Upwelling
The major upwellings in the ocean are associated with the divergence of currents that bring deeper, colder, nutrient rich waters to the surface. There are at least five types of upwelling: coastal upwelling, large-scale wind-driven upwelling in the ocean interior, upwelling associated with eddies, topographically-associated upwelling, and broad-diffusive upwelling in the ocean interior.
White-edge freshwater whipray
Like the other freshwater and euryhaline members of its family, but unlike the specialized South American river stingrays of the family Potamotrygonidae, the white-edge freshwater whipray retains the ability to synthesize urea for osmoregulation and can survive in brackish water with a salinity of 20 ppt for at least two weeks. Indeed, this ray might experience greater salinity-induced oxidative stress in freshwater than in
brackish water, possibly related to its short history of freshwater invasion. To this end, it has been suggested that there may be a possible relationship between the successful invasion of the freshwater environment by some euryhaline marine elasmobranchs and the ability of these elasmobranchs to increase the capacity of ascorbic acid synthesis to defend against hyposalinity stress. In addition, the ampullae of Lorenzini of H. signifer are intermediate in size and structure between the large, complex ampullae of its marine relatives and the small, simple ampullae of potamotrygonid stingrays, which may be a consequence of varying salinities in its environment and demands that would place on electroreception. The white-edge freshwater whipray feeds mainly on small benthic organisms, including crustaceans, molluscs, and insect larvae. Reproduction is aplacental viviparous with the developing embryos sustained by maternally produced histotroph ("uterine milk"), as is the case in other stingrays. Newborns measure across; males and females mature sexually at and across respectively.