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
Cyanobacteria Occurrence and Nitrogen Fixation Ratesin the Seagrass Meadows of the East Coast of Zanzibar: Comparisons of Sites With and Without Seaweed Farms
Stockholm University, Faculty of Science, Department of Botany. (Plant Physiology, Birgitta Bergman's group)
University of Dar es Salaam, Tanzania.
2008 (English)In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 7, no 1, 45-55 p.Article in journal (Refereed) Published
Abstract [en]

The occurrence and biological nitrogen fixation rates of epiphytic and benthic diazotrophs were studied in seagrass meadows at sites with seaweed farms and at a control site without seaweed farms from two locations, Chwaka Bay and Jambiani, along the east coast of Zanzibar. Ten species of cyanobacteria were encountered and Lyngbya majuscula and Microcoleus sp. were dominant in Chwaka Bay and Jambiani respectively. Cyanobacterial occurrence was significantly higher in seagrass meadows without seaweed farms (P<0.02), but there was no significant difference (P>0.05) in biomass (chlorophyll a). Biomass averaged 2.96±0.73 and 3.10±1.24 μg Chl a cm-2 in seaweed farms and 3.46±1.72 μg Chl a cm-2 at Chwaka Bay and 3.14±1.31 μg Chl a cm-2 at Jambiani in transects without seaweed farms. Nitrogenase activity showed no significant differences between sites with and without seaweed farms, (P=0.66 Chwaka and 0.75 at Jambiani). Fixation rates in sites without seaweed farms averaged 35.8±39.9 (Chwaka Bay) and 13.1±12.7 (Jambiani) μmol of C2H4 produced/m2/hr, while with seaweed farms averaged 22.6±22.5 and 12.8±14.9 μmol C2H4 produced/m2/hr at the same sites. There were no significant differences in nutrient levels between locations, sites with and without seaweed farms, or between tidal levels except for nitrate, which was significantly higher (P=0.01) at Jambiani than at Chwaka Bay. It was concluded that diazotrophs contribute a significant amount of exogenous nitrogen to the seagrass ecosystem, but no significant differences could be found between sites with or without seaweed farms.

Place, publisher, year, edition, pages
Zanzibar, Tanzania: Wiomsa , 2008. Vol. 7, no 1, 45-55 p.
Keyword [en]
Cyanobacteria, Nitrogen Fixation, Seagrass, Seaweed Farming
National Category
Ecology
Research subject
Marine Ecology
Identifiers
URN: urn:nbn:se:su:diva-38275OAI: oai:DiVA.org:su-38275DiVA: diva2:309239
Projects
Masma SeagrassSida/SAREC Bilateral Marine Science Programme
Available from: 2010-04-07 Created: 2010-04-07 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

Search in DiVA

By author/editor
Hamisi, Mariam
By organisation
Department of Botany
In the same journal
Western Indian Ocean journal of marine science
Ecology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 144 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