Ice Microbial Communities Research Articles

Molecular approach (PCR-DGGE) to diet analysis in young Antarctic krill Euphausia superba

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 319:155-165 (2006) - doi:10.3354/meps319155 Molecular approach (PCR-DGGE) to diet analysis in young Antarctic krill Euphausia superba Daniel L. Martin1,3, Robin M. Ross1, Langdon B. Quetin1, Alison E. Murray2,* 1Marine Science Institute, University of California, Santa Barbara, California 93106, USA 2Earth and Ecosystem Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, Nevada 89512, USA 3Present address: Department of Biological Sciences, LSCB-124, University of South Alabama, Mobile, Alabama 36688, USA *Corresponding author. Email: alison@dri.edu ABSTRACT: Antarctic krill Euphausia superba Dana comprise a key component of the Southern Ocean food web, yet despite decades of research, questions concerning the regional, seasonal and ontogenetic differences in their diet remain. All current methods used to characterize krill diet have limitations for identifying the full complement of the diet. Using DNA as a marker molecule, our goal in this study has been to evaluate the efficacy of a PCR-DGGE (denaturing gradient gel electrophoresis) approach targeting the 18S rDNA gene to discriminate among diet constituents in gut and fecal pellet samples from young Antarctic krill relative to their feeding environment — the seawater and sea ice microbial community. We conducted 2 laboratory-based feeding experiments with known food items and 3 field samplings of both the krill and their feeding environment. Sequenced PCR-DGGE phylotypes from laboratory trials clearly distinguished diatom and copepod prey, while in situ feeding analyses revealed that a broad diversity of taxa were ingested, including diatoms (Bacillariophyta, the most prevalent group detected), dinoflagellates, cryptomonads, prasinophytes, ciliates, cercozoans, choanoflagellates, turbellarians and (possibly) sponge larvae. Band image analyses allowed environmental and diet phylotypes to be matched. On average, 32% of those from the environment were present in the diet; conversely, of the phylotypes detected in the diet, an average of 59% were in common with the environment. Changes in environmental phylotypes among sampling dates were reflected by similar changes in the krill diet as potential prey diversity (richness) decreased during a phytoplankton bloom. KEY WORDS: Antarctic krill · Euphausia superba · Diet · DGGE · 18S rDNA · Sea ice microbial community · Omnivory Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 319. Online publication date: August 18, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Spatial and seasonal heterogeneity of sea ice microbial communities in the first-year ice of Terre Adélie area (Antarctica)

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 43:95-106 (2006) - doi:10.3354/ame043095 Spatial and seasonal heterogeneity of sea ice microbial communities in the first-year ice of Terre Adélie area (Antarctica) Michel Fiala1,*, Harri Kuosa2, Elzbieta E. Kopczyńska3, Louise Oriol1, Daniel Delille1 1Observatoire Océanologique, Universite P. et M. Curie, UMR-CNRS 7621, 66651 Banyuls-sur-mer cedex, France 2Finnish Institute of Marine Research, POB 33, 00931 Helsinki, Finland 3Department of Antarctic Biology, Polish Academy of Sciences, Ustrzycka 10/12, 02 141 Warszawa, Poland *Email: mfiala@obs-banyuls.fr ABSTRACT: Spatial and temporal changes in sea ice microbial communities were investigated at 4 stations located along a south-north transect on the land-fast ice of Dumont d’Urville station area (Adélie Land, 66°40’S, 141°01’E) during the ice coverage period (April to December). A seasonal pattern was observed in microalgae, bacteria and protozoan abundance distribution. A maximum chlorophyll a concentration occurred during fall ice formation in the surface layer with the highest values at the near-shore station (100 to 215 µg l–1). A second maximum was observed before ice breaking in the bottom ice (50 to 90 µg l–1). Microalgal communities were dominated by diatoms (>86% of the total cells), mainly represented by Fragilariopsis, Nitzschia, Navicula and Pseudo-nitzschia species. Fragilariopsis curta was the dominant species during the first bloom whereas Fragilariopsis cylindrus, Nitzschia longissima and Tropidoneis sp. were the main contributors during the second bloom at the bottom ice core. Maximum protozoan abundance was recorded during the fall bloom in the surface layer with dominance of ciliates, which contributed more than 75% of total cell numbers. During this period, the maximum ciliate abundance was associated with the maximum bacteria and diatom numbers and microalgal biomass. The dramatic decrease of the ice algal biomass from south to north paralleled that of the underlying water phytoplankton available for new ice incorporation. The spatial algal biomass decrease could explain the parallel decrease in the abundance of bacteria and heterotrophic ciliates through trophic interactions. KEY WORDS: Antarctica · Land-fast ice · Microbial communities · Chlorophyll a · Nutrients Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 43, No. 1. Online publication date: May 03, 2006 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2006 Inter-Research.

