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Osmoregulation

Adélie penguins are faced with extreme osmotic conditions, as their frozen habitats offer little fresh water. Such desert conditions means that the vast majority of the available water is highly saline, causing the diets of Adélie penguins to be highly saline. They manage to circumvent this problem by eating krill with internal concentrations of salt at the lower end of their possible concentrations, helping to lower the amount of ingested salts. The salt load imposed by this sort of diet is still relatively heavy, and can create complications when considering the less tolerant chicks. Adult Adélie penguins feed their chicks by regurgitating the predigested krill, which can impose a heavy salt load on the chicks. Adults address this problem by altering the ion concentrations while the food is still being held in their stomachs. By removing a portion of the sodium and potassium ions, adult Adélie penguins protect their chicks from heavy salt loads. Adélie penguins also manage their salt loads by concentrating cloacal fluids to a much higher degree than most other birds are capable of. This ability is present regardless of ontogeny in Adélie penguins, meaning that both adults and juveniles are capable of extreme levels of salt ion concentration. However, chicks do possess a greater ability to concentrate chloride ions in their cloacal fluids.

Salt glands also play a major role in the secretion of excess salts in Adélie penguins. Due to the relatively inefficient kidneys of aquatic birds, the salt gland takes on most of the responsibility of salt removal. Aquatic birds such as the Adélie penguin have highly developed salt glands which are capable of handling their intense salt loads. As a result, the avian salt gland is capable of excreting fluids even more concentrated than seawater through the nares of the bird. Specifically, the salt gland works to pump out and concentrate large quantities of sodium chloride. These excretions are crucial in the maintenance of Antartic ecosystems. Penguin rookeries can be home to thousands of penguins, all of which are concentrating waste products in their digestive tracts and nasal glands. These excretions will inevitably drop to the ground. The concentration of salts and nitrogenous wastes helps to facilitate the flow of material from the sea to the land, serving to make it habitable for bacteria which live in the soils.