near the coast, overpumping of groundwater causes saltwater to move into the aquifer
During an El Nino year
1.: trade winds weaken & warm water sloshed back to SA During a Non El Nino year: Easterly trade winds and ocean currents pool warm water in the western Pacific, allowing upwelling of nutrient rich water off the West coast of South America
Effects of El Nino
1.: upwelling decreases disrupting food chains, N US has mild winters, SW US has increased rainfall, less Atlantic Hurricanes
Nitrogen fixing
1.because atmospheric N cannot be used directly by plants it must first be converted into ammonia by bacteria
Ammonification
1.decomposers covert organic waste into ammonia
Nitrification
1.: ammonia is converted to nitrate ions (NO-3)
Denitrification
1.bacteria convert ammonia back into N
Phosphorus does not circulate as easily as N because
1.it does not exist as a gas, but is released by weathering of phosphate rocks
Because soils contain very little phosphorus
a major limiting factor for plant growth
Excess phosphorus is added to aquatic ecosystems by
1.runoff of animal wastes, fertilizer discharge of sewage