Effects of Incubation Temperature on Growth and Production of Exopolysaccharides by an Antarctic Sea Ice Bacterium Grown in Batch Culture

The sea ice microbial community plays a key role in the productivity of the Southern Ocean. Exopolysaccharide (EPS) is a major component of the exopolymer secreted by many marine bacteria to enhance survival and is abundant in sea ice brine channels, but little is known about its function there. This study investigated the effects of temperature on EPS production in batch culture by CAM025, a marine bacterium isolated from sea ice sampled from the Southern Ocean. Previous studies have shown that CAM025 is a member of the genus Pseudoalteromonas and therefore belongs to a group found to be abundant in sea ice by culture-dependent and -independent techniques. Batch cultures were grown at -2 degrees C, 10 degrees C, and 20 degrees C, and cell number, optical density, pH, glucose concentration, and viscosity were monitored. The yield of EPS at -2 degrees C and 10 degrees C was 30 times higher than at 20 degrees C, which is the optimum growth temperature for many psychrotolerant strains. EPS may have a cryoprotective role in brine channels of sea ice, where extremes of high salinity and low temperature impose pressures on microbial growth and survival. The EPS produced at -2 degrees C and 10 degrees C had a higher uronic acid content than that produced at 20 degrees C. The availability of iron as a trace metal is of critical importance in the Southern Ocean, where it is known to limit primary production. EPS from strain CAM025 is polyanionic and may bind dissolved cations such at trace metals, and therefore the presence of bacterial EPS in the Antarctic marine environment may have important ecological implications.

Development of sea ice microbial communities during autumn ice formation in the Ross Sea

Sea ice communities were sampled across the Ross Sea in the austral autumn. The biota in first-year pack ice was assessed by measuring chlorophyll a (chl a), phaeopigments, total particu- late carbon and nitrogen (POC and PON, respectively) and collecting samples for identification by microscopy. Physical and chemical parameters were also measured to characterize the environ- ment. Chl a concentrations in ice ranged from 0 to 96.9 µg l -1 in discrete samples and from 0.02 to 20.9 mg m -2 for values integrated throughout floes. Maximum values were similar to those observed in first-year pack ice at other Antarctic locations. Chl a concentrations varied with ice structure and with latitude. POC:chl a and C:N ratios (molar) were high, possibly indicating detritus accumulations. The higher chl a levels north of approximately 72° S were apparently a result of ice forming in the south early in the season with subsequent advection to the north. These dynamics would result in older ice in the mid- or northern pack ice zone that was maintained in a favorable light and temper- ature regime during the seasonal progression of formation and drift. Chlorophyll levels were low in surface-layer communities. High chlorophyll concentrations were associated with internal communi- ties. Bottom-layer algal populations, while present, did not reach the levels of high biomass reported for autumn blooms in some land-fast ice regions. Apparent nutrient and CO2 depletion were corre- lated with biomass parameters but accounted qualitatively for only a fraction of the biomass accumu- lation measured. Overall, autumn ice-associated production in the Ross Sea may be lower than expected because of the ice drift dynamics, apparently low production in the near-surface layers of first year ice flows, and the absence of rich bottom-layer assemblages.

Origin and Phylogeny of Microbes Living in Permanent Antarctic Lake Ice.

