Egil Sakshaug

Egil Sakshaug
  • Professor Emeritus at Norwegian University of Science and Technology

About

95
Publications
21,038
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7,513
Citations
Current institution
Norwegian University of Science and Technology
Current position
  • Professor Emeritus
Additional affiliations
January 1969 - July 2012
Norwegian University of Science and Technology
Position
  • Professor (Full)

Publications

Publications (95)
Article
Colored Dissolved Organic Matter (CDOM) is an important optical constituent in seawater, which significantly attenuates the violet to blue portion of visible light. Thus, CDOM reduces the radiation energy available to phytoplankton and affects remote-sensing signals. We present data from two cruises transecting the Polar Front from Atlantic to Arct...
Article
Full-text available
Recent studies have concluded that different water bodies in the ocean can contain different microbial communities. The goal of the present study was to determine if biogeographic patterns are present for aquatic microbes in waters which meet around the South Shetland Islands (SSI), Antarctica. Prokaryotic and eukaryotic marine microbial communitie...
Article
Iron(III) photoreduction and the responses of phytoplankton under ultraviolet (UV) and photosynthetically available radiation (PAR) were investigated with the presence of hydroxycarboxylic acid (glucaric acid (GA), a model compound for organic acids excreted by phytoplankton). The incubation experiments were carried out on board using seawater samp...
Conference Paper
Full-text available
* Light is fuelling the primary productivity of the oceans. * Shrinking sea ice cover increase the light availability to Arctic phototrophs. * Spectral representation of underwater light is important for accurate primary productivity estimates and modeling.
Article
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During blooms in Norwegian waters phytoplankton communities are phosphorus limited in fresh and brackish waters, and balanced or even nitrogen limited in high-salinity marine waters. This results from the high N/P ratio for available nutrients before onset of blooms in freshwater relative to seawater (N/P (atoms) >100 and 12–16, respectively). Alga...
Article
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As part of the US-AMLR program in January-February of 2006, 99 stations in the South Shetland Islands-Antarctic Peninsula region were sampled to understand the variability in hydrographic and biological properties related to the abundance and distribution of krill in this area. Concentrations of dissolved iron (DFe) and total acid-leachable iron (T...
Article
Full-text available
As part of the US-AMLR program that occupied 99 hydrographic stations in the South Shetland Islands-Antarctic Peninsula region in January–February of 2006, concentrations of dissolved iron (DFe) and total acid-leachable iron (TaLFe) were measured in the upper 150 m at 16 stations (both coastal and pelagic waters). The concentrations in the upper mi...
Chapter
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This review examines interregional linkages and gives an overview perspective oil marine ecosystem functioning in the north-eastern Atlantic. It is based on three of the 'systems' considered by the European Network of Excellence for Ocean Ecosystems Analysis (EUR-OCEANS was established in 2004 under the European Framework VI funding programme to pr...
Book
Vitenskapsmuseet ved NTNU har gitt ut ei populærvitenskapelig bok om Trondheimsfjorden. Utgivelsen er det første i en rekke av tiltak ved NTNU til feiringen av tusenårsskiftet. Vitenskapsmuseet har gitt ut boka ”Trondheimsfjorden” fordi "..fjorden er en av de største og mest produktive av de norske fjordene og byr på et usedvanlig rikt spektrum av...
Article
Light absorption by phytoplankton is both species specific and affected by photoacclimational status. To estimate oxygenic photosynthesis from pulse-amplitude-modulated (PAM) fluorescence, the amount of quanta absorbed by PSII needs to be quantified. We present here three different biooptical approaches to estimate the fraction of light absorbed by...
Article
We studied the variability of in vivo absorption coefficients and PSII-scaled fluorescence excitation (fl-ex) spectra of high light (HL) and low light (LL) acclimated cultures of 33 phytoplankton species that belonged to 13 different pigment groups (PGs) and 10 different phytoplankton classes. By scaling fl-ex spectra to the corresponding absorptio...
