Form and Function in Antarctic Seaweeds: Photobiological Adaptations, Zonation Patterns, and Ecosystem Feedbacks

Abstract

Morpho-functional traits of Antarctic seaweeds are modeled by different physical and biological factors. Due to the extreme seasonality, which imposes light limitation for extended periods, Antarctic seaweeds are shade-adapted organisms that are physiologically able to thrive at considerable depths down to 40 m. This vertical distribution is defined by a suite of bio-optical and morphological features that allow algae occupying habitats with different environmental conditions in the water column. However, various species can also colonize the highly perturbed intertidal zone where environmental setting, e.g. ice scouring, high solar radiation, extremely variable temperature, limit growth, and reproduction. In the maritime Antarctic region, large endemic brown algae attaining a massive (leathery) morphology and perennial life history dominate at depths below 10 m or less. Here, they coexist with perennial highly shade-adapted coarsely branched rhodophytes, which show understory characteristics. At shallower locations, various annual species with very rapid growth can be found. The intertidal zone, characterized by a depauperate diversity, is populated mostly by ephemeral and delicate green algae. In the present chapter, form and function of seaweeds is revisited in the context of a changing Antarctic environment. Here, the functional groups display different acclimation mechanisms, which can operate at different temporal scales and consequently with variable impact on the biogeochemical coastal processes. The role of canopy-forming algae, whose “bioengineering” processes alleviate the impact of environmental variability, is fundamental in determining the fate of the benthic communities in the coastal system.