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Research experience and interests:

Ecophysiological aspects of phytoplankton in Norwegian marine waters. The investigations cover fjord waters; Korsfjorden, Raunefjorden, Lindåspollene, Samnangerfjorden, Boknafjorden, Lysefjorden and Oslofjorden, coastal waters; Western, Southern and Eastern Norway, and oceanic waters; the Norwegian Sea, Barents Sea and the Greenland Sea. Special emphasis has been put on the regulation mechanisms of spatial and temporal distribution of phytoplankton biomass and primary production. Among the physical factors being studied are light, wind, hydrography – including water column stability, and water circulation. Besides this, physiological and behavioural effects of light (including UV) and other environmental factors on microalgae has been investigated. Among these are cell motility (studied in a specially designed artificial water column), bio-optical aspects of microalgae in general and photosynthetic response.

Within the field of light and phytoplankton interactions I cooperate with colleges (Øyvind Frette, Børge Hamre and Jakob Stamnes) from the “Optics and atomic physics” group, of which I am an associated member, at the Department of Physics and Technology, UoB. Our common research activities have a long time horizon and it is conducted in collaboration with several national and international scientific groups and institutions. In order to enhance the quality of our work and to enable us to investigate new aspects of light and phytoplankton interactions, we have established a marine bio-optical laboratory facility, with funding from the Norwegian Research Councils’ Program for “Advanced equipment”. This has resulted in several “Light and Life” projects. These are: "Light and Life in Norwegian Waters" (LLNW), "Light and Life in Icy Arctic Waters", "Light and Life in African environment" and “Light and Life in Norwegian Waters: Physics/Biology Based Approach to Satellite Monitoring of Primary Production and Algal Blooms”. Many Master and Ph.D students have been involved in the projects.

Field investigations

In Norwegian fjords the observed seasonal variations in phytoplankton biomass, species composition, primary production and vertical distribution are due to a complex interaction between physical, chemical and biological factors. We have seen that the wind regulated exchange processes between coastal and fjord water, together with light regime, are overall regulating factors. During periods of northerly winds along the coast of Western Norway, displacements of coastal waters away from the coast are accompanied by upwelling of nutrient rich deeper water into the euphotic zone. An opposite circulation pattern is seen during periods of southerly winds. These advective processes are also essential for questions concerning the autochthonous-allochthonous origin of the species. Common for the investigated fjords are strong stratifications of the water masses throughout extended periods of the growth season, which enable the deeper situated phytoplankton species to adapt to low light intensities. During time, such a strategy could result in deep maximum layers of chlorophyll a.  It is has also been found that persistent stratification of the water masses combined with stable light conditions could lead to diel rhythms in photosynthetic activity of summer phytoplankton. As a bloom proceeds and nutrients are being exhausted, grazing by micro- and macrozooplankton may become an important regulating factor phytoplankton growth. During calm weather conditions, nutrient limitation, nitrogen or phosphorus, may persist for extended periods in Norwegian fjords. Continued growth of phytoplankton in the surface layer above the pycnocline thus relies on regenerated nutrients. Both bacterio- and virioplankton have been found to be important in this context. Besides this, virioplankton may act as an internal driving force in spring bloom successions.

To better understand the role of light regime on growth of phytoplankton, information on the spatial and temporal variations of the inherent optical properties (absorption and scattering) of coastal and fjord waters (“case II water”) have been gained.   The transmission of UV radiation and the factors controlling it are important in this context. Therefore the role of coloured dissolved organic material (CDOM) has been thoroughly investigated. Possible effects of UV radiation on vertical distribution of phytoplankton and primary production have been investigated both in case I (ocean water) and case II waters. It was found that the maximum and mean potential for inhibition of primary production at a depth of 5 m were 11 and 3 % in the Greenland and Norwegian Seas, 3.2 and 0.9 % in coastal waters of south-western Norway, and 0.5 and 0.1 % in the Samnangerfjord.

Development of new methods

An experimental water column equipped with an optical detection system for the study of fine scale vertical displacement of microalgae in stratified waters has been constructed. With this system migratory patterns and swimming speeds of the algae can be deduced. An improved technique for measurements of the volume scattering function (VSF) of marine particles has also been developed. This equipment enables us to study how microalgae and other particles influence the propagation of light in the ocean. A new infrared laser equipped with confocal microscopy, including “Fluorescence Lifetime Imaging” (FLIM), has now being installed in our lab, which implies new opportunities to study basic photosynthetic processes and anatomical changes in microalgal cells as responses to light stress.

Model application

By using a spectral radiative transfer model combined with a parameterization of the inhibition of marine photosynthesis by ultraviolet radiation, it has been found that ozone depletion in polar regions during periods of sufficiently low solar elevations, compromising both open and ice-covered waters, could lead to increased photosynthesis at all depths. The reason for this is that reduced ozone concentrations not only result in enhanced levels of UV radiation but also in photosynthetic utilizable radiation (PUR), which could otherwise be limiting to primary production during periods of normal ozone concentrations.

