Biology Reference
In-Depth Information
17.7 Conclusions
Floating seaweeds are an important component of the pelagic environment, pre-
dominantly in cold temperate and subpolar regions. Although most of the common
floating algae naturally grow in benthic environments, these species show specific
adaptations to the floating lifestyle which allow for persistence at the sea surface
over prolonged time periods. These adaptations indicate selection for traits that
facilitate floating persistence, suggesting that floating is a common and integral part
of the species' life cycle (see e.g., Roth
ausler et al. 2011a ). Long-term floating
supports genetic exchange between distant populations, natural range expansion,
and regional population persistence through re-colonization after local extinctions.
Floating seaweeds significantly contribute to the complexity of the pelagic
environment providing habitat for a rich community of associated rafters. Large
patches of floating algae can be considered biodiversity hotspots, which catalyze
the accumulation of species and the development of interspecific interactions
among rafters and with their algal raft. For the associated rafters the patches of
floating algae provide a highly dynamic habitat, which is subject to continuous
changes depending on fluctuations of the biotic and abiotic environment. Consider-
able changes of the algal habitat during the pelagic journey are likely to exert strong
selective pressure on the associated rafters.
Genetic homogeneity among distant populations of seaweeds and associated
rafters, especially in the southern ocean, is the result of continuous exchange of
floating individuals across extensive areas of open ocean. Continuous large-scale
dispersal via floating algae adds a cosmopolitan dimension to marine biogeography
that might not have been achieved through dispersal of larvae and spores alone.
Acknowledgements ER and MT were supported through FONDECYT 1100749 during the
preparation of this contribution. ER is grateful for a JSPS Research Fellowship from the Japan
Society for the Promotion of Science for providing financial support.
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