February 1st to 5th 2016
Olhão, Portugal
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Population dynamics of temperate kelp near their low-latitude limit

Scientific Exhibition
Future Oceans
Wednesday, February 3, 2016 -
18:30 to 20:00

Pereira, T.R. 1 Engelen, A.H. 2 Pearson, G.A. 3 Valero, M. 4 Serrão, E.A. 5

1Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal

Due to the lack of long term monitoring efforts, little information is available on temperate kelp populations at their shallower and lower latitude distribution limits, in Northern Portugal. To overcome this, populations of Laminaria ochroleuca were monitored for two years, and Laminaria hyperborea and Saccorhiza polyschides for one year. Projection matrix models were used to assess the state and most important demographic processes for the maintenance and growth of these populations. Furthermore, during the second year of census, the Northern Portuguese coast was impacted by a strong late winter storm that caused extensive destruction in these communities, allowing an assessment of their ability to recover.Population dynamics and initial state differed strongly among species. Due to the seasonality of macroscopic sporophytes of S. polyschides in Portugal, its persistence depended totally on the survival of microscopic forms through winter. Our results show that yearly climate variation may affect their recruitment timing, making it impossible for them to reach maturity, thus impairing local spore production. In contrast, year-round production of L. ochroleuca spores offers and advantage as it is less likely to be impaired by extreme events. Nevertheless, although populations of the two species were resilient to major disturbances, L. ochroleuca took longer than two years to recover, while S. polyschides was able to recover in the next year. This indicates that if recurrence and duration of such highly energetic storms increases with climate change, these populations are expected to be affected, becoming gradually younger and providing lower canopy.In contrast, abiotic factors and insufficient dispersal from the subtidal already impaired repopulation of L. hyperborea.
keywords: 
Laminaria ochroleuca , Laminaria hyperborea , Saccorhiza polyschides , population dynamics, periodic dis

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