during the growth season. The horizontal heterogeneity of the snow-ice cover, whlch is influenced by wind at the air-ice interface, thus provides diversified bottom-ice habitats where irradiance is compatible or not with the physiological limits of the ice microalgals cells. This results in a strong patchiness in distribution of ice-bottom microalgae.

Ships' Log-Books, Sea Ice and the Cold Summer of 1816 in Hudson Bay and Its Approaches

Descriptions of sea ice in Hudson's Bay Company ships' log-books and trading post journals are used to reconstruct sea ice conditions in Hudson Bay, James Bay, and Hudson Strait in the summer of 1816. The results demonstrate that exceptionally late sea ice dispersal occurred in James Bay, southeastern Hudson Bay, and at the western extremity of Hudson Strait. A relatively intense flow of ice in the Labrador current occurred at the eastern extremity of Hudson Strait. These patterns of ice behaviour are indicative of the prevalence of northwesterly atmospheric circulation over this region in the summer of 1816. Key words: sea ice, Hudson Bay, Hudson Strait, 1816, ships' log-books

Sea ice diatoms from Manitounuk Sound, southeastern Hudson Bay (Quebec, Canada). I. Family Naviculaceae

More than 110 species of diatoms were identified from samples collected from Manitounuk Sound, Hudson Bay, in 1978. We presently deal with six genera, belonging to the family Naviculaceae; Diploneis (3 taxa), Gyrosigma (3 taxa), Pinnularia (18 taxa), Pleurosigma (4 taxa), Stauroneis (1 taxon), and Stenoneis (1 taxon).All the species were reevaluated and complete illustrated descriptions, biometric data, and worldwide distributions are given. Two new species and two varieties are described and a new combination is proposed.

Dorset Settlement Patterns in Newfoundland and Southeastern Hudson Bay

The history of dorset eskimo archaeological research now spans a half-century and appears to be fully mature. At the outset, progress in this research was sporadic, but in the last two decades momentum has increased and we have achieved many significant clarifications of the general Dorset problem. These include a firm definition of Dorset people as true Eskimos, and further insights with respect to their temporal and geographic spread throughout the central and eastern Arctic, their localized adaptations to changing environments, and, as a persistent theme, their noteworthy cultural conservatism through time. This paper deals primarily with the middle and late stages of Dorset culture as seen in marginal settlements in western Newfoundland and southeastern Hudson Bay.In reviewing past investigations of Arctic prehistory, I have been struck by our substantive preoccupation with material culture, mainly with artifacts. That is quite natural because our powers of interpretation and reconstruction are circumscribed in well-known ways by the paucity of our field data, particularly so as we are dealing with the cultures of Arctic hunter-gatherers. Therefore, we should be forgiven a natural tendency to submerge in the warm realities of artifacts and the comforting procedures of mensuration and taxonomy. These are legitimate scientific concerns, and they may lead us toward useful statistical formulations, definitions of cultural parameters and complexes, and so on. However, to the extent that we think solely in such statistical and materialistic terms, the fundamental human nature of our quest may be diminished, if not lost altogether.