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Biosynthesis of hydroxylated polybrominated diphenyl ethers and the correlation with photosynthetic pigments in the red alga Ceramium tenuicorne
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
2017 (English)In: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 133, 51-58 p.Article in journal (Refereed) Published
Abstract [en]

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been identified in a variety of marine organisms from different trophic levels indicating a large spread in the environment. There is much evidence pointing towards natural production as the major source of these compounds in nature. However, much is still not known about the natural production of these compounds. Seasonal trend studies have shown large fluctuations in the levels of OH-PBDEs in Ceramium tenuicorne from the Baltic Sea. Yet, even though indications of stimuli that can induce the production of these compounds have been observed, none, neither internal nor external, has been assigned to be responsible for the recorded fluctuations. In the present study the possible relationship between the concentration of pigments and that of OH-PBDEs in C. tenuicorne has been addressed. Significant correlations were revealed between the concentrations of all OH-PBDEs quantified and the concentrations of both chlorophyll a and Σxanthophylls + carotenoids. All of which displayed a concentration peak in mid-July. The levels of OH-PBDEs may be linked to photosynthetic activity, and hence indirectly to photosynthetic pigments, via bromoperoxidase working as a scavenger for hydrogen peroxide formed during photosynthesis. Yet the large apparent investment in producing specific OH-PBDE congeners point towards an targeted production, with a more specific function than being a waste product of photosynthesis. The OH-PBDE congener pattern observed in this study is not agreeable with some currently accepted models for the biosynthesis of these compounds, and indicates a more selective route than previously considered in C. tenuicorne.

Place, publisher, year, edition, pages
2017. Vol. 133, 51-58 p.
Keyword [en]
Ceramium tenuicorne, Ceramiaceae, Biosynthesis, OH-PBDE, Bromophenols, Pigments, Chlorophyll
National Category
Chemical Sciences
Research subject
Environmental Chemistry
Identifiers
URN: urn:nbn:se:su:diva-135593DOI: 10.1016/j.phytochem.2016.10.009ISI: 000390513000006OAI: oai:DiVA.org:su-135593DiVA: diva2:1046755
Available from: 2016-11-15 Created: 2016-11-15 Last updated: 2017-02-07Bibliographically approved
In thesis
1. Hydroxylated polybrominat­ed diphenyl ethers in Baltic Sea biota: Natural production, food web distribution and biotransformation
Open this publication in new window or tab >>Hydroxylated polybrominat­ed diphenyl ethers in Baltic Sea biota: Natural production, food web distribution and biotransformation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are naturally produced in aquatic ecosystems e.g. by algae. Many OH-PBDEs have been observed to be highly bioactive and to cause adverse effects through several pathways, e.g. via disrupting oxidative phosphorylation (OXPHOS). The levels of some OH-PBDEs have increased in Baltic biota over the past decades. This may be associated with the nutrient enrichment of the Baltic Sea, which has favored growth of some of the OH-PBDE producers.

Ceramium tenuicorne has been suggested to be a producer of OH-PBDEs in the Baltic Sea, which is supported by the results presented in this thesis. The levels of OH-PBDEs were observed to fluctuate greatly in C. tenuicorne over the summer season, and to correlate with the levels of pigments in the algae. However, the observed congener pattern in C. tenuicorne questioned theories regarding the mechanism of their biosynthesis. The results indicate a much more selective pathway for biosynthesis than previously suggested for the production of OH-PBDEs.

One of the most abundant OH-PBDEs in C. tenuicorne, 6-OH-BDE137, has previously been observed to be toxic to bacteria, fungi, and crustaceans. Furthermore, Baltic gammarids seemed to change their feeding preferences towards less grazing on C. tenuicorne during the production peek of OH-PBDEs in the alga. This suggests that OH-PBDEs may serve as allelochemical defense agents for C. tenuicorne.

The transport and fate of OH-PBDEs through a Baltic food chain was also studied, including C. tenuicorne, Gammarus spp., three-spined stickleback (Gasterosteus aculeatus), and perch (Perca fluviatilis). A small portion of the OH-PBDEs were observed to be methylated in the alga, or by associated bacteria. The methylated OH-PBDEs biomagnified in the food chain up to perch, in which they were converted back to the OH-PBDEs via demethylation. The OH-PBDEs and their methylated counterparts were also partially debrominated in the food chain, which resulted in high concentration of 6-OH-BDE47 in the perch. This congener is the most toxic OH-PBDE with regards to OXPHOS disruption.

Another biotransformation of OH-PBDEs was identified in Baltic Sea blue mussels (Mytilus edulis). High concentrations of OH-PBDEs were conjugated with lipophilic moieties, e.g. fatty acids. This increases the residence time of the OH-PBDEs in the mussels. Mussels have been suggested to conjugate steroids with fatty acids as a means to regulate hormone levels. The conjugation of OH-PBDEs to fatty acids may occur due to intrusion into this pathway. Methods were developed to include quantification of conjugated OH-PBDEs in the analysis of mussels.

OH-PBDEs were also quantified in blood from Baltic Sea grey seals (Halichoerus grypus). Seals originating from the Baltic proper were observed to be more highly exposed to 6-OH-BDE47 than seals from the Gulf of Bothnia. However, the levels of OH-PBDEs were generally low. A major effort was invested into securing these results, including development of a new analytical method. Blood obtained from dead seals is a difficult matrix for quantification of OH-PBDEs, and previous attempts using an established method yielded unsatisfactory results.

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University, 2016. 78 p.
Keyword
OH-PBDEs, Baltic Sea, Biosynthesis, Environmental fate, Wildlife exposure, Metabolism, Analytical methods, Ceramium tenuicorne, Blue mussel, Gammarus spp., Stickleback, Perch, Grey Seal
National Category
Other Chemistry Topics
Research subject
Environmental Chemistry
Identifiers
urn:nbn:se:su:diva-135789 (URN)978-91-7649-585-8 (ISBN)978-91-7649-586-5 (ISBN)
Public defence
2017-01-17, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Available from: 2016-12-22 Created: 2016-11-23 Last updated: 2016-12-08Bibliographically approved

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