Aquaculture related research

The main aspect of this research is to investigate if it is possible to increase the primary production within a fjord by artificial upwelling of deeper nutrient rich water during the summer season, when growth of phytoplankton is otherwise nutrient limited. This would be beneficial for the aquaculture industry, both concerning mussel and fish farming. We have found that by using a submerged freshwater discharge to bring about an upwelling, the algal production can be increased by a factor of 3-4, and at the same time reduce the occurrence of toxic algal flagellates. This work is in collaboration with the Jan Aure, Tore Strohmeier and Øivind Strand at the Institute of Marine Research (IMR), Bergen.

Pedagogical competence and experience

Pedagogical competence - I had my basic pedagogical education during 1992 by participating in the course “Developmental Program in University Pedagogics”. My teaching experience at university level goes back to 1985.

Teaching responsibilities at UoB and UoO - Introductory courses in Biology (120 students): - BIO 100 Biology  - (45 ECTS credits) 1993 – 1999, and - BIO 103 Botany – (15 ECTS credits) 2000 -2002, in both cases responsible for both laboratory course and lectures comprising “Physiology and anatomy of higher plants”, equivalent to 5 ECTS credits, - BIO 113 Microbiology – (10 ECTS credits), partly responsible for lectures 2003 - 2004 and for laboratory course from 2003, BIO 114 Physiology – (10 ECTS credits), partly responsible for lectures and laboratory course 2003 – 2004. Specialisation courses in Marine biology and Microbiology, chronologically from 1985 until 2006: - B 290 Algal systematics and ecology  - (15 ECTS credits), including laboratory course, partly responsible, - B 390 Marine ecological processes – (3 ECTS credits), partly responsible, - BM 202, UoO Marine ecological methods – (15 ECTS credits), including laboratory course, partly responsible, - BM 223 Algal physiology I – (15 ECTS credits), including laboratory course, partly responsible, - BM 224 Algal physiology II – (15 ECTS credits), including laboratory course, total responsible, - BFM 360 Marine pollution biology – (5 ECTS credits), partly responsible, - BM 222 Experimental algal physiology – (10 ECTS credits), including laboratory course, partly responsible, - BM 221 Microbial ecology II – (15 ECTS credits), including laboratory course, partly responsible, - MAR 314 Experimental marine microbiology – (5 ECTS credits), partly responsible - BM 321/MIK 314 Light and Microalgae in marine ecosystems – (5 ECTS credits), total responsible, - MIK 201 Eucaryote microbiology – (10 ECTS credits), including laboratory course, partly responsible. For several of the taught courses listed above, I was also responsible for editing the laboratory manual. In the case of BM 224 and BM 321/MIK 314, I was responsible for both the initiation and planning of the courses. I have also been responsible for the direction of a number of Master students at our Department and at the Department of Physics and Technology.

Scientific papers published in international journals:

Erga, S.R. and Heimdal, B.R. 1984. Ecological studies on the phytoplankton of Korsfjorden, western Norway. The dynamics of a spring bloom seen in relation to hydrographical conditions and light regime. J. Plankton Res. 6: 67-90

Erga, S.R. 1989. Ecological studies on the phytoplankton of Boknafjorden, western Norway. I. The effect of water exchange processes and environmental factors on temporal and vertical variability of biomass. Sarsia 74: 161-176

Erga, S.R. 1989. Ecological studies on the phytoplankton of Boknafjorden, western Norway. II. Environmental control of photosynthesis. J. Plankton Res. 11: 785-812

Erga, S.R. and Skjoldal, H.R. 1990. Diel variations in photosyntheticactivity of summer phytoplankton in Lindåspollene, western Norway. Mar. Ecol. Prog. Ser. 65: 73-85

Erga, S.R., Omar, A.M., Singstad, I., Steinseide, E. 1999. An optical detection system for the study of fine-scale vertical displacement of microalgae in an artificial water column. J. Phycol. 35:425-432

Erga, S.R., Dybwad, M., Frette, Ø., Lotsberg, J.K., Aursland, K. 2003. New aspects on migratory behaviour of phytoplankton in stratified waters: Effects of halocline strength and light on Tetraselmis sp. (Prasinophyceae) in an artificial water column. Limnol. Oceanogr. 48: 1202-1213

Erga, S.R., Aursland, K., Frette, Ø., Hamre, B., Lotsberg, J.K., Stamnes, J.J., Aure, J., Rey, F., Stamnes, K. 2005. UV transmission in Norwegian waters: controlling factors and possible effects on primary production and vertical distribution of phytoplankton. Mar. Ecol. Prog. Ser. 305: 79-100

Paasche, E.,  Erga, S.R. 1988. Phosphorus and nitrogen limitation of phytoplankton in the inner Oslofjord (Norway). Sarsia 73: 229-243

Frette, Ø., Erga, S.R., Stamnes, J.J., Stamnes, K. 2001. Optical remote sensing of waters with vertical structure. Appl. Opt. 40:1478-1487