A BSTRACTThe phylogenetic diversity of bacteria and cyanobacteria colonizing sediment particles in the permanent ice cover of an Antarctic lake was characterized by analyses of 16S rRNA genes amplified from environmental DNA. Samples of mineral particles were collected from a depth of 2.5 m in the 4-m-thick ice cover of Lake Bonney, McMurdo Dry Valleys, Antarctica. A rRNA gene clone library of 198 clones was made and characterized by sequencing and oligonucleotide probe hybridization. The library was dominated by representatives of the cyanobacteria, proteobacteria, and Planctomycetales, but also contained diverse clones representing many other microbial groups, including the Acidobacterium/Holophaga division, the Green Non-Sulfur division, and the Actinobacteria. Six oligonucleotide probes were made for the most abundant clades recovered in the library. To determine whether the ice microbial community might originate from wind dispersal of the algal mats found elsewhere in Taylor Valley, the probes were hybridized to 16S rDNAs amplified from three samples of terrestrial cyanobacterial mats collected at nearby sites, as well as to bacterial 16S rDNAs from the lake ice community. The results demonstrate the presence of a diverse microbial community dominated by cyanobacteria in the lake ice, and also show that the dominant members of the lake ice microbial community are found in terrestrial mats elsewhere in the area. The lake ice microbial community appears to be dominated by organisms that are not uniquely adapted to the lake ice ecosystem, but instead are species that originate elsewhere in the surrounding region and opportunistically colonize the unusual habitat provided by the sediments suspended in lake ice.

Lake ice microbial communities (LIMCO) — biology of a periodic ecotone

Lake ice microbial communities (LIMCO) — biology of a periodic ecotone

Poles apart: biodiversity and biogeography of sea ice bacteria.

This review introduces the subjects of bacterial biodiversity and biogeography. Studies of biogeography are important for understanding biodiversity, the occurrence of threatened species, and the ecological role of free-living and symbiotic prokaryotes. A set of postulates is proposed for biogeography as a guide to determining whether prokaryotes are "cosmopolitan" (found in more than one geographic location on Earth) or candidate endemic species. The term "geovar" is coined to define a geographical variety of prokaryote that is restricted to one area on Earth or one host species. This review discusses sea ice bacteriology as a test case for examining bacterial diversity and biogeography. Approximately 7% of Earth's surface is covered by sea ice, which is colonized principally by psychrophilic microorganisms. This extensive community of microorganisms, referred to as the sea ice microbial community (SIMCO), contains algae (mostly diatoms), protozoa, and bacteria. Recent investigations indicate that the sea ice bacteria fall into four major phylogenetic groups: the proteobacteria, the Cytophaga-Flavobacterium-Bacteroides (CFB) group, and the high and low mol percent gram-positive bacteria. Archaea associated with sea ice communities have also been reported. Several novel bacterial genera and species have been discovered, including Polaromonas, Polaribacter, Psychroflexus, Gelidibacter, and Octadecabacter; many others await study. Some of the gram-negative sea ice bacteria have among the lowest maximum temperatures for growth known, < 10 degrees C for some strains. The polar sea ice environment is an ideal habitat for studying microbial biogeography because of the dispersal issues involved. Dispersal between poles is problematic because of the long distances and the difficulty of transporting psychrophilic bacteria across the equator. Studies to date indicate that members of some genera occur at both poles; however, cosmopolitan species have not yet been discovered. Additional research on polar sea ice bacteria is needed to resolve this issue and extend our understanding of its microbial diversity.

A theoretical model of ultraviolet light transmission through Antarctic Sea ice

Much of the region of the Earth most affected by stratospheric ozone depletion is covered by a seasonal or perennial sea ice cover, which is the habitat of a productive and extensive sea ice microbial community. To assess the impact of enhanced incident ultraviolet irradiance on this community, a knowledge of the amount of light transmitted through a sea ice cover is necessary. A two‐stream radiative transfer model is used to estimate the penetration of ultraviolet radiation through Antarctic sea ice. Sea ice optical properties were used as proxies to infer scattering and absorption coefficients at ultraviolet wavelengths. Case studies are reported for sea ice in McMurdo Sound and in the Weddell Sea. Values of spectral transmittance are computed as well as integrated transmitted UV‐B, UV‐A, biologically effective irradiance (BEI), and photosynthetically active radiation (PAR). UV‐B light levels under meter‐thick ice are a few percent of incident values. The presence of a snow cover results in a large decrease in transmitted ultraviolet. Snow and ice ameliorate the biological impact of enhanced levels of incident ultraviolet radiation by reducing the BEI relative to the PAR.

