In the Antarctic, primary productivity is greatest in bottom ice communities, followed by surface ice communities, with internal ice communities being the least productive pack ice habitat (Figure 12). It is likely that this is also true of the Arctic but further research is required to confirm this conclusion (Thomas & Dieckmann 2003).
Productivity is affected by environmental conditions and access to nutrients; the more enclosed the environment the more productivity is hampered by reduction in nutrient availability.
Environmental gradients within the ice are steep and can change rapidly as the ice thaws and refreezes. The microalgae inhabiting this environment have several notable adaptations to survive under these extreme conditions; however these are so far poorly understood.
There is much to be learned about the structure and tolerances of these communities, with new information becoming available regularly about the composition of habitats and the relative importance of both species and habitats. Without a greater understanding of this large, important ecosystem it is likely that predictive models of climate change are going to be inaccurate, and it is difficult to predict how these ecosystems will adapt as environmental conditions change.