Article
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A relationship between nutrient concentration, cell density and pH increase due to photosynthesis was established for 3 phytoplankton species, Prorocentrum minimum (Dinophyceae), Phaeodactylum tricornutum (Bacillariophyceae) and Tetraselmis sp. (Prasinophyceae), using batch cultures. Experiments were carried out to find out whether changes in pH in...
Article
Brief overviews of the Arctic’s atmosphere, ice cover, circulation, primary production and sediment regime are given to provide a conceptual framework for considering panarctic shelves under scenarios of climate variability. We draw on past ‘regional’ studies to scale-up to the panarctic perspective. Within each discipline a synthesis of salient di...
Chapter
A key to many scientific studies of ocean and sea floor processes is an accurate description of the sea floor morphology. For Arctic scientists this has posed a particular problem because less is known about the Arctic Ocean bathymetry and physiography than for the other oceans. For nearly 60 years after Nansen’s collection of deep bathymetric soun...
Chapter
Marine bio-production in the Arctic and Subarctic is based primarily on microscopic unicellular algae (phytoplankton) in the water column and micro-algae associated with ice. Algae utilise light to produce organic matter by photosynthesis, thereby reducing CO2 while releasing O2 and producing carbohydrates which, according to the needs of the algae...
Article
This study examined the concentration, transformation and removal of various operationally defined iron species, including one control and one experimental mesocosm bag (40 m(3) each) in the landlocked basin of Hopavagen, Norway. The experimental mesocosm bag was spiked with nitrate, ammonia, phosphate and silicate as part of the MesoNor-97 project...
Chapter
General characteristics of phytoplankton Physical and chemical aspects of the Arctic and the Antarctic Interannual variability: Importance of global cyclic climatic events Rates of primary production Major factors affecting growth rates of phytoplankton Phytoplankton and the food web Possible impacts of changing climatic conditions
Article
Concentrations of different Fe species in the Trondheim fjord waters were determined in different seasons by serial columns. Colloidal Fe (ColFe), Anionic organic-Fe complexes (AnOFe), Hydrophobix-lyphophlic organic-Fe complexes (HphOFe) and Chelex labile iron (ClxLFe) were determined before, during and after large river discharges and phytoplankto...
Chapter
The Arctic can be delimited by the Arctic Circle at 66 ° 32 ‘N, which is the southern boundary of the midnight sun. For many purposes, however, it will be more meaningful to base the limits of the Arctic on climate, vegetation, or seawater characteristics (Murray 1998). In this chapter, we have chosen to define Arctic marine waters as the sea withi...
Article
Full-text available
The Joint Global Ocean Flux Study (JGOFS) has completed a decade of intensive process and time-series studies on the regional and temporal dynamics of biogeochemical processes in five diverse ocean basins. Its field program also included a global survey of dissolved inorganic carbon (DIC) in the ocean, including estimates of the exchange of carbon...
Conference Paper
This paper describes the background, idea, objectives and preliminary outcome of a programme aimed at coordinating the efforts of established research institutions working within marine engineering, marine mathematical modelling and marine biological science at NTNU in Trondheim, Norway. The programme, MODTEQ (MOdel based Development and Testing of...
Article
A Norwegian monitoring system for harmful algal blooms, consisting of an Observer Network, the State Food Hygiene Control Agency, the Oceanographic Company of Norway, the Institute of Marine Research and the Directorate for Fisheries, is reviewed. Potentially harmful algae on the Norwegian coast are found primarily in four classes of phytoplankton,...
Article
Full-text available
A global assessment of carbon flux in the world ocean is one of the major undertakings of the Joint Global Ocean Flux Study (JGOFS). This has to be undertaken using historical in situ data of primary productivity. As required by the temporal and spatial scales involved in a global study, it can be conveniently done by combining, through appropriate...
