1. what is the primary productivity of an ecosystem? 2. if a nutrient is in short supply in a ecosystem, how will it affect an organism?3. when a substance called a limiting nutrient?4. in the ocean and other saltwater environments, what is often the limiting factor?5. why do blooms occur?6. why do all organisms require nitrogen?7. what is a nitrogen fixation?8. what is denitrification?9. what is the main reservoir of nitrogen in the biosphere?10. what role does denitrification play in the nitrogen cycle?