Chapter 13 - N, P, and Biogeochemistry Flashcards
What causes N and P to enter water bodies?
Runoff
Atmospheric nitrogen is converted to…? By what?
Nitrate by lightning
Atmospheric N can be fixed as…? By what?
Organic N by bacteria and blue-green algae
What greatly alters N cycle?
agricultural activity and fossil fuel burning
Nitrate is returning to the atmosphere as what?
N2 gas
N cycle in terrestrial system
Nitrification: Atmospheric nitrogen gets fixed by nitrogen-fixing bacteria of root nodules of legumes or nitrogen-fixing bacteria in the soil. Then, converted to ammonium (also produced from decomposers)
Denitrification: Ammonium is converted to nitrites via nitrifying bacteria. Nitrites are converted to nitrates by same bacteria. Nitrates are either taken up by plants or converted back to atmospheric nitrogen via denitrifying bacteria.
Nitrogen speciation and their relationship to pH
NH3: lower pH = no NH3
NH4+: lower pH = lots of NH4+
Adverse effects of ammonia
NH3 is a major excretory product of aquatic animals. If there are high concentrations of it already in the water, then it is difficult for the aquatic animals to excrete NH3. This could damage their gills, elevate their blood pH, and disrupt their enzyme and membrane systems
Adverse effects of nitrite
Nitrite is more lethal than ammonia. Symptoms: Fish gasp for air at water surface, fish stay passive and limp near water outlets, brown gills and faster gill movement
What is the most important nutrient?
Phosphorus
Phosphorus characterisitics
Highly reactive and mostly found combined with other elements.
Phosphorus cycle
P comes from (for example) phosphate extraction from mines (or fertilizer or erosion from phosphate rocks) and becomes apart of the runoff from river and streams. In the large body of water, P becomes dissolved phosphates. This is consumed excessively by algae and other photosynthetic organisms. Hypoxia’s story begins
Mitigation strategies for eutrophication
Diversion of excess nutrients, altering nutrient ratios, physical mixing, and shading water bodies with opaque lining or water based stains