ES101 Lecture Notes - Lecture 16: Nutrient Pollution, Primary Production, Pinus Aristata
Week 7, Lecture 1: Freshwater Biodiversity
Freshwater Aquatic Systems
● Can be standing (lakes, ponds, marshes) or flowing
● Can be permanently wet or ephemeral/intermittent/seasonal
● Unlike oceans nutrients are not especially scarce
Temperature, Oxygen in Lake
● Deepest water is approximately 4 degrees celsius
● In summer, surface warms causing water to form layers that do not mix, oxygen levels at
depth are lower than at surface
● In autumn, surface layer cools and begins to sink when it reaches 4 degrees celsius
● This stimulates mixing of water, nutrients
● Whole water column has good oxygen levels after convective overturn in spring, fall
Key Human Impacts on Freshwater Systems
● Damming, diverting watercourses
● Changing littoral environment
● Chemical and nutrient pollution
● Draining wetlands and ephemeral ponds
Impacts of Dams
● Alters water levels, flows above and below
● Changes water chemistry, temperature, turbidity
● Prevents migratory species from moving up/down river (some places build fish ladders)
Alteration of Streams, Ponds, Rivers
● Increases flow of water into, through channels
● Removes habitat for insects, waterfowl, amphibians, reptiles, fish
● Sediment (runoff) into water bodies
Nutrient Pollution of Freshwater
● Adding additional nitrogen, phosphorus to water increases primary productivity (often in
form of algae blooms)
● Decreases water clarity, increases water temperature and, if severe, causes dissolved
oxygen levels to fall (fish suffocate)
● Results in fish kills, change in aquatic biodiversity
find more resources at oneclass.com
find more resources at oneclass.com
Draining Wetlands
● Wetlands collect surface drainage, slow its movement into streams, rivers
● In Ontario, vast majority of wetlands have been drained for farms, urban/suburban
construction
● Draining wetlands increases food risks, reduces habitat for aquatic animals and
waterfowl, migratory birds
Freshwater Aquatic Systems
● Are highly dynamic
● Are easily compromised by human activity
● Provide critical ecosystem services
Biomes
● Large areas with characteristic vegetation types, linked to climates
Biomes and Biodiversity
● Diff biomes tend to have own characteristic biological diversity
● Limiting factors (e.g. moisture, temperature, nutrients) are often reflected in the
characteristics of organisms
E.g. Desert Biomes
● Limiting factor = moisture
● Organisms tend to adapt in ways that conserve moisture, offset extreme temperatures
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Can be standing (lakes, ponds, marshes) or flowing. Unlike oceans nutrients are not especially scarce. Deepest water is approximately 4 degrees celsius. In summer, surface warms causing water to form layers that do not mix, oxygen levels at depth are lower than at surface. In autumn, surface layer cools and begins to sink when it reaches 4 degrees celsius. Whole water column has good oxygen levels after convective overturn in spring, fall. Alters water levels, flows above and below. Prevents migratory species from moving up/down river (some places build fish ladders) Removes habitat for insects, waterfowl, amphibians, reptiles, fish. Adding additional nitrogen, phosphorus to water increases primary productivity (often in form of algae blooms) Decreases water clarity, increases water temperature and, if severe, causes dissolved oxygen levels to fall (fish suffocate) Results in fish kills, change in aquatic biodiversity. Wetlands collect surface drainage, slow its movement into streams, rivers.