Article
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On the basis of results that largely have been derived from the Norwegian research programme Pro Mare (1984–1989), an overview of the distribution of biomass and productivity at different trophic levels of the pelagic Barents Sea ecosystem is presented, with comments on year-to-year and horizontal variations. Average biomasses for the whole Barents...
Article
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The spectral light absorption and fluorescence excitation spectra from thalli (in vivo) and thylakoid micelles (no intracellular self-shading) from the macroalgae Laminaria digitata (L.) Edmonson, Palmaria palmata (L.) Kuntze, and Ulva sp. were examined. In all the examined species, the intracellular self-shading (i.e. the package effect) was highl...
Article
Full-text available
The presence of a chlorophyll a-like (chi a) pigment, with an in vivo absorption maximum in the near-infrared region at 708 to 712 nm, was observed mainly in sedimenting material and Calanus hyperboreus fecal pellets associated with Phaeocystis cf. pouchetii Harlot blooms. (In vivo absorption is attributed to natural absorption found in naturally o...
Article
An overwiew of the pigment composition and bio-optical characteristics (spectral light absorption and fluorescence properties) in important marine phytoplankton (diatoms, dinoflagellates, prymnesiophytes, prasinophytes, chlorophytes, euglenophytes, chrysophytes, raphidophytes, cryptophytes and cyanobacteria) are presented. The species/class-specifi...
Article
Diffuse attenuation coefficients for spectral irradiance Kd((Zeta) (lambda) ) and the total Chl (alpha) + Pheo (alpha) pigment-specific absorption of light by particles ((alpha) p*((lambda) ), algae + detritus), were determined during two cruises (Cardeep 2 and 3) in the Greenland/Iceland/Norwegian (GIN)-Seas. The pigment (Chl (alpha) + Pheo (alpha...
Article
Full-text available
Biomass distribution and energetics of trophic levels in the pelagic ecosystem of the Barents Sea are presented as averages over several years for the whole Barents Sea using data from the research programme Pro Mare in 1984–1989 and mathematical ecosystem models. Average biomasses range from more than 3 tonnes carbon km–2 (zooplankton) to 0.1 kg C...
Article
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Phaeocystis species diversity has been reviewed by comparing the morphological and physiological characteristics of Phaeocystis cells and colonies of different geographical origin. These analyses gave evidence for four Phaeocystis species: P. globosa, P. scrobiculata, P. pouchetii and one undefined antarctic species, distinguishing themselves by co...
Article
Full-text available
The spectral light absorption characteristics (400 to 700 nm) of 10 main classes, covering 31 species, of bloom-forming phytoplankton (diatoms, dinoflagellates, prymnesiophytes, euglenophytes, prasinophytes, raphidophytes, cryptophytes, chlorophytes, chrysophytes and cyanobacteria) have been examined. The survey is based on in vivo chlorophyll (chl...
Article
Chlorophyll (alpha) -normalized photosynthetic parameters, e.g. the photosynthetic efficiency ((alpha) B), and the maximum photosynthetic rate (PBm), for natural phytoplankton communities exhibit extreme ranges of variation. Part of this variation is related to the species composition of the communities, another part has methodological causes, and...
Article
Photoadaptational responses to three irradiances for each of five spectral distributions of light were studied in the marine diatom Skeletonema costatum. The C : Chl a ratio increased linearly with increased absorption of light per unit Chl a within the range of irradiances studied. The quantum yield for growth decreased monotonically with increase...
Article
Photoadaptive responses in the toxic and bloom-forming dinoflagellates Gyrodinium aureolum Hulbert, Gymnodinium galatheanum Braarud, and two strains of Prorocentrum minimum (Pavillard)Schiller were evaluated with respect to pigment composition, light-harvesting characteristics, carbon and nitrogen contents, and growth rates in shade- and light-adap...
Article
Full-text available
Nutrient-sufficient cultures of a Trondheimsfjord (Norway) clone of the marine centric diatom Skeleionema costatum (Grev.) Cleve were grown at 75 μmol m−2 s−1 and 15°C at 24 and 12 h daylength to study diurnal variations and the effect of daylength on pigment and chemical composition, photosynthetic parameters, dark respiration rates and scaled flu...
