<p>Summer blooms of filamentous, diazotrophic cyanobacteria are typical of the Baltic Sea Proper, and are dominated by <i>Aphanizomenon </i>sp<i>.</i> and the toxic <i>Nodularia spumigena.</i> Although occurring every summer, the blooms vary greatly in timing and spatial distribution, making monitoring difficult and imprecise. This thesis studies how the spatial variability of Baltic cyanobacterial blooms influences estimates of abundance, vertical and horizontal distribution and N<sub>2</sub>-fixation. Implications for sampling and monitoring of cyanobacterial blooms are also discussed.</p><p>The results of the thesis confirm the importance of diazotrophic cyanobacteria in providing N for summer production in the Baltic Proper. It also highlights the large spatial and temporal variation in these blooms and argues that improved spatial coverage and replication could make monitoring data more useful for demonstrating time trends, and for identifying the factors regulating the blooms. The vertical distribution of <i>Aphanizomenon</i> and <i>Nodularia</i> was found to be spatially variable, probably as a combination of species-specific adaptations and ambient weather conditions. Vertical migration in <i>Aphanizomenon</i> was more important towards the end of summer, and is probably regulated by a trade-off between P-availability and light and temperature.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:su-7099 |
| Date | January 2007 |
| Creators | Almesjö, Lisa |
| Publisher | Stockholm University, Department of Systems Ecology, Stockholm : Systemekologiska institutionen |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
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