Antioxidative properties of marine macroalgae from the Arctic Antioxidative Eigenschaften mariner

200 Pages·2005·3.53 MB·English

Antioxidative properties of marine macroalgae
from the Arctic
Antioxidative Eigenschaften mariner Makroalgen
der Arktis
Angelika Dummermuth
Ber. Polarforsch. Meeresforsch. 458 (2003)
-
ISSN 1618 3193
Angelika Dummermuth
Alfred-Wegener-Institut füP olar- und Meeresforschung
In der Helmholtzgemeinschaft
Am Handelshafen 12
27570 Bremerhaven
Die vorliegende Arbeit ist die inhaltlich unverändert Fassung einer
kumulativen Dissertation, die in der Projektgruppe "Solare UV-Strahlung"
bei Prof. Christian Wiencke und Prof. Dr. Ulf Karsten angefertigt und
2003 dem Fachbereich 2 (BiologieIChemie) der UniversitäB remen
vorgelegt wurde.
CONTENTS
List of abbreviations
1 General introduction
1.1 The Arctic environment
1.2 Marine macroalgae and their adaptations to the polar environment
1.3 The "ozone hole" and ultraviolet radiation
1.4 Effects of UV radiation On macroalgae
1.5 Oxidative stress and reactive oxygen species
1.5.1 ROS formation in the aquatic environment
1.5.2 Biogenic ROS formation
1.6 Effects of oxidative stress
1.7 Antioxidative enzymes and antioxidants
1.8 Aims of the study
1.9 Thesis outline
2 Material and Methods
2.1 Study site and sampling
2.2 Cultivation techniques and applied irradiance
2.3 Measurement of photosynthesis
2.4 Measurement of growth
2.5 Antioxidative enzymes
2.6 Ascorbic acid
2.7 Mycosporine-like amino acids (MAAs)
2.8 Statistics
2.9 Overview On the experiments performed and the respective
parameters under investigation
3 Results
3.1 Qualitative and quantitative distribution of antioxidants in Arctic
macroalgae
Contents
3.2 Effects of UVR on the ecophysiology of Arctic marine macroalgae
3.2.1 Effects of UVR On the antioxidative defence mechanism
3.2.2 Interactive effects of UVR and salinity On the ecophysiology of
Arctic marine macroalgae
3.3 Physiological response patterns against oxidative stress
3.3.1 Short-term exposure to H202
3.3.2 Long-term exposure to H202
3.4 Seasonal variation of antioxidants, pigments and UV-protective
substances and growth
4 General discussion and conclusions
4.1 General aspects on the occurrence of antioxidative substances in
marine macroalgae
4.2 Effects of UV-exposure on the antioxidative response of marine
macroalgae
4.3 Interactive effects of UV-exposure and changes in salinity
4.4 Other factors influencing the antioxidative status of marine macroalgae
4.5 Direct oxidative stress derived by H202e xposure
4.6 Macroalgae as source for hitherto unknown antioxidative substances
4.7 Antioxidative responses and species ecology
4.7.1 Vertical zonation patterns
4.7.2 Seasonality
4.8 Methodological aspects
4.9 Concluding remarks and future perspectives
5 Publications
List of publications and my share thereof
Publication I: Enzymatic defences against photooxidative stress induced
by ultraviolet radiation in Arctic marine macroalgae. J. Aguilera, A.L.
Dummermuth, U.^Karsten, R. Schriek, C. Wiencke (2002) Polar
Bi010gy 25:432-441
Publication 11: Interactive effects of ultraviolet radiation and salinity On the
Contents
ecophysiology of two Artic red algae from shallow waters. U. Karsten,
A.L. Dummermuth, K. Hoyer, C. Wiencke (2003) Polar Biology 26:249-
25
Publication III: Responses of marine macroalgae to hydrogen-peroxide- 78
stress. A.L. Dummermuth, U. Karsten, K.M. Fisch, G.M. KönigC .
Wiencke (2003) Journal of Experimental Marine Biology and Ecology
289110 3-121
Publication IV: Antioxidative properties of three Arctic green macroalgae, 98
A.L. Dummermuth, U. Karsten, C. Wiencke. Phycological Research,
submitted
Publication V: Seasonal variation in ecophysiological patterns in two red 118
macroalgae from Arctic Kongsfjord (Spitsbergen, Norway) in a long-
term culture study with emphasis On UV protective mechanisms. I.
Palmaria palmata (L.) Greville. A.L. Dummermuth, K. Hoyer, U.
Karsten, C. Wiencke. Marine Ecology Progress Series, submitted
Publication VI: Seasonal variation in ecophysiological patterns in two red 147
macroalgae from Arctic Kongsfjord (Spitsbergen, Norway) in a long-
term culture study with emphasis On UV protective mechanisms. 11.
Devaleraea ramentcaea (L.) Guiry. A.L. Dummermuth, K. Hoyer, U.
Karsten, C. Wiencke. Marine Ecology Progress Series, submitted
6 References
Acknowledgements
111