Chapter
Full-text available
The growth of phytoplankton is fundamentally important to biogeochemical cycling in the sea, and models of this process are essential to describing the fluxes of carbon, nitrogen, and many other elements in the ocean. We address here nitrogen-based models that predict the photosynthesis and growth of phytoplankton for use in basin-scale simulations...
Article
The Barents Sea is divided into a northern and a southern part by the Polar Front (at about 75–76° N) where Atlantic waters descend under Arctic waters. Near to and north of the Polar Front, the spring bloom of phytoplankton is triggered by the stability induced in the upper 20 m by the melting of ice. The pycnocline is too strong to be eroded by w...
Article
Full-text available
The photobiological response of an isolate of the prymnesiophyte Chrysochromulina polylepis, obtained from a bloom in the Skagerrak in May-June 1988, was evaluated with respect to pigment composition, spectral dependence of light harvesting, and photosynthetic parameters of cultures grown at 75 to 120-mu-mol m-2 s-1 irradiance, 16 h day length and...
Article
This study deals with the modelling of photosynthesis and growth of polar phytoplankton and variations in relevant parameters. Polar regions arc characterised by low sun elevations (< 40−50°), extreme seasonal variations in irradiance and day length, and low sea temperatures (−1.8 to 6°C). Due to the latter, maximum phytoplankton growth rates arc l...
Article
Unialgal cultures of the prymnesiophyte, Phaeocystis cf. pouchetii, were isolated from Norwegian and United States coastal waters. Manipulation of the nutrient medium resulted in populations overwhelmingly dominated by either colonies or solitary cells of Phaeocystis. Both morphotypes exhibited temperature-dependent asymptotic increases in pigment-...
Article
Pro Mare, the Norwegian Research Program for Marine Arctic Ecology, began in 1984 and was concluded in 1989. The aim of the program was to increase our understanding of how pelagic ecosystems function in the Arctic seas, thereby improving the basis for government decision-making as well as elevating scientific competence both with respect to fish s...
Article
This study deals with the modeling of photosynthesis and growth of polar phytoplankton and variations in relevant parameters. Polar regions are characterised by low sun elevations (< 40?50°), extreme seasonal variations in irradiance and day length, and low sea temperatures (?1.8 to 6°C). Due to the latter, maximum phytoplankton growth rates arc lo...
Article
Unialgal cultures of the prymnesiophyte, Phaeocystis cf. pouchetii, were isolated from Norwegian and United States coastal waters. Manipulation of the nutrient medium resulted in populations overwhelmingly dominated by either colonies or solitary cells of Phaeocystis. Both morphotypcs were grown under a range of irradiances at 0°, 2°, 5°, 10° and 2...
Article
A mathematical model describing the development of phytoplankton blooms as a function of the depth of the wind-mixed layer, spectral distribution of light, passage of atmospheric low-pressure systems, size of the initial phytoplankton stock and loss rates is presented. Model runs represent shade-adapted, large-celled, bloom-forming diatoms. Periodi...
Article
Full-text available
Pro Mare, the Norwegian Research Program for Marine Arctic Ecology, began in 1984 and was concluded in 1989. The aim of the program was to increase our understanding of how pelagic ecosystems function in the Arctic seas, thereby improving the basis for government decision-making as well as elevating scientific competence both with respect to fish s...
Article
The models by Sakshauget al (1989, Limnology and Oceanography, 34, 198–205) and Webbet al. (1974, Oecologia, 17, 281–291), for prediction of the gross growth rate of phytoplankton and short-term photosynthesis, respectively, have been modified on the basis of experiments with cultures of the centric diatoms Thalassiosira nordenskioeldii and Chaetoc...