Hamre, B., Frette, Ø., Erga, S.R., Stamnes, J.J., Stamnes, K.  2003. Parameterisation and analysis of the optical absorption and scattering coefficients in a Western Norwegian fjord – A case II water study. Appl. Opt. 42:883-892

Kjeldstad, B., Frette, Ø., Erga, S.R., Browman, H.I., Kuhn. P., Davis, R., Miller, W., Stamnes, J.J. 2003. UV (280-400 nm) optical properties in a Norwegian fjord system and an intercomparison of underwater radiometers. Mar. Ecol. Prog. Ser. 256: 1-11

Larsen, A., Flaten, G.A.F., Sandaa, R.A., Castberg, T., Thyrhaug, R., Erga, S.R. Jaquet, S., Bratbak, G. 2004. Spring phytoplankton bloom in Norwegian coastal waters: Microbial community dynamics, succession and diversity. Limnol. Oceanogr. 49: 180-190

Frette, Ø., Erga, S.R., Hamre, B., Aure, J., Stamnes, J.J. 2004. Seasonal variability in inherent optical properties in a western Norwegian fjord. Sarsia 89: 276-291

Lotsberg, J.K., Marken, E., Stamnes, J.J., Erga, S.R., Aursland, K., Olseng, C.D. 2007. Laboratory measurements of light scattering from marine particles. Limnol. Oceanogr.: Methods 5: 34-40

Svensen, Ø., Frette, Ø, Erga, S.R. 2007. Scattering properties of microalgae: the effect of cell size and cell wall. Appl. Optics 46: 5762-5769

Aure, J., Strand, Ø., Erga, S.R., Strohmeier, T. 2007. Primary production enhancement by artificial upwelling in a western Norwegian fjord. Mar. Ecol. Prog. Ser. 352: 39-52

Hamre, B., Stamnes, J.J., Frette, Ø, Erga, S.R., Stamnes, K. 2008. Could stratospheric ozone depletion lead to enhanced aquatic primary production in polar regions. Limnol. Oceanogr. 53: 332-338

Erga, S.R., Lie, G.C., Aarø, L.H., Aursland, K., Olseng, C.D., Frette, Ø., Hamre, B. 2010. Fine scale vertical displacement of Phaeodactylum tricornutum (Bacillariophyceae) in stratified waters: Influence of halocline and day length on buoyancy control. J. Exp. Mar. Biol. Ecol. 384: 7-17

Magnesen, T., Erga, S.R., Christophersen, G. 2010. Growth of scallop spat in a raceway nursery during autumn conditions in western Norwegian coastal waters. J. Shellfish Res. 29: 45-54

Paulson, R., Knutsen, G., Erga, S.R. 2010. Isocitrate lyase activity patterns during cell cycle in synchronous cultures of Chlamydomonas reinhardtii (Chlorophyceae). Alogological. Stud. 133: 43-64

Initiation and conduction of special research projects – Projects funded by the Norwegian Research Council are: 1. “Pysiological effects of UV-radiation on key species of marine phytoplankton”, 1993-1995, in collaboration with senior scientist Francisco Rey, Institute of Marine Research, Bergen. 2. “Light and Life in Norwegian Waters (LLNW)”, a pilot project, 1997. 3. “LLNW - Program for Advanced equipment”, with the overall objective of purchasing optical equipment and instruments for laboratory and field measurements, 1998. 4. “LLNW”, a continuation and expansion of project 2, with the overall objective of developing optical instrumentation and methods to characterize optical properties, composition, underwater light levels, ocean colour, and primary production of high latitude coastal waters, 1998-2000. 5. “Light and Life in Icy Arctic Waters”, with the overall objective of modelling irradiance and primary production in a coupled atmosphere-snow-ice-ocean system, 2000-2002. 6. "Light and Life in African Environment", with the overall objective of studying the connection between light and life in Lake Victoria, in collaboration with Makarere University, Kampala, Uganda, 1998. 7.  and “LLNW: Physics/Biology Based Approach to Satellite Monitoring of Primary Production and Algal Blooms”, with the overall objective of developing, implementing, testing, and validating quantitative algorithms for characterizing and monitoring marine constituents, underwater light levels, and primary production in Norwegian coastal waters from satellite measurements of ocean colour, medio 2002- medio 2005. All the “Light and Life” projects have been conducted in close collaboration with professor Jakob J. Stamnes and associated professor Øyvind Frette at the Department of Physics and Technology, UoB.

I also have a collaboration with the senior scientists Jan Aure and Øivind Strand, and scientist Tore Strohmeier at the Institute of Marine Research (IMR), Bergen since 2005. The work is executed in the Lysefjord, Rogaland (east of Stavanger) and is funded by the Strategic Institute Programme  ”CANO; Carrying capacity in Norwegian Aquaculture" and the research programme "GATE; Growth performance and detoxification of mussels cultured in a fjord enhanced by forced upwelling of nutrients from deep water", both projects at IMR.