Contents
TMS tetramethylsilane
TSP total soluble protein (mg g" FW or mg g" DW)
UVA ultraviolet A radiation (320-400 nm)
UVB ultraviolet B radiation (280-320 nm)
UVC ultraviolet C radiation (19 0-280 nm)
UVR ultraviolet radiation (19 0-400 nm)
W watt
Summary
SUMMARY
The present study focuses on oxidative stress and the ability of Arctic marine
macroalgae to cope with it. Oxidative stress can derive from biogenic formation of
reactive oxygen species (ROS) induced by different environmental stress factors, for
example ultraviolet radiation (UVR). Also high temperature, temperature changes,
nutrient deficiency, heavy metals and other factors may induce oxidative stress. In
aquatic environments algae may also be exposed to direct oxidative stress, where
UVR induces formation of hydrogen peroxide (H202) by photoactivation of dissolved
organic material (DOM), photochemical degradation and liberation of exited
electrons, which initiate reduction of molecular oxygen. This process is particularly
promoted in surface waters, tidal pools or flat water areas, where high concentrations
of DOM and oxygen occur. Stratospheric ozone depletion leads to an increase in the
short wavelengths of UVR and in consequence to an increase in Hg02 formation in
surface waters. Elevated levels of UVR, resulting from stratospheric ozone depletion,
are the major source for oxidative stress.
The investigations presented were conducted to study the effects of oxidative stress
on the physiology of Arctic macroalgae in the laboratory and in the field. The results
present a basis for predicting future changes within Arctic coastal ecosystems with
respect to increasing UVB levels and accompanied oxidative stress.
Arctic macroalgae are subjected to strong seasonal and daily changes in the
radiation climate. They are exposed to six months of darkness during polar night, but
also suddenly exposed to high radiation in spring after break-up of the sea ice,
especially during low tide at high water transparency, leading to oxidative stress for
the algae.
When produced, active oxygen species are eliminated rapidly by efficient
antioxidative Systems as there are the enzymatic detoxifying systems of superoxide
dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione
reductase (GR), as well the antioxidant ascorbic acid and other small molecule
antioxidants (glutathione, ß-carotena nd a-tocopherol), which were not presented in
this study.
The major result of the study is that the occurrence of antioxidants in Arctic marine
macroalgae is related to the vertical depth distribution along the shore. Species living
Summary
in the intertidal and upper sublittoral exhibited higher antioxidative protection,
whereas species from deeper habitats showed lower levels of biochemical defence
against oxidative stress. Another result is the occurrence of a different antioxidant
Pattern in the Chlorophyta, Rhodophyta and Phaeophyta. Green macroalgae
exhibited highest enzyme activities and ascorbic acid contents, whereas red and
brown algal species showed lower antioxidant activities.
These antioxidative protection mechanisms are induced or inhibited in response to
the various environmental stressors. The sensitivity of photosynthesis to artificial
oxidative stress derived by exposure to H202, and the antioxidative properties of
several marine macroalgae under these conditions was investigated. Species
exhibiting high photosynthetic rates under oxidative stress were regarded as high
tolerant to H202 and equated with a high antioxidative potential. The cause of the
high antioxidative potential was different in the most tolerant species. Chaetomorpha
melagonium for example exhibited extremely high ascorbic acid contents comparable
to citrus fruits and increased GR activity, indicating an active scavenging of H202 via
the ascorbate-glutathione cycle. In Chaetomorpha linum, in contrast, photosynthetic
efficiency was decreased strongly and correlated to the low SOD activity under high
oxidative stress, indicating a direct toxicity effect by H202.T he deep water red alga
Polysiphonia arctica followed another strategy and increased APX and CAT activities
in response to H202. Additionally, two new bromophenolic compounds with
antioxidative activities were identified in this species (2,3-dibromo-4,5-
dihydroxybenzyl methyl ether, and TMS derivative of 2,3-dibromo-4,5-
dihydroxybenzyl alcohol).
The influence of other abiotic factors, such as salinity, was examined as well as the
interactive effects of UVR and salinity on photosynthesis and MAAs evaluated. Under
different salinity concentrations (15, 34 and 50 PSU) the MAA content did not rise in
Arctic Devaleraea ramentacea and Palmaria palmata, but in combination with UVR
an increase was observed. Optimum quantum yield in P. palmata was much more
strongly effected by salinity than D. ramentacea and died under 15 PSU with or
without additional UVR. While D. ramentacea exhibited euryhaline features and
acclimated well to UVR applied, P. palmata can be characterised as stenohaline due
to its high sensitivity under hyposaline conditions leading to cell death.
VII
Summary
Furthermore the effects of seasonally fluctuating daylengths and additional UVR
exposure On pigment concentrations, antioxidative enzyme activities, ascorbic acid,
MAAs and growth was investigated in D, ramentacea and P. palmata in a long-term-
culture study. Both species showed a seasonal acclimation of chlorophyll and
phycobiliproteins to the fluctuating daylength. Ascorbic acid content was high
throughout the whole year and especially in winter in thalli exposed to UVR in the
previous summer period. Further protection was provided by the antioxidative
enzyme activities, which were up-regulated in winter to prepare the algae for the
coming radiation period, indicating a photoperiodic control for the antioxidative
enzymes as well as for ascorbic acid. Additionally the UV-absorbing MAAs were up-
regulated in response to the increasing daylength and UV-exposure from spring
onwards enlarging the protection of the algae in times of high radiation stress. Slight
differences between both species may be explained by the different biogeographical
and depth distribution. Whereas the Arctic endemic D. ramentacea occupies the
uppermost habitats within the Rhodophyta at Arctic Kongsfjord from 0.5 to 8m depth,
P. palmata exhibits its northernmost distribution limit at the study site and inhabits
slightly deeper habitats with 2 to 10m depth.
All data presented demonstrate distinct inductionlinhibition patterns for the
antioxidative activities and photoprotective mechanisms present in marine
macroalgae from the Arctic. In general, the antioxidative status of marine macroalgae
depends on the oxidative stress they are subjected to in their habitat. Several factors
seem to be involved in regulation processes of the antioxidant status of marine
macroalgae but still are not proved. Future studies should therefore focus on the
regulatory processes.
VIII