Article
Full-text available
This summary paper describes the food webs in the Barents Sea and deals with the seasonal changes in the phytoplankton stock and productivity. The pelagic food web is, as elsewhere, based mainly on unicellular algae (phytoplankton) as the primary producers. Temperatures of -1.8 to 5OC set an upper limit of about 0.6-0.8 d-I for the growth rate of d...
Article
Full-text available
Nutrient-sufficient cultures of 10 arctic diatom species were grown at a combination of 9 irradiances and 4 day lengths at 0. 5 'C. The growth rate was calculated on the basis of in vivo fluorescence measurements. Maximum recorded growth rates ranged from 0.41 d-' (Amphiprora sp.) to 0.60 d-' (Thalassiosira antarctica and T. bulbosa). Growth rates...
Article
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Some of the principles governing phytoplankton growth, biomass, and species composition in 2-layered pelagic ecosystems are explored using an idealized, steady-state, mathematical model, based on simple extensions of Lotka-Volterra type equations. In particular, the properties of a food web based on 'small' and 'large' phytoplankton are investigate...
Article
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M~croscopical examination of near-surface eucaryotic microbial populations in circumcon-tinental waters of Antarctica indicated that nanoplankton ((20 btm diameter) dominated in regions with low chlorophyll concentrations (< 1 pg I-'). About 30 O/ O of the mean nanoplankton carbon consisted of heterotrophic flagellates. Heterotrophic microplankton...
Article
Studies of the marine diatom Skel etonema costatum indicate that for a given irradiance and day length, increases in the rate of supply of a limiting nutrient cause linearly proportional increases in the growth rate and the Chl : C ratio. For a given irradiance, increases in day length cause decreases in the Chl : C ratio, and the growth rate is li...
Article
Full-text available
Nutrient-saturated cultures of Skeletonema costatum were grown at 15�C and 42 combinations of photon flux density (PFD) and daylength. The growth rate increased with the daylength and PFD up to 460–630 μE m−2 s−1 (maximum 2.5 doublings day At 2000 μE m−2 s−1 the growth rate was reduced by 45%. The chlorophyll (chl) content of the cells and the rate...
Article
The response of phytoplankton to variations in the light regime was studied during the VULCAN and ACDA cruises in the Antarctic. Unenriched batch cultures of 12–19 days' duration reached chl concentrations of 10–50 μg−1 and exhibited exponential growth rates, with the maximal rate being 0.41 doubl, day−1. Ice edge algae exhibited maximum growth rat...
Chapter
Over 50% of total chlorophyll found in waters surrounding Antarctica is contained in the pico- and nanoplankton (<20mu m) size-fraction. approx 30% of the total nanoplankton biomass consists of heterotrophic flagellates. The total phytoplankton standing stock is low, averaging <0.6mu g Chl 1-1 in the East Wind Drift area. Higher concentrations are...
Article
Four marine dinoflagellates, Amphidinium carterae Hulburt, Ceratium tripos (O.F. Müll.) Nitzsch, Prorocentrum minimum (Pav.) J. Schiller, and Scrippsiella trochoidea (Stein) Loeblich III were grown as dilution cultures at 18°C, S = 29%. and 30 μE·m−2·s−1 at L:D = 14:10 h. In nutrient-saturated cultures, the growth rates (doubl·day−1) ranged from 0....
Chapter
Examines relationships between pelagic phytoplankton growth and environmental variables in polar seas with reference to the geographical and seasonal distribution of standing stock. Comments are made on the physiological ecology of Arctic and Antarctic phytoplankton, with attention drawn towards the effects of the light regime (the most significant...
Chapter
There was agreement among members of the working group that, in the next 5–10 years, the process-oriented focus of field studies should be maintained. This orientation is viewed as a third phase in the historical evolution of modern biological oceanography, in which the regional studies of the 1940s and 1950s identified the important classes of bio...
Article
Three species of diatoms, Skeletonema costatum (Grev.) Cleve, Thalassiosira gravida Cleve, and T. pseudonana (Hustedt) Hasle et Heimdal, were grown in in situ dialysis culture in the Trondheimsfjord at depths of 0.5 and 4 m. The rates of growth and the chemical composition of exponentially growing cells were monitored and related to seasonal change...
