Underwater Light Environment of Antarctic Seaweeds

Antarctic seaweeds are highly shade-adapted organisms, which can photosynthesize under very dim light. This remarkable characteristic allows them colonizing over 30 m depths and surviving extended dark periods during the polar winter. On the other hand, they are well equipped to cope with high light stress, which points to a trade-off between shade adaptation and efficient UV stress tolerance. Optical properties of water determine both the underwater light climate for photosynthesis and the risk of seaweeds for UV exposure in their habitats. Thus, understanding the natural (spatial, temporal) and anthropogenic-driven changes in spectral transparency of water and factors governing it is fundamental in evaluating the state of seaweeds under current and future environmental scenarios. In the present chapter the aspects related to the optical properties determining the underwater habitat of Antarctic seaweeds are summarized, along with the potential changes in water optics as a result of climate change, ozone depletion and other environmental and emerging threats, and their interactions.