Vertical distribution of bacteria in arctic sea ice

Heterotrophic bacteria were enumerated in north polar sea ice cores obtained near Point Barrow, Alaska. Highest concentrations of total and viable bacteria were found in the layer containing the sea ice microbial community identified by the maximum chlorophyll a content. Gas vacuolate bacteria were also found in the sea ice, a discovery which is consistent with their recent report from antarctic sea ice microbial communities. The gas vacuolate bacteria comprised 0.2% or less of the viable bacteria isolated from sea ice cores, lower than concentrations reported for most antarctic samples. Most gas vacuolate isolates from the sea ice cores were pigmented pink, orange, or yellow. An ice core from nearby saline Elson Lagoon contained an inverted sea ice microbial community with highest chlorophyll a concentrations and bacterial counts found in the top 0–20 cm of the ice. This surface layer also contained high numbers (up to 186 bacteria/ml) of a nonpigmented, gas vacuolate, elongated rod-shaped bacterium.

Effects of Antarctic sea ice biota on seeding as studied in aquarium experiments

The potential seeding impact of sea ice microbial communities was studied during late austral winter early spring 1988 in the Weddell Sea, Antarctica. Experiments were performed in seawater aquariums with natural seawater and seawater enriched with crushed ice. Algal, protozoan and bacterial cell numbers were followed, as well as nutrients and DOC levels. The results showed a potential seeding effect of sea ice communities to the water column. However, the type of ice communities differed greatly from each other and the effect of such seeding will be patchy. In our experiments seeding of seawater by ice rich in algae, flagellates and/or particulate organic carbon lead to the development of communities dominated either by diatoms or bacteria.

A bio‐optical model of Antarctic sea ice

Biogenic particulate material in sea ice can substantially influence the spectral irradiance within the ice sheet and underlying seawater. In order to simulate accurately seasonal changes in light conditions in situ, the biomass changes of the sea ice microbial community must be considered. Here we attempt to provide an improved description of the optical regime within sea ice by combining information provided by models of radiative transfer in sea ice and snow and models of solar spectral irradiance with formulations describing the attenuation of spectral irradiance by particulates observed in sea ice in McMurdo Sound, Antarctica. Emphasis has been placed on the role of biogenic particles in visible light attenuation with the intent of developing a bio‐optical model that more rigorously describes their influence on radiative transfer processes as they occur in nature. Model results simulating seasonal changes in both photosynthetically active radiation and its spectral distribution agree well with measured under‐ice spectral irradiance. Results reveal how changes in microalgal concentrations, as well as their photophysiological characteristics influence both the quantity and quality of downwelled light in sea ice and in the upper layers of the ice‐covered oceans.

Antarctic Sea Ice Biota

The sea ice surrounding Antarctica provides an extensive habitat for organisms ranging in size from bacteria to marine birds and mammals. Historically, most of the ecological work on the ice biota has focused in the nearshore land-fast ice. Only in the last decade have there been comparable studies in the deep-water pack ice regions. These studies have indicated that there are fundamental differences in structural and physical characteristics of fast and pack ice thatare a result of differing physical regimes in nearshore and oceanic regions. Other physical processes act to create heterogeneity within the ice habitat that can range from geographic and regional scales of patchiness to a pronounced vertical gradient within ice floes. The conspicuouspatterns in the distribution of the ice biota can be explained largely by these physical processes. Over 200 species have been reported living on, in, or in association with Antarctic sea ice.The ice biota includes bacteria, a variety of algae, heterotrophic protozoans and small metazoans. The diatom assemblages are the only taxonomic group that is known well enough to make comparisons among the various habitats. Studies by a number of workers suggest some specific diatom assemblages along with occurrence of species that are widelydistributed in both ice and plankton. Ice may also serve as a temporary habitat for species that also comprise planktonic communities, so that providing a “seed population” for ice edge plankton blooms may be an important role of the ice biota. Trophic interactions among organisms in ice suggest that the ice assemblage is a true community with a welldeveloped microbial food web. The ice microbial community may be an important part of the Antarctic marine food web because large consumers from the adjacent planktonic and benthic communities appear to feed on the ice biota.

