Editing Antarctic krill (section)

===Biomass and production===
The [[Biomass (ecology)|biomass]] of Antarctic krill was estimated in 2009 to be 0.05 gigatons of carbon (Gt C), similar to the total biomass of humans (0.06 Gt C).<ref>{{Cite journal|last1=Bar-On|first1=Yinon M.|last2=Phillips|first2=Rob|last3=Milo|first3=Ron|date=2018-05-21|title=The biomass distribution on Earth|journal=Proceedings of the National Academy of Sciences|language=en|volume=115|issue=25|pages=6506–6511|doi=10.1073/pnas.1711842115|issn=0027-8424|doi-access=free|pmid=29784790|pmc=6016768|bibcode=2018PNAS..115.6506B }}</ref> The reason Antarctic krill are able to build up such a high biomass and production is that the waters around the icy Antarctic continent harbour one of the largest [[plankton]] assemblages in the world, possibly ''the'' largest. The ocean is filled with [[phytoplankton]]; as the water rises from the depths to the light-flooded surface, it brings [[nutrient]]s from all of the world's oceans back into the [[photic zone]] where they are once again available to living organisms.

Thus [[primary production]]—the conversion of sunlight into organic biomass, the foundation of the food chain—has an annual carbon fixation of 1–2&nbsp;g/m<sup>2</sup> in the open ocean. Close to the ice it can reach 30–50&nbsp;g/m<sup>2</sup>. These values are not outstandingly high, compared to very productive areas like the [[North Sea]] or [[upwelling]] regions, but the area over which it takes place is enormous, even compared to other large primary producers such as [[rainforest]]s. In addition, during the Austral summer there are many hours of daylight to fuel the process. All of these factors make the plankton and the krill a critical part of the planet's ecocycle.