Seaweeds and Their Communities in Polar Regions - Seaweed Biology - page 275

use of fossil fuels (see Chap. 19 by Roleda and Hurd). When CO 2 enters the ocean
surface, CO 2 and bicarbonate concentrations will increase, and in contrast, pH and
carbon ion concentrations will decrease (Feely et al. 2004 ). As the solubility of
gases is higher in colder waters, polar regions will be most strongly affected. In
general, effects of ocean acidification on seaweeds and their communities are
poorly understood. Elevated CO 2 levels may support primary production, although
species with a carbon concentrating mechanism (Giordano et al. 2005 ) may show
less strong responses. Calcification of calcareous algae will be impaired (Leclerc
et al. 2000 ). For polar waters, there is only one publication addressing this impor-
tant question (McClintock et al. 2009 ). Therefore, we need to study the responses of
polar seaweeds to elevated CO 2 levels and ocean acidification in more detail and
also investigate possible acclimation processes.
13.6 Conclusion
In the above summary of our present knowledge about polar seaweeds, gaps are
clearly apparent. The biodiversity of polar algae must be studied more intensively
to better understand their evolutionary history, biogeographical relationships, and
their physiological performance. With respect to their phenology, an open question
is the perception of daylength, which controls seasonal growth and reproduction in
endemic Antarctic and Arctic seaweeds. Storage of photosynthetic products, their
remobilization and translocation to the meristems, and prerequisites for growth in
darkness and low light are not fully explored. Moreover, it is necessary to identify
the thresholds of tolerance to low and high light, UV radiation, temperature,
freezing, and other stresses and to quantify the related physiological processes by
genomic, proteomic, and metabolomic approaches in order to better understand the
ecology of individual species.
In seaweed communities from the Antarctic, the function of secondary
metabolites in chemical defense and functioning of these systems need to be studied
more intensively, not only with respect to herbivory, but also to biofouling. The
putative photoprotective role of phlorotannins needs to be studied in greater detail.
As the molecular structure of phlorotannins is still obscure, more studies are
necessary also in this field. An improved knowledge of these compounds should
allow us to investigate the effects of these brown algal secondary metabolites on
grazers in a better way. In particular, the effects on the digestive system of
consumers should come into the focus of science. Compared to Antarctic seaweeds,
much less is known about seaweed-herbivore relationships in the Arctic, which
therefore need to be studied much more intensively. Finally, the effect of global
climate changes, especially of global warming and ocean acidification on seaweeds
and their communities, must urgently be studied in order to develop scenarios about
changes in the functioning of polar seaweed systems. In this respect, special
emphasis should be laid on interactive effects between temperature, CO 2 level,
pH, and radiation conditions to obtain a more plastic picture of future trends.