Effects of ultraviolet radiation on marine phytoplankton

Research output: ThesisDoctoral Thesis (compilation)

Abstract

This thesis examines the effects of artificial and solar ultraviolet radiation on photosynthesis, growth rate, phototactic orientation and motility of marine phytoplankton. The effects of UV-B (280-320 nm) radiation in combination with humic substances, as well as the ability of the organisms to adapt and/or recover from exposure to UV-B radiation, were also investigated. Phototactic orientation and growth rate were significantly impaired in the dinoflagellate Gyrodinium aureolum, when exposed to artificial UV-B radiation compared to organisms only exposed to photosynthetically active radiation (PAR, 400-700 nm). The presence of humic substances during UV-B treatment reduced the inhibition of phototaxis and growth rate in G. aureolum. Four other dinoflagellates, Prorocentrum minimum (Atlantic and Kategatt strains), Heterocapsa triquetra, Amphidinium carterae and a diatom Phaeodactylum tricornutum also showed a significant inhibition in growth rate when exposed to artificial UV-B radiation. P. minimum and P. tricornutum cells pre-exposed for over a year to artificial UV-B radiation showed a higher tolerance to short-term UV-B exposure than control organisms. This UV-B tolerance was more pronounced in the diatom species. Motility of H. triquetra and the two strains of P. minimum was decreased by artificial UV-B radiation. Control and UV-B adapted cells of P. minimum, showed similar inhibition in motility with increasing UV-B. However, when the cells were transferred to control conditions (PAR only) for 24 or 48 h, motility partly recovered and the UV-B adapted cells recovered more than the control cells. No significant differences in motility of two strains of P. minimum, kept at different depths in coastal waters, were seen for in situ incubations with or without natural solar UV radiation. Oxygen evolution and carbon uptake measurements were used to determine the effects of solar and artificial UVR on photosynthesis in both natural phytoplankton populations and in laboratory cultured monocultures. Carbon uptake in natural phytoplankton communities was inhibited by solar UVR. At a depth of 50 cm in coastal waters, UV-B radiation was associated with a greater inhibition of photosynthesis than UV-A (320-400 nm), but at greater depths there were no significant differences between different light incubations. When laboratory cultured cells from the dinoflagellate P. minimum and the diatom P. tricornutum were exposed to short-term artificial UV-B radiation, both photosynthetic quantum efficiency and saturation level decreased. This was most pronounced for the diatom. Long-term UV-B adapted dinoflagellates incubated under the same artificial UV-B radiation showed an increase in quantum efficiency and also increased tolerance to short-term UV-B exposure compared to control cells. The comparisons between UV-B effects under artificial and natural radiation conditions show that field tests are necessary for correct predictions of effects of stratospheric ozone depletion.

Details

Authors
  • Tom Nielsen
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Biological Sciences

Keywords

  • UV-B, UV-A, Ultraviolet radiation, Phytoplankton, Photosynthesis, Ozone depletion PAR, Oxygen evolution, Motility, Marine ecosystem, Humic substances, Growth rate, Dinoflagellate, Carbon uptake, Diatom, Botany, Botanik, Electromagnetism, optics, acoustics, Elektromagnetism, optik, akustik
Original languageEnglish
QualificationDoctor
Awarding Institution
Supervisors/Assistant supervisor
  • [unknown], [unknown], Supervisor, External person
Award date1996 May 31
Publisher
  • Section of Plant Physiology, Lund University, P.O. Box 117. S-221 00 Lund Sweden,
Print ISBNs91-628-2069-9
Publication statusPublished - 1996
Publication categoryResearch
Externally publishedYes

Bibliographic note

Defence details Date: 1996-05-31 Time: 10:00 Place: Lund, Sweden External reviewer(s) Name: Herndl, Derhard J. Title: Dr Affiliation: [unknown] --- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Biology building (Closed 2011) (011008000)