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.
River Aire
Due to the Aire flowing through the former industrial landscape of West Yorkshire, it had a reputation as being heavily polluted. In 2007, Yorkshire Water carried out improvements to Esholt Sewage Works at a cost of £110 million under the EU's Fresh Water Fish Directive. Whilst Trout are prevalent above Keighley, the river is host to others such as Chub, Dace, Barbel & Grayling, whilst Sea Trout have been noted as far upriver as Shipley. Work is also being undertaken to make the many weirs on the river easier to negotiate for fish. These improvements have also allowed Otters and Water Voles to return to the river as the water and food quality is far superior to that when the river was polluted. Plans have been submitted to Bradford Council to allow the installation of a fish passage on a weir at Saltaire, which remains the last barrier on the river preventing eels and lamphreys from migrating upriver to spawning grounds near to Gargrave.