Biosynthesis and photosynthate allocation patterns of arctic ice algae

Biochemical composition of the sea ice microbial community was measured in populations of different light histories in the Canadian Arctic (Resolute, N.W.T.). The average composition of the particulate organic matter [soluble and insoluble polysaccharide, particulate protein, intracellular free amino acids (IFAA), lipid, and chlorophyll a] was within the published range for microalgae, but lipid was a relatively large (31–59%) and protein a small (20–24%) part of the total. Protein and IFAA pools apparently comprised about 50% of the particulate organic nitrogen, of which 6–10% was in the IFAA pool. Over the entire spring growth season, the net synthesis of protein, IFAA, and Chl a (relative to total cell carbon) decreased with increasing light while relative synthesis of lipid and soluble polysaccharide increased, consistent with patterns of short‐term photosynthate allocation. In the early growth season patterns of synthesis were relatively insensitive to light, and rates of lipid synthesis were large for all light histories. Photosynthate allocation in 24‐h incubations greatly underestimated actual rates of net lipid synthesis and probably overestimated protein synthesis. Microalgae of cold, low‐light environments can display rates of lipid synthesis much larger than rates normally encountered in microalgae without displaying a corresponding pattern of shorter term photosynthate allocation.

Biomass and production in polar planktonic and sea ice microbial communities: a comparative study

Algal and bacterial biomass and production were measured in the plankton, platelet ice and congelation ice communities at one station in McMurdo Sound, Antarctica during September and October 1986. Bacterial abundances and particulate organic carbon and nitrogen were 10 to 100 times greater in the plankton than in the sea ice, whereas the chlorophyll a concentrations in the plankton and sea ice microbial communities (SIMCO) were similar Rates of both light-limited and light-saturated photosynthesis and daily primary production were 2 to 6 times greater in the plankton than in the SIMCO. Bacterial growth rates ranges from 0.7 to 1.5 d-1 in all three communities; however, because of the greater bacterial biomass in the plankton, bacterial production was 15 to 20 times higher there than in the SIMCO. These results suggest that during the early austral spring, planktonic production contributes significantly to total production in ice-covered environments.

Gas Vacuolate Bacteria from the Sea Ice of Antarctica

Gas-vacuolate heterotrophic bacteria from marine habitats are reported here for the first time. They have been isolated from Antarctic sea ice microbial communities and the underlying water column. The predominant gas-vacuolate bacterium from the sea ice is filamentous and pigmented, whereas those of the water column are unicellular and nonpigmented. The highest concentrations of bacteria in sea ice were found in conjunction with the highest algal (chlorophyll a) concentrations.

Recent diatom record of McMurdo Sound, Antarctica: Implications for history of sea ice extent

Analyses of diatom assemblages within surface sediments from McMurdo Sound, Antarctica, document the regional circulation patterns in this large embayment in the southwestern Ross Sea. Thalassiosira spp., indicative of water column primary productivity, is most common in eastern and portions of northwestern McMurdo Sound as a result of its advection into these regions from areas of open water primary productivity. Surface sediments from southwestern McMurdo Sound are composed mainly of Nitzschia curta, a small pennate form commonly found both as a member of the sea ice microbial community as well as a dominant component in ice edge blooms in the Ross Sea. The northward advection of oligotrophic water into the western Sound from beneath the McMurdo Ice Shelf results in the dominance of an autochthonous flora in the southwestern Sound. Sediments deposited during the past 500 years also have been dominated by Thalassiosira spp. and Nitzschia curta. Thalassiosira spp. concentrations reached a maximum between 1600 and 1875 A.D., corresponding to the time of the “Little Ice Age.” More persistent winds may have been responsible for more prevalent polynyas at that time, resulting in greater amounts of open water primary productivity and subsequent higher percentages of Thalassiosira spp. Increased areal extent and/or duration of coastal polynyas during the “Little Ice Age” suggests that within the southwestern Ross Sea, the production of High Salinity Shelf Water, and hence Antarctic Bottom Water, may have been greater at that time.

