Excretion
Water and Ion Regulation
Example of a reticulate kidney from Otariinae.
Whales do not drink water from the ocean, they get their water from the food they eat. Their kidneys regulate water and electrolyte levels and have adapted to allow them to live in a marine environment where they inevitably swallow salt water. Whales have a reniculate kidney, also known as a multilobed kidney, which has a larger surface area than the kidneys of terrestrial animals allowing for more efficiency when removing waste and excess ions. In order to maintain homeostasis they produce urine that is hypertonic to their body fluids. The extra thick walls of their kidneys allow them to hold a high solute concentration while preventing osmosis from diluting the urine.Furthermore, cetaceans lose less water through respiration than terrestrial animals because they breathe less frequently. They also lack sebaceous glands and do not lose water or ions through their skin.(Birukawa, et al 2005) Whales also release ions and water through their feces.
Whale Poop
Whale feces is quite important to the ocean’s ecosystem. When it is released it comes out watery, flocculent, and floats to the surface until it is dissolved into smaller pieces. Most fecal matter tends to sink, bringing the nutrients down with it. Whale fecal matter is less dense than the ocean water so it brings nutrients to the surface and has a similar effect to nutrient upwelling, some scientists refer to this process as “the whale pump”. The fecal matter contains high levels of nitrogen and iron which are important for phytoplankton to feed on. Through their normal metabolism phytoplankton as a whole are able to capture about 40% of the world's carbon dioxide and produce about 50% of the earth's oxygen levels. Even in nutrient rich waters nitrogen is the limiting factor for phytoplankton population growth. In the time of global warming caused by greenhouse gases this is incredibly important. (Roman and McCarthy 2010)
