10/7/24
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_________ by bacteria inside legume ______ ________
Nitrogen fixation; root nodules
Nitrogen fixation
N2 (gas) –> NH4 (great fertilizer)
Describe the nitrogen cycle
Bacteria: nitrogen gas (N2) -> nitrogen-fixing bacteria: NH3 (via N fixation) -> assimilation (bacteria, plants, animals): N-protein (animal, plant) -> bacteria: NH3 (via decomp) -> bacteria: NO3
Eutrophication leads to
over-fertilized waters
T or F: Freshwater fish contain more 13C than marine fish
F: Marine fish contain more 13C than freshwater fish
The fish problem
Decrease in water quality of freshwater Increase in demand for (water) power Overfishing of freshwater fish
Shifting baselines
Change evaluated based on current state - Each generation = new baseline
What assumption is made in Shifting baselines?
“current state is normal”
Aquaculture
Raising aquatic organisms under controlled conditions
What are the benefits of aquaculture?
Reliability (controlling conditions) Can be small-scale Reduce fishing of wild stocks Uses less fossil fuel than capturing fishing - Less use of boats to travel from place to place to capture fish • reduces by-catch
Environmental impacts of aquaculture
High density → disease, antibiotics Waste production - High amounts of waste(urine, feces) is produced Farmed fish escape to interbreed with or spred disease to wild fish Animals often fed fish meal - Salmon chow
What happens during by-catch
“Non-target” species are caught Non-specific equipent i used (e.g., nets) - there is no target-specific catching system to only catch the target
What are example of modern gillnet by-catch?
sea lion sharks sea turtles
By-catch impact =
discards (what we throw away) / total caught (what we catch)
Why did the steller’s sea cow go extinct?
Slow Similar to beef in taste Blubber for cooking - Rendered for lamp oil Milk of cows, butter Hide → functional equipment (shoes, belts) Time to reproductive maturity (manatee: 5 years) Low reproductive output (1 calf/litter, 12 month gestation) Only found in the pacific northwest (low distribution)
What is the main cause of death for marine whales?
collisions with boats
Where does most of today’s nitrogen fixation come from?
Fertilizer BNG (agr) Combustion
What are the most important sources of N?
Commercial fertilizer (53%) Livestock manure (31%) Legumes (9%) Sewage (6%) Industry (1%)
Dead zone
Reduced levels of oxygen in the water
Describe how eutrophication leads to dead zones.
Lost agr fertilization (nutrients) —> Mississippi river —> gulf of mexico —> algal growth —> dead algae (organic compounds —> decomp bacteria consume CO2 —> fish, etc killed —> dead zone