Sea ice microbial communities (SIMCO)

Sea ice microbial communities (SIMCO) grow luxuriantly within several microhabitats of sea ice, indicating that the microorganisms comprising these communities are well adapted to the physicochemical gradients which characterize sea ice. We used SIMCO obtained from the bottom of congelation ice in McMurdo Sound, Antarctica, to test the hypothesis that low temperature limits microbial productivity in polar oceans and also to investigate the effect of salinity on rates of autotrophic and heterotrophic metablism. Substantial rates of carbon fixation, incorporation of thymidine, and uptake of glutamate occurred at the in situ temperatures of-1.9°C, with maximum rates at temperatures considerably warmer but below 15°C. Microalgae and bacteria of SIMCO are thus indicated to be psychrophiles. The relative rates of autotrophic and heterotrophic microbial growth (based on rates of fixation of 14CO2 by microalgae and incorporation of 3H-thymidine by bacteria, respectively) were similar and overlapped from 4° and 7°C. These data suggest that a recent hypothesis proposing the uncoupling of primary production and bacterial production in cold water, due to differential growth of phytoplankton and bacterioplankton at low temperatures, is refuted with respect to SIMCO. Maximum rates of carbon fixation by autotrophs of SIMCO occurred at salinities which characterized the ice from which the SIMCO were collected. In contrast, heterotrophs of SIMCO exhibited a more stenohaline response to variable salinity, with maximum incorporation of thymidine and uridine from 20‰ to 30‰. Adaptations by autotrophs and heterotrophs of SIMCO that permit substantial metabolism and growth at very low temperatures and variable salinities are significant when considering production and trophodynamics in polar oceans. Actively growing microorganisms in these unique communities contribute to overall production in polar oceans, provide carbon for food webs associated with sea ice, and upon release from melting ice may contribute to microbial blooms in marginal ice edge zones, which in turn support cryopelagic food webs.

HETEROTROPHY AND PHOTOHETEROTROPHY BY ANTARCTIC MICROALGAE: LIGHT‐DEPENDENT INCORPORATION OF AMINO ACIDS AND GLUCOSE 1

ABSTRACTDiatoms isolated from the benthic, planktonic and sea ice microbial communities in McMurdo Sound, Antarctica assimilated ambient concentrations of dissolved amino acids and glucose in both the light and dark. Uptake of amino acids but not glucose was influenced by the iucubation irradiance and amino acid uptake rates were up to 250 times greater than those of glucose. Amino acids were incorporated into proteins and other complex polymers and the rates of assimilation and patterns of polymer synthesis were similar to those of the light‐saturated photosynthetic incorporation of inorganic carbon. This suggests that these diatoms can use exogenous amino acids to synthesize the essential macromolecules for heterotrophic growth. The assimilation of dissolved organic substrates could supplement light‐limited growth during the austral spring and summer as well as potentially support the heterotrophic growth of these diatoms throughout the aphotic polar winter.

PHOTOSYNTHESIS AND CELL DIVISION BY ANTARCTIC MICROALGAE: COMPARISON OF BENTHIC, PLANKTONIC AND ICE ALGAE1

ABSTRACTIrradiance‐dependent rates of photosynthesis and cell division of six species of microalgae isolated from the benthos, plankton and sea ice microbial community in McMurdo Sound, Antarctica were compared. Microalgae isolated from different photic environments had distinct photosynthetic and growth characteristics. For benthic and ice algae, photosynthesis saturated at 6 to 20 μE.m−2.s−1 and was photoinhibited at 10 to 80 μE.m−2.s−1 while for the planktonic algae, saturation irradiances were up to 13 times higher and photoinhibition was not detected. The slope of the light‐limited portion of the P‐I relationship was up to 50 times greater for the benthic algae than for either the ice or planktonic algae suggesting that benthic algae used the low irradiances more efficiently for carbon uptake. Cell division was dependent on the incubation irradiance for all but one microalga examined. The dependence of division rates on irradiance was however much smaller than for carbon uptake, suggesting that cell division buffers the influence of short term variations of irradiance on cellular metabolism.

Sea ice microbial communities. VI. Growth and primary production in bottom ice under graded snow cover

Sea ice microbial communities. VI. Growth and primary production in bottom ice under graded snow cover