Article
During May and June of 1975 and 1976, unialgal blooms of the marine diatom Skeletonema costatum in the Trondheimsfjord exhibited significant alkaline phosphatase activity, as measured by a fluorometric method. The fairly high activities of some populations correlated well with clear indications of P-limitation obtained by measurement of N/P, β-l,3-...
Article
The chemical composition of nutrient-saturated cultures of Emiliania huxleyi, Amphidinium carterae , and Staurastrum luetkemuelleri was studied. The variation in chemical composition of natural phytoplankton communities in the North Sea, the Trondheimsfjord, and a eutrophic lake was also studied. Nutrient status was evaluated by measurement of the...
Article
The uptake of 14C-labeled extracellular products from Skeletonema costatum by native bacterial populations was analyzed during a bloom of this alga in the Trondheimsfiord, Nor- way. Data in agreement with the linear predictions of a mixed-substrate kinetic model were obtained on each of 10 separate occasions. Changes in the kinetic parameters indic...
Article
The variation in chemical composition of Skeletonema costatum (Grev.) Cleve and Pavlova lutheri (Droop) Green was studied in batch cultures with N-, P-, and Fe-deficient media under continuous light. In vivo fluorescence, chlorophyll a, ATP, cellular nitrogen, carbon, and phosphorus, and cell density were measured. The exponential growth rate was 2...
Article
Dialysis cultures of Skeletonema costatum (Grev.) Cleve and Asterionella japonica Cleve & Möller ex Gran were grown in tanks in running sea water pumped from a depth of 6 m during March–June, at 50 % of the surface light intensity and at a temperature range of 2–17 °C. The exponential growth rate was exponentially related to temperature at surface...
Article
Full-text available
The quantitative composition of the chloroplast pigments of phytoplankton sampled weekly at one station in the Trondheimsfjord was studied by circular paper chromatography throughout 18 months. The concentrations of total chlorophyll a (T-chl a obtained by the trichromatic method) as well as of chromatographically purified chlorophyll a (chl a) fol...
Article
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Quantitative phytoplankton sampling was carried out at weekly intervals at one station in the central part of the Trondheimsfjord and at irregular intervals at one station near Trondheim Harbour during March–October, 1970 and 1971. Various developmental stages of diatom blooms have been observed, which have been related to variations in freshwater...
Article
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Samples of phytoplankton populations from the Trondheimsfjord, collected in 1970 and the first five months of 1971, have been analysed for carbohydrate, protein, lipid, and phosphorus. Lipid was in all cases less than 10% of the organic dry matter. The ratio was remarkably constant, but the ratio protein/carbohydrate varied between wide limits. For...
Article
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The production of protein and cellular and extracellular polysaccharides of dinoflagellate Amphidium carteri Hulburt was studied during growth in N- and P-limited media. There was no sign of increased carbohydrate per cell towards growth phases. The weight ration of protein to carbohydrate was rather constant, being independent of the growth phase...
Article
A simple, automatic water sampler has been constructed and used to study in detail the variations in phytoplanktonic densities around populations of the edible mussel (Mytilus edulis L.). Very rapid fluctuations were observed in the plankton counts. A good correlation between these and the total carotenoid content of the mussels was found, together...
Article
The seasonal variation in total carotenoids of the edible sea mussel (Mytilus edulis L.) has been determined for two populations in the Trondheimsfjord. The pigment concentration varied markedly throughout the year, with peaks in spring and autumn and minima in winter and summer. A good correlation with the occurrence of phytoplankton in the open f...
Article
Full-text available
T he goal of remote sensing (RS) of ocean colour is to obtain quantitative and qualitative information regarding dissolved substances and particles present in the water (optically active water constitu-ents). The basic premise is that because different substances have different ab-sorption and scattering characteristics in the visible wavelength ba...

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