Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Nitrogen fixation by epiphytic and epibenthic diazotrophs associated with seagrass meadows along the Tanzanian coast, Western Indian Ocean
Stockholm University, Faculty of Science, Department of Botany. (Plant Physiology, Birgitta Bergman's group)
University of Dar es Salaam, Tanzania.
University of Dar es Salaam, Tanzania.
Stockholm University, Faculty of Science, Department of Botany. (Plant Physiology, Birgitta Bergman's group)
2009 (English)In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 57, 33-42 p.Article in journal (Refereed) Published
Abstract [en]

Seasonal, diurnal, and age-dependent variations in nitrogen fixation (nitrogenase activity) by epiphytic diazotrophs colonizing the seagrasses Halodule uninervis, Cymodocea rotundata, Thalassodendron ciliatum, and Thalassia hemprichii, and by epibenthic diazotrophs associated with seagrass-vegetated and nonvegetated sediments, were estimated at 2 sites along the Tanzanian coast, Western Indian Ocean. Acetylene reduction-gas chromatography showed that nitrogenase activity values were significantly higher (p = 0.0004) at the site with low nutrient levels (Mjimwema) than at the site with higher nutrient levels (Ocean Road). The nitrogenase activity ranged from 10 to 192 nmol N g–1 h–1 for H. uninervis, 7 to 80 nmol N g–1 h–1 for C. rotundata, 10 to 75 nmol N g–1 h–1 for Thalassia hemprichii, and from 4 to 61 nmol N g–1 h–1 for Thalassodendron ciliatum. Nitrogenase activity values in sediments covered by seagrasses were significantly higher than in surrounding nonvegetated sediments (t = 4.021, p = 0.0005). Significant variations in nitrogenase activity were apparent depending on leaf age and season, with highest activity being found in mid-aged leaves during the northeastern monsoon (NEM), and in older leaves during the southeastern monsoon (SEM). Daytime nitrogenase activity was appreciable on above-ground seagrass parts, while rhizosphere activity peaked at night-time. Collectively our data show that diazotrophs (cyanobacteria and other bacteria) are associated with seagrasses (leaves and roots), and potentially constitute an integral part of the ecosystem. They show highly dynamic nitrogenase activity and a succession in seagrass colonization, and we concluded that their presence may contribute to the productivity of the seagrass beds.

Place, publisher, year, edition, pages
Germany: Inter-Research , 2009. Vol. 57, 33-42 p.
Keyword [en]
Nitrogen fixation, Diazotrophs, Epibenthic, Epiphytes, Seagrass, Western Indian Ocean
National Category
Ecology
Research subject
Marine Ecology
Identifiers
URN: urn:nbn:se:su:diva-38264DOI: 10.3354/AME01323ISI: 000271056500003OAI: oai:DiVA.org:su-38264DiVA: diva2:308484
Projects
Sida/SAREC Bilateral Marine Science Programme
Available from: 2010-04-06 Created: 2010-04-06 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Genetic variability and nitrogenase activity of cyanobacterial communities associated with tropical seagrass meadows (western Indian Ocean)
Open this publication in new window or tab >>Genetic variability and nitrogenase activity of cyanobacterial communities associated with tropical seagrass meadows (western Indian Ocean)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Tropical seagrass ecosystems are highly productive and important for sustaining marine life and associated coastal societies. In this study, the diversity and role of nitrogen-fixing cyanobacteria associated with five common seagrass genera in coastal regions of the western Indian Ocean (WIO; Tanzania) were examined, as well as the impact of anthropogenic activities. Cyanobacteria were characterized morphologically and genetically (16S rRNA and nifH gene phylogeny), as were diel variations in nifH gene expression, NifH protein levels and nitrogenase activity. The results revealed that WIO seagrass beds supported rich cyanobacterial diversity and that these represented approx. 83% of total clones obtained (DNA and RNA nifH clone libraries). Non-heterocystous genera, such as Oscillatoria, Lyngbya, Leptolyngbya, Phormidium and Microcoleus dominated, while heterocystous morphotypes such as Calothrix were less frequent and unicellular morphotypes (e.g. Gloeocapsa, Chroococcus and Chroococcidiopsis) were few. Additionally, the phylogenetic analysis revealed several novel uncharacterized cyanobacterial clades. Cyanobacterial composition and nitrogenase activity varied over seasons and between the seagrass species. Day time nitrogenase activity originated primarily from heterocystous phylotypes, while non-heterocystous filamentous phylotypes fixed nitrogen at night. The highest activity in the diel cycle was 358 ± 232 nmol C2H4 g-1 h-1at 09.00 associated with epiphytes of the seagrass Cymodocea. Nitrogenase activity was consistently lower in anthropogenically disturbed (eutrophication) seagrass sites. Such data suggest that diazotrophic cyanobacteria may be a significant source of ‘new’ nitrogen in the often oligotrophic coastal regions of tropical oceans. It is also proposed that the rapid shifts in the cyanobacterial population and function found may also be used as early disturbance indicator in coastal management practices.

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2010. 57 p.
Keyword
cyanobacteria, nitrogenase activity, diazotrophs, seagrass, western Indian ocean
National Category
Botany
Research subject
Plant Physiology
Identifiers
urn:nbn:se:su:diva-38278 (URN)978-91-7447-001-7 (ISBN)
Public defence
2010-05-06, föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
SIDA SAREC Bilateral Marine Sciences ProjectThe Swedish Foundation for International Cooperation in Research and Higher Education
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript. Available from: 2010-04-14 Created: 2010-04-07 Last updated: 2010-04-14Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Hamisi, MariamBergman, Birgitta
By organisation
Department of Botany
In the same journal
Aquatic Microbial Ecology
Ecology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 81 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf